Water towers are considered to be the areas that generate high stream flows in comparison with others. Within the Nile basin, highlands and other elevated areas greatly contribute to total stream flow of the major rivers in the basin. These areas, referred to as water towers, normally receive more rainfall than their lower surroundings. They also usually lose less water to evapotranspiration because temperatures are lower. The major water towers within the Nile Basin are shown in the figure below.