Optimizing pumping rates of Hallabat-Khalidiya Wellfield using finite-difference model: a case study for evaluating overpumped aquifers in arid areas (Jordan)

This study was carried out to quantify the ground-water budget, calibrate aquifer characteristics and to predict the drawdown of the upper aquifer in the Hallabat-Khalidiya Wellfield in the eastern part of Jordan, for the next 25 years (the year 2025). There are two aquifers, the upper one composed of basalt and carbonates of the Upper Cretaceous age, while the lower one is composed of Lower Cretaceous Kurnub sandstones. The total annual recharge to the upper aquifer is modeled to be about 6 x 10(6) m(3) divided into inflow from Jebel El-Arab through the basalt being 4.5 x 10(6) m(3) and from the return irrigation flow and excess rainfall being 1.5 x 10(6) m(3). Leakage from the upper aquifer through the A(1)/A(6) aquitard to the sandstone aquifer is calculated to be about 0.5 x 10(6) m(3) which is about 8% of the total recharge to the upper aquifer, and outflow across the western boundary towards Wadi Zarqa reaches about 5.5 x 10(6) m(3). The maximum water level decline will reach 33 and 21.6 m, by the year 2025, due to abstraction of 16 x 10(6) and 8 x 10(6) m(3), respectively, and will reach 40 and 25 m for the same respective abstraction rate after correction. However, with 4 x 10(6) m(3) pumping, water levels will recover in most of the wellfield area and the small drawdown values (less than 10 cm year(-1)) in the intensive pumping area will be negligible. Therefore, the optimal use of ground-water resources should not exceed 6 x 10(6) m(3). (C) 2002 Published by Elsevier Science Ltd.