The environmental impacts of dams have come under renewed examination in recent years.
Dam proponents have historically understood that dams largely improve the status of water-related energy and environmental issues by, for example, producing hydroelectric power and increasing the water supply for irrigation. Recently however, the negative impacts of dams have come increasingly into focus. Discussion over whether dam projects are ultimately beneficial or detrimental--to both the environment and surrounding human populations--has emerged with a particular gravity following various public debates about the construction of Three Gorges Dam and other similar projects throughout Asia, Africa and Latin America. In evaluating the effects of dam projects, experts tend to discuss the advantages and disadvantages of river development in terms of upstream and downstream impacts. Since dams are essentially walls built across rivers, the upstream/downstream vocabulary facilitates organized discussion of the environmental and localized effects of dams, although all effects are intertwined and not necessarily easily divided.
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