The Study on the Groundwater Resources …open_jicareport.jica.go.jp/pdf/11873395_06.pdfThe Study on...
Transcript of The Study on the Groundwater Resources …open_jicareport.jica.go.jp/pdf/11873395_06.pdfThe Study on...
The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin
-Supporting Report- Chapter 9 Hydrogeology
9-24
9.5 Productivity Analysis and Hydrogeological Map
9.5.1 Productivity Analysis
Productivity distribution of groundwater was presumed by the geological condition, yield of existing
wells, rainfall, topographic feature and the result of satellite image analysis
(1) Yield of existing wells
The yield value in the borehole catalogue was referred by its distribution map. In this regard,
analysis method of pumping test was doubtable mentioning in the borehole catalogue. For example,
although the yield value was very high, if the drawdown was much deeper than water struck, it
could be considered that the test was conducted to exceed the possibility of aquifer.
The yield distribution map is shown in Figure 9-9. Although the data distribution is uneven and the
data are including some error, the distribution map can show the feature of productivity in whole
IDB area relatively.
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0 30 60 90 12015Kilometers
µ
Legend"/ Region Capital
!. District Capital
Borehole Location
MajorFaults
Lake
SubBasins
Yield (m3/h) - 1
1.0 - 2.0
2.0 - 3.0
3.0 - 4.0
4.0 - 5.0
5.0 - 6.5
6.5 - 8.0
8.0 - 10.0
10.0 - 15.0
15.0 - 20.0
20.0 -
Figure 9-9 Well Yield Distribution of Existing Wells
The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin
-Supporting Report- Chapter 9 Hydrogeology
9-25
(2) Rainfall
Average annual rainfall for 30 years up to 1970th was referred. Details in Chapter 2.
(3) Topography
Recharge areas or direction of flow are read from topography. Top of mountain and steep slope area
are considered to be impossible to develop groundwater. These areas are eliminated as masked area.
(4) Satellite Image Analysis
Mainly VSW index map was referred for this analysis. Comparison between the VSW index map
and the existing geological map can be used for the interpretation of Productivity analysis.
In the VSW map, Blue shows water (moisture), Green shows vegetation, Red shows soil, basically.
Other colors should be interpreted. Especially, in this area, lakes and swamps show the different
colors. Table 9-8 Interpretation of VSW Map
Groundwater productivity was estimated from geological condition and above data. Productivity
distribution map is shown in Figure 9-10. The feature of productivity distribution is assembled in
Table 9-9.
Color Phenomenon Representative place
Blue Water Lake Babati, Lake Singida, some other small lakes
Dark green Wet forest Several part (not large area) Light green Forest, congestion of trees Uyui, Sikonge, Manyoni Orange Sand area Around Singida
Bare land Sediment in Massai Steppe Red Volcanic ash Northern part of IDB
Purple-red Saline lake, swamp Lake Natron, Lake Eyasi, Lake Manyara, Bahi swamp, part of Bubu river
Mbuga clay Several places at locally low area Purple Basaltic rocks Around volcanoes
The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin
-Supporting Report- Chapter 9 Hydrogeology
9-26
Fig
ure
9-10
G
roun
dwat
er P
rodu
ctiv
ity
Cla
ssif
icat
ion
for
Hyd
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olog
ical
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eter
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end
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y go
od (
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d (8
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r A (
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3/h)
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r B
(3
- 7
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h)
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r C
(2
- 4
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h)
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r (1
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y P
oor
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ati
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o
The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin
-Supporting Report- Chapter 9 Hydrogeology
9-27
Table 9-9 Groundwater Productivity Condition in IDB Estimated
Productivity (m3/h)
Place Description
Excellent over 20 Along large scale fault Fracture zone related to the Great Rift Valley System
The belt area from west of Mbulu district through east of Hanang disrtrict and west of Babati district to Kondoa district
Boundary area between granitic rock area and Usagaran metamorphic rock area.
Foot of volcanoes Much amount of recharge is expected from the mountains
Very Good 10 - 20
The south of Loliondo Much rainfall in Usagaran metamorphic rock area
The west of Shinyanga town, around Maswa town, north of Tinde village, south of Igunga district, west of Singida rural district, northwest of Dodoma town, around Loliondo town. Uyui and Sikonge district
The place which has many fault or lineament and inselberg in granitic rock area
Karatu district Much amount of recharge is expected from Ngorongoro mountain
Good 8 - 15
Around Loliondo Much rainfall in Usagaran metamorphic rock area
Kishapu district, Igunga district, the north of Igunga district
Most of granitic rock area
Around Kiteto town, Mbulu district
Hilly area of Usagaran metamorphic rockFair A 5 - 10
Around Lake Manyara, Lake Manyara sediment has groundwater recharge from surounding mountain.
Between Maswa and Kishapu districs
Plateau of granitic area has low recharge of groundwater
Bahi lowland area Clayey sand Fair B 3 - 7 southern part of Monduli district and the northeast of Babati district
Usagaran metamorphic rock (Xs-a)
Eastern part of Meatu district Fresh granitic rock is distributed Lowland surrounding Manonga river, Lake kitangiri, Lake Eyasi, and Wembere swamp
Clayey sediment Fair C 2 – 4
Masai Steppe Less rainfall Shinyanga Rural district Less recharge of groundwater Oldubai to Lake Natron Less recharge of groundwater Poor 1 – 3 West of Longido Volcanic ash West of Uyui district, east of Meatu town
Less fracture of granitic rock
Very Poor 0.5 – 1.5 Lowland surrounding Kitumbeine mountain
High evaporation
The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin
-Supporting Report- Chapter 9 Hydrogeology
9-28
9.5.2 Hydrogeological Mapping
Adding the geological distribution, water quality and water level to the productivity distribution,
Hydrogeological Map was completed. The hydrogeological map is shown in Figure 9-11.
Mbuga clay areas which become marsh in rainy season are shown in the map by grey in colour. It is
difficult to construct a water supply facility in this area.
Steep slope areas, which are cliff of fault and top of mountain area, are shown as impossible area for
development of groundwater.
Groundwater potential by district is roughly evaluated based on the hydrogeological map. Score of the
evaluation is divided into three. The criteria are shown in Table 9-10. The result is shown in Table
9-11. According to this result, Karatu district and Babati district have high potential for groundwater
development.
Detailed potential evaluation is discussed in chapter 5.
Table 9-10 Criteria of the Evaluation of Groundwater Potential
Score
Item
Good Fair Poor
Drilling depth Less than 80 m 80 - 150 m Over 150 m
Static Water
LevelLess than 20 m 20 - 40 m Over 40 m
Productivity Over 10 m3/h 2 - 10 m3/h Less than 2 m3/h
Salinity Less than 100 mS/m 100 - 300 mS/m over 300 mS/m
Fluoride Less than 1.5 mg/l 1.5 - 4.0 mg/l Over 4.0 mg/l
The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin
-Supporting Report- Chapter 9 Hydrogeology
9-29
Table 9-11 Outline of Groundwater Development Potential by District
Region District Drilling depth
SWLProduc-
tivity Salinity Fluoride Comment
MonduliNorthern part: relativeru good Southern part Poor
Arumeru High fluoride contents
NgorongoroNothern highland and Southern part are goodEastern and western lowlands are poor
Arusha
Karatu
BabatiHighland is good, Magugu area has saline groundwater
Mbulu
HanangAround Mt. Hanang: high fluoride, Basotu lowland has saline water
KitetoNdedo, Makame lowland has saline groundwater
Manyara
Simanjiro
Dodoma Bahi lowland has saliine groundwater Dodoma
Kondoa
Singida High productivity area along faults
Manyoni Singida
Iramba Locally high salinity groundwater
Shinynga Locally high Fluoride contents, West sided of Shinyanga town has high productivity
Maswa Around Maswa town has high productivity
Meatu High fluoride and salinity area
Shinaynga
Kishapu High fluoride and salinity area
IgungaLocally high fluoride contents, Lowland area has saline groundwater
Nzega
Uyui Locally high saline groundwater andhigh fluoride contents near Wembere swamp
Tabora
Sikonge
The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin
-Supporting Report- Chapter 9 Hydrogeology
9-30
Fig
ure
9-11
Hyd
roge
olog
ical
Map
of
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rnal
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inag
e B
asin
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36 36
37 37
-6-6
-5-5
-4-4
-3-3
-2-2
030
6090
120
15K
ilom
eter
s
Leg
end
Pro
du
ctiv
ity
Exc
elle
nt (
over
20
m3/
h)
Ver
y go
od (
10 -
20
m3/
h)
Goo
d (8
- 1
5 m
3/h)
Fai
r A (
5 -
10 m
3/h)
Fai
r B
(3
- 7
m3/
h)
Fai
r C
(2
- 4
m3/
h)
Poo
r (1
- 3
m3/
h)
Ver
y P
oor
(0.5
- 1
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evel
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ater
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4