Ground-water modelling and long-term management of the Azraq basin as an example of arid area conditions (Jordan)

The Azraq basin in Jordan is considered to be one of the most important basins that supply Jodanian major cities with drinking water. There are three aquifers in the basin, the upper one is the most important, due to its low drilling cost and good quality of ground-water. The average annual infiltration for the period 1965/66–1994/95 was 35×106m3, which comprises about 3% of the total annual rainfall. Around 1×106m3flows through the Sirhan structure into the adjacent areas, and approximately 9×106m3is lost by evapotranspiration, meaning that the net recharge is about 25×106m3. Due to an increase in demand for drinking water (55×106m3), the basin started to suffer from a depletion of ground-water levels. As a result, the Azraq oasis is now completely dry. This study indicates that pumping wells are irregularly distributed, especially in the well field area which is where most of the pumping occurs. Saline water intrusion has started and is predicted to accelerate in the near future. The ground-water balance of the model shows that the underflow recharge from the north is about 35×106m3, the upward movement is nearly 1×106m3, and the downward leakage is approximately 0·13×106m3. Increasing ground-water pumping accelerates the upward movement and causes a decrease in the downward leakage. The safe yield of the basin was calculated to be around 25×106m3. Dividing the basin into three zones (well field, northern part and eastern part) shows that any reduction in pumping of the sub-basin or zone, particularly in the well field, has a positive effect on the other two zones.