الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Subsurface drainage is an efficient tool to remove excess water and salts from the soil profile in order to enhance crop growth, In Egypt, the constraints to agriculture production are the very limited availability of agriculture land and the soil problems of waterlogging and salinization due to perennial irrigation after the construction of the Aswan High Dam. The Egyptian agriculture area is about seven million feddans of which about five million feddans are provided with subsurface drainage system. The performance of the existing drainage systems is governed by design and construction quality or operation and maintenance conditions. The performance assessment of the existing drainage systems is required for evaluating design criteria and quality of construction, introducing a better operational and maintenance arrangement, and implementing rehabilitation programs if found necessary. The monitoring of the drainage system in the 80000 feddans of the integrated soil and water improvement project, ISAWIP in Dakahliya Egypt, was carried out for the evaluation of its performance.
Some performance indicators were used to assess the drainage system components. The study includes evaluation of the drainage rates, the groundwater table depth and soil properties. A total of eight collectors serving an area of 500 feddans were chosen from the ISAWIP project area which had different soil properties, drain spacing, and drainage installation dates. The study covered three cropping seasons, summer 1996, winter 1996-97 and the summer season of 1997. The study of drainage collector performance includes a probability frequency analysis of the drainage rates, calculation of the drainage rates corresponding to the measured hydraulic gradient of the collectors and the overpressure head in the collector pips. Also, an analysis is made for the lateral drain spacing to evaluate the design values on the basis of the actual performance of the water table levels. The groundwater depth studies include the measurement of the fluctuations of groundwater according to the cropping type and a probability frequency analysis of its existence within the plant root-zone. The changes in soil properties analysis are also considered to evaluate the development of soil salinity and soil sodicity after the installation of the drainage system and their effect on the crop yield. Finally, the collected data from a specific part of the monitored area is used to test the validity of the simulation DRAINMOD-S model for future use in this area.