Abstract
El Dakhla depression occupies a structurally localized depression at 100 to140 m (amsl), below a 400 m escarpment bordering the Libyan Plateau, Western Desert of Egypt. In this area, groundwater of the Nubian Sandstone aquifer is the unique source of fresh water. The increasing demand of groundwater in El Dakhla depression has resulted in an indiscriminate exploitation of this source causing environmental hazards such as decline of groundwater levels. In this paper, the study of this problem is conducted. The methodology introduced in this paper includes application of mathematical and genetic algorithm (GA) techniques. The proposed model of optimization is based on the combination of the MODFLOW simulation with GA. The performance of the proposed model is tested on groundwater management problem (maximization of total pumping rate from Nubian aquifer at steady-state). The results of the simulation show that the present groundwater extractions (511783 m3/day) will affect the groundwater flow patterns in the northeastern areas of El Dakhla depression causing a significant head decline of about 26 m in some wells at the year 2050. The increase of the groundwater extractions from the concerned aquifer by 25% (126355 m3/day) will cause a great head decline of about 60 m in some wells and accordingly a cone of depression around the wells in the year 2050. In addition, the GA solutions solve these management problems in the groundwater of Nubian aquifer. The results show that under the increasing of pumping rate by 25% (which equalizes an increase in the cultivated area by 6000 ha), the optimal pumping rate and drawdown range from 638137.9 to 595977.9 m3/day and from 4.292 to 10.36 m respectively. This result seems to be the best for optimal management of groundwater.
Key words: Hydrogeology, Nubian Sandstone aquifer, optimal management, genetic algorithm, MODFLOW, Dakhla depression, Egypt.
