Abstract
Abstract An assessment of the total hydrologic response of arid and semi-arid river basins to various scenarios of climate change by considering evapotranspiration, streamflow, and snowmelt is essential for sustainable management of water resources. The Diyala River Basin in Iraq has been chosen as a typical case study of dozens of river basins in arid and semi-arid regions. Here, the Long Ashton Research Station-Weather Generator (LARS-WG), the Soil and Water Assessment Tool (SWAT), and the SWAT Calibration and Uncertainty Program (CUP) were used to evaluate the total response by considering three Representative Concentration Pathways (RCPs); RCPs 2.6, 4.5, and 8.5 over three periods, 2021–2040, 2041–2061, and 2061–2080. The results indicate that by the year 2080, the basin will experience a temperature increase by 6.6, 10.1, and 16.6% for RCP 2.6, RCP 4.5, and RCP 8.5, respectively. The corresponding reduction in precipitation will be 3.2, 6.4, and 8.7%, resulting in 38.8, 47.9, and 52.8% fall in streamflow for RCPs 2.6, 4.5, and 8.5, respectively. Due to the increase in temperature, an earlier and less contribution of snowmelt is expected in the projected streamflow. Our findings provide a useful reference and a guide to decision makers for developing adaption plans to sustainably manage water resources in the Diyala River Basin and other similar basins in arid and semi-arid regions.
Highlights
Climate change is affecting almost every inhabited region worldwide, with human activities contributing to many recorded extreme weather and climate events (Intergovernmental Panel on Climate Change (IPCC) 2018)
The global sensitivity analysis method provided by the Soil and Water Assessment Tool (SWAT)-Calibration and Uncertainty Program (CUP) introduced the most sensitive hydrologic parameters for both watersheds based on t-Stat and P-value
The average Nash–Sutcliffe efficiency (NSE) (R2) given in Table 4 for the considered stations was found in the range of 0.96 and 0.98 (0.97) for both watersheds, whereas, for Tmin and Tmax, the NSE and R2 were found to be 0.99
Summary
Climate change is affecting almost every inhabited region worldwide, with human activities contributing to many recorded extreme weather and climate events (Intergovernmental Panel on Climate Change (IPCC) 2018). Extreme drought and flood events are becoming more commonplace and more prolonged due to climate change (Elsner et al 2010). The projected weather in Middle East and North Africa (MENA) suggests that the region will tend to become drier and hotter, with the associated streamflow declining by 20–30% (Milly et al 2005). Lelieveld et al (2012) reported that the MENA region is greatly impacted by climate change, putting significant strain on the already scarce water and agriculture resources. The expanded fifth phase of the Coupled Model Intercomparison Project Phase 5 (CMIP5) considers policy issues that simulate greenhouse emissions based on four Representative Concentration Pathways (RCPs 2.6, 4.5, 6, and 8.5) (Taylor et al 2012)
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