DESCRIPTION OF THE STUDY AREA AND DATA INVENTORY - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 103

entrance of the main drain Edko to the lake, there is a fixed measuring point of the flow to the lake;
monthly average records are available at this point from the years 2000-2006.
Figure (5-13): locations of pumping stations
Tidal Water Levels
The other main component in the hydrodynamic data set is the Tidal Water Levels variations. No
permanent station measures tidal flow at the lake exit channel to the sea. The Coastal Research
Institute performs some spot checks but does not keep systematic records. To overcome the lack of
tidal time series, which is a crucial input to the hydrodynamic model, a detailed survey in the literature
was done to understand the tidal properties at the location of the exit channel to the Mediterranean
Sea. Based on this information the WX-Tide software package was used to predict the tide and
currents according to the geographical location of the study area for a duration of six months.
Groundwater
Another important component of the hydrodynamic data sets is the information on the ground water
flow rates and pezometric heads in the western delta region around the lake area. That information is
needed to interpret for the water losses from the lake to the ground water table. The groundwater
aquifer underlying the Nile valley and Delta is recharged by seepage losses from the Nile, the
irrigation canals and drains, and deep percolation of water from irrigated lands. The total available
storage of the Nile aquifer is estimated at about 500 BCM but the maximum renewable amount (the
aquifer safe yield) is around 7.5 BCM. The existing rate of groundwater abstraction in the Valley and
Delta regions is about 4.8 BCM/year, which is still below the potential safe yield of the aquifer.
Field and laboratory experiments were carried out to determine the hydraulic parameters for the Nile
Delta aquifer. According to Sherif et al, (2002) and based on field data, an isotropic hydraulic
conductivity of 100.0 m/day and a storativity of about 10 -4 to 10 -3 were considered representative of
the regional values of the aquifer. Farid (1980) reported different values for hydraulic conductivity and
storativity at various locations. The hydraulic conductivity of the aquifer decreased toward the south
and west. An effective porosity of 0.3 was considered to represent the aquifer medium. The free water
table is measured at various locations. When this information is missing it is generally assumed to be
1.0 m below the ground surface. The piezometric head is measured periodically through an intensive-