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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!. 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



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



9-26

Fig

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9-10

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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



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



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



9-30

Fig

ure

9-11

Hyd

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Map

of

Inte

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4

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