Quantification of the Impact of Integrated Soil and Water Conservation Measures on Groundwater Availability in Mendae Catchment, Abraha We-Atsebaha, eastern Tigray, Ethiopia

The paper tries to evaluate the impact of integrated soil and water conservation measures on water availability in Mendae catchment (10.37 km2), which is located in the northeastern Tigray. Historical background of the catchment with respect to its land use was obtained from the local Bureau of Agriculture and Rural Development office. The hydrology of the area was characterized based on its land use, soil, slope, rainfall,  temperature, evapotranspiration, and runoff. Thornthwaite method and Thornthwaite soil-water balance model were used to determine potential and actual evapotranspiration, respectively. The mean annual runoff from the catchment was computed using runoff coefficient method. Before the intervention, the area was severely degraded and known with scarcity of water. Integrated soil and water conservation (physical and biological measures) was introduced to the area since 1993. The catchment is characterized by two rainy season and three dry seasons during the year. The rainy seasons in total have four months whereas the dry seasons comprises of eight months. The mean annual rainfall of the catchment is 565.8 mm, out of which rainy season accounts for 86.13% and the dry season for 13.87%. The rain that occurs with a very high concentration accounts 73.20 % of the mean annual rainfall of the catchment and this occur only in two months (July and August).The mean annual potential and actual evapotranspiration was found to be 832.67 mm and 405.61mm, respectively. The volume of runoff before and after the intervention was found to be 26.88 % and 17.19 % of the mean annual rainfall of the catchment, respectively. The groundwater recharge before and after the intervention was found to be 1.43 % and 19.04% of the mean annual rainfall of the catchment, respectively. The availability of groundwater has increased more than 10 times since 1993. Though the groundwater is being used for both complimentary and supplementary irrigation during the dry and rainy season, respectively, construction of additional physical conservation structures is suggested to further improve the groundwater availability in the area. Keywords : Groundwater, Mendae catchment, Surface runoff, Water balance, Tigray, Ethiopia.