SubSurface Dams - Sustainable Sanitation and Water Management ...

More documents

Recommendations

Info

PerchedwaterImpermeablelayer“Main”groundwaterA) Observation well of theall-strainer typeB) Set of piezometers of differentdepthsFig. 6.2: Structure of two types of groundwater observation well51
6-2 Results of observation of meteorology and rate of streamflowThe fossil valley where the subsurface dam was built is probably buried along the KolongoRiver. A close relationship is thus suggested between the recharge of groundwater stored bythe subsurface dam and the rainfall within the Kolongo River basin. In addition, as this areais located in an semi-arid region, much of the water provided by rainfall is probably lostthrough evapotranspiration.For a quantitative evaluation of the effectiveness of water storage by the subsurface dam, it isthus necessary to know not only the groundwater level, but also the rainfall within theKolongo River basin, the amount of evapotranspiration and the rate of streamflow of theKolongo River. However, almost no such observation has been carried out by the presentlocal authorities. Therefore, observation of these parameters was carried out as a part of thisproject.(1) Observation of daily rainfallThe observation of daily rainfall started in 1997 in the Koulikare Quarter, in which thesubsurface dam was built, in Nare Village, and in the Kossonkore Quarter of the same village.In 1998, the observation of daily rainfall also started in Ouanobian Village and Noka Villagelocated in the upstream area of the Kolongo River. Table 6.2 shows the results of theobservation carried out in Koulikare in Nare Village.Table 6.2: Rainfall in the Koulikare Quarter in Nare Village from 1997 to 2002Year ofobservationMonthly rainfall (mm)Mar Apr May Jun Jul Aug Sept Oct N-F**Annualrainfall (mm)Cereal harvest1997* 0.5 19.9 31.9 73.9 123.9 81.0 102.0 35.0 0 468.1 Poor1998* 0 1.3 55.2 90.8 139.5 157.4 138.9 28.6 0 611.7 Good1999 0 0.7 13.1 26.8 166.0 189.4 178.2 0 0 574.2 Average2000 0 8.3 0.9 56.1 112.6 43.5 74.8 20.7 0 316.9 Very poor2001 0 0.1 20.3 52.0 113.1 169.6 43.5 6.7 0 405.3 Average2002 0 3.0 75.6 80.2 131.0 166.1 77.8 67.8 0 601.5 Good* Although the data for 1997 and 1998 were those of the Kossonkore Quarter in Nare Village, theycan be considered as almost the same as those of the Koulikare Quarter.** "N-F" in the last column of "Monthly rainfall" represents the total rainfall from November toFebruary of the following year.Year 2000 was "a year of extraordinary drought" according to the inhabitants. That year’srainfall was only 316.9 mm as shown in Table 6.2. From just after the dry season of 2000until just before the rainy season of 2001, the groundwater level in the reservoir area of thesubsurface dam dropped markedly. This extraordinary drop in groundwater level wasconsidered due to the exceptional drought of 2000.The annual rainfall in the Kolongo River basin is shown in Table 6.3. This shows thetendency that the further upstream (to the west-south-west), the greater the annual rainfall.52
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 28 and 29: 3-4-2 Field explorationAt the 5 sit
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 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
show all

SubSurface Dams - Sustainable Sanitation and Water Management ...

Create successful ePaper yourself

Delete template?

Save as template?