Integrated Analysis of Land Use, Soil Saturation, and Runoff Generation in Hydrologically Sensitive Zones of an Choke Agricultural Watershed

Evaluation of hydrologically sensitive areas was a big challenging issue, especially to identify and locate the particular areas. In the upper Blue Nile basin, hydrological sensitivity was a more and intensive phenomenon that leads to watershed alternativeltity with influencing the streamflow parameters. This watershed area leads to hydrologic sensitivity due to anthropogenic and natural factors, which particularly existed in river morphology. This study focuses on, the identifications of hydrologically sensitive areas in the Ziya (choke) watershed area, depend on the topographic, slope and hydraulic roughness parameters. For the analysis of the sensitive area, it was used the soil topographic index (STI), topographic witness index (TWI) and considered TOPOMODEL for surface runoff evaluation. An investigation made on selections of sensitive area and prone regions, high regions generate more amount of surface runoff accompanied by land use/cover change, variable surface area, climate change. In Lowest, parts of the watershed have low soil moisture contents in Belg seasons with a range of 25.53 NMC, 38.7 FC, and 27.24 PWP. The TWI values in this watershed range from -3 through 28.6 with the threshold of values identifying areas of significant wetness between 9 and 29.5. The TOPMODEL result shows that a large amount of surface runoff has occurred in the upper parts of a watershed with a range of 320 mm/ year. The lower reaches also suffered by high levels of sedimentation rate with a value of 3.873 t/ha. Generally, the watershed has suffered under hydrological sensitivity with a high level of severity. Therefore, the remedial measure should have been applied by an intervention of ecological and social welfare. Keywords: TWI, Hydrological sensitivity, STI, VSA