Estimation of water budget components under climate change in Al-Shour Valley Basin, Northern Iraq

Climate change is one of the natural phenomena affecting the volume of water resources in the world. From this standpoint, the current study came to estimate the components of the Al-Shour Valley Basin water budget under two expected climate change scenarios: RCP4.5 and RCP8.5, and for different periods, including the near future (2021-2050) and the far future (2051-2100). Future climate conditions were obtained by entering climate elements into the statistical downscaling model (SDSM), and then entering the modeling and analysis results into the water evaluation and planning (WEAP) to obtain the components of the basin's water budget, which included rainfall, evapotranspiration, surface runoff, base flow, Inter flow, increase and decrease in soil moisture. The WEAP simulations show that rainfall will decrease, especially in the far future (2051-2100), where the annual rainfall decreases by 5.92% to reach 139.62 Mm(3)/year for the RCP4.5 scenario and 128.65 Mm(3)/year or 13.70% for the RCP8.5 scenario. With decreasing evapotranspiration reaching 65.45 Mm(3)/year and 64.30 Mm(3)/year for both scenarios, respectively. The decrease continued with the annual surface runoff by 16.26%, reaching 19.09 Mm(3)/year for the RCP4.5 scenario, and 16.74 Mm(3)/year or 27.30%, for the RCP8.5 scenario, also for the far future. In addition to the above, this study demonstrated that climate changes may lead to a decrease in water availability in the basin. Therefore, this indicates the actual need to develop appropriate strategies for sustainable water management in the basin. The study results provide clear insights and important and necessary guidelines towards sustainable water resources management in the future.