| The Fayoum basin of Egypt is a closed basin with a lack of natural drainage outlets. The saline drainage water disposed of and impounded into Lake Qaroun is subject to evapoconcentration. As a result of these physical and environmental constraints, water and salt management are generally hampered, and salt accumulation in the lake can reach hazardous levels. In order to assess alternative water and salt management scenarios, mathematical models of lake evaporation, as well as lake routing and basin water balance were developed and tested.; Findings from model simulations showed that the most suitable scenario for reducing salinity in Lake Qaroun was to divide the lake into two compartments. The smaller compartment, located at the east end of Lake Qaroun, will have relatively fresh water with a salinity level of 13.3 dS/m, and a water level of −43.79 m MSL. The other compartment, located at the west end of Lake Qaroun, will have saline water (72.2 dS/m). Evaporation ponds of 6 km 2 are required to evacuate the salt load of 620,000 tonnes/year.; Based on water balance simulations, it was recommended that the water level of Upper Wadi Rayan Lake be −8.7 m MSL, and total inflows into Lake Qaroun and the basin be 417 MCM/year, and 2430 MCM/year, respectively. It was further concluded that increasing the reuse of drainage water can conflict with expansion of the irrigated area. Therefore, it is recommended that the potential for drainage water reuse be limited to a maximum of 275 MCM/year, which allows for a high overall irrigation efficiency of 70%, and a reclamation of 2,226 ha.; Further water balance simulations showed that without increasing the total irrigation intake amount, water shortages can be avoided by improving the match between supply and crop water demand. With an overall irrigation efficiency of 70%, and expansion of irrigated land of 2,226 ha, the drainage water reuse is a maximum of 195 MCM/year. |
