Assessment of Urmia water levels fluctuation and increasing salt area in the North West of Iran

Lake Urmia in the northwestern corner of Iran is one of the largest permanent hyper saline lakes in the world and the largest lake in the Middle East. It extends as much as 140 km from north to south and is as wide as 85 km east to west during high water periods. Qualitative and quantitative degradation of water resources is one of the major challenges in the way of sustainable development، Baghvand et al.، 2010; Nasrabadi et al.، 2010a; Nasrabadi et al.، 2010b; Rowshan et al.، 2007; Serbaji et al.، 2012; Guinder et al.، 2012; Li et al.، 2012; Siddiqui، 2011; Pei et al.، 2011; Ying et al.، 2011،. Features and phenomena in the earth’s surface have been changed over time; the lakes as one of these features and due to having a closed environment are not considered as an exception. Due to climatic changes such as reduced rainfall، increased temperature and also uncontrolled use of surface water resources in watershed areas، distinguished changes are exposed، Sadatipour et al.، 2012; Sandeep et al.، 2012; Madani et al.، 2012; Mirbegheri et al.، 2012; Arias et al.، 2012،. Monitoring such changes should be considered as an important issue in the national and regional development and natural resource management. Currently، monitoring the coastal areas and extraction of water at different intervals is regarded as an infrastructural research interest due to the significance of coastal zone management and dynamic nature e of such sensitive ecological environments، Reveshty and Maruyama، 2010; Nasrabadi et al.، 2009; Pamer et al.، 2011; Kavian et al.، 2011; Karbassi et al.، 2011; Mortazavi and Sharifian، 2011; Lei et al.، 2011; Hudak، 2011،. Urmia lake is the twentieth largest lake of the world and at the same time one of the most unique and invaluable global water ecosystems، Karbassi، et al.، 2010; Ahmadi et al.، 2011; Ahmadzadeh Kokya et al.، 2011; Farzin et al.، 2012، . The lake’s surface area has been estimated to have been as large as 5620 km2 but since 1989 it has generally been declining and was estimated from satellite data to be only 2032 km2 in August of 2011، Land sat data،. The decline is generally blamed on a combination of drought، increased water diversion for irrigated agriculture within the lake’s watershed and mismanagement. The main sight of this study are to Assessment and analyze of Urmia water levels fluctuation and increasing salt area، to model the lake surface fluctuation regime by linking the observed data to satellite data in the north west of Iran. Lake Urmia is an endorheic or terminal lake meaning that water leaves the lake only by evaporation. As is generally the case، this leads to a saltwater body and in the case of Lake Urmia، salinity is quite high. The lake is bounded between 37°5´ -38°16´ latitudes and 45°01´ - 46°longitudes at 1275 m above sea level. Its surface area ranges from4750 to 6100 km2 and the average and greatest depths account for 6 and 16 m، respectively. In order to study the fluctuations of Urmia Lake surface area، multi temporal Land sat Images، ETM، TM sensors، over a 23-year period، 1989 to 2011، were used. In the present study، the coastlines extraction for each year was done in two major steps using the ERADS software & ARC GIS. Firstly، geometric and radiometric corrections as well as different filters on the selected images were applied to make the spectral difference of objects more clear. Secondly، supervised classification method has been used to extract coastlines. To use the supervised classification، the preparation of the training area from the lake surface has been carried out. The reflection values in these areas have been generalized to the entire lake surface using the software and thus، the border between the lake and surrounding areas has been set precisely. Finally، through the algorithm for conversion of two vectors، the coastline limits have been drawn for different years. To carry out the analysis of images the ARC GIS software has been used. Satellite altimeter data measured the lake’s level in 1989 to be at its highest level of any time in the past 30 years. This is in agreement with Hassanzadeh and others، 2011، who state a measured water level of roughly 1 278 m above sea level for the same time. Both measures show a steady decline from that year forward with the most recent satellite altimeter data indicating a drop of approximately 7/40 meters between 1989 and 2011. Because Lake Urmia is a terminal lake with no significant water outflow the only way water leaves the lake is by evaporation. Therefore، if the lake declines it is either by increased evaporation or a decrease in water coming into the system. The Zarrineh Rood River is the largest of the thirteen main rivers discharging into Lake Urmia which are the source of the majority of the Lake’s water budget. Additional input comes from rainfall directly over the lake، floodwater from the immediate watershed and a very small fraction from groundwater flow. The main objective of this study was to assess lake water levels fluctuation using satellite images and geographic information system. To achieve this goal along with field observations and the satellite images of Land sat Multi-spectral images of the years، 2011-1989، sensors، TM، ETM +،. were used and processed. Based on the results achieved during the 23-year-old when the final models، an indication average height Lake water level to the level of 7/40 meter and the decrease in 3588 square kilometers of surface area of Lake water and land turned into the arid soil and sediment salts salt in the last few decades. Most changes due to water loss height، especially in the South East and the east coast of the lake is visible. The rise of water level fluctuations during the study period was significantly accelerated change and backward along the coastal lines 1 to 8/5 km coastline is.