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Greater Mexico City (''Zona Metropolitana del Valle de México''), a metropolitan area with more than 19 million inhabitants including Mexico's capital (''Distrito Federal'', or DF) with about 9 million inhabitants, faces tremendous water challenges. These include groundwater overexploitation, land subsidence, the risk of major flooding, the impacts of increasing urbanization, poor water quality, inefficient water use, a low share of wastewater treatment, health concerns about the reuse of wastewater in agriculture, and limited cost recovery. Overcoming these challenges is complicated by fragmented responsibilities for water management in Greater Mexico City: * The Federal government is in charge of regulating the use of water resources, contributing to the financing of investments and supplying bulk water from other basins through the National Water Commission Conagua; * The State of Mexico provides bulk water, treats wastewater and assists municipalities in providing water and sanitation services in its part of Greater Mexico City; * 59 municipal governments in the part of Greater Mexico City located in the State of Mexico and one municipality in Hidalgo State are in charge of water distribution and sanitation for their constituents; * the government of Federal District provides water supply and sanitation services to its constituents through its water department; and * two irrigation districts in Hidalgo state are in charge of irrigation with wastewater from Greater Mexico City. Given the size and political importance of Greater Mexico City, a major flood or a major water supply interruption would be a national political crisis potentially threatening the stability of the federal government. The security of water supply and the functioning of the storm water drainage of the metropolitan area thus are major concerns for the local, state, district and federal governments. In response to the challenges outlined above, the Federal Government, the State of Mexico and the Federal District initiated a US$2.8 billion Water Sustainability Program in 2007. In parallel, the government of the Federal District launched a Green Plan which includes water conservation as an important element. Investments envisaged under both plans include an increase in wastewater treatment, the import of groundwater from irrigated areas North of the city where the groundwater table increased due to irrigation with wastewater, the construction of a major new storm water drainage tunnel, increased water imports from an expansion of the energy-intensive Cutzamala system that pumps water up over more than 1000 meters, and the reduction of non-revenue water from 36% to 25%. == Geography and climate == The climate of the Valley of Mexico ranges from a semi-arid belt in the north to a tropical one in the south. The valley receives about of annual rainfall, which is concentrated from June through to September/October with little or no precipitation during the remainder of the year. There are hardly any permanent rivers today. Groundwater is the main water resource in the valley.〔 The valley has no natural drainage outlet for the waters that flow from the mountainsides, making the city vulnerable to flooding. It was artificially opened through the use of canals and tunnels starting in the 17th century, entirely draining what used to be Lake Texcoco. The rural southern portion of the Federal District and of the Valley of Mexico, in particular the Sierra Chichinautzin is the most important natural recharge zone for the Mexico City Aquifer due to relatively high levels of precipitation and the high permeability of its basalt rock.〔(Mexico City's Water Supply:Improving the Outlook for Sustainability ), National Research Council, Academia Nacional de la Investigación Científica, A.C., Academia Nacional de Ingeniería, A.C., NATIONAL ACADEMY PRESS, Washington, D.C. 1995, Chapter 4〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Water management in Greater Mexico City」の詳細全文を読む スポンサード リンク
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