[A water reservoir is an artificial lake created when a dam on a river is built to serve one or more purposes, such as generating hydroelectric power, providing a water supply for drinking, irrigation and flood protection] (www.eea.europa.eu). The effects of water tanks on the environment have caused controversy since their introduction. Although water reservoirs can bring many desired improvements to a society, they can negatively impact natural habitats and cause a number of environmental complications. The debate over whether water reservoirs are actually beneficial or harmful to human populations continues as new projects like China's Three Gorges are concluded. In the following essay I will give a critical review of the various disadvantages arising from the creation of a water tank. The creation of a water reservoir will have a significant impact on the natural habitats that existed before its construction. The surrounding areas of the dam will be flooded and reclaimed as part of the newly created water reservoir. Runoff from the initial filling of the reservoir will cause existing plant life to die and decompose. During the first few years, stabilization will take place where decaying plant life releases an abundance of carbon into the atmosphere. Further, the decomposition of plant matter that settles at the bottom of the reservoir will produce and release large quantities of methane. A weakness in the argument that a water tank is environmentally friendly. Not only does local plant and animal life suffer from this loss of land, but the river itself is affected by the vaporization. A water reservoir creates a larger surface area through which more water evaporates and is exhausted from the middle of the paper...and produces a pollution factor comparable to that of an oil-fired power plant. http://dams.org/httpwww.newscientist.com/article/dn7046http://www.cdc.gov/hab/cyanobacteria/facts.htmhttp://www.atsdr.cdc.gov/HAC/pha/DonnaReservoir/ DonnaReservoirPublicCommentPHA06302010 .pdfhttp://www.eea.europa.eu/themes/water/european-waters/reservoirs-and-damshttp://www.newscientist.com/article/dn7046http://www.internationalrivers.org/en/ node /1636http://docs.google.com/viewer?a=v&q=cache:Jkl8Z9b7mFYJ:rdgs.dk/djg/pdfs/103/1/09.pdf+flood+recession+cropping+reservoir&hl=en&gl=us&pid= bl&srcid =ADGEESjo6QDhkvxWgGiBUo92nXL0IwSNtOE_8trCQT_BL5cyXA07KOy-lWH0oV1GNfDtvFH8eYFSww2TwOR2S-ExPDaiUAwpjnLrp1BR00lZKejjXiVrCo8Ee4i9yo9OLSWjFISQ0gGz&s ig=AHIEt bRopK9vzHwGeWcwyFlZ-WIkBylIvA (Recession crops) http://www.cdc.gov/parasites/schistosomiasis/disease.html