Numerical modeling of a multi-aquifer system in Eastern Saudi Arabia

A numerical quasi-three-dimensional groundwater flow model was constructed for a multiequifer system in eastern Saudi Arabia to determine the hydraulic properties of the system and to evaluate the consequences of various development alternatives. The aquifers modeled were the Alat, the Khobar and the Umm Er Radhuma of Paleocene-Eocene age, which are hydraulically connected with intervening aquitards. Steady-state and transient model calibrations demonstrated considerable spatial variations in transmissivities of the aquifers and vertical leakances of the aquitards. The reliabilities of these parameters were checked through sensitivity analysis. The model results have confirmed the hydraulic interaction between the aquifers via intervening aquitards. The calibrated model was subsequently utilized to predict responses of the aquifers over a planning horizon of 14 years (1987-2000) under three development alternatives. The model results indicated that the Khobar aquifer has a limited productivity in the Abqaiq region where dewatering is expected to occur if the existing trends in extraction rates are continued. The Umm Er Radhuma aquifer, however, has demonstrated relatively low declines in water levels, indicating very high potential for productivity. Freezing the current extraction rates throughout the planning period showed little change from the present conditions. Gradual introduction of conservation measures would be more effective in ensuring the long-term productivity of the aquifers.