Urban Water Supply and Demand

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1 – INTRODUCTION Water availability critically influences human well-being and directly affects ecosystems and the environment. Water supply and demand issues are especially more complicated in areas of rapid urban and population growth. Projections say that 46 to 52 countries and a total population of 3 billion people will be water stressed by 2025 (Rosegrant, 1997). And to increase a little bit more the complexity, there is the fact that water availability is not homogeneous. Water is irregularly distributed and, consequently, water problems are region-specific. Water supply and demand problems usually fall into the wicked problem category. Their complexity is based on the fact that they have many interdependencies, are …show more content…
Groundwater supplies and surface water supplies outside of the local catchment area are commonly used when the local surface water supply is insufficient. Increasing levels of groundwater exploitation can significantly decrease groundwater levels, leading to several environmental problems. An example is what’s been occurring in the North China Plain, where the mean depth to water changed from 7.23 m in 1983 to 11.52 m in 1993, characterizing a decrease of approximately 0.5 m per year (Changming et al, 2001). Groundwater table drops at those rates can severely impact the environment. Groundwater depletion can lead to the formation of depression cones, which can often cause land subsidence. Water level drops in coastal areas result in intrusion of seawater, deteriorating the water quality. And, in urban centres and surroundings, water resources are threatened by untreated urban and industrial wastewater discharge. The increasing demand for water resources can severely affect natural ecosystems. For the construction of a dam, a large area is going to end up under water, severely impacting terrestrial ecosystems. Overexploitation of water for irrigation can seriously affect aquatic ecosystems. An example of that is what happened in the Klamath River (Oregon, USA): more than 30,000 salmon perished because farmers were allowed to withdraw unsustainable

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