Watershed storage dynamics in the upper blue Nile basin: The anjeni experimental watershed, ethiopia

Abstract

Understanding functions of a watershed is important for implementing appropriate soil and water conservation measures and for planning and development of sustainable water resources use. Watershed storage is a significant part of a catchment water budget and its quantification provides a clue to understand the fundamental catchment hydrological processes. This study is aimed to investigate the dynamics of watershed storage of the Anjeni experimental watershed in the Upper Blue Nile basin for which a long series of rainfall and runoff data is available for this study. A daily water balance equation was used to quantify the watershed storage over the distinct rainy season. On average, 86 % of the annual rainfall occurs during distinct rainy season. The study showed that the watershed storage increases with the increase of cumulative rainfall till the watershed stores its maximum capacity. After this maximum capacity, the watershed storage remains constant, even if rainfall continuous. The Anjeni watershed stores an average of 380 mm of water after a cumulative effective rainfall of 625 mm. Before the maximum storage was reached, about 60 % of the effective rainfall is used to wet up the watershed. Then, the remainder becomes surface runoff and interflow, during which about 40 % of the flow appeared at the outlet.