Regionalization of mean annual flow for ungauged catchments in case of Abbay River Basin, Ethiopia

Abstract

Streamflow measurement is one of the features of Ethiopia and other developing countries suffer to estimate. Climate variable (rainfall) and physiographic variables (catchment area, land slope, and elevation) were selected to develop a regression model equation that can be used to estimate the mean annual flow for ungauged catchments in the Abbay river basin. 70% of 27 hydrometric stations were used to train the regression model, and the remaining 30% were used for validation. Furthermore, statistical tests were used for selecting the best trustworthy model. The result shows that both catchment area (A) as the only predictor with both coefficients of determination (R2) and Nash–Sutcliffe efficiency (NSE) value of 0.93 and catchment area (A), mean annual rainfall (MAR), and the average elevation (AE) as predictors with both coefficients of determination (R2) and Nash–Sutcliffe efficiency (NSE) value of 0.96 regression equations were the trustworthy models. Moreover, the validation analysis was performed for nine stations distributed in the study area and resulting from a statistical test and graphical visualization the second regression model equation was a trustworthy model. The model parameters (catchment characteristics) are easily accessible for practitioners that want to estimate the mean annual flow in the study area.