Urban population growth has been an uninterrupted and accelerating phenomenon throughout this century. By the year 2000 almost 50percent (2850 million) of the world's people will have become urban dwellers. Urbanization has profound impacts on the hydrological cycle, at varying scales. Many cities are situated on aquifers whose abundant, but fragile, groudwater resources are being rapidly degraded by inadequately controlled exploitation and indiscriminate effluent and waste disposal practices. This degradation is a contributory cause of increasing water resource scarcity, escalating water supply costs and growing health hazards.
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