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Concordia University (1994)

Optimization of surface subsurface flow for an arid wadi-reservoir system

Saleh, Walid

Titre : Optimization of surface/subsurface flow for an arid wadi-reservoir system

Auteur : Saleh, Walid

Université de soutenance : Concordia University

Grade : Doctor of Philosophy (Ph.D.) 1994

Résumé
Arid and semi-arid lands suffer from scarce water conditions. Rainfall occurs over brief intervals and has an erratic behavior producing short intensive floods. If intermittent surface water floods are optimally managed they may help respond to the increasing demands for water in arid countries. One of the appropriate uses of such water is the recharge of ground water aquifer systems. Underground storage represents a cost-free augmentation of surface storage. Also, water stored in the underground can be used to cover a part of the increasing need arising from rapidly expanding urbanization, as well as industrial and agricultural demands. An optimization procedure employing dynamic programming is presented for obtaining optimal water recharge from a network of reservoirs in an arid watershed. The final solution yields an optimal releases and storages from the study’s reservoir network. The optimization procedure takes into account evaporation losses while meeting the irrigation demands of two selected crops (wheat and barley). The objective function was formulated to give maximum infiltration. The procedure employed produces more or less uniform infiltration by maximizing the minimum infiltration volume. That is, during drought periods, a "hedging rule" places high penalty on large deficits than on small ones. Its main function is to increase infiltration during periods of low flow. Since wadis are not gauged to provide records of flow, monthly as well as weekly inflows were generated using a watershed model. The model provided an assessment of flood wave movement through the dry wadi and the flood occurrence of some rainfall events. The overall optimization approach has a simulation process nested in the optimization procedure. A generalized numerical infiltration simulation component based on the control volume method was integrated into the optimization procedure for the simulation of ground water flow. It helps evaluate the soil moisture redistribution and the horizontal and vertical wetting front corresponding to optimal conditions. The optimization procedure was carried out for a system of farming reservoirs in the Muwagar watershed south east of Amman, Jordan. The study area consisted of a 74 km$\sp2$ watershed with three existing reservoirs and several irrigated agriculture lots. The results obtained correspond to an optimal release and storage policies, for one, and three reservoirs on monthly as well as weekly basis, and for five reservoirs on a monthly basis only. The ground water recharge model using the optimal storage and release policies showed a substantial increase in the horizontal wetting front in comparison with the present situation

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