Proc IAHS 377 57ndash66 2018httpsdoiorg105194piahs-377-57-2018copy Author(s) 2018 This work is distributed underthe Creative Commons Attribution 40 License

Open Access

Waterquality

andsedim

enttransportissuesin

surfacew

ater

Sedimentation and Its ImpactsEffects on River Systemand Reservoir Water Quality case Study of Mazowe

Catchment Zimbabwe

Colleta Tundu1 Michael James Tumbare2 and Jean-Marie Kileshye Onema3

1Zimbabwe National Water Authority PO Box Cy617 Causeway Harare Zimbabwe2Department of Civil Engineering University of Zimbabwe PO Box MP167

Mt Pleasant Harare Zimbabwe3WaterNet Secretariat PO Box MP600 Mount Pleasant Harare Zimbabwe

Correspondence Colleta Tundu (ctundugmailcom)

Received 7 June 2017 ndash Accepted 10 October 2017 ndash Published 16 April 2018

Abstract Sediment delivery into water sources and bodies results in the reduction of water quantity and qualityincreasing costs of water purification whilst reducing the available water for various other uses The paper givesan analysis of sedimentation in one of Zimbabwersquos seven rivers the Mazowe Catchment and its impact onwater quality The Revised Universal Soil Loss Equation (RUSLE) model was used to compute soil lost fromthe catchment as a result of soil erosion The model was used in conjunction with GIS remotely sensed data andlimited ground observations The estimated annual soil loss in the catchment indicates soil loss ranging from0 to 65 t ha yrminus1 Bathymetric survey at Chimhanda Dam showed that the capacity of the dam had reduced by39 as a result of sedimentation and the annual sediment deposition into Chimhanda Dam was estimated tobe 330 t with a specific yield of 226 t kmminus2 yrminus1 Relationship between selected water quality parameters TSSDO NO3 pH TDS turbidity and sediment yield for selected water sampling points and Chimhanda Dam wasanalyzed It was established that there is a strong positive relationship between the sediment yield and the waterquality parameters Sediment yield showed high positive correlation with turbidity (063) and TDS (064) Waterquality data from Chimhanda treatment plant water works revealed that the quality of water is deteriorating as aresult of increase in sediment accumulation in the dam The study concluded that sedimentation can affect thewater quality of water sources

1 Introduction

Sedimentation is a process whereby soil particles are erodedand transported by flowing water or other transporting me-dia and deposited as layers of solid particles in water bod-ies such as reservoirs and rivers It is a complex process thatvaries with watershed sediment yield rate of transportationand mode of deposition (Ezugwu 2013) Sediment deposi-tion reduces the storage capacity and life span of reservoirsas well as river flows (Eroglu et al 2010)

Sedimentation continues to be one of the most importantthreats to river eco-systems around the world A study wasdone on the worldrsquos 145 major rivers with consistency longterm sediment records and the results show that about 50

of the rivers have statistically a significantly downward flowtrend due to sedimentation (Walling and Fang 2003) Sumiand Hirose (2009) reported that the global reservoir grossstorage capacity is about 6000 km3 and annual reservoir sedi-mentation rates are about 31 km3 (052 ) This suggests thatat this sedimentation rate the global reservoir storage capac-ity will be reduced to 50 by year 2100

Studies on some dams in Zimbabwe show that reservoircapacities are being affected by sedimentation (Sawunyamaet al 2006 Dalu et al 2013 Chitata et al 2014)

Water is vital for all anthropogenic activities Water bodieshave been contaminated with various pollutants due to director indirect interference of men causing an adverse impact onhuman health and aquatic life (Lawson 2011) The quality of

Published by Copernicus Publications on behalf of the International Association of Hydrological Sciences

58 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

water is getting vastly deteriorated due to improper land man-agement and carelessness to the environment Off late sedi-ment transport in the water bodies has proved to be one of themajor contributors to poor water quality Due to land degra-dation and sheet erosion the top soil is carried into the waterbodies resulting in excess levels of turbidity Silt and clayparticles are primary carriers of adsorbed chemicals such asnitrogen and phosphorus

This study uses the Mazowe Catchment area as a casestudy in analyzing river and reservoir sedimentation and itsimpact on water quality Sedimentation in the rivers andreservoirs within the Mazowe Catchment area has becomea major challenge for the policy makers as well as the watermanagers

11 Study area

Mazowe Catchment is one of the seven water managementcatchments in Zimbabwe It lies between 16470 S (lati-tude) and 18240 S (latitude) and between 30680 E (lon-gitude) and 33000 E (longitude) The catchment has a totalarea of 38 005 km2 and is in the northern part of the countryThere are 30 major dams built along the main river and someof the tributaries There are 13 functional gauging stationswithin the catchment The catchment is composed of twenty-four (24) hydrological sub-zones Rainfall for the Catchmentaverages 500 mm to 1200 mm yrminus1 while the mean annualrunoff is 131 mm with a coefficient of variation (CV) of126 (Zinwa 2009) There are 17 water quality monitor-ing sampling points within the catchment Six (6) samplingwater points were selected for the study these points were se-lected basing on the continuity of the available data meaningto say the points had less missing gaps

Chimhanda Dam in Lower Mazowe Sub-Catchment waschosen for the assessment of the levels of sedimentation inresevoirs Chimhanda Dam is located on the confluence ofRunwa and Mwera Rivers which are tributaries of MazoweRiver The dam is located in hydrological sub zone DM1with latitude 1640prime and longitude 3206prime The dam wascompleted in 1988 with a design capacity of 52times 106 m3

and covering a catchment area of 687 km2 which mainlyconsists of communal lands

2 Materials and methods

21 Data collection

Remote sensing images of the study area were downloadedfrom Landsat TM 4-5 LandSat LE7 and LandSat 8 scenefrom the website (httpsglovisusgsgov) for paths 168ndash170and rows 71ndash73 for the period 2000 2005 2008 and 2014The study period was selected basing on the major changesin land use and land cover as a result of the Zimbabwe landreform programme which started in year 2000 and peakingduring year 2003 The composite map was obtained by glu-

Figure 1 Mazowe Catchment and location of Chimhanda Dam

ing and merging the tiles from the different scenes whichwas performed using Integrated Land and Water InformationSystem (ILWIS) software Normalized Differences Vegeta-tion Index (NDVI) was extracted from the images and thiswas used to calculate the cover and management practice fac-tor (C factor) SRTM DEM of 90m resolution was obtainedfrom Earth Explorer website (httpEarthExplorercom) TheDEM was used to calculate the slope length and slope steep-ness factor (LS factor) The erodibility factor was obtainedfrom the soil map of Zimbabwe that was downloaded fromwebsite (wwwfaoorggeonetwork Rainfall data was ob-tained from the Zimbabwe Meteorological Services Depart-ment and was used to come up with the erosivity factor Thegrab sample method was used to obtain samples for sedimentloads from the flow gauges for the 20142015 rainfall seasonHistorical data for sediment loads from flow gauging stationswere obtained from the Zimbabwe National Water Author-ity (ZINWA) Historical water quality data for selected waterquality monitoring stations was obtained from Environmen-tal Management Agency (EMA)

Siltation historical data for selected reservoirs within thecatchment was obtained from ZINWA A bathymetric surveywas done to assess the level of sedimentation of Chimhandadam which lies within the Mazowe Catchment

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

58 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

water is getting vastly deteriorated due to improper land man-agement and carelessness to the environment Off late sedi-ment transport in the water bodies has proved to be one of themajor contributors to poor water quality Due to land degra-dation and sheet erosion the top soil is carried into the waterbodies resulting in excess levels of turbidity Silt and clayparticles are primary carriers of adsorbed chemicals such asnitrogen and phosphorus

This study uses the Mazowe Catchment area as a casestudy in analyzing river and reservoir sedimentation and itsimpact on water quality Sedimentation in the rivers andreservoirs within the Mazowe Catchment area has becomea major challenge for the policy makers as well as the watermanagers

11 Study area

Mazowe Catchment is one of the seven water managementcatchments in Zimbabwe It lies between 16470 S (lati-tude) and 18240 S (latitude) and between 30680 E (lon-gitude) and 33000 E (longitude) The catchment has a totalarea of 38 005 km2 and is in the northern part of the countryThere are 30 major dams built along the main river and someof the tributaries There are 13 functional gauging stationswithin the catchment The catchment is composed of twenty-four (24) hydrological sub-zones Rainfall for the Catchmentaverages 500 mm to 1200 mm yrminus1 while the mean annualrunoff is 131 mm with a coefficient of variation (CV) of126 (Zinwa 2009) There are 17 water quality monitor-ing sampling points within the catchment Six (6) samplingwater points were selected for the study these points were se-lected basing on the continuity of the available data meaningto say the points had less missing gaps

Chimhanda Dam in Lower Mazowe Sub-Catchment waschosen for the assessment of the levels of sedimentation inresevoirs Chimhanda Dam is located on the confluence ofRunwa and Mwera Rivers which are tributaries of MazoweRiver The dam is located in hydrological sub zone DM1with latitude 1640prime and longitude 3206prime The dam wascompleted in 1988 with a design capacity of 52times 106 m3

and covering a catchment area of 687 km2 which mainlyconsists of communal lands

2 Materials and methods

21 Data collection

Remote sensing images of the study area were downloadedfrom Landsat TM 4-5 LandSat LE7 and LandSat 8 scenefrom the website (httpsglovisusgsgov) for paths 168ndash170and rows 71ndash73 for the period 2000 2005 2008 and 2014The study period was selected basing on the major changesin land use and land cover as a result of the Zimbabwe landreform programme which started in year 2000 and peakingduring year 2003 The composite map was obtained by glu-

Figure 1 Mazowe Catchment and location of Chimhanda Dam

ing and merging the tiles from the different scenes whichwas performed using Integrated Land and Water InformationSystem (ILWIS) software Normalized Differences Vegeta-tion Index (NDVI) was extracted from the images and thiswas used to calculate the cover and management practice fac-tor (C factor) SRTM DEM of 90m resolution was obtainedfrom Earth Explorer website (httpEarthExplorercom) TheDEM was used to calculate the slope length and slope steep-ness factor (LS factor) The erodibility factor was obtainedfrom the soil map of Zimbabwe that was downloaded fromwebsite (wwwfaoorggeonetwork Rainfall data was ob-tained from the Zimbabwe Meteorological Services Depart-ment and was used to come up with the erosivity factor Thegrab sample method was used to obtain samples for sedimentloads from the flow gauges for the 20142015 rainfall seasonHistorical data for sediment loads from flow gauging stationswere obtained from the Zimbabwe National Water Author-ity (ZINWA) Historical water quality data for selected waterquality monitoring stations was obtained from Environmen-tal Management Agency (EMA)

Siltation historical data for selected reservoirs within thecatchment was obtained from ZINWA A bathymetric surveywas done to assess the level of sedimentation of Chimhandadam which lies within the Mazowe Catchment

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C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 59

22 Calculation of RUSLE Factors

The Revised Universal Soil Erosion (RUSLE) model wasused in this study to calculate the soil that was lost from thecatchment The model predicted the long term annual lossfrom the basin and is given by Eq (1 Renard et al 1997)

A= RtimesK timesLStimesCtimesP (1)

where A= annual soil loss (t ha yrminus1) R = rain erosiv-ity factor (MJ mm haminus1 hminus1) K = soil erodibility factor(t ha h MJminus1 mmminus1) LS= slope length and slope steep-ness length (m) C = land cover and crop managementP =management practice

221 Rain Erosivity Factor (R factor)

Rainfall data was processed into average annual rainfallRain erosivity was calculated from the rainfall point map us-ing Eq (2 Merritt et al 2003)

R = 385+ 035timesP (2)

where R =Rain Erosivity Factor (Joule mminus2) P =MeanAnnual Rainfall (mm yrminus1)

222 Soil Erodibility Factor (K factor)

The soil erodibility factor (K Factor) was calculated usingEq (3) with the parameters obtained from the soil map (Teh2011)

K =(10times 10minus4(12minusOM114

+ 45(F minus 3)+ 30(P minus 2))100

(3)

where K = Soil Erodibility M = ( fine sand +finesand)]times (100minusclay) O = of organic matter F =SoilStructure P =Permeability

223 Land Cover and Crop Management Factor (Cfactor)

The C factor was calculated using the Normalized Differ-ence Vegetation Index (NDVI) which is a tool for assessingchanges in vegetation cover (Pettorelli et al 2005 Gusso etal 2014) NDVI was calculated from the bands using Eq (4Deering 1992)

NDVI=(NIRminusRed)(NIR+Red)

(4)

where NIR= band 3 for landSat images 1 to 7 and band 4for landSat 8 Red= band 4 for landSat 1 to 7 and band 5 forlandSat 8

The calculated NDVI was then used to calculate the C fac-tor from Eq (5)

C factor map= 12708timesNDVI+ 02585 (5)

224 Management Practice Factor (P Factor)

The P factor reflects the control of conservation methods onsoil loss P values range from 001 to 1 with the value 001being given to areas of maximum conservation support andthe value 1 being given to areas with minimal or no con-servation practices (Renard et al 1997) The P values werederived from the land use map of the study area Differentvalues were assigned to each type of land use as guided byliterature and the P factor map was produced (Jang et al1996)

23 Quantifying the sediment yield in the Catchment

The estimated soil loss was calculated from Eq (6)

A= RtimesK timesLStimesCtimesP (6)

where A=Average Soil Loss (t ha yrminus1) R =R factor mapK =K factor map LS=LS factor map C =C factor mapP =P factor

Soil loss from the catchment cannot be taken as sedimentcontribution to a river flow system since it does not accountfor deposition that occurs along the path (de Vente et al2011) Therefore the estimated soil loss was multiplied by thesediment delivery ratio (SDR) to obtain the sediment yield ofthe catchment Sediment delivery ratios represent the fractionof the total soil loss that is washed into rivers and was calcu-lated from using Eq (7 USDA 1972)

SDR= 05656CAminus011 (7)

where SDR=Sediment Delivery Ratio CA=WatershedArea km2

After determination of the sediment delivery ratio the av-erage sediment yield was determined using Eq (8) by Wis-chmeier and Smith (1978)

SR= SDRtimesA (8)

where SR=Sediment yield (t ha yrminus1) SDR=Sedimentdelivery ratio A=Average soil loss (t ha yrminus1)

24 Sediment yield from field measurements

Seven out of the thirteen functional ZINWA gauging sta-tions were selected for collection of sediment concentrationsamples (Fig 2) Water samples were collected from vari-ous flow gauging stations for the period November 2014 toMarch 2015 using grab sampling method An average of 20samples was collected from each gauging station The sam-ples were analyzed in a laboratory using the weighing and fil-tration method inorder to determine the sediment concentra-tion in mg Lminus1 The sediment load was determined by mul-tiplying the sediment load at a particular gauge by the areaof influence

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

60 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Figure 2 Gauges in the catchment and areas of influence

25 Assessing the current sedimentation levels ofChimhanda Dam

A bathymetric survey was carried out at Chimhanda dam todetermine the siltation level of the dam The survey was con-ducted using a SonTek River Surveyor system and a theodo-lite to come up with a basin survey map The plotted map wasdigitized to get the surface area between contours The areawas then multiplied by the contour interval to get the volumeof each contour using Simpsonrsquos formula

Vcontour =A1+ (A1timesA2)12

+A2

3(9)

where Vcontour = contour Volume (m3) A1 =Area1 (m2)A2 =Area2 (m2)

The calculated volumes for each contour were accumu-lated to get the new capacity of the dam

26 Water quality trend from sedimentation

Water quality historical data from six selected water sam-pling points were obtained from the Environmental Manage-ment Agency records The points were selected basing onthe consistency of the data and less gaps The trend for theselected water quality parameters TSS DO NO3 pH TDSand turbidity for the corresponding predicted sediment yieldyears were analysed The water quality parameters werecompared with the Environmental Management Agency Ef-fluent and Solid Waste Disposal Regulations Statutory Instru-ment number 6 of 2007 (EMA 2007) shown on Table 1 Wa-ter quality data for Chimhanda water supply treatment plantfrom the Zimbabwe National Water Authority was also re-lated to the change in level of sedimentation of ChimhandaDam

27 Investigation the relationship betweensedimentation and water quality

Selected water quality parameters were correlated with thecorresponding sediment yield to determine the relationshipbetween sediment yield and water quality Pearson Correla-tion was used to estimate the strength of relationship betweensediment yield and some physical water quality

3 Results and discussions

31 Results of the RUSLE factors

The erosivity map (R factor) depicts rainfall energy inthe various areas within the catchment The rainfall ero-sivity ranges between 200 and 500 (MJ mm haminus1 hminus1 yr)A greater part of the catchment is averaging a rainfallerosivity value of 276 MJ mm haminus1 hminus1 yr Highest rainfallerosivity values are in the Kairezi sub-catchment of thestudy area Erodability (K factor) values range from 0 to05 t haminus1yrminus1 MJminus1 mmminus1 Some parts in the south west ofthe catchment have high values of erodibility the highestK value is dominated by very fine sand with silt particleswhich give rise to higher soil erodibility (Kamaludin et al2013) Highest slope length steepness (LS) values of 16 mwere found in the eastern part of the catchment The north-ern part of the catchment experiences average LS values of7 m

Cover Management and Practice (C factor) ranges fromminus1 to 1 The C factor is depicted by NDVI which is a func-tion of photosynthesis The C factor is high in the east-ern highlands area some parts of Kairezi sub-catchmentand along the Mufurudzi area This is possible because theKairezi area experiences high rainfall while Mufurudzi be-ing a game park has more vegetation High C values wereobserved with high vegetation cover (Pettorelli et al 2005)The P value of 1 was observed in Lower Mazowe and UpperRwenya subcatchment areas respectively Areas like Mufu-rudzi and parts of Kairezi experienced an average P value of08

32 Soil loss from the catchment

The average annual soil loss for the different years are shownon Fig 3 and the temporal variation of actual soil loss is tab-ulated on Table 2

The estimated soil loss from the catchment ranges from0 to 203 t ha yrminus1 The estimated average soil loss is54 t ha yrminus1 The highest soil loss is being experienced inMiddle Mazowe and Nyagui sub-catchments High soil lossin Middle Mazowe sub-catchment can be associated withhigh gold panning activities in the Mazowe valley whilst inNyagui sub-catchment this can be associated with high cropfarming activities in the area When the soil is made looseits structure is altered hence increase in erodibility

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C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 61

Table 1 Effluent and solid waste disposal regulations

BANDS

PARAMETER Blue Green Yellow Red TestMethods

Sensitive Normal

DO saturation gt 75 gt 60 gt 50 gt 30 gt 15 SAZS 573

Nitrates NO3 mg Lminus1 lt 10 lt 10 lt 20 lt 30 lt 50PH 60ndash75 60ndash90 5ndash6 9ndash10 4ndash5 10ndash12 0ndash4 12ndash14 SAZS 483TDS lt 100 lt 500 lt 1500 lt 2000 lt 3000 SAZS 576Turbidity (NTU) lt 5 lt 5 SAZS 478TSS mg Lminus1 lt 10 lt 25 lt 50 lt 100 lt 150 SAZS 478

Figure 3 Estimated Average Soil Loss for 2000 2005 2008 and2014

The average soil loss value of 54 t ha yrminus1 concurred withother studies that were carried out in the country Whit-low (1986) found that 76 t of soil is lost per hectare peryear through soil erosion in most parts of the country An-other study by Mutowo and Chikodzi (2013) ldquoErosion haz-ards mapping in the Runde Catchmentrdquo concluded that mostof the areas in the catchment fall in the category range of 0ndash50 t ha yrminus1 Makwara and Gamira (2012) reported that themost serious type of erosion being sheet erosion is estimatedto remove an average 50 t ha yrminus1 from Zimbabwersquos commu-nal lands

There is no uniform trend in the soil loss over the study pe-riod In year 2000 the soil loss was 54t ha yrminus1 The increaseof soil loss in 2005 from the 2000 figure can be explained bythe land reform programme which started in year 2000 and

Table 2 Temporal Variation of Estimated Soil Loss

Year Average SoilLoss (t ha yrminus1)

2000 542005 652008 362014 62

was at its peak around 2003 There was a lot of deforesta-tion as new farmers were clearing land for agricultural pur-poses (Mambo and Archer 2007) Some areas which weremeant for animal rearing and forest were also converted tocrop agricultural areas In 2008 the soil loss rate decreasedto 36 t ha yrminus1 The reduction can be attributed to a numberof factors Year 2008 experienced low erosivity as a resultof low rainfall which could also lead to low annual soil lossThe economy of Zimbabwe was almost at a stand-still duringthe period 2007 to 2009 with an inflation rate record of over231 million percent in July 2008 (Hanke and Kwok 2009)As a result there was less farming activities during that pe-riod

The soil loss rate almost doubled in year 2014 as comparedto 2008 This can be explained by the increase in the numberof small scale gold miners in the catchment and alluvial goldpanning in streams and rivers Mining within the catchmentis not only limited to the river beds and banks miners arealso targeting the inland areas of the catchment such as theMazowe Valley and Mufurudzi Game Park and as a resultsoil erodibility is also increasing Increase in rate of unem-ployment caused by low capital investment and continuingclosure of industries in Zimbabwe has resulted in the pop-ulation resorting to other sources of income such as illegalgold mining and alluvial gold panning A study that was car-ried out in the Lower Manyame sub ndash catchment along DandeRiver on the analysis of the implications of cross- sectionalcoordination of the management of gold panning activities

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62 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Table 3 Measured sediment Load from flow gauges for the period December 2014 to March 2015

Silt Gauge Name or River Area of Sediment LoadInfluence (km2) load (t kmminus2) (t)

D75 Mazowe 20 380 14 28536D50 Nyamasanga 13 024 3D42 Mupfurudzi 163 192 31356D41 Mazowe 3300 086 2836D6 Shavanhowe 1166 051 58965D58 Nyagui 983 2425 14293D48 Mwenje 399 036 334

Table 4 Summarized Results from the silt survey

1988 2003 2015

Capacity at FSL (times106 m3) 52 3470 3194Loss Of Storage () 0 333 386Dam Surface Area (Ha) 9300 7400 6404

and its impacts (Zwane et al 2006) identified river bed goldpanning activities as a cause of degradation of river chan-nels and banks as well as accelerated erosion and siltation inmany areas of Zimbabwe

321 Sediment Yield

Figure 4 shows the sediment yield distribution map Sed-iment yield ranges from less than 1 t ha yrminus1 to a maxi-mum of 245t ha yrminus1 with an average value of 604 t ha yrminus1

over the catchment area The highest sediment yield is inthe Middle Mazowe sub catchment area with an averageof 672 t ha yrminus1 and a maximum of 245t ha yrminus1 The highvalue can be associated with high gold panning activities inthe Mazowe valley The lowest value is in the Lower Ruyasub-catchment with an average of 4 t ha yrminus1 The resultsare almost in line with a study by Rooseboom and Engi-neers (1992) that estimated the average sediment yield in thenine defined sediment regions in Southern Africa to vary be-tween 30 and 330 t ha yrminus1 with an average of 15 t ha yrminus1A study which was also carried out in the catchment areaof Pahang River basin in Malasyia gave a sediment yieldranging from 0ndash1379 t ha yrminus1 (Kamaludin et al 2013) Thetotal sediment yield for the catchment was calculated to be63 million t yrminus1

322 Measured Sediment Loads

Results from the measured sediment loads were highest atD75 which is along Mazowe River in the Zambezi valleyD41 located in Middle Mazowe sub catchment recorded arelatively high sediment load of 2836 t D58 and D6 are bothin Nyagui Sub-catchment recorded 14293 and 58965 t re-

Figure 4 Sediment Yield within the Catchment

Table 5 Results for the correlation between sediment yield and wa-ter quality parameters

Sediment Ave AverageTurbidity TSS

Sediment Pearson Correlation 1 634 647Sig (2-tailed) 366 353N 28 28

spectively D50 which is in Upper Mazowe sub catchmentrecorded a low figure of 3 t The results are concurring withthose from RUSLE model where high sediment yields wererecorded from Middle Mazowe and Nyagui sub catchmentsrespectively

33 Sedimentation in Chimhanda Dam from BathymetricSurvey

Table 4 summarizes the results of the silt survey forChimhanda Dam

The capacity of the dam decreased from the original5200times 106 to 3470times 106 and 3194times 106 m3 in years2003 and 2015 respectively There was 333 loss in stor-

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C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 63

Figure 5 Chimhanda Dam Capacity comparison over the years

age up to 2003 and a storage loss of 386 up to 2015 inreference to the design capacity Figure 5 shows reservoir ca-pacity changes over the years

Results from the 10 samples of river inflows collectedgave an average sediment concentration of 39 mg Lminus1 Therewas a decrease in trend in the sediment concentration asthe rainfall season was progressing The sediment accumu-lation in the reservoir was found to be 330 t yrminus1 and the spe-cific sediment yield was 226 t kmminus2 yrminus1 The usefulness ofChimhanda Dam has reduced from the initial design life of50 to 37 years A study by Godwin et al (2011) on ChesaCauseway Weir in the same catchment gave a specific yieldof 510 t km2 yrminus1 The usefulness of the dam was reducedfrom the initial design life of 50 to 25 years

Generally the results support the existing literature thatmost of the small to medium dams are being affected byhigh rates of sedimentation in Zimbabwe (Sawunyama et al2006 Godwin et al 2011 Dalu et al 2013 Chitata et al2014)

34 Water Quality Trend from Sedimentation

Figures 6 to 10 show the results for the historically measuredwater parameters for the years 2000 2008 2010 and 2014

341 Turbidity

Results for the years did not meet the permissible turbid-ity of 5 NTU The highest turbidity values were recordedin 2000 and 2005 respectively High values in 2005 corre-sponds to the high soil loss of 65 t ha yrminus1 that was recordedduring that particular year The high values in 2000 can beexplained by high rainfalls that were experienced during thatparticular year as compared with the other years (Met 2005)Low turbidity values were recorded during the year 2008the same year recorded the lowest soil loss of 36 t ha yrminus1High Turbidity levels are associated with poor water quality(Adekunle et al 2007) WHO (2008) highligted that highturbidity waters can facilitate the formation of nuclei wheregastrointestinal disease pathogens can attach If that water

Figure 6 Turbidity variation among sampling points

Figure 7 Total Suspended Solids variation among sampling points

is consumed improperly treated it can cause diseases Highturbidity leves also render the treatment of water expensive

342 Total Suspended Solids

2008 values were below the recommended limit of15 mg Lminus1 as shown on Fig 7 High values were recordedduring year 2000 2005 and 2014 The high values are inagreement with the high soil loss that were recorded in thoseparticular years Total suspended solids are closely relatedto sedimentation (Chapman 1996) When these suspendedparticles settles at the bottom of a water body they becomesediments Suspended solids consist of inorganic and organicfractions Part of the organic fractions is bacterial and thatmight be detrimental to human health if the water is con-sumed without adequate treatment (Hoko 2008)

343 Dissolved Oxygen (DO)

Dissolved Oxygen was above the lower limit for EMA at allthe stations for all the years Year 2000 and 2005 recorded saturation of 125 and 100 respectively Oxygen levels canbe higher due to excess aquatic plants in the water which

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

64 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Figure 8 Dissolved Oxygen variation among sampling points

Figure 9 Nitrates variation along sampling points

produce oxygen Most living organisms require oxygen fortheir basic metabolic processes

344 Nitrates (NO3)

Results for nitrates for the years under consideration were allbelow the recommended EMA levels of 6 mg Lminus1 Nitratesare washed by runoff from agricultural lands into water bod-ies High concentration of nitrates in water bodies cause eu-trophication resulting in competition for oxygen by aquaticorganisms and high water treatment costs (Dike et al 2010)

345 PH

pH values for all the years were within the normal limits cat-egory according to EMA upper and lower limits of 6 and9 units respectively Year 2005 had one sampling point thathad a value slightly lower than the recommended Bhadjaand Vaghela (2013) indicated that activities in the water shedsuch as increased leaching of soils soil erosion and heavyprecipitation affects the pH levels downstream pH levels ashigh as 90 and as low as 5 affects the life span of aquaticorganisms (Addo et al 2011) Low pH values do not havedirect effect to human health but can have indirectly effect

Figure 10 pH variations along sampling points

since it causes leaching of metal irons such as copper zincand lead into the water (WHO 2008)

35 Relationship between sedimentation and river waterquality

Pearson correlation was used to determine the relationshipbetween two water quality parameters and sediment yieldThe parameters are related to sediment yield and these areturbidity and suspended solids (Bhadja and Vaghela 2013)The results are shown on Table 5

There is a close positive relationship between turbidity andsediment yield of 063 Total Suspended Solids have a posi-tive relation of 064 The results show that the two water qual-ity parameters can be indicators of sedimentation Highervalues of total suspended solids and turbidity indicate highervalues of sediment yield in water bodies

36 Variation in reservoir water quality

The variation in two selected reservoir water quality indica-tors turbidity and pH was determined A significant variationin turbidity was noted for the years 1988 to 2014 with a p-value of 002 which is less than 005 The mean value of tur-bidity for 1988 2003 and 2014 are 156 344 and 417 NTUrespectively The values show an increasing trend in turbid-ity which may be as a result of anthropogenic activities oc-curring upstream of the dam which has resulted in increasedsoil erosion hence more sediment on the reservoir pH resultsshowed that there is no significant change between 1988 and2014 (p-value gt 005) This might be because pH is a chemi-cal parameter that is determined by the type of sediments thatare carried into the river not the sediment load

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C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 65

4 Conclusions and recommendations

41 Conclusion

The objective of the study was to analyze sedimentation andits impact on river system and reservoir water quality in Ma-zowe Catchment Zimbabwe The studyrsquos major findings are

The catchment is generally experiencing moderate soilloss however there are some pockets under high and extremesoil loss which gave rise to siltation and water quality deteri-oration of available water bodies

There is reduction in capacity of reservoirs within thecatchment due to sedimentation Chimhanda Dam capacityhas been reduced by 386 from the initial design capac-ity as of April 2015 reducing the usefulness of the dam to37 years from the initial design life of 50 years due to silta-tion

Sediment deposition in rivers affects water quality and wa-ter quality parameters can be used as an indicator for sedi-mentation

42 Recommendations

In order to curb erosion and sedimentation in rivers and reser-voirs there is need to develop and implement an integratedwater resources management plan by all stakeholders

In order to maintain the lifespan of Chimhanda dam bestland management practices such as contour ploughing andre-forestation should be employed around the catchment areaof the Dam and this is an area that could be considered forfurther research

Data availability The main data used in the research is rainfalldata that was obtained from the meteorological department waterquality data obtained from Environmental management Agency aswell as sediment Data from Zinwa The data can be obtained fromthese departments

Competing interests The authors declare that they have no con-flict of interest

Special issue statement This article is part of the special issueldquoWater quality and sediment transport issues in surface waterrdquo Itis a result of the IAHS Scientific Assembly 2017 Port ElizabethSouth Africa 10ndash14 July 2017

Acknowledgements This paper contains part of research resultsfrom the MSc Thesis of the corresponding author Colleta Tundusubmitted to the University of Zimbabwe Special thanks go toFaith Chivava for her assistance in GIS ZINWA EMA and theZimbabwe Meteorological Services Department is appreciated forproviding data

Edited by Akhilendra B GuptaReviewed by Rajendra Prasad and one anonymous referee

References

Addo M A Okley G M Affum HA Acquah S Gbadago JK Senu J K and Botwe B O Water Quality and level ofsome heavy metals in water and sediments of Kpeshie LagoonLa-Accra Ghana Research Journal of Environmental and EarthSciences 3 487ndash497 2011

Adekunle I M Adetunji M T Gbadebo A M and Banjoko OB Assessment of groundwater quality in a typical rural settle-ment in Southwest Nigeria Int J Env Res Pub He 4 307ndash3182007

Bhadja P and Vaghela A Assessment of Physico-Chemical pa-rameters and water quality Index of reservoir water Internationaljournal of plant animal and environmental sciences 3 89ndash952013

Chapman D Water quality assessments ndash A guide to use of Biotasediments and water in Environmental monitoring 2nd EdnChapman and Hall London 191ndash193 1996

Chitata T Mugabe F T and Kashaigili J J Estimation ofSmall Reservoir Sedimentation in Semi-Arid Southern Zim-babwe Journal of Water Resource and Protection 6 48909 12ndash14 2014

Dalu T Tambara E M Clegg B Chari L D and NhiwatiwaT Modeling sedimentation rates of Malilangwe reservoir in thesouth-eastern lowveld of Zimbabwe Applied Water Science 3133ndash144 2013

Dearing J Sediment yields and sources in a welsh upland lake-catchment during the past 800 years Earth Surf Proc Land 171ndash22 1992

de Vente J Verduyn R Verstraeten G Vanmaercke M andPoesen J Factors controlling sediment yield at the catchmentscale in NW Mediterranean geoecosystems J Soil Sediment11 690ndash707 2011

Dike L Keramat A and Amirkolaie S Environmental impactof nutrient discharged by aquaculture waste water on the Harazriver Journal of Agriculture and Biological Science 3 275ndash2792010

EMA Effluent and Solid Waste Disposal Regulations SI 6 of 2007government printers of Zimbabwe 2007

Eroglu H Ccedilakır G Sivrikaya F and Akay A E Using highresolution images and elevation data in classifying erosion risksof bare soil areas in the Hatila Valley Natural Protected AreaTurkey Stoch Env Res Risk A 24 699ndash704 2010

Ezugwu C Sediment Deposition in Nigeria Reservoirs Impactsand Control Measures Innovative Systems Design and Engineer-ing 4 54ndash62 2013

Godwin A M Gabriel S Hodson M and Wellington D Sedi-mentation impacts on reservoir as a result of land use on a se-lected catchment in Zimbabwe International Journal of Engi-neering Science amp Technology 3 2011

Gusso A G A Veronez M R Robinson F Roani V and DaSilva R C Evaluating the thermal spatial distribution signaturefor environmental management and vegetation health monitor-ing International Journal of Advanced Remote Sensing and GIS3 433ndash445 2014

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

66 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Hanke S H and Kwok A K On the measurement of Zimbabwersquoshyperinflation Cato J 29 353ndash364 2009

Hoko Z An assessment of quality of water from boreholes inBindura District Zimbabwe Phys Chem Earth 33 824ndash8282008

Jang C Shin Y Kum D Kim R Yang J E Kim S CHwang S I Lim K J Yoon J-K and Park Y S Assessmentof soil loss in South Korea based on land-cover type Stoch EnvRes Risk A 1ndash15 1996

Kamaludin H Lihan T Ali Rahman Z Mustapha M AIdris W M R and Rahim S A Integration of re-mote sensing RUSLE and GIS to model potential soil lossand sediment yield (SY) Hydrol Earth Syst Sci Discusshttpsdoiorg105194hessd-10-4567-2013 2013

Lawson E O Physico- chemical parameters and heavy metal con-tents of water from the mangroves swamps of logos lagon logosNigeria Advances in biological research 5 8ndash21 2011

Makwara E and Gamira D About to Lose all the Soil in ZakarsquosWard 5 Zimbabwe Rewards of Unsustainable Land Use Euro-pean Journal of Sustainable Development 1 457ndash476 2012

Mambo J and Archer E An assessment of land degradation in theSave catchment of Zimbabwe Area 39 380ndash391 2007

Merritt W S Letcher R A and Jakeman A J A review oferosion and sediment transport models Env Modell Softw 18761ndash799 2003

Met Meteorological data available at httpswwwwmointdatastatwmodata_enhtml| last access 3 March 2015

Mutowo G and Chikodzi D Erosion Hazard Mapping in theRunde Catchment Implications for Water Resources Manage-ment Journal of Geosciences and Geomatics 1 22ndash28 2013

Pettorelli N Vik J O Mysterud A Gaillard J-M Tucker CJ and Stenseth N C Using the satellite-derived NDVI to as-sess ecological responses to environmental change Trends EcolEvol 20 503ndash510 2005

Renard K G Foster G R Weesies G A McCool D and Yo-der D Predicting soil erosion by water a guide to conservationplanning with the revised universal soil loss equation (RUSLE)Agriculture Handbook Washington 703 1997

Rooseboom A and Engineers S B C Sediment transport in riversand reservoirs a Southern African perspective Water ResearchCommission 297192489 1992

Sawunyama T Senzanje A and Mhizha A Estimation of smallreservoir storage capacities in Limpopo River Basin using ge-ographical information systems (GIS) and remotely sensed sur-face areas Case of Mzingwane catchment Phys Chem Earth31 935ndash943 2006

Sumi T and Hirose T Accumulation of sediment in reservoirsWater storage transport and distribution UNESCO-IHE andEOLSS Publishers Co Ltd Paris France 224ndash252 2009

Teh S H Soil erosion modeling using RUSLE and GIS onCameron highlands Malaysia for hydropower development MSThe School for Renewable Energy Science Iceland 41 pp2011

USDA Procedure for computing sheet and rill equation on projectareas Technical Release No 51 (Geology) US GovernmentPrinting Office Washington DC 1972

Walling D and Fang D Recent trends in the suspended sedimentloads of the worldrsquos rivers Global Planet change 39 111ndash1262003

Whitlow R Mapping erosion in Zimbabwe a methodology forrapid survey using aerial photographs Appl Geogr 6 149ndash1621986

WHO Guidelines for drinking water quality Third edition incor-porating the first and second addenda volume 1 additions 2008

Wischmeier W and Smith D Predicting rainfall erosion lossesAgricultural Handbook 537 Agricultural Research ServiceUnited States Department of Agriculture 1978

Zinwa D R Assessment of Surface Water Resources of Zimbabweand Guidelines for Planning in Management ZINWA Researchand Data Department Ministry of Water Resources Developmentand Management Harare Zimbabwe Harare 59 pp 2009

Zwane N Love D Hoko Z and Shoko D Managing the im-pact of gold panning activities within the context of integratedwater resources management planning in the Lower ManyameSub-Catchment Zambezi Basin Zimbabwe Phys Chem Earth31 848ndash856 2006

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

60 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Figure 2 Gauges in the catchment and areas of influence

25 Assessing the current sedimentation levels ofChimhanda Dam

A bathymetric survey was carried out at Chimhanda dam todetermine the siltation level of the dam The survey was con-ducted using a SonTek River Surveyor system and a theodo-lite to come up with a basin survey map The plotted map wasdigitized to get the surface area between contours The areawas then multiplied by the contour interval to get the volumeof each contour using Simpsonrsquos formula

Vcontour =A1+ (A1timesA2)12

+A2

3(9)

where Vcontour = contour Volume (m3) A1 =Area1 (m2)A2 =Area2 (m2)

The calculated volumes for each contour were accumu-lated to get the new capacity of the dam

26 Water quality trend from sedimentation

Water quality historical data from six selected water sam-pling points were obtained from the Environmental Manage-ment Agency records The points were selected basing onthe consistency of the data and less gaps The trend for theselected water quality parameters TSS DO NO3 pH TDSand turbidity for the corresponding predicted sediment yieldyears were analysed The water quality parameters werecompared with the Environmental Management Agency Ef-fluent and Solid Waste Disposal Regulations Statutory Instru-ment number 6 of 2007 (EMA 2007) shown on Table 1 Wa-ter quality data for Chimhanda water supply treatment plantfrom the Zimbabwe National Water Authority was also re-lated to the change in level of sedimentation of ChimhandaDam

27 Investigation the relationship betweensedimentation and water quality

Selected water quality parameters were correlated with thecorresponding sediment yield to determine the relationshipbetween sediment yield and water quality Pearson Correla-tion was used to estimate the strength of relationship betweensediment yield and some physical water quality

3 Results and discussions

31 Results of the RUSLE factors

The erosivity map (R factor) depicts rainfall energy inthe various areas within the catchment The rainfall ero-sivity ranges between 200 and 500 (MJ mm haminus1 hminus1 yr)A greater part of the catchment is averaging a rainfallerosivity value of 276 MJ mm haminus1 hminus1 yr Highest rainfallerosivity values are in the Kairezi sub-catchment of thestudy area Erodability (K factor) values range from 0 to05 t haminus1yrminus1 MJminus1 mmminus1 Some parts in the south west ofthe catchment have high values of erodibility the highestK value is dominated by very fine sand with silt particleswhich give rise to higher soil erodibility (Kamaludin et al2013) Highest slope length steepness (LS) values of 16 mwere found in the eastern part of the catchment The north-ern part of the catchment experiences average LS values of7 m

Cover Management and Practice (C factor) ranges fromminus1 to 1 The C factor is depicted by NDVI which is a func-tion of photosynthesis The C factor is high in the east-ern highlands area some parts of Kairezi sub-catchmentand along the Mufurudzi area This is possible because theKairezi area experiences high rainfall while Mufurudzi be-ing a game park has more vegetation High C values wereobserved with high vegetation cover (Pettorelli et al 2005)The P value of 1 was observed in Lower Mazowe and UpperRwenya subcatchment areas respectively Areas like Mufu-rudzi and parts of Kairezi experienced an average P value of08

32 Soil loss from the catchment

The average annual soil loss for the different years are shownon Fig 3 and the temporal variation of actual soil loss is tab-ulated on Table 2

The estimated soil loss from the catchment ranges from0 to 203 t ha yrminus1 The estimated average soil loss is54 t ha yrminus1 The highest soil loss is being experienced inMiddle Mazowe and Nyagui sub-catchments High soil lossin Middle Mazowe sub-catchment can be associated withhigh gold panning activities in the Mazowe valley whilst inNyagui sub-catchment this can be associated with high cropfarming activities in the area When the soil is made looseits structure is altered hence increase in erodibility

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 61

Table 1 Effluent and solid waste disposal regulations

BANDS

PARAMETER Blue Green Yellow Red TestMethods

Sensitive Normal

DO saturation gt 75 gt 60 gt 50 gt 30 gt 15 SAZS 573

Nitrates NO3 mg Lminus1 lt 10 lt 10 lt 20 lt 30 lt 50PH 60ndash75 60ndash90 5ndash6 9ndash10 4ndash5 10ndash12 0ndash4 12ndash14 SAZS 483TDS lt 100 lt 500 lt 1500 lt 2000 lt 3000 SAZS 576Turbidity (NTU) lt 5 lt 5 SAZS 478TSS mg Lminus1 lt 10 lt 25 lt 50 lt 100 lt 150 SAZS 478

Figure 3 Estimated Average Soil Loss for 2000 2005 2008 and2014

The average soil loss value of 54 t ha yrminus1 concurred withother studies that were carried out in the country Whit-low (1986) found that 76 t of soil is lost per hectare peryear through soil erosion in most parts of the country An-other study by Mutowo and Chikodzi (2013) ldquoErosion haz-ards mapping in the Runde Catchmentrdquo concluded that mostof the areas in the catchment fall in the category range of 0ndash50 t ha yrminus1 Makwara and Gamira (2012) reported that themost serious type of erosion being sheet erosion is estimatedto remove an average 50 t ha yrminus1 from Zimbabwersquos commu-nal lands

There is no uniform trend in the soil loss over the study pe-riod In year 2000 the soil loss was 54t ha yrminus1 The increaseof soil loss in 2005 from the 2000 figure can be explained bythe land reform programme which started in year 2000 and

Table 2 Temporal Variation of Estimated Soil Loss

Year Average SoilLoss (t ha yrminus1)

2000 542005 652008 362014 62

was at its peak around 2003 There was a lot of deforesta-tion as new farmers were clearing land for agricultural pur-poses (Mambo and Archer 2007) Some areas which weremeant for animal rearing and forest were also converted tocrop agricultural areas In 2008 the soil loss rate decreasedto 36 t ha yrminus1 The reduction can be attributed to a numberof factors Year 2008 experienced low erosivity as a resultof low rainfall which could also lead to low annual soil lossThe economy of Zimbabwe was almost at a stand-still duringthe period 2007 to 2009 with an inflation rate record of over231 million percent in July 2008 (Hanke and Kwok 2009)As a result there was less farming activities during that pe-riod

The soil loss rate almost doubled in year 2014 as comparedto 2008 This can be explained by the increase in the numberof small scale gold miners in the catchment and alluvial goldpanning in streams and rivers Mining within the catchmentis not only limited to the river beds and banks miners arealso targeting the inland areas of the catchment such as theMazowe Valley and Mufurudzi Game Park and as a resultsoil erodibility is also increasing Increase in rate of unem-ployment caused by low capital investment and continuingclosure of industries in Zimbabwe has resulted in the pop-ulation resorting to other sources of income such as illegalgold mining and alluvial gold panning A study that was car-ried out in the Lower Manyame sub ndash catchment along DandeRiver on the analysis of the implications of cross- sectionalcoordination of the management of gold panning activities

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

62 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Table 3 Measured sediment Load from flow gauges for the period December 2014 to March 2015

Silt Gauge Name or River Area of Sediment LoadInfluence (km2) load (t kmminus2) (t)

D75 Mazowe 20 380 14 28536D50 Nyamasanga 13 024 3D42 Mupfurudzi 163 192 31356D41 Mazowe 3300 086 2836D6 Shavanhowe 1166 051 58965D58 Nyagui 983 2425 14293D48 Mwenje 399 036 334

Table 4 Summarized Results from the silt survey

1988 2003 2015

Capacity at FSL (times106 m3) 52 3470 3194Loss Of Storage () 0 333 386Dam Surface Area (Ha) 9300 7400 6404

and its impacts (Zwane et al 2006) identified river bed goldpanning activities as a cause of degradation of river chan-nels and banks as well as accelerated erosion and siltation inmany areas of Zimbabwe

321 Sediment Yield

Figure 4 shows the sediment yield distribution map Sed-iment yield ranges from less than 1 t ha yrminus1 to a maxi-mum of 245t ha yrminus1 with an average value of 604 t ha yrminus1

over the catchment area The highest sediment yield is inthe Middle Mazowe sub catchment area with an averageof 672 t ha yrminus1 and a maximum of 245t ha yrminus1 The highvalue can be associated with high gold panning activities inthe Mazowe valley The lowest value is in the Lower Ruyasub-catchment with an average of 4 t ha yrminus1 The resultsare almost in line with a study by Rooseboom and Engi-neers (1992) that estimated the average sediment yield in thenine defined sediment regions in Southern Africa to vary be-tween 30 and 330 t ha yrminus1 with an average of 15 t ha yrminus1A study which was also carried out in the catchment areaof Pahang River basin in Malasyia gave a sediment yieldranging from 0ndash1379 t ha yrminus1 (Kamaludin et al 2013) Thetotal sediment yield for the catchment was calculated to be63 million t yrminus1

322 Measured Sediment Loads

Results from the measured sediment loads were highest atD75 which is along Mazowe River in the Zambezi valleyD41 located in Middle Mazowe sub catchment recorded arelatively high sediment load of 2836 t D58 and D6 are bothin Nyagui Sub-catchment recorded 14293 and 58965 t re-

Figure 4 Sediment Yield within the Catchment

Table 5 Results for the correlation between sediment yield and wa-ter quality parameters

Sediment Ave AverageTurbidity TSS

Sediment Pearson Correlation 1 634 647Sig (2-tailed) 366 353N 28 28

spectively D50 which is in Upper Mazowe sub catchmentrecorded a low figure of 3 t The results are concurring withthose from RUSLE model where high sediment yields wererecorded from Middle Mazowe and Nyagui sub catchmentsrespectively

33 Sedimentation in Chimhanda Dam from BathymetricSurvey

Table 4 summarizes the results of the silt survey forChimhanda Dam

The capacity of the dam decreased from the original5200times 106 to 3470times 106 and 3194times 106 m3 in years2003 and 2015 respectively There was 333 loss in stor-

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 63

Figure 5 Chimhanda Dam Capacity comparison over the years

age up to 2003 and a storage loss of 386 up to 2015 inreference to the design capacity Figure 5 shows reservoir ca-pacity changes over the years

Results from the 10 samples of river inflows collectedgave an average sediment concentration of 39 mg Lminus1 Therewas a decrease in trend in the sediment concentration asthe rainfall season was progressing The sediment accumu-lation in the reservoir was found to be 330 t yrminus1 and the spe-cific sediment yield was 226 t kmminus2 yrminus1 The usefulness ofChimhanda Dam has reduced from the initial design life of50 to 37 years A study by Godwin et al (2011) on ChesaCauseway Weir in the same catchment gave a specific yieldof 510 t km2 yrminus1 The usefulness of the dam was reducedfrom the initial design life of 50 to 25 years

Generally the results support the existing literature thatmost of the small to medium dams are being affected byhigh rates of sedimentation in Zimbabwe (Sawunyama et al2006 Godwin et al 2011 Dalu et al 2013 Chitata et al2014)

34 Water Quality Trend from Sedimentation

Figures 6 to 10 show the results for the historically measuredwater parameters for the years 2000 2008 2010 and 2014

341 Turbidity

Results for the years did not meet the permissible turbid-ity of 5 NTU The highest turbidity values were recordedin 2000 and 2005 respectively High values in 2005 corre-sponds to the high soil loss of 65 t ha yrminus1 that was recordedduring that particular year The high values in 2000 can beexplained by high rainfalls that were experienced during thatparticular year as compared with the other years (Met 2005)Low turbidity values were recorded during the year 2008the same year recorded the lowest soil loss of 36 t ha yrminus1High Turbidity levels are associated with poor water quality(Adekunle et al 2007) WHO (2008) highligted that highturbidity waters can facilitate the formation of nuclei wheregastrointestinal disease pathogens can attach If that water

Figure 6 Turbidity variation among sampling points

Figure 7 Total Suspended Solids variation among sampling points

is consumed improperly treated it can cause diseases Highturbidity leves also render the treatment of water expensive

342 Total Suspended Solids

2008 values were below the recommended limit of15 mg Lminus1 as shown on Fig 7 High values were recordedduring year 2000 2005 and 2014 The high values are inagreement with the high soil loss that were recorded in thoseparticular years Total suspended solids are closely relatedto sedimentation (Chapman 1996) When these suspendedparticles settles at the bottom of a water body they becomesediments Suspended solids consist of inorganic and organicfractions Part of the organic fractions is bacterial and thatmight be detrimental to human health if the water is con-sumed without adequate treatment (Hoko 2008)

343 Dissolved Oxygen (DO)

Dissolved Oxygen was above the lower limit for EMA at allthe stations for all the years Year 2000 and 2005 recorded saturation of 125 and 100 respectively Oxygen levels canbe higher due to excess aquatic plants in the water which

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

64 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Figure 8 Dissolved Oxygen variation among sampling points

Figure 9 Nitrates variation along sampling points

produce oxygen Most living organisms require oxygen fortheir basic metabolic processes

344 Nitrates (NO3)

Results for nitrates for the years under consideration were allbelow the recommended EMA levels of 6 mg Lminus1 Nitratesare washed by runoff from agricultural lands into water bod-ies High concentration of nitrates in water bodies cause eu-trophication resulting in competition for oxygen by aquaticorganisms and high water treatment costs (Dike et al 2010)

345 PH

pH values for all the years were within the normal limits cat-egory according to EMA upper and lower limits of 6 and9 units respectively Year 2005 had one sampling point thathad a value slightly lower than the recommended Bhadjaand Vaghela (2013) indicated that activities in the water shedsuch as increased leaching of soils soil erosion and heavyprecipitation affects the pH levels downstream pH levels ashigh as 90 and as low as 5 affects the life span of aquaticorganisms (Addo et al 2011) Low pH values do not havedirect effect to human health but can have indirectly effect

Figure 10 pH variations along sampling points

since it causes leaching of metal irons such as copper zincand lead into the water (WHO 2008)

35 Relationship between sedimentation and river waterquality

Pearson correlation was used to determine the relationshipbetween two water quality parameters and sediment yieldThe parameters are related to sediment yield and these areturbidity and suspended solids (Bhadja and Vaghela 2013)The results are shown on Table 5

There is a close positive relationship between turbidity andsediment yield of 063 Total Suspended Solids have a posi-tive relation of 064 The results show that the two water qual-ity parameters can be indicators of sedimentation Highervalues of total suspended solids and turbidity indicate highervalues of sediment yield in water bodies

36 Variation in reservoir water quality

The variation in two selected reservoir water quality indica-tors turbidity and pH was determined A significant variationin turbidity was noted for the years 1988 to 2014 with a p-value of 002 which is less than 005 The mean value of tur-bidity for 1988 2003 and 2014 are 156 344 and 417 NTUrespectively The values show an increasing trend in turbid-ity which may be as a result of anthropogenic activities oc-curring upstream of the dam which has resulted in increasedsoil erosion hence more sediment on the reservoir pH resultsshowed that there is no significant change between 1988 and2014 (p-value gt 005) This might be because pH is a chemi-cal parameter that is determined by the type of sediments thatare carried into the river not the sediment load

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 65

4 Conclusions and recommendations

41 Conclusion

The objective of the study was to analyze sedimentation andits impact on river system and reservoir water quality in Ma-zowe Catchment Zimbabwe The studyrsquos major findings are

The catchment is generally experiencing moderate soilloss however there are some pockets under high and extremesoil loss which gave rise to siltation and water quality deteri-oration of available water bodies

There is reduction in capacity of reservoirs within thecatchment due to sedimentation Chimhanda Dam capacityhas been reduced by 386 from the initial design capac-ity as of April 2015 reducing the usefulness of the dam to37 years from the initial design life of 50 years due to silta-tion

Sediment deposition in rivers affects water quality and wa-ter quality parameters can be used as an indicator for sedi-mentation

42 Recommendations

In order to curb erosion and sedimentation in rivers and reser-voirs there is need to develop and implement an integratedwater resources management plan by all stakeholders

In order to maintain the lifespan of Chimhanda dam bestland management practices such as contour ploughing andre-forestation should be employed around the catchment areaof the Dam and this is an area that could be considered forfurther research

Data availability The main data used in the research is rainfalldata that was obtained from the meteorological department waterquality data obtained from Environmental management Agency aswell as sediment Data from Zinwa The data can be obtained fromthese departments

Competing interests The authors declare that they have no con-flict of interest

Special issue statement This article is part of the special issueldquoWater quality and sediment transport issues in surface waterrdquo Itis a result of the IAHS Scientific Assembly 2017 Port ElizabethSouth Africa 10ndash14 July 2017

Acknowledgements This paper contains part of research resultsfrom the MSc Thesis of the corresponding author Colleta Tundusubmitted to the University of Zimbabwe Special thanks go toFaith Chivava for her assistance in GIS ZINWA EMA and theZimbabwe Meteorological Services Department is appreciated forproviding data

Edited by Akhilendra B GuptaReviewed by Rajendra Prasad and one anonymous referee

References

Addo M A Okley G M Affum HA Acquah S Gbadago JK Senu J K and Botwe B O Water Quality and level ofsome heavy metals in water and sediments of Kpeshie LagoonLa-Accra Ghana Research Journal of Environmental and EarthSciences 3 487ndash497 2011

Adekunle I M Adetunji M T Gbadebo A M and Banjoko OB Assessment of groundwater quality in a typical rural settle-ment in Southwest Nigeria Int J Env Res Pub He 4 307ndash3182007

Bhadja P and Vaghela A Assessment of Physico-Chemical pa-rameters and water quality Index of reservoir water Internationaljournal of plant animal and environmental sciences 3 89ndash952013

Chapman D Water quality assessments ndash A guide to use of Biotasediments and water in Environmental monitoring 2nd EdnChapman and Hall London 191ndash193 1996

Chitata T Mugabe F T and Kashaigili J J Estimation ofSmall Reservoir Sedimentation in Semi-Arid Southern Zim-babwe Journal of Water Resource and Protection 6 48909 12ndash14 2014

Dalu T Tambara E M Clegg B Chari L D and NhiwatiwaT Modeling sedimentation rates of Malilangwe reservoir in thesouth-eastern lowveld of Zimbabwe Applied Water Science 3133ndash144 2013

Dearing J Sediment yields and sources in a welsh upland lake-catchment during the past 800 years Earth Surf Proc Land 171ndash22 1992

de Vente J Verduyn R Verstraeten G Vanmaercke M andPoesen J Factors controlling sediment yield at the catchmentscale in NW Mediterranean geoecosystems J Soil Sediment11 690ndash707 2011

Dike L Keramat A and Amirkolaie S Environmental impactof nutrient discharged by aquaculture waste water on the Harazriver Journal of Agriculture and Biological Science 3 275ndash2792010

EMA Effluent and Solid Waste Disposal Regulations SI 6 of 2007government printers of Zimbabwe 2007

Eroglu H Ccedilakır G Sivrikaya F and Akay A E Using highresolution images and elevation data in classifying erosion risksof bare soil areas in the Hatila Valley Natural Protected AreaTurkey Stoch Env Res Risk A 24 699ndash704 2010

Ezugwu C Sediment Deposition in Nigeria Reservoirs Impactsand Control Measures Innovative Systems Design and Engineer-ing 4 54ndash62 2013

Godwin A M Gabriel S Hodson M and Wellington D Sedi-mentation impacts on reservoir as a result of land use on a se-lected catchment in Zimbabwe International Journal of Engi-neering Science amp Technology 3 2011

Gusso A G A Veronez M R Robinson F Roani V and DaSilva R C Evaluating the thermal spatial distribution signaturefor environmental management and vegetation health monitor-ing International Journal of Advanced Remote Sensing and GIS3 433ndash445 2014

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

66 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Hanke S H and Kwok A K On the measurement of Zimbabwersquoshyperinflation Cato J 29 353ndash364 2009

Hoko Z An assessment of quality of water from boreholes inBindura District Zimbabwe Phys Chem Earth 33 824ndash8282008

Jang C Shin Y Kum D Kim R Yang J E Kim S CHwang S I Lim K J Yoon J-K and Park Y S Assessmentof soil loss in South Korea based on land-cover type Stoch EnvRes Risk A 1ndash15 1996

Kamaludin H Lihan T Ali Rahman Z Mustapha M AIdris W M R and Rahim S A Integration of re-mote sensing RUSLE and GIS to model potential soil lossand sediment yield (SY) Hydrol Earth Syst Sci Discusshttpsdoiorg105194hessd-10-4567-2013 2013

Lawson E O Physico- chemical parameters and heavy metal con-tents of water from the mangroves swamps of logos lagon logosNigeria Advances in biological research 5 8ndash21 2011

Makwara E and Gamira D About to Lose all the Soil in ZakarsquosWard 5 Zimbabwe Rewards of Unsustainable Land Use Euro-pean Journal of Sustainable Development 1 457ndash476 2012

Mambo J and Archer E An assessment of land degradation in theSave catchment of Zimbabwe Area 39 380ndash391 2007

Merritt W S Letcher R A and Jakeman A J A review oferosion and sediment transport models Env Modell Softw 18761ndash799 2003

Met Meteorological data available at httpswwwwmointdatastatwmodata_enhtml| last access 3 March 2015

Mutowo G and Chikodzi D Erosion Hazard Mapping in theRunde Catchment Implications for Water Resources Manage-ment Journal of Geosciences and Geomatics 1 22ndash28 2013

Pettorelli N Vik J O Mysterud A Gaillard J-M Tucker CJ and Stenseth N C Using the satellite-derived NDVI to as-sess ecological responses to environmental change Trends EcolEvol 20 503ndash510 2005

Renard K G Foster G R Weesies G A McCool D and Yo-der D Predicting soil erosion by water a guide to conservationplanning with the revised universal soil loss equation (RUSLE)Agriculture Handbook Washington 703 1997

Rooseboom A and Engineers S B C Sediment transport in riversand reservoirs a Southern African perspective Water ResearchCommission 297192489 1992

Sawunyama T Senzanje A and Mhizha A Estimation of smallreservoir storage capacities in Limpopo River Basin using ge-ographical information systems (GIS) and remotely sensed sur-face areas Case of Mzingwane catchment Phys Chem Earth31 935ndash943 2006

Sumi T and Hirose T Accumulation of sediment in reservoirsWater storage transport and distribution UNESCO-IHE andEOLSS Publishers Co Ltd Paris France 224ndash252 2009

Teh S H Soil erosion modeling using RUSLE and GIS onCameron highlands Malaysia for hydropower development MSThe School for Renewable Energy Science Iceland 41 pp2011

USDA Procedure for computing sheet and rill equation on projectareas Technical Release No 51 (Geology) US GovernmentPrinting Office Washington DC 1972

Walling D and Fang D Recent trends in the suspended sedimentloads of the worldrsquos rivers Global Planet change 39 111ndash1262003

Whitlow R Mapping erosion in Zimbabwe a methodology forrapid survey using aerial photographs Appl Geogr 6 149ndash1621986

WHO Guidelines for drinking water quality Third edition incor-porating the first and second addenda volume 1 additions 2008

Wischmeier W and Smith D Predicting rainfall erosion lossesAgricultural Handbook 537 Agricultural Research ServiceUnited States Department of Agriculture 1978

Zinwa D R Assessment of Surface Water Resources of Zimbabweand Guidelines for Planning in Management ZINWA Researchand Data Department Ministry of Water Resources Developmentand Management Harare Zimbabwe Harare 59 pp 2009

Zwane N Love D Hoko Z and Shoko D Managing the im-pact of gold panning activities within the context of integratedwater resources management planning in the Lower ManyameSub-Catchment Zambezi Basin Zimbabwe Phys Chem Earth31 848ndash856 2006

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 61

Table 1 Effluent and solid waste disposal regulations

BANDS

PARAMETER Blue Green Yellow Red TestMethods

Sensitive Normal

DO saturation gt 75 gt 60 gt 50 gt 30 gt 15 SAZS 573

Nitrates NO3 mg Lminus1 lt 10 lt 10 lt 20 lt 30 lt 50PH 60ndash75 60ndash90 5ndash6 9ndash10 4ndash5 10ndash12 0ndash4 12ndash14 SAZS 483TDS lt 100 lt 500 lt 1500 lt 2000 lt 3000 SAZS 576Turbidity (NTU) lt 5 lt 5 SAZS 478TSS mg Lminus1 lt 10 lt 25 lt 50 lt 100 lt 150 SAZS 478

Figure 3 Estimated Average Soil Loss for 2000 2005 2008 and2014

The average soil loss value of 54 t ha yrminus1 concurred withother studies that were carried out in the country Whit-low (1986) found that 76 t of soil is lost per hectare peryear through soil erosion in most parts of the country An-other study by Mutowo and Chikodzi (2013) ldquoErosion haz-ards mapping in the Runde Catchmentrdquo concluded that mostof the areas in the catchment fall in the category range of 0ndash50 t ha yrminus1 Makwara and Gamira (2012) reported that themost serious type of erosion being sheet erosion is estimatedto remove an average 50 t ha yrminus1 from Zimbabwersquos commu-nal lands

There is no uniform trend in the soil loss over the study pe-riod In year 2000 the soil loss was 54t ha yrminus1 The increaseof soil loss in 2005 from the 2000 figure can be explained bythe land reform programme which started in year 2000 and

Table 2 Temporal Variation of Estimated Soil Loss

Year Average SoilLoss (t ha yrminus1)

2000 542005 652008 362014 62

was at its peak around 2003 There was a lot of deforesta-tion as new farmers were clearing land for agricultural pur-poses (Mambo and Archer 2007) Some areas which weremeant for animal rearing and forest were also converted tocrop agricultural areas In 2008 the soil loss rate decreasedto 36 t ha yrminus1 The reduction can be attributed to a numberof factors Year 2008 experienced low erosivity as a resultof low rainfall which could also lead to low annual soil lossThe economy of Zimbabwe was almost at a stand-still duringthe period 2007 to 2009 with an inflation rate record of over231 million percent in July 2008 (Hanke and Kwok 2009)As a result there was less farming activities during that pe-riod

The soil loss rate almost doubled in year 2014 as comparedto 2008 This can be explained by the increase in the numberof small scale gold miners in the catchment and alluvial goldpanning in streams and rivers Mining within the catchmentis not only limited to the river beds and banks miners arealso targeting the inland areas of the catchment such as theMazowe Valley and Mufurudzi Game Park and as a resultsoil erodibility is also increasing Increase in rate of unem-ployment caused by low capital investment and continuingclosure of industries in Zimbabwe has resulted in the pop-ulation resorting to other sources of income such as illegalgold mining and alluvial gold panning A study that was car-ried out in the Lower Manyame sub ndash catchment along DandeRiver on the analysis of the implications of cross- sectionalcoordination of the management of gold panning activities

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

62 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Table 3 Measured sediment Load from flow gauges for the period December 2014 to March 2015

Silt Gauge Name or River Area of Sediment LoadInfluence (km2) load (t kmminus2) (t)

D75 Mazowe 20 380 14 28536D50 Nyamasanga 13 024 3D42 Mupfurudzi 163 192 31356D41 Mazowe 3300 086 2836D6 Shavanhowe 1166 051 58965D58 Nyagui 983 2425 14293D48 Mwenje 399 036 334

Table 4 Summarized Results from the silt survey

1988 2003 2015

Capacity at FSL (times106 m3) 52 3470 3194Loss Of Storage () 0 333 386Dam Surface Area (Ha) 9300 7400 6404

and its impacts (Zwane et al 2006) identified river bed goldpanning activities as a cause of degradation of river chan-nels and banks as well as accelerated erosion and siltation inmany areas of Zimbabwe

321 Sediment Yield

Figure 4 shows the sediment yield distribution map Sed-iment yield ranges from less than 1 t ha yrminus1 to a maxi-mum of 245t ha yrminus1 with an average value of 604 t ha yrminus1

over the catchment area The highest sediment yield is inthe Middle Mazowe sub catchment area with an averageof 672 t ha yrminus1 and a maximum of 245t ha yrminus1 The highvalue can be associated with high gold panning activities inthe Mazowe valley The lowest value is in the Lower Ruyasub-catchment with an average of 4 t ha yrminus1 The resultsare almost in line with a study by Rooseboom and Engi-neers (1992) that estimated the average sediment yield in thenine defined sediment regions in Southern Africa to vary be-tween 30 and 330 t ha yrminus1 with an average of 15 t ha yrminus1A study which was also carried out in the catchment areaof Pahang River basin in Malasyia gave a sediment yieldranging from 0ndash1379 t ha yrminus1 (Kamaludin et al 2013) Thetotal sediment yield for the catchment was calculated to be63 million t yrminus1

322 Measured Sediment Loads

Results from the measured sediment loads were highest atD75 which is along Mazowe River in the Zambezi valleyD41 located in Middle Mazowe sub catchment recorded arelatively high sediment load of 2836 t D58 and D6 are bothin Nyagui Sub-catchment recorded 14293 and 58965 t re-

Figure 4 Sediment Yield within the Catchment

Table 5 Results for the correlation between sediment yield and wa-ter quality parameters

Sediment Ave AverageTurbidity TSS

Sediment Pearson Correlation 1 634 647Sig (2-tailed) 366 353N 28 28

spectively D50 which is in Upper Mazowe sub catchmentrecorded a low figure of 3 t The results are concurring withthose from RUSLE model where high sediment yields wererecorded from Middle Mazowe and Nyagui sub catchmentsrespectively

33 Sedimentation in Chimhanda Dam from BathymetricSurvey

Table 4 summarizes the results of the silt survey forChimhanda Dam

The capacity of the dam decreased from the original5200times 106 to 3470times 106 and 3194times 106 m3 in years2003 and 2015 respectively There was 333 loss in stor-

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 63

Figure 5 Chimhanda Dam Capacity comparison over the years

age up to 2003 and a storage loss of 386 up to 2015 inreference to the design capacity Figure 5 shows reservoir ca-pacity changes over the years

Results from the 10 samples of river inflows collectedgave an average sediment concentration of 39 mg Lminus1 Therewas a decrease in trend in the sediment concentration asthe rainfall season was progressing The sediment accumu-lation in the reservoir was found to be 330 t yrminus1 and the spe-cific sediment yield was 226 t kmminus2 yrminus1 The usefulness ofChimhanda Dam has reduced from the initial design life of50 to 37 years A study by Godwin et al (2011) on ChesaCauseway Weir in the same catchment gave a specific yieldof 510 t km2 yrminus1 The usefulness of the dam was reducedfrom the initial design life of 50 to 25 years

Generally the results support the existing literature thatmost of the small to medium dams are being affected byhigh rates of sedimentation in Zimbabwe (Sawunyama et al2006 Godwin et al 2011 Dalu et al 2013 Chitata et al2014)

34 Water Quality Trend from Sedimentation

Figures 6 to 10 show the results for the historically measuredwater parameters for the years 2000 2008 2010 and 2014

341 Turbidity

Results for the years did not meet the permissible turbid-ity of 5 NTU The highest turbidity values were recordedin 2000 and 2005 respectively High values in 2005 corre-sponds to the high soil loss of 65 t ha yrminus1 that was recordedduring that particular year The high values in 2000 can beexplained by high rainfalls that were experienced during thatparticular year as compared with the other years (Met 2005)Low turbidity values were recorded during the year 2008the same year recorded the lowest soil loss of 36 t ha yrminus1High Turbidity levels are associated with poor water quality(Adekunle et al 2007) WHO (2008) highligted that highturbidity waters can facilitate the formation of nuclei wheregastrointestinal disease pathogens can attach If that water

Figure 6 Turbidity variation among sampling points

Figure 7 Total Suspended Solids variation among sampling points

is consumed improperly treated it can cause diseases Highturbidity leves also render the treatment of water expensive

342 Total Suspended Solids

2008 values were below the recommended limit of15 mg Lminus1 as shown on Fig 7 High values were recordedduring year 2000 2005 and 2014 The high values are inagreement with the high soil loss that were recorded in thoseparticular years Total suspended solids are closely relatedto sedimentation (Chapman 1996) When these suspendedparticles settles at the bottom of a water body they becomesediments Suspended solids consist of inorganic and organicfractions Part of the organic fractions is bacterial and thatmight be detrimental to human health if the water is con-sumed without adequate treatment (Hoko 2008)

343 Dissolved Oxygen (DO)

Dissolved Oxygen was above the lower limit for EMA at allthe stations for all the years Year 2000 and 2005 recorded saturation of 125 and 100 respectively Oxygen levels canbe higher due to excess aquatic plants in the water which

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

64 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Figure 8 Dissolved Oxygen variation among sampling points

Figure 9 Nitrates variation along sampling points

produce oxygen Most living organisms require oxygen fortheir basic metabolic processes

344 Nitrates (NO3)

Results for nitrates for the years under consideration were allbelow the recommended EMA levels of 6 mg Lminus1 Nitratesare washed by runoff from agricultural lands into water bod-ies High concentration of nitrates in water bodies cause eu-trophication resulting in competition for oxygen by aquaticorganisms and high water treatment costs (Dike et al 2010)

345 PH

pH values for all the years were within the normal limits cat-egory according to EMA upper and lower limits of 6 and9 units respectively Year 2005 had one sampling point thathad a value slightly lower than the recommended Bhadjaand Vaghela (2013) indicated that activities in the water shedsuch as increased leaching of soils soil erosion and heavyprecipitation affects the pH levels downstream pH levels ashigh as 90 and as low as 5 affects the life span of aquaticorganisms (Addo et al 2011) Low pH values do not havedirect effect to human health but can have indirectly effect

Figure 10 pH variations along sampling points

since it causes leaching of metal irons such as copper zincand lead into the water (WHO 2008)

35 Relationship between sedimentation and river waterquality

Pearson correlation was used to determine the relationshipbetween two water quality parameters and sediment yieldThe parameters are related to sediment yield and these areturbidity and suspended solids (Bhadja and Vaghela 2013)The results are shown on Table 5

There is a close positive relationship between turbidity andsediment yield of 063 Total Suspended Solids have a posi-tive relation of 064 The results show that the two water qual-ity parameters can be indicators of sedimentation Highervalues of total suspended solids and turbidity indicate highervalues of sediment yield in water bodies

36 Variation in reservoir water quality

The variation in two selected reservoir water quality indica-tors turbidity and pH was determined A significant variationin turbidity was noted for the years 1988 to 2014 with a p-value of 002 which is less than 005 The mean value of tur-bidity for 1988 2003 and 2014 are 156 344 and 417 NTUrespectively The values show an increasing trend in turbid-ity which may be as a result of anthropogenic activities oc-curring upstream of the dam which has resulted in increasedsoil erosion hence more sediment on the reservoir pH resultsshowed that there is no significant change between 1988 and2014 (p-value gt 005) This might be because pH is a chemi-cal parameter that is determined by the type of sediments thatare carried into the river not the sediment load

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 65

4 Conclusions and recommendations

41 Conclusion

The objective of the study was to analyze sedimentation andits impact on river system and reservoir water quality in Ma-zowe Catchment Zimbabwe The studyrsquos major findings are

The catchment is generally experiencing moderate soilloss however there are some pockets under high and extremesoil loss which gave rise to siltation and water quality deteri-oration of available water bodies

There is reduction in capacity of reservoirs within thecatchment due to sedimentation Chimhanda Dam capacityhas been reduced by 386 from the initial design capac-ity as of April 2015 reducing the usefulness of the dam to37 years from the initial design life of 50 years due to silta-tion

Sediment deposition in rivers affects water quality and wa-ter quality parameters can be used as an indicator for sedi-mentation

42 Recommendations

In order to curb erosion and sedimentation in rivers and reser-voirs there is need to develop and implement an integratedwater resources management plan by all stakeholders

In order to maintain the lifespan of Chimhanda dam bestland management practices such as contour ploughing andre-forestation should be employed around the catchment areaof the Dam and this is an area that could be considered forfurther research

Data availability The main data used in the research is rainfalldata that was obtained from the meteorological department waterquality data obtained from Environmental management Agency aswell as sediment Data from Zinwa The data can be obtained fromthese departments

Competing interests The authors declare that they have no con-flict of interest

Special issue statement This article is part of the special issueldquoWater quality and sediment transport issues in surface waterrdquo Itis a result of the IAHS Scientific Assembly 2017 Port ElizabethSouth Africa 10ndash14 July 2017

Acknowledgements This paper contains part of research resultsfrom the MSc Thesis of the corresponding author Colleta Tundusubmitted to the University of Zimbabwe Special thanks go toFaith Chivava for her assistance in GIS ZINWA EMA and theZimbabwe Meteorological Services Department is appreciated forproviding data

Edited by Akhilendra B GuptaReviewed by Rajendra Prasad and one anonymous referee

References

Addo M A Okley G M Affum HA Acquah S Gbadago JK Senu J K and Botwe B O Water Quality and level ofsome heavy metals in water and sediments of Kpeshie LagoonLa-Accra Ghana Research Journal of Environmental and EarthSciences 3 487ndash497 2011

Adekunle I M Adetunji M T Gbadebo A M and Banjoko OB Assessment of groundwater quality in a typical rural settle-ment in Southwest Nigeria Int J Env Res Pub He 4 307ndash3182007

Bhadja P and Vaghela A Assessment of Physico-Chemical pa-rameters and water quality Index of reservoir water Internationaljournal of plant animal and environmental sciences 3 89ndash952013

Chapman D Water quality assessments ndash A guide to use of Biotasediments and water in Environmental monitoring 2nd EdnChapman and Hall London 191ndash193 1996

Chitata T Mugabe F T and Kashaigili J J Estimation ofSmall Reservoir Sedimentation in Semi-Arid Southern Zim-babwe Journal of Water Resource and Protection 6 48909 12ndash14 2014

Dalu T Tambara E M Clegg B Chari L D and NhiwatiwaT Modeling sedimentation rates of Malilangwe reservoir in thesouth-eastern lowveld of Zimbabwe Applied Water Science 3133ndash144 2013

Dearing J Sediment yields and sources in a welsh upland lake-catchment during the past 800 years Earth Surf Proc Land 171ndash22 1992

de Vente J Verduyn R Verstraeten G Vanmaercke M andPoesen J Factors controlling sediment yield at the catchmentscale in NW Mediterranean geoecosystems J Soil Sediment11 690ndash707 2011

Dike L Keramat A and Amirkolaie S Environmental impactof nutrient discharged by aquaculture waste water on the Harazriver Journal of Agriculture and Biological Science 3 275ndash2792010

EMA Effluent and Solid Waste Disposal Regulations SI 6 of 2007government printers of Zimbabwe 2007

Eroglu H Ccedilakır G Sivrikaya F and Akay A E Using highresolution images and elevation data in classifying erosion risksof bare soil areas in the Hatila Valley Natural Protected AreaTurkey Stoch Env Res Risk A 24 699ndash704 2010

Ezugwu C Sediment Deposition in Nigeria Reservoirs Impactsand Control Measures Innovative Systems Design and Engineer-ing 4 54ndash62 2013

Godwin A M Gabriel S Hodson M and Wellington D Sedi-mentation impacts on reservoir as a result of land use on a se-lected catchment in Zimbabwe International Journal of Engi-neering Science amp Technology 3 2011

Gusso A G A Veronez M R Robinson F Roani V and DaSilva R C Evaluating the thermal spatial distribution signaturefor environmental management and vegetation health monitor-ing International Journal of Advanced Remote Sensing and GIS3 433ndash445 2014

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

66 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Hanke S H and Kwok A K On the measurement of Zimbabwersquoshyperinflation Cato J 29 353ndash364 2009

Hoko Z An assessment of quality of water from boreholes inBindura District Zimbabwe Phys Chem Earth 33 824ndash8282008

Jang C Shin Y Kum D Kim R Yang J E Kim S CHwang S I Lim K J Yoon J-K and Park Y S Assessmentof soil loss in South Korea based on land-cover type Stoch EnvRes Risk A 1ndash15 1996

Kamaludin H Lihan T Ali Rahman Z Mustapha M AIdris W M R and Rahim S A Integration of re-mote sensing RUSLE and GIS to model potential soil lossand sediment yield (SY) Hydrol Earth Syst Sci Discusshttpsdoiorg105194hessd-10-4567-2013 2013

Lawson E O Physico- chemical parameters and heavy metal con-tents of water from the mangroves swamps of logos lagon logosNigeria Advances in biological research 5 8ndash21 2011

Makwara E and Gamira D About to Lose all the Soil in ZakarsquosWard 5 Zimbabwe Rewards of Unsustainable Land Use Euro-pean Journal of Sustainable Development 1 457ndash476 2012

Mambo J and Archer E An assessment of land degradation in theSave catchment of Zimbabwe Area 39 380ndash391 2007

Merritt W S Letcher R A and Jakeman A J A review oferosion and sediment transport models Env Modell Softw 18761ndash799 2003

Met Meteorological data available at httpswwwwmointdatastatwmodata_enhtml| last access 3 March 2015

Mutowo G and Chikodzi D Erosion Hazard Mapping in theRunde Catchment Implications for Water Resources Manage-ment Journal of Geosciences and Geomatics 1 22ndash28 2013

Pettorelli N Vik J O Mysterud A Gaillard J-M Tucker CJ and Stenseth N C Using the satellite-derived NDVI to as-sess ecological responses to environmental change Trends EcolEvol 20 503ndash510 2005

Renard K G Foster G R Weesies G A McCool D and Yo-der D Predicting soil erosion by water a guide to conservationplanning with the revised universal soil loss equation (RUSLE)Agriculture Handbook Washington 703 1997

Rooseboom A and Engineers S B C Sediment transport in riversand reservoirs a Southern African perspective Water ResearchCommission 297192489 1992

Sawunyama T Senzanje A and Mhizha A Estimation of smallreservoir storage capacities in Limpopo River Basin using ge-ographical information systems (GIS) and remotely sensed sur-face areas Case of Mzingwane catchment Phys Chem Earth31 935ndash943 2006

Sumi T and Hirose T Accumulation of sediment in reservoirsWater storage transport and distribution UNESCO-IHE andEOLSS Publishers Co Ltd Paris France 224ndash252 2009

Teh S H Soil erosion modeling using RUSLE and GIS onCameron highlands Malaysia for hydropower development MSThe School for Renewable Energy Science Iceland 41 pp2011

USDA Procedure for computing sheet and rill equation on projectareas Technical Release No 51 (Geology) US GovernmentPrinting Office Washington DC 1972

Walling D and Fang D Recent trends in the suspended sedimentloads of the worldrsquos rivers Global Planet change 39 111ndash1262003

Whitlow R Mapping erosion in Zimbabwe a methodology forrapid survey using aerial photographs Appl Geogr 6 149ndash1621986

WHO Guidelines for drinking water quality Third edition incor-porating the first and second addenda volume 1 additions 2008

Wischmeier W and Smith D Predicting rainfall erosion lossesAgricultural Handbook 537 Agricultural Research ServiceUnited States Department of Agriculture 1978

Zinwa D R Assessment of Surface Water Resources of Zimbabweand Guidelines for Planning in Management ZINWA Researchand Data Department Ministry of Water Resources Developmentand Management Harare Zimbabwe Harare 59 pp 2009

Zwane N Love D Hoko Z and Shoko D Managing the im-pact of gold panning activities within the context of integratedwater resources management planning in the Lower ManyameSub-Catchment Zambezi Basin Zimbabwe Phys Chem Earth31 848ndash856 2006

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

62 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Table 3 Measured sediment Load from flow gauges for the period December 2014 to March 2015

Silt Gauge Name or River Area of Sediment LoadInfluence (km2) load (t kmminus2) (t)

D75 Mazowe 20 380 14 28536D50 Nyamasanga 13 024 3D42 Mupfurudzi 163 192 31356D41 Mazowe 3300 086 2836D6 Shavanhowe 1166 051 58965D58 Nyagui 983 2425 14293D48 Mwenje 399 036 334

Table 4 Summarized Results from the silt survey

1988 2003 2015

Capacity at FSL (times106 m3) 52 3470 3194Loss Of Storage () 0 333 386Dam Surface Area (Ha) 9300 7400 6404

and its impacts (Zwane et al 2006) identified river bed goldpanning activities as a cause of degradation of river chan-nels and banks as well as accelerated erosion and siltation inmany areas of Zimbabwe

321 Sediment Yield

Figure 4 shows the sediment yield distribution map Sed-iment yield ranges from less than 1 t ha yrminus1 to a maxi-mum of 245t ha yrminus1 with an average value of 604 t ha yrminus1

over the catchment area The highest sediment yield is inthe Middle Mazowe sub catchment area with an averageof 672 t ha yrminus1 and a maximum of 245t ha yrminus1 The highvalue can be associated with high gold panning activities inthe Mazowe valley The lowest value is in the Lower Ruyasub-catchment with an average of 4 t ha yrminus1 The resultsare almost in line with a study by Rooseboom and Engi-neers (1992) that estimated the average sediment yield in thenine defined sediment regions in Southern Africa to vary be-tween 30 and 330 t ha yrminus1 with an average of 15 t ha yrminus1A study which was also carried out in the catchment areaof Pahang River basin in Malasyia gave a sediment yieldranging from 0ndash1379 t ha yrminus1 (Kamaludin et al 2013) Thetotal sediment yield for the catchment was calculated to be63 million t yrminus1

322 Measured Sediment Loads

Results from the measured sediment loads were highest atD75 which is along Mazowe River in the Zambezi valleyD41 located in Middle Mazowe sub catchment recorded arelatively high sediment load of 2836 t D58 and D6 are bothin Nyagui Sub-catchment recorded 14293 and 58965 t re-

Figure 4 Sediment Yield within the Catchment

Table 5 Results for the correlation between sediment yield and wa-ter quality parameters

Sediment Ave AverageTurbidity TSS

Sediment Pearson Correlation 1 634 647Sig (2-tailed) 366 353N 28 28

spectively D50 which is in Upper Mazowe sub catchmentrecorded a low figure of 3 t The results are concurring withthose from RUSLE model where high sediment yields wererecorded from Middle Mazowe and Nyagui sub catchmentsrespectively

33 Sedimentation in Chimhanda Dam from BathymetricSurvey

Table 4 summarizes the results of the silt survey forChimhanda Dam

The capacity of the dam decreased from the original5200times 106 to 3470times 106 and 3194times 106 m3 in years2003 and 2015 respectively There was 333 loss in stor-

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 63

Figure 5 Chimhanda Dam Capacity comparison over the years

age up to 2003 and a storage loss of 386 up to 2015 inreference to the design capacity Figure 5 shows reservoir ca-pacity changes over the years

Results from the 10 samples of river inflows collectedgave an average sediment concentration of 39 mg Lminus1 Therewas a decrease in trend in the sediment concentration asthe rainfall season was progressing The sediment accumu-lation in the reservoir was found to be 330 t yrminus1 and the spe-cific sediment yield was 226 t kmminus2 yrminus1 The usefulness ofChimhanda Dam has reduced from the initial design life of50 to 37 years A study by Godwin et al (2011) on ChesaCauseway Weir in the same catchment gave a specific yieldof 510 t km2 yrminus1 The usefulness of the dam was reducedfrom the initial design life of 50 to 25 years

Generally the results support the existing literature thatmost of the small to medium dams are being affected byhigh rates of sedimentation in Zimbabwe (Sawunyama et al2006 Godwin et al 2011 Dalu et al 2013 Chitata et al2014)

34 Water Quality Trend from Sedimentation

Figures 6 to 10 show the results for the historically measuredwater parameters for the years 2000 2008 2010 and 2014

341 Turbidity

Results for the years did not meet the permissible turbid-ity of 5 NTU The highest turbidity values were recordedin 2000 and 2005 respectively High values in 2005 corre-sponds to the high soil loss of 65 t ha yrminus1 that was recordedduring that particular year The high values in 2000 can beexplained by high rainfalls that were experienced during thatparticular year as compared with the other years (Met 2005)Low turbidity values were recorded during the year 2008the same year recorded the lowest soil loss of 36 t ha yrminus1High Turbidity levels are associated with poor water quality(Adekunle et al 2007) WHO (2008) highligted that highturbidity waters can facilitate the formation of nuclei wheregastrointestinal disease pathogens can attach If that water

Figure 6 Turbidity variation among sampling points

Figure 7 Total Suspended Solids variation among sampling points

is consumed improperly treated it can cause diseases Highturbidity leves also render the treatment of water expensive

342 Total Suspended Solids

2008 values were below the recommended limit of15 mg Lminus1 as shown on Fig 7 High values were recordedduring year 2000 2005 and 2014 The high values are inagreement with the high soil loss that were recorded in thoseparticular years Total suspended solids are closely relatedto sedimentation (Chapman 1996) When these suspendedparticles settles at the bottom of a water body they becomesediments Suspended solids consist of inorganic and organicfractions Part of the organic fractions is bacterial and thatmight be detrimental to human health if the water is con-sumed without adequate treatment (Hoko 2008)

343 Dissolved Oxygen (DO)

Dissolved Oxygen was above the lower limit for EMA at allthe stations for all the years Year 2000 and 2005 recorded saturation of 125 and 100 respectively Oxygen levels canbe higher due to excess aquatic plants in the water which

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

64 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Figure 8 Dissolved Oxygen variation among sampling points

Figure 9 Nitrates variation along sampling points

produce oxygen Most living organisms require oxygen fortheir basic metabolic processes

344 Nitrates (NO3)

Results for nitrates for the years under consideration were allbelow the recommended EMA levels of 6 mg Lminus1 Nitratesare washed by runoff from agricultural lands into water bod-ies High concentration of nitrates in water bodies cause eu-trophication resulting in competition for oxygen by aquaticorganisms and high water treatment costs (Dike et al 2010)

345 PH

pH values for all the years were within the normal limits cat-egory according to EMA upper and lower limits of 6 and9 units respectively Year 2005 had one sampling point thathad a value slightly lower than the recommended Bhadjaand Vaghela (2013) indicated that activities in the water shedsuch as increased leaching of soils soil erosion and heavyprecipitation affects the pH levels downstream pH levels ashigh as 90 and as low as 5 affects the life span of aquaticorganisms (Addo et al 2011) Low pH values do not havedirect effect to human health but can have indirectly effect

Figure 10 pH variations along sampling points

since it causes leaching of metal irons such as copper zincand lead into the water (WHO 2008)

35 Relationship between sedimentation and river waterquality

Pearson correlation was used to determine the relationshipbetween two water quality parameters and sediment yieldThe parameters are related to sediment yield and these areturbidity and suspended solids (Bhadja and Vaghela 2013)The results are shown on Table 5

There is a close positive relationship between turbidity andsediment yield of 063 Total Suspended Solids have a posi-tive relation of 064 The results show that the two water qual-ity parameters can be indicators of sedimentation Highervalues of total suspended solids and turbidity indicate highervalues of sediment yield in water bodies

36 Variation in reservoir water quality

The variation in two selected reservoir water quality indica-tors turbidity and pH was determined A significant variationin turbidity was noted for the years 1988 to 2014 with a p-value of 002 which is less than 005 The mean value of tur-bidity for 1988 2003 and 2014 are 156 344 and 417 NTUrespectively The values show an increasing trend in turbid-ity which may be as a result of anthropogenic activities oc-curring upstream of the dam which has resulted in increasedsoil erosion hence more sediment on the reservoir pH resultsshowed that there is no significant change between 1988 and2014 (p-value gt 005) This might be because pH is a chemi-cal parameter that is determined by the type of sediments thatare carried into the river not the sediment load

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 65

4 Conclusions and recommendations

41 Conclusion

The objective of the study was to analyze sedimentation andits impact on river system and reservoir water quality in Ma-zowe Catchment Zimbabwe The studyrsquos major findings are

The catchment is generally experiencing moderate soilloss however there are some pockets under high and extremesoil loss which gave rise to siltation and water quality deteri-oration of available water bodies

There is reduction in capacity of reservoirs within thecatchment due to sedimentation Chimhanda Dam capacityhas been reduced by 386 from the initial design capac-ity as of April 2015 reducing the usefulness of the dam to37 years from the initial design life of 50 years due to silta-tion

Sediment deposition in rivers affects water quality and wa-ter quality parameters can be used as an indicator for sedi-mentation

42 Recommendations

In order to curb erosion and sedimentation in rivers and reser-voirs there is need to develop and implement an integratedwater resources management plan by all stakeholders

In order to maintain the lifespan of Chimhanda dam bestland management practices such as contour ploughing andre-forestation should be employed around the catchment areaof the Dam and this is an area that could be considered forfurther research

Data availability The main data used in the research is rainfalldata that was obtained from the meteorological department waterquality data obtained from Environmental management Agency aswell as sediment Data from Zinwa The data can be obtained fromthese departments

Competing interests The authors declare that they have no con-flict of interest

Special issue statement This article is part of the special issueldquoWater quality and sediment transport issues in surface waterrdquo Itis a result of the IAHS Scientific Assembly 2017 Port ElizabethSouth Africa 10ndash14 July 2017

Acknowledgements This paper contains part of research resultsfrom the MSc Thesis of the corresponding author Colleta Tundusubmitted to the University of Zimbabwe Special thanks go toFaith Chivava for her assistance in GIS ZINWA EMA and theZimbabwe Meteorological Services Department is appreciated forproviding data

Edited by Akhilendra B GuptaReviewed by Rajendra Prasad and one anonymous referee

References

Addo M A Okley G M Affum HA Acquah S Gbadago JK Senu J K and Botwe B O Water Quality and level ofsome heavy metals in water and sediments of Kpeshie LagoonLa-Accra Ghana Research Journal of Environmental and EarthSciences 3 487ndash497 2011

Adekunle I M Adetunji M T Gbadebo A M and Banjoko OB Assessment of groundwater quality in a typical rural settle-ment in Southwest Nigeria Int J Env Res Pub He 4 307ndash3182007

Bhadja P and Vaghela A Assessment of Physico-Chemical pa-rameters and water quality Index of reservoir water Internationaljournal of plant animal and environmental sciences 3 89ndash952013

Chapman D Water quality assessments ndash A guide to use of Biotasediments and water in Environmental monitoring 2nd EdnChapman and Hall London 191ndash193 1996

Chitata T Mugabe F T and Kashaigili J J Estimation ofSmall Reservoir Sedimentation in Semi-Arid Southern Zim-babwe Journal of Water Resource and Protection 6 48909 12ndash14 2014

Dalu T Tambara E M Clegg B Chari L D and NhiwatiwaT Modeling sedimentation rates of Malilangwe reservoir in thesouth-eastern lowveld of Zimbabwe Applied Water Science 3133ndash144 2013

Dearing J Sediment yields and sources in a welsh upland lake-catchment during the past 800 years Earth Surf Proc Land 171ndash22 1992

de Vente J Verduyn R Verstraeten G Vanmaercke M andPoesen J Factors controlling sediment yield at the catchmentscale in NW Mediterranean geoecosystems J Soil Sediment11 690ndash707 2011

Dike L Keramat A and Amirkolaie S Environmental impactof nutrient discharged by aquaculture waste water on the Harazriver Journal of Agriculture and Biological Science 3 275ndash2792010

EMA Effluent and Solid Waste Disposal Regulations SI 6 of 2007government printers of Zimbabwe 2007

Eroglu H Ccedilakır G Sivrikaya F and Akay A E Using highresolution images and elevation data in classifying erosion risksof bare soil areas in the Hatila Valley Natural Protected AreaTurkey Stoch Env Res Risk A 24 699ndash704 2010

Ezugwu C Sediment Deposition in Nigeria Reservoirs Impactsand Control Measures Innovative Systems Design and Engineer-ing 4 54ndash62 2013

Godwin A M Gabriel S Hodson M and Wellington D Sedi-mentation impacts on reservoir as a result of land use on a se-lected catchment in Zimbabwe International Journal of Engi-neering Science amp Technology 3 2011

Gusso A G A Veronez M R Robinson F Roani V and DaSilva R C Evaluating the thermal spatial distribution signaturefor environmental management and vegetation health monitor-ing International Journal of Advanced Remote Sensing and GIS3 433ndash445 2014

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

66 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Hanke S H and Kwok A K On the measurement of Zimbabwersquoshyperinflation Cato J 29 353ndash364 2009

Hoko Z An assessment of quality of water from boreholes inBindura District Zimbabwe Phys Chem Earth 33 824ndash8282008

Jang C Shin Y Kum D Kim R Yang J E Kim S CHwang S I Lim K J Yoon J-K and Park Y S Assessmentof soil loss in South Korea based on land-cover type Stoch EnvRes Risk A 1ndash15 1996

Kamaludin H Lihan T Ali Rahman Z Mustapha M AIdris W M R and Rahim S A Integration of re-mote sensing RUSLE and GIS to model potential soil lossand sediment yield (SY) Hydrol Earth Syst Sci Discusshttpsdoiorg105194hessd-10-4567-2013 2013

Lawson E O Physico- chemical parameters and heavy metal con-tents of water from the mangroves swamps of logos lagon logosNigeria Advances in biological research 5 8ndash21 2011

Makwara E and Gamira D About to Lose all the Soil in ZakarsquosWard 5 Zimbabwe Rewards of Unsustainable Land Use Euro-pean Journal of Sustainable Development 1 457ndash476 2012

Mambo J and Archer E An assessment of land degradation in theSave catchment of Zimbabwe Area 39 380ndash391 2007

Merritt W S Letcher R A and Jakeman A J A review oferosion and sediment transport models Env Modell Softw 18761ndash799 2003

Met Meteorological data available at httpswwwwmointdatastatwmodata_enhtml| last access 3 March 2015

Mutowo G and Chikodzi D Erosion Hazard Mapping in theRunde Catchment Implications for Water Resources Manage-ment Journal of Geosciences and Geomatics 1 22ndash28 2013

Pettorelli N Vik J O Mysterud A Gaillard J-M Tucker CJ and Stenseth N C Using the satellite-derived NDVI to as-sess ecological responses to environmental change Trends EcolEvol 20 503ndash510 2005

Renard K G Foster G R Weesies G A McCool D and Yo-der D Predicting soil erosion by water a guide to conservationplanning with the revised universal soil loss equation (RUSLE)Agriculture Handbook Washington 703 1997

Rooseboom A and Engineers S B C Sediment transport in riversand reservoirs a Southern African perspective Water ResearchCommission 297192489 1992

Sawunyama T Senzanje A and Mhizha A Estimation of smallreservoir storage capacities in Limpopo River Basin using ge-ographical information systems (GIS) and remotely sensed sur-face areas Case of Mzingwane catchment Phys Chem Earth31 935ndash943 2006

Sumi T and Hirose T Accumulation of sediment in reservoirsWater storage transport and distribution UNESCO-IHE andEOLSS Publishers Co Ltd Paris France 224ndash252 2009

Teh S H Soil erosion modeling using RUSLE and GIS onCameron highlands Malaysia for hydropower development MSThe School for Renewable Energy Science Iceland 41 pp2011

USDA Procedure for computing sheet and rill equation on projectareas Technical Release No 51 (Geology) US GovernmentPrinting Office Washington DC 1972

Walling D and Fang D Recent trends in the suspended sedimentloads of the worldrsquos rivers Global Planet change 39 111ndash1262003

Whitlow R Mapping erosion in Zimbabwe a methodology forrapid survey using aerial photographs Appl Geogr 6 149ndash1621986

WHO Guidelines for drinking water quality Third edition incor-porating the first and second addenda volume 1 additions 2008

Wischmeier W and Smith D Predicting rainfall erosion lossesAgricultural Handbook 537 Agricultural Research ServiceUnited States Department of Agriculture 1978

Zinwa D R Assessment of Surface Water Resources of Zimbabweand Guidelines for Planning in Management ZINWA Researchand Data Department Ministry of Water Resources Developmentand Management Harare Zimbabwe Harare 59 pp 2009

Zwane N Love D Hoko Z and Shoko D Managing the im-pact of gold panning activities within the context of integratedwater resources management planning in the Lower ManyameSub-Catchment Zambezi Basin Zimbabwe Phys Chem Earth31 848ndash856 2006

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 63

Figure 5 Chimhanda Dam Capacity comparison over the years

age up to 2003 and a storage loss of 386 up to 2015 inreference to the design capacity Figure 5 shows reservoir ca-pacity changes over the years

Results from the 10 samples of river inflows collectedgave an average sediment concentration of 39 mg Lminus1 Therewas a decrease in trend in the sediment concentration asthe rainfall season was progressing The sediment accumu-lation in the reservoir was found to be 330 t yrminus1 and the spe-cific sediment yield was 226 t kmminus2 yrminus1 The usefulness ofChimhanda Dam has reduced from the initial design life of50 to 37 years A study by Godwin et al (2011) on ChesaCauseway Weir in the same catchment gave a specific yieldof 510 t km2 yrminus1 The usefulness of the dam was reducedfrom the initial design life of 50 to 25 years

Generally the results support the existing literature thatmost of the small to medium dams are being affected byhigh rates of sedimentation in Zimbabwe (Sawunyama et al2006 Godwin et al 2011 Dalu et al 2013 Chitata et al2014)

34 Water Quality Trend from Sedimentation

Figures 6 to 10 show the results for the historically measuredwater parameters for the years 2000 2008 2010 and 2014

341 Turbidity

Results for the years did not meet the permissible turbid-ity of 5 NTU The highest turbidity values were recordedin 2000 and 2005 respectively High values in 2005 corre-sponds to the high soil loss of 65 t ha yrminus1 that was recordedduring that particular year The high values in 2000 can beexplained by high rainfalls that were experienced during thatparticular year as compared with the other years (Met 2005)Low turbidity values were recorded during the year 2008the same year recorded the lowest soil loss of 36 t ha yrminus1High Turbidity levels are associated with poor water quality(Adekunle et al 2007) WHO (2008) highligted that highturbidity waters can facilitate the formation of nuclei wheregastrointestinal disease pathogens can attach If that water

Figure 6 Turbidity variation among sampling points

Figure 7 Total Suspended Solids variation among sampling points

is consumed improperly treated it can cause diseases Highturbidity leves also render the treatment of water expensive

342 Total Suspended Solids

2008 values were below the recommended limit of15 mg Lminus1 as shown on Fig 7 High values were recordedduring year 2000 2005 and 2014 The high values are inagreement with the high soil loss that were recorded in thoseparticular years Total suspended solids are closely relatedto sedimentation (Chapman 1996) When these suspendedparticles settles at the bottom of a water body they becomesediments Suspended solids consist of inorganic and organicfractions Part of the organic fractions is bacterial and thatmight be detrimental to human health if the water is con-sumed without adequate treatment (Hoko 2008)

343 Dissolved Oxygen (DO)

Dissolved Oxygen was above the lower limit for EMA at allthe stations for all the years Year 2000 and 2005 recorded saturation of 125 and 100 respectively Oxygen levels canbe higher due to excess aquatic plants in the water which

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

64 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Figure 8 Dissolved Oxygen variation among sampling points

Figure 9 Nitrates variation along sampling points

produce oxygen Most living organisms require oxygen fortheir basic metabolic processes

344 Nitrates (NO3)

Results for nitrates for the years under consideration were allbelow the recommended EMA levels of 6 mg Lminus1 Nitratesare washed by runoff from agricultural lands into water bod-ies High concentration of nitrates in water bodies cause eu-trophication resulting in competition for oxygen by aquaticorganisms and high water treatment costs (Dike et al 2010)

345 PH

pH values for all the years were within the normal limits cat-egory according to EMA upper and lower limits of 6 and9 units respectively Year 2005 had one sampling point thathad a value slightly lower than the recommended Bhadjaand Vaghela (2013) indicated that activities in the water shedsuch as increased leaching of soils soil erosion and heavyprecipitation affects the pH levels downstream pH levels ashigh as 90 and as low as 5 affects the life span of aquaticorganisms (Addo et al 2011) Low pH values do not havedirect effect to human health but can have indirectly effect

Figure 10 pH variations along sampling points

since it causes leaching of metal irons such as copper zincand lead into the water (WHO 2008)

35 Relationship between sedimentation and river waterquality

Pearson correlation was used to determine the relationshipbetween two water quality parameters and sediment yieldThe parameters are related to sediment yield and these areturbidity and suspended solids (Bhadja and Vaghela 2013)The results are shown on Table 5

There is a close positive relationship between turbidity andsediment yield of 063 Total Suspended Solids have a posi-tive relation of 064 The results show that the two water qual-ity parameters can be indicators of sedimentation Highervalues of total suspended solids and turbidity indicate highervalues of sediment yield in water bodies

36 Variation in reservoir water quality

The variation in two selected reservoir water quality indica-tors turbidity and pH was determined A significant variationin turbidity was noted for the years 1988 to 2014 with a p-value of 002 which is less than 005 The mean value of tur-bidity for 1988 2003 and 2014 are 156 344 and 417 NTUrespectively The values show an increasing trend in turbid-ity which may be as a result of anthropogenic activities oc-curring upstream of the dam which has resulted in increasedsoil erosion hence more sediment on the reservoir pH resultsshowed that there is no significant change between 1988 and2014 (p-value gt 005) This might be because pH is a chemi-cal parameter that is determined by the type of sediments thatare carried into the river not the sediment load

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 65

4 Conclusions and recommendations

41 Conclusion

The objective of the study was to analyze sedimentation andits impact on river system and reservoir water quality in Ma-zowe Catchment Zimbabwe The studyrsquos major findings are

The catchment is generally experiencing moderate soilloss however there are some pockets under high and extremesoil loss which gave rise to siltation and water quality deteri-oration of available water bodies

There is reduction in capacity of reservoirs within thecatchment due to sedimentation Chimhanda Dam capacityhas been reduced by 386 from the initial design capac-ity as of April 2015 reducing the usefulness of the dam to37 years from the initial design life of 50 years due to silta-tion

Sediment deposition in rivers affects water quality and wa-ter quality parameters can be used as an indicator for sedi-mentation

42 Recommendations

In order to curb erosion and sedimentation in rivers and reser-voirs there is need to develop and implement an integratedwater resources management plan by all stakeholders

In order to maintain the lifespan of Chimhanda dam bestland management practices such as contour ploughing andre-forestation should be employed around the catchment areaof the Dam and this is an area that could be considered forfurther research

Data availability The main data used in the research is rainfalldata that was obtained from the meteorological department waterquality data obtained from Environmental management Agency aswell as sediment Data from Zinwa The data can be obtained fromthese departments

Competing interests The authors declare that they have no con-flict of interest

Special issue statement This article is part of the special issueldquoWater quality and sediment transport issues in surface waterrdquo Itis a result of the IAHS Scientific Assembly 2017 Port ElizabethSouth Africa 10ndash14 July 2017

Acknowledgements This paper contains part of research resultsfrom the MSc Thesis of the corresponding author Colleta Tundusubmitted to the University of Zimbabwe Special thanks go toFaith Chivava for her assistance in GIS ZINWA EMA and theZimbabwe Meteorological Services Department is appreciated forproviding data

Edited by Akhilendra B GuptaReviewed by Rajendra Prasad and one anonymous referee

References

Addo M A Okley G M Affum HA Acquah S Gbadago JK Senu J K and Botwe B O Water Quality and level ofsome heavy metals in water and sediments of Kpeshie LagoonLa-Accra Ghana Research Journal of Environmental and EarthSciences 3 487ndash497 2011

Adekunle I M Adetunji M T Gbadebo A M and Banjoko OB Assessment of groundwater quality in a typical rural settle-ment in Southwest Nigeria Int J Env Res Pub He 4 307ndash3182007

Bhadja P and Vaghela A Assessment of Physico-Chemical pa-rameters and water quality Index of reservoir water Internationaljournal of plant animal and environmental sciences 3 89ndash952013

Chapman D Water quality assessments ndash A guide to use of Biotasediments and water in Environmental monitoring 2nd EdnChapman and Hall London 191ndash193 1996

Chitata T Mugabe F T and Kashaigili J J Estimation ofSmall Reservoir Sedimentation in Semi-Arid Southern Zim-babwe Journal of Water Resource and Protection 6 48909 12ndash14 2014

Dalu T Tambara E M Clegg B Chari L D and NhiwatiwaT Modeling sedimentation rates of Malilangwe reservoir in thesouth-eastern lowveld of Zimbabwe Applied Water Science 3133ndash144 2013

Dearing J Sediment yields and sources in a welsh upland lake-catchment during the past 800 years Earth Surf Proc Land 171ndash22 1992

de Vente J Verduyn R Verstraeten G Vanmaercke M andPoesen J Factors controlling sediment yield at the catchmentscale in NW Mediterranean geoecosystems J Soil Sediment11 690ndash707 2011

Dike L Keramat A and Amirkolaie S Environmental impactof nutrient discharged by aquaculture waste water on the Harazriver Journal of Agriculture and Biological Science 3 275ndash2792010

EMA Effluent and Solid Waste Disposal Regulations SI 6 of 2007government printers of Zimbabwe 2007

Eroglu H Ccedilakır G Sivrikaya F and Akay A E Using highresolution images and elevation data in classifying erosion risksof bare soil areas in the Hatila Valley Natural Protected AreaTurkey Stoch Env Res Risk A 24 699ndash704 2010

Ezugwu C Sediment Deposition in Nigeria Reservoirs Impactsand Control Measures Innovative Systems Design and Engineer-ing 4 54ndash62 2013

Godwin A M Gabriel S Hodson M and Wellington D Sedi-mentation impacts on reservoir as a result of land use on a se-lected catchment in Zimbabwe International Journal of Engi-neering Science amp Technology 3 2011

Gusso A G A Veronez M R Robinson F Roani V and DaSilva R C Evaluating the thermal spatial distribution signaturefor environmental management and vegetation health monitor-ing International Journal of Advanced Remote Sensing and GIS3 433ndash445 2014

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

66 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Hanke S H and Kwok A K On the measurement of Zimbabwersquoshyperinflation Cato J 29 353ndash364 2009

Hoko Z An assessment of quality of water from boreholes inBindura District Zimbabwe Phys Chem Earth 33 824ndash8282008

Jang C Shin Y Kum D Kim R Yang J E Kim S CHwang S I Lim K J Yoon J-K and Park Y S Assessmentof soil loss in South Korea based on land-cover type Stoch EnvRes Risk A 1ndash15 1996

Kamaludin H Lihan T Ali Rahman Z Mustapha M AIdris W M R and Rahim S A Integration of re-mote sensing RUSLE and GIS to model potential soil lossand sediment yield (SY) Hydrol Earth Syst Sci Discusshttpsdoiorg105194hessd-10-4567-2013 2013

Lawson E O Physico- chemical parameters and heavy metal con-tents of water from the mangroves swamps of logos lagon logosNigeria Advances in biological research 5 8ndash21 2011

Makwara E and Gamira D About to Lose all the Soil in ZakarsquosWard 5 Zimbabwe Rewards of Unsustainable Land Use Euro-pean Journal of Sustainable Development 1 457ndash476 2012

Mambo J and Archer E An assessment of land degradation in theSave catchment of Zimbabwe Area 39 380ndash391 2007

Merritt W S Letcher R A and Jakeman A J A review oferosion and sediment transport models Env Modell Softw 18761ndash799 2003

Met Meteorological data available at httpswwwwmointdatastatwmodata_enhtml| last access 3 March 2015

Mutowo G and Chikodzi D Erosion Hazard Mapping in theRunde Catchment Implications for Water Resources Manage-ment Journal of Geosciences and Geomatics 1 22ndash28 2013

Pettorelli N Vik J O Mysterud A Gaillard J-M Tucker CJ and Stenseth N C Using the satellite-derived NDVI to as-sess ecological responses to environmental change Trends EcolEvol 20 503ndash510 2005

Renard K G Foster G R Weesies G A McCool D and Yo-der D Predicting soil erosion by water a guide to conservationplanning with the revised universal soil loss equation (RUSLE)Agriculture Handbook Washington 703 1997

Rooseboom A and Engineers S B C Sediment transport in riversand reservoirs a Southern African perspective Water ResearchCommission 297192489 1992

Sawunyama T Senzanje A and Mhizha A Estimation of smallreservoir storage capacities in Limpopo River Basin using ge-ographical information systems (GIS) and remotely sensed sur-face areas Case of Mzingwane catchment Phys Chem Earth31 935ndash943 2006

Sumi T and Hirose T Accumulation of sediment in reservoirsWater storage transport and distribution UNESCO-IHE andEOLSS Publishers Co Ltd Paris France 224ndash252 2009

Teh S H Soil erosion modeling using RUSLE and GIS onCameron highlands Malaysia for hydropower development MSThe School for Renewable Energy Science Iceland 41 pp2011

USDA Procedure for computing sheet and rill equation on projectareas Technical Release No 51 (Geology) US GovernmentPrinting Office Washington DC 1972

Walling D and Fang D Recent trends in the suspended sedimentloads of the worldrsquos rivers Global Planet change 39 111ndash1262003

Whitlow R Mapping erosion in Zimbabwe a methodology forrapid survey using aerial photographs Appl Geogr 6 149ndash1621986

WHO Guidelines for drinking water quality Third edition incor-porating the first and second addenda volume 1 additions 2008

Wischmeier W and Smith D Predicting rainfall erosion lossesAgricultural Handbook 537 Agricultural Research ServiceUnited States Department of Agriculture 1978

Zinwa D R Assessment of Surface Water Resources of Zimbabweand Guidelines for Planning in Management ZINWA Researchand Data Department Ministry of Water Resources Developmentand Management Harare Zimbabwe Harare 59 pp 2009

Zwane N Love D Hoko Z and Shoko D Managing the im-pact of gold panning activities within the context of integratedwater resources management planning in the Lower ManyameSub-Catchment Zambezi Basin Zimbabwe Phys Chem Earth31 848ndash856 2006

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

64 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Figure 8 Dissolved Oxygen variation among sampling points

Figure 9 Nitrates variation along sampling points

produce oxygen Most living organisms require oxygen fortheir basic metabolic processes

344 Nitrates (NO3)

Results for nitrates for the years under consideration were allbelow the recommended EMA levels of 6 mg Lminus1 Nitratesare washed by runoff from agricultural lands into water bod-ies High concentration of nitrates in water bodies cause eu-trophication resulting in competition for oxygen by aquaticorganisms and high water treatment costs (Dike et al 2010)

345 PH

pH values for all the years were within the normal limits cat-egory according to EMA upper and lower limits of 6 and9 units respectively Year 2005 had one sampling point thathad a value slightly lower than the recommended Bhadjaand Vaghela (2013) indicated that activities in the water shedsuch as increased leaching of soils soil erosion and heavyprecipitation affects the pH levels downstream pH levels ashigh as 90 and as low as 5 affects the life span of aquaticorganisms (Addo et al 2011) Low pH values do not havedirect effect to human health but can have indirectly effect

Figure 10 pH variations along sampling points

since it causes leaching of metal irons such as copper zincand lead into the water (WHO 2008)

35 Relationship between sedimentation and river waterquality

Pearson correlation was used to determine the relationshipbetween two water quality parameters and sediment yieldThe parameters are related to sediment yield and these areturbidity and suspended solids (Bhadja and Vaghela 2013)The results are shown on Table 5

There is a close positive relationship between turbidity andsediment yield of 063 Total Suspended Solids have a posi-tive relation of 064 The results show that the two water qual-ity parameters can be indicators of sedimentation Highervalues of total suspended solids and turbidity indicate highervalues of sediment yield in water bodies

36 Variation in reservoir water quality

The variation in two selected reservoir water quality indica-tors turbidity and pH was determined A significant variationin turbidity was noted for the years 1988 to 2014 with a p-value of 002 which is less than 005 The mean value of tur-bidity for 1988 2003 and 2014 are 156 344 and 417 NTUrespectively The values show an increasing trend in turbid-ity which may be as a result of anthropogenic activities oc-curring upstream of the dam which has resulted in increasedsoil erosion hence more sediment on the reservoir pH resultsshowed that there is no significant change between 1988 and2014 (p-value gt 005) This might be because pH is a chemi-cal parameter that is determined by the type of sediments thatare carried into the river not the sediment load

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 65

4 Conclusions and recommendations

41 Conclusion

The objective of the study was to analyze sedimentation andits impact on river system and reservoir water quality in Ma-zowe Catchment Zimbabwe The studyrsquos major findings are

The catchment is generally experiencing moderate soilloss however there are some pockets under high and extremesoil loss which gave rise to siltation and water quality deteri-oration of available water bodies

There is reduction in capacity of reservoirs within thecatchment due to sedimentation Chimhanda Dam capacityhas been reduced by 386 from the initial design capac-ity as of April 2015 reducing the usefulness of the dam to37 years from the initial design life of 50 years due to silta-tion

Sediment deposition in rivers affects water quality and wa-ter quality parameters can be used as an indicator for sedi-mentation

42 Recommendations

In order to curb erosion and sedimentation in rivers and reser-voirs there is need to develop and implement an integratedwater resources management plan by all stakeholders

In order to maintain the lifespan of Chimhanda dam bestland management practices such as contour ploughing andre-forestation should be employed around the catchment areaof the Dam and this is an area that could be considered forfurther research

Data availability The main data used in the research is rainfalldata that was obtained from the meteorological department waterquality data obtained from Environmental management Agency aswell as sediment Data from Zinwa The data can be obtained fromthese departments

Competing interests The authors declare that they have no con-flict of interest

Special issue statement This article is part of the special issueldquoWater quality and sediment transport issues in surface waterrdquo Itis a result of the IAHS Scientific Assembly 2017 Port ElizabethSouth Africa 10ndash14 July 2017

Acknowledgements This paper contains part of research resultsfrom the MSc Thesis of the corresponding author Colleta Tundusubmitted to the University of Zimbabwe Special thanks go toFaith Chivava for her assistance in GIS ZINWA EMA and theZimbabwe Meteorological Services Department is appreciated forproviding data

Edited by Akhilendra B GuptaReviewed by Rajendra Prasad and one anonymous referee

References

Addo M A Okley G M Affum HA Acquah S Gbadago JK Senu J K and Botwe B O Water Quality and level ofsome heavy metals in water and sediments of Kpeshie LagoonLa-Accra Ghana Research Journal of Environmental and EarthSciences 3 487ndash497 2011

Adekunle I M Adetunji M T Gbadebo A M and Banjoko OB Assessment of groundwater quality in a typical rural settle-ment in Southwest Nigeria Int J Env Res Pub He 4 307ndash3182007

Bhadja P and Vaghela A Assessment of Physico-Chemical pa-rameters and water quality Index of reservoir water Internationaljournal of plant animal and environmental sciences 3 89ndash952013

Chapman D Water quality assessments ndash A guide to use of Biotasediments and water in Environmental monitoring 2nd EdnChapman and Hall London 191ndash193 1996

Chitata T Mugabe F T and Kashaigili J J Estimation ofSmall Reservoir Sedimentation in Semi-Arid Southern Zim-babwe Journal of Water Resource and Protection 6 48909 12ndash14 2014

Dalu T Tambara E M Clegg B Chari L D and NhiwatiwaT Modeling sedimentation rates of Malilangwe reservoir in thesouth-eastern lowveld of Zimbabwe Applied Water Science 3133ndash144 2013

Dearing J Sediment yields and sources in a welsh upland lake-catchment during the past 800 years Earth Surf Proc Land 171ndash22 1992

de Vente J Verduyn R Verstraeten G Vanmaercke M andPoesen J Factors controlling sediment yield at the catchmentscale in NW Mediterranean geoecosystems J Soil Sediment11 690ndash707 2011

Dike L Keramat A and Amirkolaie S Environmental impactof nutrient discharged by aquaculture waste water on the Harazriver Journal of Agriculture and Biological Science 3 275ndash2792010

EMA Effluent and Solid Waste Disposal Regulations SI 6 of 2007government printers of Zimbabwe 2007

Eroglu H Ccedilakır G Sivrikaya F and Akay A E Using highresolution images and elevation data in classifying erosion risksof bare soil areas in the Hatila Valley Natural Protected AreaTurkey Stoch Env Res Risk A 24 699ndash704 2010

Ezugwu C Sediment Deposition in Nigeria Reservoirs Impactsand Control Measures Innovative Systems Design and Engineer-ing 4 54ndash62 2013

Godwin A M Gabriel S Hodson M and Wellington D Sedi-mentation impacts on reservoir as a result of land use on a se-lected catchment in Zimbabwe International Journal of Engi-neering Science amp Technology 3 2011

Gusso A G A Veronez M R Robinson F Roani V and DaSilva R C Evaluating the thermal spatial distribution signaturefor environmental management and vegetation health monitor-ing International Journal of Advanced Remote Sensing and GIS3 433ndash445 2014

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

66 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Hanke S H and Kwok A K On the measurement of Zimbabwersquoshyperinflation Cato J 29 353ndash364 2009

Hoko Z An assessment of quality of water from boreholes inBindura District Zimbabwe Phys Chem Earth 33 824ndash8282008

Jang C Shin Y Kum D Kim R Yang J E Kim S CHwang S I Lim K J Yoon J-K and Park Y S Assessmentof soil loss in South Korea based on land-cover type Stoch EnvRes Risk A 1ndash15 1996

Kamaludin H Lihan T Ali Rahman Z Mustapha M AIdris W M R and Rahim S A Integration of re-mote sensing RUSLE and GIS to model potential soil lossand sediment yield (SY) Hydrol Earth Syst Sci Discusshttpsdoiorg105194hessd-10-4567-2013 2013

Lawson E O Physico- chemical parameters and heavy metal con-tents of water from the mangroves swamps of logos lagon logosNigeria Advances in biological research 5 8ndash21 2011

Makwara E and Gamira D About to Lose all the Soil in ZakarsquosWard 5 Zimbabwe Rewards of Unsustainable Land Use Euro-pean Journal of Sustainable Development 1 457ndash476 2012

Mambo J and Archer E An assessment of land degradation in theSave catchment of Zimbabwe Area 39 380ndash391 2007

Merritt W S Letcher R A and Jakeman A J A review oferosion and sediment transport models Env Modell Softw 18761ndash799 2003

Met Meteorological data available at httpswwwwmointdatastatwmodata_enhtml| last access 3 March 2015

Mutowo G and Chikodzi D Erosion Hazard Mapping in theRunde Catchment Implications for Water Resources Manage-ment Journal of Geosciences and Geomatics 1 22ndash28 2013

Pettorelli N Vik J O Mysterud A Gaillard J-M Tucker CJ and Stenseth N C Using the satellite-derived NDVI to as-sess ecological responses to environmental change Trends EcolEvol 20 503ndash510 2005

Renard K G Foster G R Weesies G A McCool D and Yo-der D Predicting soil erosion by water a guide to conservationplanning with the revised universal soil loss equation (RUSLE)Agriculture Handbook Washington 703 1997

Rooseboom A and Engineers S B C Sediment transport in riversand reservoirs a Southern African perspective Water ResearchCommission 297192489 1992

Sawunyama T Senzanje A and Mhizha A Estimation of smallreservoir storage capacities in Limpopo River Basin using ge-ographical information systems (GIS) and remotely sensed sur-face areas Case of Mzingwane catchment Phys Chem Earth31 935ndash943 2006

Sumi T and Hirose T Accumulation of sediment in reservoirsWater storage transport and distribution UNESCO-IHE andEOLSS Publishers Co Ltd Paris France 224ndash252 2009

Teh S H Soil erosion modeling using RUSLE and GIS onCameron highlands Malaysia for hydropower development MSThe School for Renewable Energy Science Iceland 41 pp2011

USDA Procedure for computing sheet and rill equation on projectareas Technical Release No 51 (Geology) US GovernmentPrinting Office Washington DC 1972

Walling D and Fang D Recent trends in the suspended sedimentloads of the worldrsquos rivers Global Planet change 39 111ndash1262003

Whitlow R Mapping erosion in Zimbabwe a methodology forrapid survey using aerial photographs Appl Geogr 6 149ndash1621986

WHO Guidelines for drinking water quality Third edition incor-porating the first and second addenda volume 1 additions 2008

Wischmeier W and Smith D Predicting rainfall erosion lossesAgricultural Handbook 537 Agricultural Research ServiceUnited States Department of Agriculture 1978

Zinwa D R Assessment of Surface Water Resources of Zimbabweand Guidelines for Planning in Management ZINWA Researchand Data Department Ministry of Water Resources Developmentand Management Harare Zimbabwe Harare 59 pp 2009

Zwane N Love D Hoko Z and Shoko D Managing the im-pact of gold panning activities within the context of integratedwater resources management planning in the Lower ManyameSub-Catchment Zambezi Basin Zimbabwe Phys Chem Earth31 848ndash856 2006

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality 65

4 Conclusions and recommendations

41 Conclusion

The objective of the study was to analyze sedimentation andits impact on river system and reservoir water quality in Ma-zowe Catchment Zimbabwe The studyrsquos major findings are

The catchment is generally experiencing moderate soilloss however there are some pockets under high and extremesoil loss which gave rise to siltation and water quality deteri-oration of available water bodies

There is reduction in capacity of reservoirs within thecatchment due to sedimentation Chimhanda Dam capacityhas been reduced by 386 from the initial design capac-ity as of April 2015 reducing the usefulness of the dam to37 years from the initial design life of 50 years due to silta-tion

Sediment deposition in rivers affects water quality and wa-ter quality parameters can be used as an indicator for sedi-mentation

42 Recommendations

In order to curb erosion and sedimentation in rivers and reser-voirs there is need to develop and implement an integratedwater resources management plan by all stakeholders

In order to maintain the lifespan of Chimhanda dam bestland management practices such as contour ploughing andre-forestation should be employed around the catchment areaof the Dam and this is an area that could be considered forfurther research

Data availability The main data used in the research is rainfalldata that was obtained from the meteorological department waterquality data obtained from Environmental management Agency aswell as sediment Data from Zinwa The data can be obtained fromthese departments

Competing interests The authors declare that they have no con-flict of interest

Special issue statement This article is part of the special issueldquoWater quality and sediment transport issues in surface waterrdquo Itis a result of the IAHS Scientific Assembly 2017 Port ElizabethSouth Africa 10ndash14 July 2017

Acknowledgements This paper contains part of research resultsfrom the MSc Thesis of the corresponding author Colleta Tundusubmitted to the University of Zimbabwe Special thanks go toFaith Chivava for her assistance in GIS ZINWA EMA and theZimbabwe Meteorological Services Department is appreciated forproviding data

Edited by Akhilendra B GuptaReviewed by Rajendra Prasad and one anonymous referee

References

Addo M A Okley G M Affum HA Acquah S Gbadago JK Senu J K and Botwe B O Water Quality and level ofsome heavy metals in water and sediments of Kpeshie LagoonLa-Accra Ghana Research Journal of Environmental and EarthSciences 3 487ndash497 2011

Adekunle I M Adetunji M T Gbadebo A M and Banjoko OB Assessment of groundwater quality in a typical rural settle-ment in Southwest Nigeria Int J Env Res Pub He 4 307ndash3182007

Bhadja P and Vaghela A Assessment of Physico-Chemical pa-rameters and water quality Index of reservoir water Internationaljournal of plant animal and environmental sciences 3 89ndash952013

Chapman D Water quality assessments ndash A guide to use of Biotasediments and water in Environmental monitoring 2nd EdnChapman and Hall London 191ndash193 1996

Chitata T Mugabe F T and Kashaigili J J Estimation ofSmall Reservoir Sedimentation in Semi-Arid Southern Zim-babwe Journal of Water Resource and Protection 6 48909 12ndash14 2014

Dalu T Tambara E M Clegg B Chari L D and NhiwatiwaT Modeling sedimentation rates of Malilangwe reservoir in thesouth-eastern lowveld of Zimbabwe Applied Water Science 3133ndash144 2013

Dearing J Sediment yields and sources in a welsh upland lake-catchment during the past 800 years Earth Surf Proc Land 171ndash22 1992

de Vente J Verduyn R Verstraeten G Vanmaercke M andPoesen J Factors controlling sediment yield at the catchmentscale in NW Mediterranean geoecosystems J Soil Sediment11 690ndash707 2011

Dike L Keramat A and Amirkolaie S Environmental impactof nutrient discharged by aquaculture waste water on the Harazriver Journal of Agriculture and Biological Science 3 275ndash2792010

EMA Effluent and Solid Waste Disposal Regulations SI 6 of 2007government printers of Zimbabwe 2007

Eroglu H Ccedilakır G Sivrikaya F and Akay A E Using highresolution images and elevation data in classifying erosion risksof bare soil areas in the Hatila Valley Natural Protected AreaTurkey Stoch Env Res Risk A 24 699ndash704 2010

Ezugwu C Sediment Deposition in Nigeria Reservoirs Impactsand Control Measures Innovative Systems Design and Engineer-ing 4 54ndash62 2013

Godwin A M Gabriel S Hodson M and Wellington D Sedi-mentation impacts on reservoir as a result of land use on a se-lected catchment in Zimbabwe International Journal of Engi-neering Science amp Technology 3 2011

Gusso A G A Veronez M R Robinson F Roani V and DaSilva R C Evaluating the thermal spatial distribution signaturefor environmental management and vegetation health monitor-ing International Journal of Advanced Remote Sensing and GIS3 433ndash445 2014

proc-iahsnet377572018 Proc IAHS 377 57ndash66 2018

66 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Hanke S H and Kwok A K On the measurement of Zimbabwersquoshyperinflation Cato J 29 353ndash364 2009

Hoko Z An assessment of quality of water from boreholes inBindura District Zimbabwe Phys Chem Earth 33 824ndash8282008

Jang C Shin Y Kum D Kim R Yang J E Kim S CHwang S I Lim K J Yoon J-K and Park Y S Assessmentof soil loss in South Korea based on land-cover type Stoch EnvRes Risk A 1ndash15 1996

Kamaludin H Lihan T Ali Rahman Z Mustapha M AIdris W M R and Rahim S A Integration of re-mote sensing RUSLE and GIS to model potential soil lossand sediment yield (SY) Hydrol Earth Syst Sci Discusshttpsdoiorg105194hessd-10-4567-2013 2013

Lawson E O Physico- chemical parameters and heavy metal con-tents of water from the mangroves swamps of logos lagon logosNigeria Advances in biological research 5 8ndash21 2011

Makwara E and Gamira D About to Lose all the Soil in ZakarsquosWard 5 Zimbabwe Rewards of Unsustainable Land Use Euro-pean Journal of Sustainable Development 1 457ndash476 2012

Mambo J and Archer E An assessment of land degradation in theSave catchment of Zimbabwe Area 39 380ndash391 2007

Merritt W S Letcher R A and Jakeman A J A review oferosion and sediment transport models Env Modell Softw 18761ndash799 2003

Met Meteorological data available at httpswwwwmointdatastatwmodata_enhtml| last access 3 March 2015

Mutowo G and Chikodzi D Erosion Hazard Mapping in theRunde Catchment Implications for Water Resources Manage-ment Journal of Geosciences and Geomatics 1 22ndash28 2013

Pettorelli N Vik J O Mysterud A Gaillard J-M Tucker CJ and Stenseth N C Using the satellite-derived NDVI to as-sess ecological responses to environmental change Trends EcolEvol 20 503ndash510 2005

Renard K G Foster G R Weesies G A McCool D and Yo-der D Predicting soil erosion by water a guide to conservationplanning with the revised universal soil loss equation (RUSLE)Agriculture Handbook Washington 703 1997

Rooseboom A and Engineers S B C Sediment transport in riversand reservoirs a Southern African perspective Water ResearchCommission 297192489 1992

Sawunyama T Senzanje A and Mhizha A Estimation of smallreservoir storage capacities in Limpopo River Basin using ge-ographical information systems (GIS) and remotely sensed sur-face areas Case of Mzingwane catchment Phys Chem Earth31 935ndash943 2006

Sumi T and Hirose T Accumulation of sediment in reservoirsWater storage transport and distribution UNESCO-IHE andEOLSS Publishers Co Ltd Paris France 224ndash252 2009

Teh S H Soil erosion modeling using RUSLE and GIS onCameron highlands Malaysia for hydropower development MSThe School for Renewable Energy Science Iceland 41 pp2011

USDA Procedure for computing sheet and rill equation on projectareas Technical Release No 51 (Geology) US GovernmentPrinting Office Washington DC 1972

Walling D and Fang D Recent trends in the suspended sedimentloads of the worldrsquos rivers Global Planet change 39 111ndash1262003

Whitlow R Mapping erosion in Zimbabwe a methodology forrapid survey using aerial photographs Appl Geogr 6 149ndash1621986

WHO Guidelines for drinking water quality Third edition incor-porating the first and second addenda volume 1 additions 2008

Wischmeier W and Smith D Predicting rainfall erosion lossesAgricultural Handbook 537 Agricultural Research ServiceUnited States Department of Agriculture 1978

Zinwa D R Assessment of Surface Water Resources of Zimbabweand Guidelines for Planning in Management ZINWA Researchand Data Department Ministry of Water Resources Developmentand Management Harare Zimbabwe Harare 59 pp 2009

Zwane N Love D Hoko Z and Shoko D Managing the im-pact of gold panning activities within the context of integratedwater resources management planning in the Lower ManyameSub-Catchment Zambezi Basin Zimbabwe Phys Chem Earth31 848ndash856 2006

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018

66 C Tundu et al Sedimentation and Its ImpactsEffects on River System and Reservoir Water Quality

Hanke S H and Kwok A K On the measurement of Zimbabwersquoshyperinflation Cato J 29 353ndash364 2009

Hoko Z An assessment of quality of water from boreholes inBindura District Zimbabwe Phys Chem Earth 33 824ndash8282008

Jang C Shin Y Kum D Kim R Yang J E Kim S CHwang S I Lim K J Yoon J-K and Park Y S Assessmentof soil loss in South Korea based on land-cover type Stoch EnvRes Risk A 1ndash15 1996

Kamaludin H Lihan T Ali Rahman Z Mustapha M AIdris W M R and Rahim S A Integration of re-mote sensing RUSLE and GIS to model potential soil lossand sediment yield (SY) Hydrol Earth Syst Sci Discusshttpsdoiorg105194hessd-10-4567-2013 2013

Lawson E O Physico- chemical parameters and heavy metal con-tents of water from the mangroves swamps of logos lagon logosNigeria Advances in biological research 5 8ndash21 2011

Makwara E and Gamira D About to Lose all the Soil in ZakarsquosWard 5 Zimbabwe Rewards of Unsustainable Land Use Euro-pean Journal of Sustainable Development 1 457ndash476 2012

Mambo J and Archer E An assessment of land degradation in theSave catchment of Zimbabwe Area 39 380ndash391 2007

Merritt W S Letcher R A and Jakeman A J A review oferosion and sediment transport models Env Modell Softw 18761ndash799 2003

Met Meteorological data available at httpswwwwmointdatastatwmodata_enhtml| last access 3 March 2015

Mutowo G and Chikodzi D Erosion Hazard Mapping in theRunde Catchment Implications for Water Resources Manage-ment Journal of Geosciences and Geomatics 1 22ndash28 2013

Pettorelli N Vik J O Mysterud A Gaillard J-M Tucker CJ and Stenseth N C Using the satellite-derived NDVI to as-sess ecological responses to environmental change Trends EcolEvol 20 503ndash510 2005

Renard K G Foster G R Weesies G A McCool D and Yo-der D Predicting soil erosion by water a guide to conservationplanning with the revised universal soil loss equation (RUSLE)Agriculture Handbook Washington 703 1997

Rooseboom A and Engineers S B C Sediment transport in riversand reservoirs a Southern African perspective Water ResearchCommission 297192489 1992

Sawunyama T Senzanje A and Mhizha A Estimation of smallreservoir storage capacities in Limpopo River Basin using ge-ographical information systems (GIS) and remotely sensed sur-face areas Case of Mzingwane catchment Phys Chem Earth31 935ndash943 2006

Sumi T and Hirose T Accumulation of sediment in reservoirsWater storage transport and distribution UNESCO-IHE andEOLSS Publishers Co Ltd Paris France 224ndash252 2009

Teh S H Soil erosion modeling using RUSLE and GIS onCameron highlands Malaysia for hydropower development MSThe School for Renewable Energy Science Iceland 41 pp2011

USDA Procedure for computing sheet and rill equation on projectareas Technical Release No 51 (Geology) US GovernmentPrinting Office Washington DC 1972

Walling D and Fang D Recent trends in the suspended sedimentloads of the worldrsquos rivers Global Planet change 39 111ndash1262003

Whitlow R Mapping erosion in Zimbabwe a methodology forrapid survey using aerial photographs Appl Geogr 6 149ndash1621986

WHO Guidelines for drinking water quality Third edition incor-porating the first and second addenda volume 1 additions 2008

Wischmeier W and Smith D Predicting rainfall erosion lossesAgricultural Handbook 537 Agricultural Research ServiceUnited States Department of Agriculture 1978

Zinwa D R Assessment of Surface Water Resources of Zimbabweand Guidelines for Planning in Management ZINWA Researchand Data Department Ministry of Water Resources Developmentand Management Harare Zimbabwe Harare 59 pp 2009

Zwane N Love D Hoko Z and Shoko D Managing the im-pact of gold panning activities within the context of integratedwater resources management planning in the Lower ManyameSub-Catchment Zambezi Basin Zimbabwe Phys Chem Earth31 848ndash856 2006

Proc IAHS 377 57ndash66 2018 proc-iahsnet377572018