Hydrogeology and siting of micro-dams around Léo Burkina Faso

Hydrogeology and siting of micro-dams around Léo, Burkina Faso14 June 2010The soil in the riverbed consists of clay on top of a very sandy clay/laterite. To the sides of the riverbedthe clay is covered by a mixture of weathered rocks, silt and sand which have been eroded from theslopes. Within the catchment vast areas were bushfires had burned can be seen. At some locationsthis has clearly led to increased erosion. This poses a significant risk for the potential micro-dam assiltation might be a problem.Although there are some scoopholes present near the surface water reservoir, this water was onlyused for washing cloths. The water from the reservoir itself is being used for cattle and brick making.No agriculture takes places near the surface water. It remains unclear why.Drinking water is being fetched from a number of boreholes in the village and an old deep open well,both a few hundred meter away from the dam. Since the construction of the boreholes a few yearsago, the stress on this well has decreased and it now has water all year round, where before it driedup at the end of the dry season.5.5 TékouraTékoura (or Tiékoura as indicated on some maps) is located about 12 km South-West of Léo, at theborder Burkina Faso – Ghana border.The catchment area of this proposed dam site has a surface area of 31.1 km 2 and is largely located inGhana.Figure 25 Overview of the Tékoura dam siteThe proposed dam site is located near a depression in the riverbed were surface water was standing.The slope of the riverbanks is relatively flat on both sides, so a potential dam should be relatively long.The soil in the riverbed consists of clay on top of laterite.There are a few scoopholes present near the surface water reservoir which are used for washingcloths and to provide drinking water for cattle when the surface water reservoir dries up. Thereservoir dries up most of the years, especially since cattle from neighbouring villages comes to drinkhere as the other surface water reservoirs in the area have dried up. The water from the reservoiritself is being used for cattle and brick making. No agriculture takes places near the surface water. Itremains unclear why.Drinking water is being fetched from a borehole in the village and an old deep open well, both a fewhundred meter away from the dam. There is great stress on the well as a new borehole that wasconstructed last year by CREDO, doesn’t function properly. CREDO is in dispute with the constructor toget it fixed, but after fixing it breaks down again quickly. It is unclear what the problem is, possiblysand is entering the borehole.26