Effect of new Nag Hammadi Barrage on groundwater and drainage conditions and suggestion of mitigation measures

The government of Egypt has decided to construct a new barrage with hydropower facilities, 3.5 km downstream of the existing old one. The water levels in the head pond for the new barrage will be continuously maintained at a level with approximately 0.5 m higher than water level in the head pond of the existing one. To evaluate the effect of increasing the head pond water level on the groundwater and drainage, there is a need to enhance linking reservoir and stream/aquifer system. Visual MODFLOW has been used to simulate the surface water/groundwater interaction in the area of proposed new barrage. The model has been calibrated against the available historical groundwater levels for 25 observation wells based on the steady state conditions. Numerical modeling suggests that river stage is the primary control of rapid groundwater hydraulic head fluctuations in the aquifer system. At present the area at which the depth to groundwater table less than one meter is about 30 110 feddans ( 1 feddan = 4200 m(2)). This area will increase to be about 40 610 feddans after the construction of the new barrage and increasing the head pond water level. The mitigation measures to overcome the effect of construction of the new barrage have been discussed and their costs have been estimated and evaluated. Increasing the efficiency of existing drainage system by maintenance/upgrading and constructing a new pump station is recommended.