تأثيرالتغير المناخي على تغذية المياه الجوفية في حوض الدبدبة, العراق

Effect of Climate Change on the Groundwater Recharge in Dibdibba Basin, Iraq

In Iraq, groundwater is considered as an alternate water resource, essentially for areas far away from surface water. Groundwater is affected by many factors including climate change, industrial human activities, unplanned urbanization and industrialization. This study deals with the development model to generate future climate data in order to estimate future groundwater recharge. For the current study, Dibdibba unconfined aquifer in Karbala city, Iraq was chosen as a case study. It depended on rainfall recharge, which is associated to change in temperature and rainfall. The historical data for the period 1979-2018 were used to predict future climate data for two future periods 2040 and 2099 by using general circulation model (GCMs), CanESM2, based on three emission scenarios RCP2.6, RCP4.5 and RCP8.5 by using statistical downscaling model (SDSM) program. These data were divided into two groups: data from, 1979 to 2000 was used for building the downscale model and for calibration, while for validating the models use data from, 2001 to 2018. The calibration results of SDSM model gave a coefficient of determination (R²) ranged from
(0.877 to 0.905).
After testing (SDSM) capacity to produce climatic data depended on the period 1979 to 2018, climate data (rainfall and temperature) will generated for the next periods 2040 and 2099. Following this, a Groundwater Modeling System (GMS) model is constructed in order to assess the groundwater recharge under future climate data.
The results indicate that the temperature was expected to increase between (0.5 to 0.7) ºC at 2040, and between (0.5 to 1.07) ºC at 2099, and the rainfall expected to decrease by 6.3%, 10.3%, and 23.8% for near future 2040, and by 13.8%, 17.5%, and 21.3% for far future 2099 for RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. Six predicted
scenarios for groundwater recharge were selected for each scenario of climate data for the two periods 2040 and 2099 after calibrated the model in GMS. The model matched the observed head of groundwater with R² =0.99 for steady state condition. The results show that the recharge of groundwater decreases by 6.4%, 10%, and 27.6 % for near future 2040 and decrease by 13.6%, 17.6%, and 25.3% for far future 2099 compared to the year 2018 under RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively.