Water from Small Dams

As soon as an earth dam has been built and is holding water, people will bring theirlivestock for watering and that is the beginning of siltation. Later on, if people startbuilding houses near the dam and clearing land for agriculture without soil conservation,then siltation may reduce the lifetime of an earth dam to 8 years, or even less.Catchment protection on farmland can be implemented in several ways such as:Maintaining the natural vegetation cover within the catchment by avoiding overgrazingby livestock and cutting of trees for timber and charcoalContour lines of fodder grassesContour lines of fodder grasses, such asNapier Grass or the more droughtresistantBana Grass, can be grown oncontour banks, called Fanya Juu, toprevent a dam reservoir from silting up.The intervals between the banks dependon the gradient of the land. On landsloping about 3 cm per 100 cm, thedistance should be about 20 metres. Onsteeper land the distance between thebanks should be reduced.Fodder grasses grow on the contour banks.Contour lines with multi-purpose treesMulti-purpose trees, such as Prosopis,Leucaena, Melia Volkensii andAzadirachta Indica (Neem), and bananasgrow well in the ditches from where soilwas taken to make the contour banks.Contour lines of trees make windbreaksthereby reducing wind erosion of barefarmland. Windbreaks also reduceevaporation from water reservoirs byreducing the wind speed over surfacewater. Contour lines of trees improverainwater infiltration for growing crops, Bananas planted in the ditch behind a contourand provide windbreaks, firewood, bank, called a Fanya Juu.charcoal, fodder and timber.53