Application of Physically Based Hydrologic Model for Estimation of Major Components of the Hydrologic Cycle: the case of Meki River Basin, Ethiopia

Abstract

The purpose of this study was to estimate the major components of the hydrologic cycle of Meki River basin using physically based hydrologic water balance simulation model WaSiM-ETH. The model was calibrated for two years of record of daily flow data (2000 - 2 001) measured at the outlet of Meki watershed. The model was then validated using three years (1997 - 1999) and five years (1997 - 2001) of measured river flow records. The calibrated model is generally found to be capable of reproducing the historically recorded flow of Meki River with R 2 of 78% in calibration and 71 % and 68 % in validation. However, it was also seen that the model was unable to capture extreme flow conditions during rainy season. According to the water balance calculation, out of the total aerial precipitation around 75.7% is lost by evapotranspiration, 14 . 9% is total runoff, and 9.7% is interception loss. Similarly, the partitioning of the flow of Meki Ri ver showed that 62. 3% is lnterflow, 23.1 % is surface runoff and 13 . 8% is base flow. The result of the water balance was found comparable with other previous studies of similar nature done in the study area and proved the model can be used in any future studies in Meki watershed. Grid outputs of the model for major water balance components showed that the model was able to capture the catchment heterogeneities. This capability of the model becomes very essential for developing relationships between hydrologic components with deferent environmental variables at grid cell level.