Abstract
Climate change has potential effects on future hydrologic characteristics of arid and semi-arid river basins. The Lesser Zab River in Iraq was selected as a representative example of arid and semi-aird river basin. In this paper, the minimum and maximum temperatures (Tmin and Tmax) and precipitation (Pcp) for Lesser Zab Basin (LZB) were projected using Long Ashton Research Station-Weather Generator (LARS-WG) considering three future periods P1 (2021–2040), P2 (2041–2060), and P3 (2061–2080) under five global climate models (GCMs) and three representative concentration pathways (RCPs 2.6, 4.5, and 8.5). The projected weather variables were inserted into the Soil and Water Assessment Tool (SWAT) for the same scenarios and future periods. The results showed that LZB is expected to suffer from hot weather and drought by end of P3 due to an increase in Tmin by 16.78, 27.9, and 44.05%; an increase in Tmax by 8.4, 13.67 and 21.5%; and a decrease in Pcp by 0.07, 5.26, and 5.31%, under RCPs 2.6, 4.5, and 8.5, respectively. Moreover, the projected evapotranspiration also tended to increase by 5.52, 8.37, and 12.61% under RCPs 2.6, 4.5, and 8.5, respectively. Consequently, the projected streamflow of LZB is expected to decrease by 16.7, 27.15, and 31.23% under RCPs 2.6, 4.5, and 8.5, respectively. The paper introduced novel findings based on LARS-WG and SWAT simulations that contribute to a better understanding of future climate and hydrologic trends in arid and semi-arid river basins. The study outcomes assist sustainable management of water resources and decision-making process involved in climate change adaptation policies.