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Sustainability Of Natural Lakes As Affected By Agricultural Water Use

Congress: 2015
Author(s): Amin Alizadeh (Mashhad), Amin Alizadeh, Amin Alizadeh
Ferdowsi University of Mashhad, Iran1

Keyword(s): Sub-theme 10: Management of water resources,
AbstractINTRODUCTION Lake Uromiyeh is a large shallow, hypersaline Lake at the north-western end of Iran. In 1995 the average depth of the water at this lake was 19 meter with a water surface area of 6500 sq. km. However, during the last 10 years, the Lake has desiccated significantly. Many factors are blamed to be responsible for this detrimental happening. However, it seems that agricultural and water resources developments that have been implemented around the Lake Uromiyeh may be most important factor for this phenomenon. Because of these developments the area of cultivation around the Lake has increased from 280,000 Ha in 1990 to 450,000 Ha in 2013. Consequently, water use for agriculture has also increased from 1.8 BCM/yr to 5.6 BCM/yr respectively. Since all the water which are used for agriculture is either supplied from the aquifers around the Lake or diverting from the rivers ending the Lake, hydrological parameters, as well as the ecology of the lake, is no more balanced. MATERIALS AND METHODS Lake Uromiyeh is located at the northwestern corner of Iran. This lake, with hypersaline water is one of the largest lakes in the world. It is the largest in the whole Middle East [1]. Lake Uromiyeh is the twentieth large lake of the word and the third largest saline water lake on the earth. North-South length of this lake during the time of high water level is more than 140 km and its East-West width is 85 km [2]. Lake Uromiyeh and its surrounded wetlands have deep cultural, social, and economical bonds with the people of the region. It is estimated that 75 million people live within 500 km around the lake [3]. This Lake also possesses environmental functions at national and international levels. Lake Uromiyeh has a high ecological value. The Lake is protected as a national park and was declared a Wetland of International Importance by the Ramsar Convention in 1971. It has also been designated by UNESCO as a Biosphere Reserve in 1976 [4]. Lake Uromiyeh is the home to some 212 species of migratory birds including ducks, flamingos, pelicans and etc [5]. It is the home to 41 species of reptiles, 7 amphibians and 27 species of mammals too. The Lake itself is also the home to a unique salt water shrimp species, Artemia uramiana. This macro-zooplankton is the link in the food chain of the Lake, consuming algae and in turn consumed by migratory birds [5, 6]. RESULTS AND DISCUSSION Lake Oromiyeh is the dead end of a 5000 mountainous drainage system. Evaporation from the surface of the lake varies between 1000 to 2100 mm per year. The Lake is one-fourth as salty as Dead Sea, with salt content of 30 percent or 300 g/L which is 8 times as salty as sea water [7]. Because of the high salinity, Lake Uromiyeh does not support any fish or plants except some macro zooplankton like Artemia uramiana. However, in 2012, salt concentration of the Lake reached up to 550 gram/lit which threatens the life of this salt tolerant species too. Average annual precipitation on the lake is estimated to be 350 mm which is not enough to compensate its surface evaporation. Therefore, most of the water needed for supporting ecological sustainability of the lake should be supplied from the rivers ending to it. On the average these rivers discharge 5300 MCM/yr into the Lake which makes the hydrology of the Lake to become balanced. Surface area of the Lake depends on the level of water. Its maximum level was recorded in 1995 which was 1287 meter above sea level. At that time average depth of the water was 19 meter, and its area was 6500 sq. km. The level of water was also recorded in 2009 which was 1271 MASL which was 14 meters less than that of 1995. At this time, the average depth of water was only 3.3 meter, and the Lake had a surface area of 2700 At the year of 2012, average depth of the lake was estimated to be 3.0 meter with a water surface area of 2300 sq. km. Long term average level of water surface, during the last 45 years, has been recorded to be 1275 MASL and the average depth of water has been 7.5 meter. It has been shown that during the last decade the surface area of Lake Uromiyeh is rapidly declining [5]. Climate change and drought, have been raised to be responsible for desiccation of the Lake. However, it seems that the recent agricultural and water resources development around the Lake may be more elucidate. Because the predominant people's activity in the Lake Uromiyeh basin is agriculture, the area of cultivation has increased from 280,000 Ha in 1990 to up to 450,000 Ha in 2013. Therefore, annual water use for agriculture has increased from 1.8 BCM/yr to 5.6 BCM/yr. All the water needed for agriculture is either supplied from the aquifers around the Lake or diverting from the rivers ending the Lake. During the last three decades, 40 dams have been built on the rivers ending the Lake, 12 dams are also under construction and 28 other dam projects are under study. Supplied water from new dams may bring another 225,000 Ha of lands under cultivation. While the water potential of the Basin is not more than 8.0 BCM/yr, at present, about 5.6 BCM/yr is used for agriculture and 0.5 BCM/yr for domestic purposes. Therefore, only 2.0 BCM/yr is left to be discharged into the Lake for its sustainability. Considering the amount of 5.0 BCM/yr of evaporation from the Lake surface and 1.2 BCM/yr of annual rainfall over the Lake, it seems there is a need of 3.8 BCM/yr of more water to maintain the ecological sustainability of Lake Uromiyeh. CONCLUSION Considering the above mentioned facts, The possible solution which is left may be the management of water resources. Among the proposed managing steps are: (1) Decreasing agricultural water use by 2.5 BCM/yr. (2) Stopping the implemention of the dams undergoing construction or studying. (3) Decreasing water demand for agriculture. (4) Increasing water productivity in agricultural sector. (5) Establishing a powerful Integrated Water Management Institute. [1] Karbassi, A., Bidhendi, G., Pejman, A., & Bidhendi, M. (2010) Environmental impacts of desalination on the ecology of Lake Urmia. Journal of great lakes research, 36(3), pp 419-424, [2] Jalili, S., Kirchner, I., Livingstone, D. & Morid., S. (2010) The influence of large-scale atmospheric circulation weather types on variations in water level of Lake Urmia, Iran. International journal of climatology, 10.1002/joc.2422. [3] SEDAC. (Gridded population of the world. Future estimate. (Socio-economic data and application center.. [4]UNESCO,UNESCO-MAB Biosphere Reserves Directory.(2012). [5] Scott, D. (1970) The birds of Lake Orumieh and adjacent wetlands. (Islamic republic of Iran-results of surveys carried out by the Omithology Unit of the Department of the Environment.. [6] Abbaspour, M. & Nazaridoust, A., (2007) Determination of environmental water requirements of Lake Urmia, An ecological approach. International journal of environmental studies.64 (2), pp 161-169 [7] Eimanifar, A., & Mohebbi, F., (2007) Urmia Lake: A brief review . Saline system 3, 5.
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