NHANCEMENT OF WELL HYDRAULICS NSIDERING THE EFFICIENCY OF SCREENS

Abstract

Due to the continuous increase on population, successive governments in Egypt have encouraged agriculture and establishment of new communities in the desert fringes of the Nile valley. When initiating a new communities or a major agriculture in a desert area, the greatly challenge is to maintain sustainable water resources and waste management programs. Construction of new communities in the east of the Nile delta such as the tenth of Ramadan, badr, Al Shrouk, El-Obour, New Heliopolis, new Cairo, and Al Salheyah cities. Encompass most of the growing population in the delta reclamation have targeted the sand flood plain in east of the Nile delta because of the good potential for water resources and transportation accessibility. In Egypt, groundwater is the second most important water resource, after the Nile River, and recently its development and management have become extremely important. El-Obour is a newly constructed city in east delta located 25 km from Cairo. The city covers almost 200 km2 and is characterized by variations in topography and geology. The area concerning is characterized by a low relief, while it is bounded from the north by Hamza ridge (220-210 m above MSL) it shows a variable topographic features, from about 30 m above MSL in the south to about 173 m above MSL in the north, sloping regionally in a south ward directions geologic structure, especially the faults, has a direct influence on the topographic features of the study. The variations in topography in the study area helped to collect water from the various sources up to the clay layer which led to rising water levels above the ground layer of the clay layer up a reservoir surface. Over the time and the continued leakage of water from surface sources of ground water level rise gradually until it reached a level close to the surface of the earth, especially in low-lying areas. This problem is severely recorded at the southern part of the city where the area is topographically low especially in 6th and 7th districts. The distribution of the clayey layers clearly coincides with the areas facing water logging problems. The closer these clay layers are situated near the surface and the larger their thickness the more water logging is observed. Hence, the distribution of these clay layers was used as a key factor to design dewatering strategies Another problem concerns the efficiency of vertical filter drains which used as a dewatering solution for the problem of water logging in the study area. These drains were clogged by fine sand particles and their efficiency decreased. In these lower parts, problems arise because of water logging and groundwater mounding. Where the ground water appeared at different places in the city and at different times, where in some places appeared at drilling depths ranging from 1 to 2 meters from the ground surface, as well as appeared in some areas of the sixth and seventh district and some areas of the Industrial Zone. Also problem of depositions in vertical filter drains regarded • In order to simulate the existing conditions and study the effect of the proposed solutions, a numerical model was constructed using the Visual MODFLOW Package. The constructed numerical model was calibrated using the field observed data. Visual MODFLOW was selected to simulate the proposed dewatering solution of vertical filters drain. The model described a new method for simulation by using the wall boundary condition to simulate the vertical drain and simulate the clogging process by changing the outlet area of the drain. Three scenarios for clogging to simulate the deposition problem in the area of screen and filters of the drain used. This model enhanced the proposed dewatering solution by a downward value