Sensitivity of SWAT simulated streamflow to climatic changes within the Eastern Nile River basin

Recently Dereje T. Mengistu and Asgeir Sorteberg published a paper on the river flows in the Eastern Nile basin. This study is a part of the EMAPS research. (pdf file)

The paper is published in:Hydrology and Earth System Sciences 2012; 16: 391–407.

The Abstract of the paper is.

The hydrological model SWAT was run with daily station based precipitation and temperature data for the whole Eastern Nile basin including the three subbasins: the Abbay (Blue Nile), BaroAkobo and Tekeze. The daily and monthly streamflows were calibrated and validated at six out- lets with station-based streamflow data in the three different subbasins. The model performed very well in simulating the monthly variability while the validation against daily data revealed a more diverse performance. The simulations in- dicated that around 60 % of the average annual rainfalls of the subbasins were lost through evaporation while the esti- mated runoff coefficients were 0.24, 0.30 and 0.18 for Ab- bay, BaroAkobo and Tekeze subbasins, respectively. About half to two-thirds of the runoff could be attributed to surface runoff while the other contributions came from groundwater.

Twenty hypothetical climate change scenarios (perturbed temperatures and precipitation) were conducted to test the sensitivity of SWAT simulated annual streamflow. The result revealed that the annual streamflow sensitivity to changes in precipitation and temperature differed among the basins and the dependence of the response on the strength of the changes was not linear. On average the annual streamflow responses to a change in precipitation with no temperature change were 19 %, 17 %, and 26 % per 10 % change in precipitation while the average annual streamflow responses to a change in temperature and no precipitation change were

47 temperature and precipitation scenarios from 19 AOGCMs participating inCMIP3 were used to estimate fu- ture changes in streamflow due to climate changes. The cli- mate models disagreed on both the strength and the direc- tion of future precipitation changes. Thus, no clear conclu- sions could be made about future changes in the Eastern Nile streamflow. However, such types of assessment are impor- tant as they emphasise the need to use several an ensemble of AOGCMs as the results strongly dependent on the choice of climate models.