Abstract

Geological studies conducted on approximately 100 m thick sequence of Urmia lake sediments indicates that the lake at the end of the last glacial period (about twelve thousands years ago) was converted to a playa. A similar condition occurred in the Van Lake that is located in neighborhood of Urmia lake. Precise satellite altimetry measurements show that from 1995 to the present lake water level has fallen about 9 meters. However, the level of Van lake, in the same period shows a quite stable level. We are to analyze the role of natural and human impacts on the recent drying up of Urmia lake. For this aim, the role of annual rainfall in the catchment area of the lake has been studied. Average precipitation in three cities of Tabriz, Urmia and Saqez in the years 1995 to 2010 compared to an average of years 1951 to 2010 shows an average reduction of 58 mm. Based on the time series of annual rainfall in the city of Van in Turkey average rainfall in the period 1995 to 2010 compared to an average of years 1973 to 2010, three mm increase is observed. In this study, the impact of human factors such as loss of water from dams and groundwater withdrawals as factors reducing the water level of the lake has been introduced. According to Iranian Ministry of energy data, there are 36 dams in operation in 2009 in Urmia basin. Apart from Zarineh¬Rud and Mahabad reservoirs, which dates back to the early 70s, the average volume of reservoir dams constructed by the year 1995, is estimated about 1 million cubic meters. Since 1995, dams with large repositories volume started. Accumulated volume of reservoir dams constructed since 1995 shows a negative correlation with lake water level. Other factors that seems to reduce surface water level are increasing groundwater withdrawals and changing patterns of water use from the mid 90's. Keywords: Urmia lake, Van lake, annual precipitation, dam, underground water, paleoclimate evidence.