Water from Small Dams

Since there are no documented guidelines or training on constructing charco dams, theTanzanian farmers build their dams in any shape, although circular and oval designsare preferred, because:1) They give maximum storage volume for a minimum of work.2) The internal and external pressures are evenly distributed and this preventscave-in of the soil in the walls of the water reservoir.3) In sandy soils, they can be lined successfully with clayey soil, because theshapes do not have any corners.The size of a charco dam depends on the following factors:1) A farmer’s financial capacity to hire labourers to assist him with excavation.2) The expected volume of run-off water from the catchment.3) The area available for constructing the pond.4) The soil type.Recommended plan and profiles for a standard design of charco dams.19