In this past years Rwanda has suffered of severe water shortages in different catchments, even though large amounts of water continue to annually flood out to sea from the country. The problem is that the sporadic, spatial and temporal distribution of precipitation rarely coincides with demand. Whether the demand is for natural processes or human needs, the only way water supply can match demand is through storage. The main water storage system being applied in Rwanda is the construction of dam which is defined as a barrier built across a watercourse for impounding water.