Assessment of the groundwater yield and sustainability of the transboundary Dibdibba aquifer using numerical modelling approach

This study investigates the sustainable yield of a shared/regional aquifer that covers a hydrogeological basin, Dibdibba Delta Aquifer Basin (DDAB). The aquifer extends over an area of 60,000 km² in three countries: Iraq, Kuwait, and Saudi Arabia. The groundwater resources of DDAB are used by these countries for agricultural and industrial purposes. The study aims at assessing the sustainable yield of DDAB accounting its recharge, discharge rates including submarine groundwater discharge (SGD) rates, and trans-boundary fluxes. The methodology adopted in this study is based on hydrogeological investigations, modified Chloride Mass Balance (CMB) for brackish aquifers to approximate recharge rates from rainfall, HEC-GeoHMS–SCS–CN model with suitable GIS tools to determine runoff rates from rainfall, numerical flow and salinity modeling. These calibrated numerical models were used to simulate the effect of utilization plan of brackish groundwater from the DDAB from 1975 until 2030. The results of the study show that aquifer recharge from rainfall is on average 9.6% and runoff rate from rainfall is about 10%. The simulation results show that SGD rates from Kuwait and Iraq to the Arabian Gulf were 184 and 43 Mm³/yr, respectively. The current pumping activities in the DDAB can be increased from the existing utilization level at 425 Mm³/yr to the sustainable yield level at 515 Mm³/yr with a consequence of increasing the drawdown to 12 m and salinity deterioration of 205% in some areas.