Egypt is presently involved in a comprehensive program of land reclamation. Surface water has already been exhausted in meeting the urgent needs of agricultural expansion. If irrigation efficiency were increased, large amounts of surface water would be saved. However, this entails complex social, technical and political problems outside the scope of this paper. Ground‐water development has priority over increasing irrigation efficiency (which would take a longer time). This paper deals with identification of the intruded salt‐water wedge in the huge artesian Delta aquifer. The case is unique because most of this aquifer is invaded by salt water, and the major portion of its annual ground‐water recharge is derived from the direct seepage from the Nile River and the huge net of irrigation canals serving about 3 million acres (∼ 11,561 km2) of fertile land, as well as the infiltration of excess irrigation water. The annual overall ground‐water recharge to the aquifer was estimated as 6·40 km3/yr as explained later. Methods of salt‐water control and various techniques of water resources management are discussed in this paper. Because of the great variation in the depth of the aquifer, two unconventional methods for identifying the salt‐water wedge are also presented.

The free surface in two-dimensional gravity flow systems is determined by a simple equation in one iterative cycle. The base pressures at the impervious boundaries, as well as the pore-water pressures or total hydraulic heads within the flow medium, can easily be determined after the free surface is located. Two problems are analyzed: vertical dam cores and earth dams or embankments with sloping sides. In both problems Dupuit-Forchheimer assumptions are eliminated. In the second case, the effects of both the upstream and downstream slopes are taken into consideration. Although the two cases are under steady-state conditions, it is believed that the method is promising for solving problems under transient conditions whether the flow system is two-dimensional or radial. Introduction. The upper boundary of theflow region in a gravity flow system must be determined before the solution of flow problems can be found. Two-dimensional problems of this type are shown in Figures' I and 2: a vertical dam core and an earth dam or embankment with sloping sides. The general equation for steady-state conditions is the two-dimensional Laplace equation: where As a matter of fact, equation 2 would be Bernoulli's equation for steady flow if the velocity head term were neglected; this is normally the case in ground flow systems. The derivation of equation I is based on the usual assumptions that the soil is homogeneous and isotropic and that Darcy's law is valid. Evaporation, capillary flow, infiltration, and leakage effects are also neglected. Rigorous mathematical solutions are available for gravity flow systems [Polubarinova-Kochina, 1962]. These solutions are more or less limited in their practical applications, however. This has led to the use of other methods, such as numerical solutions [Shaw and Southwell, 1941; Kashef et al., 1952], and to the introduction of some simplified assumptions, such as Dupuit-Forchheimer assumptions.The proposed method is essentially based on the relationship between the seepage force, the * A, proposed method; B, relaxation method.

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