Estimation of Water Balance Components Using J2000 Model in a Semi-Arid Region, The Case of Upper Illala Catchment, Tigray

Abstract

Upper Illala catchment, located northeast of Mekelle city, is one of the most water-stressed areas in Tigray region, with a short rainy period from mid-June to mid-September. The main objective of this research was to estimate the spatially distributed groundwater recharge, surface runoff and evapotranspiration, using J2000 hydrological model. Long term temporal metrological data series, runoff discharge gauging data, land use/cover and soil depth profiles in the study area were the inputs for the model. These input data were prepared in the form of digital maps using remote sensing images, GIS tools, and the PSpad text editor. Results of the J2000 model, for the upper Illala Bridge runoff gauging station appeared to be correct in its periodicity and its magnitude. However the simulated and observed hydrographs revealed model errors and uncertainties due to parameter; data and model structure uncertainties. Accordingly, about 70.28% of the precipitation in the study area is lost through evapotranspiration (58.64%) and canopy interception (11.63%), about 14.92% is surface runoff, 8.0% is groundwater recharge and 5.7% is soil moisture. These outputs were obtained after the model was validated through KGE_mod approach. In addition, these outputs were verified using other independent approaches— namely the WetSpass hydrological model and geochemical methods. Eventually, the J2000 model has produced reasonably acceptable results with a better fit KGE values and quite similar results with the outputs of the independent approaches.

Keywords:Water balance, J2000 hydrological model, Mekelle

DOI: 10.7176/JEES/13-4-01

Publication date:June 30^th 2023