Application of Hydrological Models for Climate Sensitivity Estimation of the Atbara Sub-basin

Abstract

Hydrological models have a wide range of applications in water resources planning and management as well as flood forecasting and climate impact assessments. In the latter case, they are usually coupled to meteorological or climate models. In this study, two hydrological models (Hydrologiske Byran avdeling for Vattenbalans (HBV) and Nile Forecast System (NFS)) are applied to the Atbara catchment, Nile River basin area to study the sensitivity of runoff to changes in rainfall and potential evapotranspiration. The HBV model is a conceptual lumped model while the other NFS is a conceptual distributed model. Atbara River is the last major tributary of the Nile River and has a highly seasonal pattern with very high flows during the flood season and almost zero flows during the dry season. These features pose problems to the calibration of hydrological models. However, both models were able to capture the main features of the monthly flow time series of the Atbara (Nash efficiency index reached 0.92 for HBV and 0.68 for NFS). Results indicate a very high climate sensitivity of the catchment where rainfall increases of 10, 20 and 30% result in runoff increases of 29, 62, and 97%, respectively. The catchment runoff is also sensitive to changes in potential evapotranspiration but to a lesser extent. These results are confirmed by the two used models with slight differences.