The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin -Supporting Report- Chapter 9 Hydrogeology
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.
32 33 34/RQJLWXGH GHJUHH 35 36 37 -2 .! µ -2
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/" Region Capital .! .! District Capital Borehole Location /" MajorFaults /DWLWXGH GHJUHH .! -5 Lake -5 SubBasins Yield (m3/h) .! - 1 1.0 - 2.0 2.0 - 3.0 .! 3.0 - 4.0 4.0 - 5.0 -6 -6 5.0 - 6.5 6.5 - 8.0 8.0 - 10.0 10.0 - 15.0 015 30 60 90 120 15.0 - 20.0 Kilometers 20.0 -
32 33 34 35 36 37 Figure 9-9 Well Yield Distribution of Existing Wells
9-24 The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin -Supporting Report- Chapter 9 Hydrogeology
(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 Color Phenomenon Representative place Lake Babati, Lake Singida, some Blue Water 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 Lake Natron, Lake Eyasi, Lake Purple-red Saline lake, swamp Manyara, Bahi swamp, part of Bubu river Mbuga clay Several places at locally low area Purple Basaltic rocks Around volcanoes
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.
9-25 The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin -Supporting Report- Chapter 9 Hydrogeology -2 -3 -4 -5 -6 ! . Kilometers 37 37 " / Arusha Kiteto ! . ! . Monduli 15 0 306090120 36 36 Babati ! . " / " / Kondoa Karatu ! . Loliondo Dodoma Mbulu ! . ! . ! . 35 35 ! . " / Singida Manyoni ! . Kiomboi ! . Meatu /RQJLWXGH GHJUHH 34 34 ! . ! . ! . Igunga Kishapu Maswa " / ! . Shimyanga Nzega 33 33 " / Figure 9-10 Figure Map Hydrogeological Classification for Productivity Groundwater 32 32 Excellent (over20 m3/h) good (10 - 20 m3/h) Very (8Good - 15 m3/h) m3/h) - 10 (5 A Fair BFair (3 - 7 m3/h) m3/h) - 4 (2 C Fair 3 m3/h) (1 -Poor Poor (0.5 - 1.5 m3/h) Very Undevelopable Lake, Swamp Clay Mbuga Capital Region Capital District Sub Basin Major Fault " / ! . 4
Legend Productivity -2 -3 -4 /DWLWXGH GHJUHH -5 -6
9-26 The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin -Supporting Report- Chapter 9 Hydrogeology
Table 9-9 Groundwater Productivity Condition in IDB Estimated Productivity Place Description (m3/h) Along large scale fault Fracture zone related to the Great Excellent over 20 Rift Valley System The belt area from west of Boundary area between granitic rock Mbulu district through east of area and Usagaran metamorphic Hanang disrtrict and west of rock area. Babati district to Kondoa district Very Good 10 - 20 Foot of volcanoes Much amount of recharge is expected from the mountains The south of Loliondo Much rainfall in Usagaran metamorphic rock area The west of Shinyanga town, The place which has many fault or around Maswa town, north of lineament and inselberg in granitic Tinde village, south of Igunga rock area district, west of Singida rural district, northwest of Dodoma town, around Loliondo town. Good 8 - 15 Uyui and Sikonge district Karatu district Much amount of recharge is expected from Ngorongoro mountain Around Loliondo Much rainfall in Usagaran metamorphic rock area Kishapu district, Igunga district, Most of granitic rock area the north of Igunga district Around Kiteto town, Mbulu Hilly area of Usagaran metamorphic Fair A 5 - 10 district rock Around Lake Manyara, Lake Manyara sediment has groundwater recharge from surounding mountain. Between Maswa and Kishapu Plateau of granitic area has low districs recharge of groundwater Bahi lowland area Clayey sand Fair B 3 - 7 southern part of Monduli district Usagaran metamorphic rock (Xs-a) and the northeast of Babati district Eastern part of Meatu district Fresh granitic rock is distributed Lowland surrounding Manonga Clayey sediment Fair C 2 – 4 river, Lake kitangiri, Lake Eyasi, and Wembere swamp Masai Steppe Less rainfall Shinyanga Rural district Less recharge of groundwater Poor 1 – 3 Oldubai to Lake Natron Less recharge of groundwater West of Longido Volcanic ash West of Uyui district, east of Less fracture of granitic rock Meatu town Very Poor 0.5 – 1.5 Lowland surrounding High evaporation Kitumbeine mountain
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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 Good Fair Poor Item 2 ' & Drilling depth Less than 80 m 80 - 150 m Over 150 m Static Water Less than 20 m 20 - 40 m Over 40 m Level 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
9-28 The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin -Supporting Report- Chapter 9 Hydrogeology
Table 9-11 Outline of Groundwater Development Potential by District Drilling Produc- 㩷 Region District SWL Salinity Fluoride Comment depth tivity
Northern part: relativeru good Monduli & & & ' ' Southern part Poor Arumeru & & 2 ' & High fluoride contents Arusha Nothern highland and Southern part are Ngorongoro ' 2 ' ' ' good Eastern and western lowlands are poor Karatu 2 2 2 2 2 㩷 Highland is good, Magugu area has Babati 2 2 2 2 2 saline groundwater Mbulu 2 ' ' 2 2 㩷 Around Mt. Hanang: high fluoride, Manyara Hanang & & ' ' & Basotu lowland has saline water
Ndedo, Makame lowland has saline Kiteto & & & & ' groundwater Simanjiro & ' & & ' 㩷 Dodoma & ' 2 ' 2 Bahi lowland has saliine groundwater Dodoma Kondoa & ' 2 2 2 㩷 Singida ' 2 ' ' & High productivity area along faults Singida Manyoni ' ' ' 2 2 㩷 Iramba ' 2 ' ' & Locally high salinity groundwater Locally high Fluoride contents, West Shinynga 2 2 ' & & sided of Shinyanga town has high productivity Around Maswa town has high Shinaynga Maswa 2 2 ' & & productivity Meatu 2 2 ' & & High fluoride and salinity area Kishapu 2 2 ' & & High fluoride and salinity area Locally high fluoride contents, Lowland Igunga 2 ' ' ' ' area has saline groundwater Nzega 2 2 ' ' 2 㩷 Tabora Locally high saline groundwater Uyui 2 ' ' 2 2 andhigh fluoride contents near Wembere swamp Sikonge 2 ' ' 2 2 㩷
9-29 The Study on the Groundwater Resources Development and Management in the Internal Drainage Basin -Supporting Report- Chapter 9 Hydrogeology -2 -3 -4 -5 -6
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0 5 33 33 Figure 9-11 Hydrogeological Map of Internal Drainage Basin Map of Internal Hydrogeological 9-11 Figure 32 32 Excellent (over 20 m3/h) (over Excellent good 20 - m3/h) (10 Very (8 15 - m3/h) Good m3/h) -(5 10 A Fair BFair (3 7- m3/h) m3/h) - 4 (2 C Fair 3 -m3/h) (1 Poor Poor (0.5 - 1.5Very m3/h) Undevelopable SwampLake, SedimentCenozoic Rock Volcanic Pyroclastic Sediment Granite Bukoban Usagaran Nyanzian Dodoman Clay Mbuga Basin Sub Major Fault Flow Groundwater (m) Level Water Static EC (mS/m) 4
Legend Productivity Unit Geological -2 -3 -4 /DWLWXGH GHJUHH -5 -6
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