Tehran: Impacts of Urban Expansion on Water Resources
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Tehran: Impacts of urban expansion on water resources 1975 The Iranian capital of Tehran The following images extends from the southern slopes (1,700 show how "Greater Tehran" has meters above sea level) of the Alborz expanded from 1975 to 2000. "Greater Tehran" is Mountains into the Dasht-e Kavir desert in a geographic and administrative expression for Tehran the south (1,100 meters above sea level). and the immediately adjacent built-up area. Compared with Iran's many ancient cities Tehran once received adequate water supplies from the Amir Kabir it is a relative newcomer, having served Dam on the Karaj River (in the extreme upper left of the image; the as the capital city for only 200 years. shadows of the surrounding mountains make it appear dark) and the Latian Dam (on the right of the image, above the city) Ranking among the world's largest Photo: Steve Rode on the Jaj-Rud. metropolises, Tehran is also part of Iran's most densely A RM E AZERBAIJAN N I A Clouds cover small parts of the image. To the TURKMENISTAN IRAN populated province. The latest census (1996) records a CASPIAN SEA south and west of the urban area lies a belt of fertile TURKEY population of 11 million for Tehran province, with 6.7 million Source: UNCS Source: land, which appears as green. TEHRAN in the city itself. While the city's annual population growth The joint cartographic visualization of the built zone of dropped to only 0.9 per cent from 1986 to 1996, the the years 1975, 1988, and 2000 illustrates Tehran's urban AFGHANISTAN province as a whole has grown by 4.7 per cent per year, growth. IRAQ and is projected to exceed 15 million individuals by 2012. KUWAIT Tehran's consistent rapid expansion and population PERSIAN GOLF PAKISTAN growth are significant factors contributing to several The Lar Dam was completed in 1980 SAUDI ARABIA 1988 (see lake in the extreme upper right of BAHRAIN environmental problems. Among these problems, the OMAN 25.07.1975 Landsat MSS colour composite RGB, bands (1,4,3 National capital QATAR the image) to meet Tehran's growing International boundary UNITED ARAB 0 100 200 300 km shortage of potable water is of major concern. The province EMIRATES Provincial boundary OMAN 0 100 200 mi contains only two per cent of the total water resources of demand for potable water. The dam is Caspian Sea semi-arid Iran but already houses 20 per cent of the built on the River Lar, which discharges country's population. Geologically, the Tehran plain can be northwards into the Caspian Sea. likened to a bowl, limited to the north by high mountains and to the south by the hills of Kahrizak. Tehran is far from any Amir Kabir Dam major river and relies on water supplies located at a distance Lar Dam Damavand Pick 5699m. from the city. Karaj Latian Dam The slow development of reservoirs, water mismanagement Tehran and a series of dry years have combined recently to diminish water resources dramatically. Meanwhile, the lack of sufficient Kasraeean Nasrolah Photo: sewage facilities results in most human wastes being discharged untreated into domestic sewage wells, a situation leading to 2000 18.07.2000 Landsat ETM+ colour composite 19.09.1988 Landsat TM colour composite RGB, bands (1,4,3) RGB,bands (1,4,3) deterioration of the groundwater quality. At the same time and as the city has grown, more potable water is being imported into the This image illustrates the city's geographic expansion and increased density, as well city. This water in turn is used and adds to the existing polluted as the significant decline in reservoir levels. It also reveals the important loss of groundwater, particularly in lower, southern Tehran, where flooding often occurs. green spaces in the north of the city. Figure 1, which has been created by rectifying and vectorizing old maps of Tehran, illustrates the The expansion and growing density of the city are quite notable in the west historical growth of the city. and northwest. The mountains to the north and east and the desert in the south are natural obstacles to Tehran's further sprawl. The urban texture is increasingly expanding towards the west of the city, where there are no natural limits to development. Karaj 1956 18.07.2000 Landsat ETM+ colour composite RGB, bands (1,4,3) G R I D Here the city nearly connects with the province's biggest suburban area, Karaj (not included in the E u r o p e 1941 8 http://www.grid.unep.ch 7 available images; Tehran's expansion, however, is so extensive 6 that a part of Karaj is visible in the left side of the image of 1925 5 year 2000 in Figure 1). 4 3 Given its geographic circumstances, one can ask DIVISION OF EARLY WARNING AND ASSESSMENT population (million) population 2 whether Tehran is reaching its natural limits of Prepared with the support of the Swiss Agency for the Environment, Forests and Landscape 1889 1 For more information, please contact: Saman Salari Sharif, UNEP/DEWA~GRID-Europe, 0 expansion, or whether its water problems 1901 1921 1941 1961 1981 2003 International Environment House, 11 Chemin des Anémones, 1219 Châtelaine, Switzerland 1891 1911 1931 1951 1971 1991 year will eventually limit further growth. Tel +41 22 917-8294 Fig 1. Historical growth of Tehran 1881-1956 on the image of 18.07.2000 Fig 2. Population in Tehran municipality Fax +41 22 917-8029 The boundaries and names shown and the designations used on these maps do not imply official endorsement or acceptance by the United Nations. 1891 - 2001 Created at UNEP/DEWA/GRID-Europe; March 2005 E-mail [email protected].