Impact of Climate Change on the Spatiotemporal Distribution of Stream Flow and Sediment Yield of Darbandikhan Watershed, Iraq

Abstract

The impact of climate change on stream flow and sediment yield inDarbandikhan Watershed is an important challenge facing the waterresources in Diyala River, Iraq. This impact was investigated using fiveGlobal Circulation Models (GCM) based climate change projectionmodels from the A1B scenario of medium emission. The Soil and WaterAssessment Tool (SWAT) was used to compute the temporal and spatialdistribution of streamflow and sediment yield of the study area for theperiod 1984 to 2050. The daily-observed flow recorded in DarbandikhanDam for the period from 1984 to 2013 was used as a base period forfuture projection. The initial results of SWAT were calibrated andvalidated using SUFI-2 of the SWAT-CUP program in daily time stepconsidering the values of the Nash-Sutcliffe Efficiency (NSE) coefficient ofdetermination (R2) as a Dual objective function. Results of NSE and R2during the calibration (validation) periods were equal to 0.61 and0.62(0.53 and 0.68), respectively. In addition, the average futureprediction for the five climate models indicated that the average yearlyflow and sediment yield in the watershed would decrease by about 49%and 44%, respectively, until the year 2050 compared with these of the baseperiod from 1984 to 2013. Moreover, spatial analysis shows that 89.6 %and 90 % of stream flow and sediment come from the Iranian part ofDarbandikhan watershed while the remaining small percent comes fromIraq, respectively. However, the middle and southern parts ofDarbandikhan Watershed contribute by most of the stream flow of thewatershed while the parts of lack land cover and steep slopes producemost the sediment.