Comparative study of streamflow and salt loadfrom selected catchments in the wheatbelt ofWestern Australia

R. B. Salama and G. A. Bartle

Technical Report No. 23/98, May 98

1

ABSTRACT

In the wheatbelt of Western Australia, stream flow and salt loads were comparedbetween catchments differing in vegetative cover and topographic shape.

In an uncleared catchment, stream flow in a first order stream was very low and onlyoccurred in times when heavy rain fell. Surface runoff was fresh (less than 500 mgl

-1

TSS) and discharge of saline groundwater did not occur. Therefore, annual salt loadwas less than 1 tonne.

By contrast, stream flow in a paired cleared catchment was continuous in winter andspring in all years. Stream salinity fluctuated between 2000 and 30 000 mgl

-1 TSS due

to the variable discharge of groundwater along a 4-km length of the stream channel.Annual salt load ranged from 500 to 4000 tonnes.

Hydrogeomorphic controls affect stream flow and salinity in third and fourth orderstreams. Reduction in flow and salt losses occurs in areas with low gradients whereflow is controlled by structures. Water evaporates and the concentrated brines infiltratedownwards causing highly saline groundwater bodies to develop.

2

INTRODUCTION

Stream and land salinisation is a major problem in southwest Western Australia. Morethan 4430 km

2 of previously arable land in the south-west of Western Australia is now

affected by secondary salinity (George, 1990). Less than 50% of the divertible surfacewater resources remain fresh (Western Australian Water Resources Council, 1986).

Detailed studies of streams and catchments have been carried out in the Darling Range,where most of Perth water supplies are obtained from dams (Peck and Williamson,1987; Schofield and Ruprecht, 1989). Detailed hydrogeological studies have also beenconducted in the wheatbelt (George, 1992; McFarlane and George, 1992; Salama etal., 1993a-e). However, as yet no detailed studies of streamflow and salt loads havebeen conducted in the wheatbelt catchments.

This work is mainly aimed at providing a new set of hydrological data for catchmentsin the wheatbelt, and to answer some of the questions relating to stream and landsalinisation. Other concerns include comparing streamflow and salt load fromuncleared and cleared catchments. The relationship between groundwater salinity andgroundwater discharge and their effect on salt load is also discussed.

DESCRIPTION OF CATCHMENTS

Wallatin Creek Catchment

The catchment is located northwest of the Doodlakine town site and has a total area ofabout 250 km

2 (Fig. 1a&b). The catchment is relatively long and narrow (30 km long

and 8-12 km wide). Elevation at the catchment divide is about 390 m and falls 130 mto the confluence of the major drainage line, the Yilgarn River.

A detailed study of the drainage pattern in Wallatin Creek catchment shows that, in thenorthern half of the catchment, the main stream follows a north to northwest direction,whereas the tributaries of the main stream follow a northeast direction. The tributariesin the southern half of the catchment follow an east-west direction.

Logs of wells drilled in the catchment (Fig. 2) show that there are three aquifersystems. The first is an unconfined aquifer which is present above a clay layer in thesandplain and valleys; the second is a semiconfined aquifer below this clay layer andthe third aquifer is a deeper, semiconfined to confined regional aquifer which occurs inthe weathered zone above the bed rock and extends into the sediments of the relictchannels in the valleys and the flanking areas.

East Perenjori Catchment

The catchment is located 30 km east of Perenjori and has an area of 139 km2 (Fig. 1c).

The catchment takes the form of a narrow elongated basin (23 km long and 5-8 kmwide). Elevations range from 270 m to 366 m above mean sea level.

3

In the East Perenjori catchment surface water drains northeast into Mongers Lakethrough a main channel which originates in the upper area of the southern part of thecatchment (Fig. 1c). The channel follows a northeast lineament which passes through azone constricted by basement rock and along the central area of the catchment wherethe gradient is very subdued. The stream enters Mongers Lake through an incisedchannel in red loamy sand with layers of calcrete. A hard pan layer, which is usuallyencountered between 2-5 m, plays an important role in the shallow groundwatermovement in the valley floor of the catchment (Fig. 2). Where shallow sandy layers arepresent on top of the hardpan, a perched aquifer develops during the wet season. In theabsence of the hardpan, a shallow unconfined aquifer exists on top of the clay layer. Asecond unconfined aquifer which extends below the sandplain and over most of thealluvial channels can also become semiconfined below clayey layers. A thirdsemiconfined to confined aquifer which extends over most of the catchment is formedof highly weathered material near the catchment divide and fluvial sediments orweathered material in the valleys.

The climate in both catchments is Mediterranean with hot dry summers and mild wetwinters. The average annual rainfall ranges from 310 mm at East Perenjori to 350 mmat Wallatin Creek.

MATERIALS AND METHODS

Streamflow and salt load in two catchments in the wheatbelt of Western Australia havebeen monitored at several cross sections for the period from 1988 to 1992 (Fig 3 andTable 1). The sections were selected to enable comparisons of streamflow and salt loadto be made between a cleared (Wimmera section) and an uncleared subcatchment(Durokoppin reserve section), between constrained groundwater flow (Wallatin Roadsection in Wallatin Creek catchment) and unconstrained flow in a broad valley(Goldfield road section in Wallatin Creek catchment), and between flow in narrow-defined channels (Rabbit Proof fence in East Perenjori) and broad valleys (Mason roadin East Perenjori). The four sections in Wallatin Creek and the two sections in EastPerenjori catchment were also used to compare changes in flow and salinity in thestream at points starting upstream and ending downstream in the catchment. Eachsection was selected to cross a straight stretch of the river (Fig. 1 and Table 2).

Vegetation in the uncleared (Durokoppin) catchment consists of a mosaic of perennialwoodland, mallee, shrub and heathland.

Measurements

Streamflow and surface water quality

Gauging at each section was carried out in stilling wells using conductance probes andrecorders. Measurements were taken every 30 minutes and recorded. In WallatinCreek, stage height/velocity measurements were taken during low flow for calibration,but most of the rating curve was constructed using Manning’s formula. In Durokoppinreserve a V notch weir was constructed to measure the flow. The sections in EastPerenjori crossed a newly constructed trapezoidal drain.

4

Streamflow samples were collected daily between autumn and spring using automaticsamplers installed in each section. The samples were analysed for chloride (Cl) andbromide (Br). Streamflow and salt load were calculated using HYDSYS (1992).

In May 1989 following the onset of winter rainfall when about 50 mm of rain fell,surface water samples were collected from 40 sites along the tributaries and maindrainage lines of Wallatin Creek catchment. At each site surface water was sampledjust upstream and downstream of the junction to assess change in water quality fromthe contribution of each stream. The samples were analysed for sodium (Na), chloride(Cl) and total soluble salts (TSS). Only TSS is reported in this study.

Groundwater flow and quality

Monitoring wells were drilled in each cross section (Fig. 2) to define the groundwatercomponents of the stream and to calculate groundwater flow across the section. Eachwell was fitted with a conductance probe and a recorder which measured water levelsevery hour and recorded any change to the previous reading. Groundwater sampleswere collected from each well, before and after the wet season. Samples were analysedfor major cations and anions, EC and pH.

In this paper groundwater flow refers to groundwater not discharging at the surface.Groundwater flow was calculated using Darcy's formula, and the cross section areamethod.

Rainfall

Each section had been installed with automatic rain gauges. A weather stationmeasuring rainfall, temperature, short and long wave radiation, wind velocity andbarometric pressure was also installed in the Wimmera subcatchment in Wallatin Creekcatchment. Rainfall samples were collected for chemical analysis.

RESULTS

Wallatin Creek catchment

Stream flow

In the uncleared catchment (Durokoppin reserve), stream flow only occurred acrossthe section after periods of heavy rain (Fig. 4b). In 1989, a year of above averagerainfall, stream flow in winter and spring was less than 0.01 m3s-1 with a brief rise to0.1 m3s-1. A peak flow of 2.5 m3s-1 was recorded in June following high intensityrainfall. In 1990, when rainfall was average, stream flow was recorded on threeoccasions in winter at a rate less than 0.002 m3s-1. No stream flow was recorded in1991 when rainfall was below average (Fig. 4b).

By contrast, in a paired catchment that had been cleared (Wimmera), stream flowacross the section was higher in all years and continued throughout the wet season(Fig. 4a).

5

In the central area of the catchment, stream flow across the Wallatin Rd section (Fig.4c) was higher, more frequent and continued for longer than the flow at the section atthe lower end of the catchment (Goldfields Rd section) (Fig. 4d). At the Wallatin Rdsection the flow was above 0.01 m3s-1 for several months, with flows frequently risingabove 0.1 m3s-1. In 1989 stream flow was continuous from May to October, whereasat the Goldfields Rd section flow only occurred from May to mid-August (Fig. 4d).

Streamflow quality

The results from the detailed sampling of May 1989 (Fig. 5) showed that stream waterquality in the northern upstream parts of the catchment was relatively fresh in both theuncleared and cleared parts of the catchment (300-400 mg l-1). TSS from the reservealso showed that stream salinity was slightly increased by a stream which enters thereserve from the cleared areas at the east. Although TSS in the stream water in thecleared subcatchment (Wimmera) started at low levels at the top of the subcatchment(400 mg l-1) it increased to very high levels before reaching the subcatchment outlet(27 000 mg l-1). TSS increased in the stream at the central part of Wallatin Creekcatchment near Wallatin Rd (20 600 mg l-1). Further downstream, TSS decreased to19 400 mg l-1 near the Goldfield section, despite the fact that the main stream receivessome saline water from its tributaries.

Stream load

TSS of the stream water from the uncleared catchment (Durokoppin reserve) wasalways less than 500 mg l-1 and the annual export from the reserve catchment was lessthan 1 ton in both 1989 and 1990, and none in 1991 (Fig. 6). On the other hand, TSSof stream flow from the cleared catchment (Wimmera) was always above 10 000 mg l-1, with the result that the salt export was 523, 3912 and 429 tonnes for 1989, 1990and 1991, respectively (Fig. 6). TSS in the stream water was also much higher in thecentral part of the catchment (Wallatin Rd) than further downstream (Goldfield Rd).This resulted in a much higher salt load in the stream at Wallatin Rd section than at theGoldfield Rd section, i.e., 4150, 20 274 and 13641 tonnes at Wallatin Rd, compared to308, 5519 and 3974 tonnes for Goldfield Rd, for 1989, 1990 and 1991, respectively.

Groundwater flow

The results show that groundwater flow is relatively small at the upper reaches of thecatchment and increases progressively further downstream. Groundwater flow fromthe cleared subcatchment (Wimmera) was estimated to range between 5 m3d-1 insummer to 10 m3d-1 in winter. Groundwater flow from the uncleared subcatchment(Durokoppin Reserve) was calculated to be less than 1 m3d-1 for the small crosssection along which the weir was constructed.

Further downstream at the broader stretch of the stream (Wallatin Rd section),groundwater flow ranged from 40 m3d-1 in summer to 80 m3d-1 in winter. At theGoldfield Rd section (near the catchment outlet) groundwater flow was higher, rangingfrom 60 m3d-1 in summer to 120 m3d-1 in winter.

6

East Perenjori catchment

Streamflow

Streamflow through the Mason section was more frequent and continued for longerperiods of time than at the Rabbit Proof section (RPS) (Fig. 7). At the same time,discharge rates at the Mason section were always higher than at the RPS. Whiledischarge rates at the RPS were, on average, less than 0.02 m3 s-1, the rates werealways above 0.1 m3 s-1 at the Mason section.

Streamflow quality and salt load

In contrast to streamflow, surface water salinity of the RPS fluctuated between verylow and very high values, while the Mason section salinity was always high (Fig. 8). Inall the years measured, salt export was higher from the Mason section than from theRPS. Salt load at Mason section was 38800, 8800 and 420 tonnes for 1989, 1990 and1991 respectively, compared to the load at the RPS which was 3400, 4300 and 220tonnes for the same years.

Groundwater flow

Estimated groundwater flow from Mason section ranged from 60 to 120 m3d-1compared to the RPS which was between 5 m3d-1 and 10 m3d-1.

DISCUSSION

Streamflow characteristics

In the uncleared catchments of the wheatbelt major drainage lines are depressionscovered by trees and perennial shrubs (Salama, 1993a). The low stream flow recordedin the uncleared catchment is a reflection of the high water use of eucalypt trees andperennial shrubs with the consequent reduction in surface runoff and recharge into thegroundwater. Annual interception rates of trees generally fall between 10 and 37 percent of annual rainfall (Greenwood, 1992). In the Durrokoppin reserve transpirationhas been found to average about 0.5 mmd-1 in trees from woodlands (Farrington et al.,1992), and evaporation from the heathland and shrublands frequently exceeded 1.0mmd-1 (Farrington et al., 1992). The low flow is consistent with findings that inuncleared catchments there was virtualy no runoff except when heavy rain fell.Following clearing, the increased stream flow is the result of decreased water use byannual crops and pastures which increases runoff and recharge. The higher rechargeinto the aquifer ultimately leads to rising groundwater levels and increasedgroundwater discharge into the stream, which during the drier months becomes amajor component of stream flow.

Flow in the stream in the central area of both catchments was found to be less than thatfurther downstream near the catchment mouth. The reduction in flow can result fromthree mechanisms causing water loss. These are (a) increased evaporation followingsurface ponding behind natural obstructions such as dunes or basement highs orartificial barriers caused by roads and embankments; (b) increased evaporation when a

7

change in slope reduces the stream gradient and slows the flow; and (c) increasedwater drainage into aquifers resulting from an increase in the transmissivity or width ofchannel. Water transmitted through the aquifer can be discharged back into the streamif the aquifer transmissivity or the channel shape changes.

In the Wallatin Creek and East Perenjori catchments, the reduction in stream flowoccurs when the wide flat valleys are flooded and water ponds in flat areas behindobstructions caused by basement highs running across the stream beds downstream ofthe Wallatin Rd and Mason sections. The basement highs have been shown to impedeboth surface and groundwater flow with the result that groundwater salinities are thehighest in the catchments (Salama et al., 1993a). In Wallatin Creek, some water lossthrough groundwater underflow may occur beneath the Goldfields Rd section becausethe transmissivity of the aquifer is relatively higher than at the Wallatin Rd section (dueto increase in thickness of the aquifer material which have the same hydraulicconductivty data). Loss from this mechanism is not significant in the East Perenjoricatchment because the underflow beneath the RPS is much less than under the Masonsection.

Salt export

Previous studies have examined the relationships between rainfall, salt storage, streamsalinity and salt load in catchments of the Darling Range and found that the salinity ofstreams in catchments increases as annual rainfall decreases and the salt storageincreases (Schofield and Ruprecht, 1989; Johnston et al., 1980; Peck and Williamson,1987). The results of this study show that stream salinity and salt export in the wheatbelt catchments show a similar trend to those in the Darling Range. The difference isthat in the wheat belt groundwater salinities and salt storage are higher because therainfall is lower and there are different hydrogeological patterns controlling thedistribution, storage and mobilisation of salt (Salama et al., 1994).

This study also shows that export of salt is controlled mainly by groundwaterdischarge. In the uncleared subcatchment (Durrokoppin) no salt is exported despite thepresence of highly saline groundwater because the water level is still 7 m deep andthere is no groundwater discharge. The small salt export recorded comes from leachingof salt into surface runoff during heavy rainfall. By comparison, salt export from thesmall, cleared subcatchment (Wimmera), which accounts for almost 20 per cent of thetotal export from the Wallatin Creek catchment, comes from groundwater dischargeinto the stream.

In the cleared catchments, groundwater levels are at the surface in most of the low-lying areas, and groundwater discharge is taking place along the channels, upstream ofstructures. In order to account for the salt load in the stream in the Wimmerasubcatchment, groundwater discharge has to take place along a 4 km stretch of thestream channel. The minimum amount of groundwater discharge which can cause thisamount of salt load is approximately 80-120 m3d-1, for a groundwater salinity of 0.03tonnes m3.

Another finding previously unreported is the loss of salt from the stream in the broadvalleys in the centre of the catchments, which occurred as a result of the reduction in

8

stream flow described earlier. The loss usually took place in hydrogeomorphic areaswhich are characterized by lower slope compared to the upstream area. The streamchannels are usually less defined and large areas of the landscape are flooded.

The cause of the extremely high salinity recorded in the groundwater in these areas inthe centre of the two catchments downstream from the Wallatin Rd and Masonsections has been attributed to concentration of groundwater following diffusivedischarge upstream from a geological structure (Salama et al., 1993a). However,another mechanism suggested by Wooding (1989) which is based on the density drivenflow in lake beds may also have contributed to the increase in salinity. As water isponded in flat areas behind a geological structure, water evaporates leaving behind adense saline layer. Leakage occurs by gravity along a saline "finger" created by theinstability of the more dense saline layer overlying the less dense saline layer. Thedownward movement of the saline finger will be balanced by an upward movement ofthe same volume of less dense water. As this process continues salinity accumulates inthe aquifer.

The increase in groundwater discharge will expand the areas affected by salinity in thevalley floor of the catchments in two ways. As discharge increases the stream flow,more of the lower lying areas will be flooded by saline water. As the water evaporatesthe area will become more saline. Concurrently groundwater will continue to rise withthe result there will be more diffusive discharge of saline groundwater in the valleyfloor. The extent of the area affected by salinity will depend on the hydrauliccharacteristics of the floor, the volume of groundwater discharge and the type of thesalt crust which develops (Salama et al., 1993d and e).

CONCLUSIONS

Salinities in streams in the wheatbelt of Western Australia have reached very highlevels (up to 30 000 mgl-1) and are rising continuously. Much of the rise in salinity isdue to the increasing discharge of saline groundwater following clearing. The resultsshow that in uncleared subcatchments stream flow only occurs after periods of heavyrainfall and is low in salinity. Annual salt load is less than 1 tonne. The high water useof the perennial vegetation kept the water levels well below the surface and preventedany groundwater discharge. Clearing a similar subcatchment greatly increased the flow,salinity and salt export of the stream with the result that the annual salt load fluctuatedbetween 500 and 4000 tonnes and contributed about 20 per cent of the salt exportfrom the entire catchment. Much of the high salt load came from saline groundwaterdischarging along an extensive length of the stream channel. Hydrogeomorphiccontrols were found to reduce streamflow and salt load in the broad valleys present inthe central area of the catchments.

9

REFERENCES

Farrington, P., Salama, R.B., Watson G.D. and Bartle G. 1992. Water use ofagricultural and native plants in a Western Australia Wheat Belt catchment.Agricultural Water Management 22:357-367.

George, R.J. 1990. The 1989 saltland survey. J. Agric. W. Aust. (4th Series) 31:159-66.

George, R.J. 1992. Hydraulic properties of groundwater systems in the saprolite andsediments of the wheatbelt, Western Australia. J. Hydrol. 130:251-278.

Greenwood, E.G.A., Klein, L., Bresford, J.D. and Watson G.D. 1985. Differences inannual evaporation between grazed pasture and Eucalyptu s species in plantationson a saline farm catchment. J. Hydrol. 78:261-278.

Greenwood, E.A.N. 1992. Deforestation, revegetation water balance and climate: anoptimistic path through the plausible, impracticable and controversial Advances inBioclimatology Vol. 1 pp 89-154. Springer-Verlag.

HYDSYS. 1992. Time series data management program. Hydsys Ltd, Canberra.

Johnston, C.D., McArthur, W.M. and Peck, A.J. 1980. Distribution of soluble salts insoils of the Manjimup woodchip licence area, Western Australia. CSIRO, LandResources Management Technical Paper 5, pp. 29.

McFarlane, D.J. and George, R.J. 1992. Factors affecting dryland salinity in twowheatbelt catchments in Western Australia. Aust. J. Soil. Res. 30:85-100

Peck, A.J. and Williamson, D.R. 1987. Effects of forest clearing on groundwater. J.Hydrol. 94:47-66.

Ruprecht, J.K and Schofield, N.J. 1989. Analysis of streamflow generation followingdeforestation in southwest Western Australia. J. Hydrol. 105:1-17.

Salama, R.B. 1994. The evolution of salt lakes in the relict drainage of the YilgarnRiver of Western Australia. In: Renaut, R. and Last, W. (eds) Sedimentology andGeochemistry of Modern and Ancient Saline Lakes. SEPM (Society forSedimentary Geology) Special Publication No. 50:189:199.

Salama, R.B. and Hawkes, G.E. 1993. Surficial geology and stratigraphy of the Wallatin Creek area: a Western Australian model of Cainozoic sedimentary deposition on theYilgarn craton. CSIRO Div. of Water Res. Divisional report 93/4.

Salama, R.B., Bartle, G.A. and Farrington, P. 1994. Water use of plantation Eucalyptuscamaldulensi s estimated by groundwater hydrograph separation techniques and heatpulse method. J. Hydrol. 156: 163-180.

10

Salama, R.B., Farrington, P., Bartle, G.A. and Watson, G.D. 1993a. The role ofgeological structures and relict channels in the development of dryland salinity in thewheat-belt of Western Australia. Aust. J. Earth Sci. 40:45-56.

Salama, R.B., Farrington, P., Bartle, G.A. and Watson, G.D. 1993b. The chemicalevolution of groundwater in a first-order catchment and the process of saltaccumulation in the soil profile. J. Hydrol. 143:233-258.

Salama, R.B., Farrington, P., Bartle, G.A. and Watson G.D. 1993c. Distribution ofrecharge and discharge areas in a first-order catchment as interpreted from waterlevel patterns. J. Hydrol. 143:259-277.

Salama, R.B., Laslett, D. and Farrington, P. 1993d. Predictive modelling ofmanagement options for the control of salinity in Cuballing catchment. J. Hydrol.145:19-40.

Salama, R.B., Farrington, P., Bartle, G.A. and Watson G.D. 1993e. Salinity trends inthe wheatbelt of Western Australia: Results of water and salt balance studies fromCuballing catchment. J. Hydrol. 145:41-63.

Schofield, N.J. and Ruprecht, J.K. 1989. Regional analysis of stream salinisation insouthwest Western Australia. J. Hydrol. 112:19:39.

Western Australian Water Resources Council. 1986. Water Resources PerspectivesWestern Australia: Report 2, Water Resources and Water use summary of data forthe 1985 National survey. Publ. No. WRC 7/86.

Wooding, R.A. 1989. Convective regime of saline groundwater below a "dry" lakebed. CSIRO Centre of Environmental Mechanics Technical Report No. 27. 20 pp.

11

Table 1

Location and characteristic of sections

Catchment Section Numberand name

Catchmentorder

Characteristic of section

Wallatin Creek 1. Wimmerra First order cleared catchment2. Durrokoppin First order uncleared catchment3. Wallatin Rd Fourth order centre of catchment4. Goldfield Rd Fourth order outlet of catchment

East Perenjori 5. Rapid Proof Rd Third order outlet of catchment6. Mason Rd Third order centre of catchment

Table 2

Cross section details

Section number andname

Width Depth Gradient

1. Wimmerra 12.0 0.44 0.00772. Durrokoppin 2.6 0.55 0.10703. Wallatin Rd 12.8 1.58 0.00274. Goldfield Rd 13.3 1.30 0.00205. Rapid Proof Rd 3.1 1.18 0.00166. Mason Rd 2.85 1.20 0.0019

12

Table 3

Monthly salt loads (tonnes) for each section for the period 1989 - 1990

YEAR1989

Sec.No.

JAN FEB MAR APR MAY JUN JULY AUG SEP OCT NOV DEC TOTAL

1 266 207 48 >1 >1 0 5232 >1 0 0 0 0 13 1130 1395 1567 38 20 41504 308 0 0 0 0 3085 10413 16637 7498 346 0 0 388716 1154 1384 866 0 0 0 3404

Year1990

Sec.No.

JAN FEB MAR APR MAY JUN JULY AUG SEP OCT NOV DEC TOTAL

1 0 0 1 >1 1 3 13 43 46 3747 10 47 39122 0 0 0.4 0.2 0 0 0 0 0 0 0 0 13 2786 7 1051 1638 1216 1514 2041 2569 1948 1207 147 120 202744 1608 2210 769 34 5 46 442 335 >1 70 0 0 55195 2550 4398 0 206 0 121 194 329 442 155 476 0 88716 243 416 0 0 111 888 721 1039 209 669 0 0 4296

Year1991

Sec.No.

JAN FEB MAR APR MAY JUN JULY AUG SEP OCT NOV DEC TOTAL

1 37 7 17 14 10 59 125 111 34 15 4292 0 0 0 0 0 0 0 0 0 03 205 17 174 757 1354 1520 3051 3404 3159 136414 1 0 63 0 59 498 2002 1292 60 39745 57 0 23 120 141 0 79 5 3 4286 0 0 0 0 0 10 216 216

Location of catchments

1. Wallatin Creek catchment2. East Perenjori catchment

Approximate boundaryof the Wheat Belt

0 200

600Isohyet of averageannual rainfall (mm)

Locality

Aust.

Perth

N

1200

1000

800

2502Perenjori

1200

500

300

400

Merredin1

Geraldton

kilometres

a)

Fig. 1a Location map, showing location of Wallatin Creek and East Perenjoricatchments in the wheatbelt of Western Australia

2

1

3

4

metres

0 40002000

N

YilgarnRiver

BaandeeLakes

Piezometer / well

Catchment boundary

Current drainage

b)

Fig. 1b Location map, showing location of the cross sections in Wallatin Creek catchment:(1) Wimmera section, (2) Durokoppin Reserve section, (3) Wallatin Road section, and(4) Goldfield Road section

5

6

0 40002000

metres

Current drainage

N

MongersLake

Catchment boundary

Piezometer / well

c)

Fig. 1c Location map, showing location of cross sections in East Perenjori catchment:(5) Rabbit Proof Fence section, and (6) Mason Road section

(a)

Alluvial

Sandplain

Bonser's claystone

Peat

Extremely weathered bedrock

Weathered bedrock

36 81

8538

37

36

35

34

33

0 200 m

m A

HD

(b)

Alluvial

Sandplain

Colluvium

Bonser's claystone

Peat

Kodj Kodjin sandstone

Forsyths conglomerate (?)

Extremely weathered bedrock

Weathered bedrock

Bedrock

295

285

275

265

0 200 m

104

103102

22101

100

m A

HD

Fig. 2 a-b Geological cross sections for (a) Wimmera and (b) Wallatin Road(modified from Salama and Hawkes, 1993)

(c)

115 109 114

mA

SL

270

260

250

240

230

Alluvial

Sandplain

Bonser's claystone

Kodj Kodjin sandstone

Forsthys conglomerate (?)

Extremely weathered bedrock

Weathered bedrock

Bedrock

111 110

0 400 m

(d)

Fig. 2c-d Geological cross sections for (c) Goldfield Rd and (d) Mason Rd(modified from Salama and Hawkes, 1993)

0.7K 0.10.3 1K0.80.60.40.2

15

10

5

1

0.5

metr

es

metr

es

Streamsection

Regionalsection

W

W

E

E

5 10 15 metres

6

4

2

200 400 600 800 1K

metr

es

0.5

1

metr

es

0 5 metres

Streamprofile

Regionalsection

E

E

W

W

1K 1K 2K

Curr

ent st

ream

5

10

15

20 Regionalsection

5 10 15 metres

1

0.5

metr

es

metr

es

Streamprofile

EW

EW

a)

b)

c)

Fig. 3a-c Details of regional and stream cross sections for (a) Wimmera, (b) Wallatin Rd, (c) Goldfield Rd

1K 500 m 500 m 1K

W

W

E

E

41.8 cm

MS5 MS4

49.8 22.3

0.6 m

2.85

1.7

1.28

MS3

10.291.4 m

MS2

100 m10.9 cm

100 m

201.6 m172.1 m

RP11.18RP2

100 m26.42 m 21.9 m

100 m

3.1

1.95

0.850.33

1.26

N S

d)

e)

Fig. 3d-e Details of regional and stream cross sections for (d) Mason Rd, and(e) Rabbit Proof Fence (stream section only)

0.1

0.01

0.001

0.0001337.24Cumecs Cumecs

MetresMetres

mm.mm.

337.44

337.64

337.84

338.04

338.2480

44

8

335.4

335.6

335.8

3368

44 336.2

336.480 1

0.1

0.01

0.001

CumecsMetres

mm.

mm.

mmmm

10

1

0.1

0.01

Rd section in Wallatin Creek catchment

0.001

levels in wells (m) for (a) Wimmera section, (b) Durokoppin Reserve, (c) Wallatin Rd, and (d) Goldfield

Cumecs

CumecsCumecs

Metres

MetresMetres290.88

Fig. 4 Cross sections showing the relationship between rainfall (mm), stream discharge (m3s-1), and water

291.08

291.28

291.48

291.68

291.8880

44

8

0.01

0.1

1

1080

44

8

261.9

262.3

262.7

263.1

263.5

263.9

19891989 19901990 19911991 19921992

a)

c) d)

b)

Lake Baandee17.5

19.9

20.820.149.8

19.4

19.0

18.9 12.0

18.119.8

19.3

18.415.3

15.0

17.4

23.214.8

31.123.8

27.5 9.418.519.8 0.3

0.30.3

0.2

0.2

0.5

0.3

Sampling point

Nature reserve

Catchment boundary

Drainage line

20.618.1

31.2

32.623.3

0.4

1.3

0.6

Fig. 5 Location of detailed sampling points in Wallatin Creek catchment, showing values of EC in mS m–1

100000

80000

60000

40000

20000

0

hsgrsg

wsgdsg

1989 1990 1991

100

80

60

40

20

0

Tonn

es/D

ayTo

nnes

/Day

0.5

0.4

0.3

0.2

0.1

0

a)

salt load for (b) Wimmera and (c) Durokoppin Reserve

b)

Reserve section; wsg, Wallatin Rd section; dsg, Goldfield Rd section. Figure also shows

c)

Fig. 6 Stream salinity in Wallatin Creek catchment (a). hsg, Wimmera section; rsg, Durokoppin

mg/L

800

640

480

320

160

0

600

500

400

300

200

100

0199119901989

Ton

nes/

Day

Ton

nes/

Day

d)

e)

1800

4500

Fig. 6d-e Salt load for Wallatin Rd (d) and Goldfield Rd (e).

1

0.1

0.01277.5

277.9

278.3

278.7

279.1

279.580

44

8

Cumecs

Metres

mm

10

1

0.1

0.01

0.001289.8

290.2

290.6

291

291.4

291.880

44

8

1989 1990 1991 1992Cumecs

Cumecs

Metres

Metres

mm

mm

a)

b)

Fig. 7 East Perenjori sections showing the relationship between rainfall (mm), stream discharge(m3s–1) and groundwater levels (m) in wells. (a) Mason section and (b) Rabbit Proof Fence

80000

64000

48000

32000

16000

0

Salin

ityCu

mecs

Cume

cs

1

1

0.1

0.1

0.01

0.01

0.001

0.001

section and (c) Rabbit Proof Fence section

b)

a)

1989 1990 1991

c)

Fig. 8 (a) Stream salinity for East Perenjori; stream discharge (m3s-1) for (b) Mason

199119901989

0

Ton

nes/

Day

200

400

600

800

1000

0

400

800

1200

1600

2000

1989 1990 1991

Ton

nes/

Day

d)

e)

Fig. 8d-e Salt load for Mason section (d) and Rabbit Proof Fence (e)