SubSurface Dams - Sustainable Sanitation and Water Management ...

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3-4-2 Field explorationAt the 5 sites selected by interpreting the satellite images and aero-photographs andpreliminary exploration, a detailed field exploration was carried out to assess the feasibility ofconstructing a subsurface dam, also taking into account the results of the electric soundingsmentioned below (see Section 3-4-3).During the field exploration, the following surveys were carried out, and the distribution ofvillages was grasped.(1) Grasping landform and geologyThe landform and geology of the sites were grasped to detect the presence of shallowgroundwater and to estimate its structure.In these surveys, the landform classification maps drawn from aero-photographs were used astopographical maps and preliminary examination charts. Indeed, in surveying an area whereflat relief predominates without precise topographical maps, it is sometimes impossible notonly to understand the geomorphological significance of the phenomena observed in the field,but also to confirm the present location, without these land classification maps oraero-photographs themselves.(2) Survey of existing wellsTo grasp the presence of groundwater, the following surveys of existing wells were carried out.In these surveys, most of the useful information was obtained from “dug wells” whose sidewalls were not covered by concrete.1) Confirmation of the locations of the wells, and landform and geology2) Measurement of the groundwater level in the wells3) Confirmation of seasonal fluctuation in the groundwater level by listening toinhabitants4) Confirmation of geology of the aquifer and its upper strata by observation of theinterior of the wells and the surplus soil produced by digging, as well as by listeningto inhabitants(3) Confirmation of the distribution of unconsolidated sedimentGrasping the distribution of unconsolidated sediment that can form aquifers of shallowgroundwater was attempted. When it was difficult to directly grasp their distribution, it wasestimated from the distribution of the outcrop of the basement rock, which was grasped bycareful survey, of the lateritic crust in particular.25
Grasping general conditions of landform andgeologySurvey of thedistribution of villagesSurvey of the distribution of the lateritic crustSurvey of the distribution ofunconsolidated sedimentSurvey of existing wellsBasement rockFig. 3.5: Points of field explorationEstimateddistributionarea ofsedimentLateritic crustWellFig.3.6:Relation between the distribution of the lateritic crust and unconsolidated sediment26
Page 2 and 3: Photo: Construction of the subsurfa
Page 4 and 5: Subsurface DamSmall-Scale Surface D
Page 6 and 7: ContentsIntroduction1. General desc
Page 8 and 9: 1. General description of the Model
Page 10 and 11: Department of the Environmentand Fr
Page 12 and 13: According to the results of an anal
Page 14 and 15: A large amount of waterevaporates f
Page 16 and 17: y adopting an appropriate dam struc
Page 18 and 19: 2-5 "Fossil valley", a suitable sit
Page 20 and 21: temperature of 30 to 34 degrees and
Page 22 and 23: 3-3 Distribution of fossil valleys
Page 24 and 25: 3-4 Surveys carried out in this pro
Page 26 and 27: Satellite image of the area around
Page 30 and 31: 3-4-3 Geophysical surveyAt the 5 si
Page 32 and 33: Groundwater level assumed from the
Page 34 and 35: 3-5 Detailed field surveys (test dr
Page 36 and 37: Groundwater level isalmost the same
Page 38 and 39: The village is on a peneplain with
Page 40 and 41: In this project at Nare, the "earth
Page 42 and 43: DownstreamFilled back soil3mCoarseg
Page 44 and 45: All the results of the quality test
Page 46 and 47: Photo 4.3: Construction of the subs
Page 48 and 49: 4) Basal stratum of the fossil vall
Page 50 and 51: 6. Observation of the water storage
Page 52 and 53: Table 6.1: Features of the faciliti
Page 54 and 55: PerchedwaterImpermeablelayer“Main
Page 56 and 57: Table 6.3: Annual rainfall in the K
Page 58 and 59: 3) The reserved water level during
Page 60 and 61: Ground surface level: 275.73mGround
Page 62 and 63: 6-4 Analysis of seasonal fluctuatio
Page 64 and 65: SandysiltSiltSand(white)Sand(moist)
Page 66 and 67: (1) Relation between the rainfall w
Page 68 and 69: 4) Subsequently, the cycle in which
Page 70 and 71: 7. Other studiesIn addition to the
Page 72 and 73: these facilities:- 3 mill stations,
Page 74 and 75: Photo 7.3: Water-supply station for
Page 76 and 77: 8. Recommendations for future subsu
Page 78 and 79:
advisable to arrange rainfall stati
Page 80:
AcknowledgementsThe Model Project t
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