Hydrogeology and siting of micro-dams around Léo Burkina Faso

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Hydrogeology and siting of micro-dams around Léo, Burkina Faso14 June 2010Figure 18 Overview of the wells and scoopholes near the Sissili micro-damThe measured water levels at the proposed dam site of Sissili show the hydrological situation of a sitewithout a dam (since the dam has breached and lost it’s purpose). Figure 19 shows the longitudinalcross-section on the riverbanks, close to the river.18
Hydrogeology and siting of micro-dams around Léo, Burkina Faso14 June 2010Figure 19 Longitudinal profile along the river at Sissili. The brown line is the ground level, theblue line the shallow groundwater table. The numbers correspond to the well numbers inFigure 18.The groundwater table is gently sloping downstream, no effects of a dam can be seen. The water tablein all wells and the single scoophole are all more or less at the same depth and thus get their waterfrom the same aquifer (at least at the time of visit).It is however remarkable that the villagers claim that both wells in the agricultural plot downstream ofthe dam (the two on the left side of Figure 19, depth around 8 m) dry up around March as well as themuch deeper well (on the right side of Figure 19, around 20 m deep) about 200 m upstream. Thismight indicate that the lower part of the deep well is in a very poor aquifer. Meaning that once theupper aquifer (were the wells get their water from now) has dried up, the well can hardly extract anywater from the deeper aquifer. The planned measurements of the monitoring program should givemore information on whether this is the case or not.The cross-sectional profile (Figure 20) shows a groundwater table that is nearly flat, or slightlydecreasing towards the riverbanks. The slight decrease might be caused by the extractions from thesewells and scoophole, or might be the residual result of the short period that the dam was still intactand there was water infiltrating from the river towards the riverbanks. The planned measurementsshould tell more about this.Figure 20 Cross-sectional profile along the river at Sissili. The brown line is the ground level,the blue line the shallow groundwater table. The numbers correspond to the well numbers inFigure 18.19
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Page 39: Appendix 1Topographic map
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Page 49 and 50: Sander de Haas02-03-2010Waterlevel
Page 51 and 52: If the waterlevel in the reservoir
Page 53: If there is water near the dam, mea
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Hydrogeology and siting of micro-dams around Léo Burkina Faso

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