Vertical Leakage in Egypt's Nile Valleys Estimation and Implications

The determination of vertical ground‐water leakage is particularly important for irrigated agriculture where adequate drainage is required to prevent high water tables and related problems of salt buildup and waterlogging. This paper presents results from six different methods that were used to estimate vertical leakage for the Nile Valley in Egypt: (1) Calculation by Darcy's law; (2) rate of water table decline; (3) water budgets; (4) leaky aquifer test; (5) analytical solution; and (6) numerical ground‐water modeling. Considering the basic differences in the underlying assumptions of each method, the results were in relatively good agreement. The average vertical leakage determined for the entire Nile Valley was about 0.65ċ10-3m/day. This value is quite low, much lower than previously reported elsewhere in the literature. This low rate of natural drainage results in high water tables that cannot be lowered without the use of artificial drains. A salt concentration balance indicated that given the small value of vertical leakage in the absence of artificial drainage, the salinity of the ground water in the Nile Valley may increase to the point where it would hinder crop production.