Egypt suffers from a lack of rainwater and hot weather most of the year, which represents a challenge to the current trend to achieve optimum utilization of newly reclaimed land. Egypt's agriculture depends on irrigation that consumes about 85% of the available water resources. How this problem is managed is the aim of the study, where the controlled drainage (CD) application was evaluated as a water-saving tool and the long-term impacts of using such practice on crop productivity and soil salinity were predicted using DRAINMOD-S for El-Tina plain in the northwestern corner in Sinai. Soil texture of the plain varies between sandy loam to clay. Collected data of wheat and corn as winter and summer crops, respectively, were used to check the model reliability. The water table fluctuations were monitored on a daily basis. At the same time, drains discharges and salinities were also monitored during the whole growing season. The salinities of the topsoil till 1.0 m depth were measured. The obtained results from the model were assessed compared with the observed values of the daily water table fluctuations; lateral discharges, salt concentrations in the soil profile, and relative crop yield during each season. Simulation results satisfactorily matched the data collected from the field. Simulation values obtained for 10 years indicated that the average quantity of drain discharge increased by increasing the managed drainage depth which makes (CD) a promising tool for regulating the draining intensity, a remarkable increase in the soil salinity of the root zone will take place if the irrigation water salinity reaches values above 800 ppm, and consequently the high irrigation water salinity values will badly affect most of the crops that grow normally in the field under study except the high salt tolerance ones as wheat. A noticeable decrease in crop yields will be the inevitable result if both the managed drainage depth and water salinity are increased. The outputs of the study can be considered as guidelines for how to utilize the controlled drainage application under Egyptian conditions.

In this paper the problem of draining a heavy clay layer of low hydraulic conductivity over-lying an impermeable layer is treated mathematically by means of a combined system of pipe and mole drains. The complex potential, the stream functions, and the velocity potential are provided. New discharge formulas for both tile and mole drains are established. Formulas for calculating the velocity components at any point are provided. Effects of the different variables, the top clay cap thickness below drain center ,D, mole drain diameter ,d2, height of water above tile drain center midway between two successive tile drains, H, mole spacing ,a, and the vertical distance between tile drains and mole drains ,b, are studied.