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Agricultural development is a complex undertaking because of the numerous factors involved, including those of a physical and non-physical nature. Land and water have often been (and are nowadays sometimes still) regarded as a means to grow crops. This approach, based on the utility principle, may lead to dismal failures. Fertile lands were thus turned into a saline wilderness within a relatively short period. In the above approach the management problem, i.e. the problem of cause-and-effect relations has been neglected. More than is the case at present, proper planning must relate the physical, environmental, economical, and social factors involved. But the integration of all these factors encounters some major difficulties of which insufficient data and lack of an exact and comprehensive methodology are the most serious. But planning cannot be postponed indefinitely or until the last information has been obtained. Effective development of agriculture, of which water resources management forms an important part, is undoubtedly one of the greatest needs of to-day's world. The complexity of the problem has outgrown traditional problem-solving methods. The principal aim of this article is to describe in brief some recent developments in water resources management methods and water supply optimization techniques. Two models are discussed: a linear programming model for finding optimum solutions of water supply and a mathematical groundwater basin model, which is capable of simulating various extraction and replenishment flows and predicting the consequences of future engineering works. The unique feature of these two models is that the output of the linear programming model can be used direcly on the groundwater basin model to test the physical validity of the economic solution.