Hydrological Modeling of Lake Hawassa Sub-basin Using SW AT (Rift Valley Basin, Ethiopia

Abstract

n recent years, distributed watershed models are increasingly used Water resources management and hydrologic modeling studies. Even though, these models are capable of better representing the complex natures of the hydrological processes occurring at basin scale, they suffer from different types of uncertainties in the predictions. Hence, it is essential for these models to pass through a careful calibration tests and uncertainty analysis for gating reliable results. This study is about hydrological modeling of the Lake Hawassa sub-basin, which is one of the fresh closed lakes in the main Ethiopian rift valley basin, through a basin scale distributed hydrological model with consideration of the spatial heterogeneity of hydrological characteristics and the possible uncertainties in modeling, which are essential for obtaining more reliable estimates of the catchment water balance. A SWAT model has been applied for simulating the daily water balance of the catchment. The model calibration and 1:1r�_cert_c1in�� analysis, validation was done using SUFI-2. The uncertainty analysis process has provide good fit with acceptable range NS and R 2 values and it was possible to bracket about 76% of the measured data at 95PPU range, through which all ' source of uncertainties are reflected. The base flow is the dominant component of the stream flow, contributing more than the surface runoff and Lateral flow. And almost 78% or the rainfall over the catchment is lost through evapotranspiration. Finally a Spread sheet model was used for simulation of the monthly water balance of the lake. The average annual of open water evaporation from the lake surface is 163 MCM per year, Areal rainfall 127 MCM per year, surface runoff from Lake Catchment 143 MCM per year.