The world’s third largest hypersaline lake, Urmia Lake is located 1267 meters above sea level in a closed continental drainage basin in northwestern Iran. The lake and its associated wetlands are home to 27 species of mammals, including the endangered Mesopotamian Fallow Deer, 212 species of birds, 41 reptiles and 7 amphibians. High levels of salinity – 200 ppt, which is 5.5 times more than average seawater – limits the fauna and flora that can survive within the lake. The most dominant flora is a green algae and the only marine zooplankton is a unique brine shrimp; Artemia urmiana, which plays a key role in the lake’s food chain, in particular as the primary source of food for migratory birds such as flamingos.
Although the unique and fragile environment of Urmia Lake is protected under the United Nations Ramsar Convention and registered as a UNESCO Biosphere Reserve location, the lake and its surrounding wetlands have been subject to extensive disturbances since the early 1980s. One of the main developments that severely impacted the lake’s environment was construction of the dyke-type “Kalantari” highway to connect two major cities across the lake. As a consequence, natural water circulation, sedimentation pattern and evaporation rates have been significantly altered and high levels of heavy metal contaminants have been introduced to the lake environment.
Our study of the elemental distribution patterns in the lake’s sediments reveals high mercury contamination near the Kalantari highway. Moderate mercury contamination is also detected in the main rivers that supply water to the lake, indicating progressive human development in the Lake’s catchment basins. Another major anthropogenic disturbance comes from excessive damming on the Urmia Lake’s tributaries and poor water management in their watershed areas. As a result, the lake’s water level has dropped by as much as 9 meters over the last two decades. The lake has also been losing water to enhanced evaporation in its southern “sub-basin” due to construction of the Kalantari highway.
Covering an area of 5000 km2, Urmia Lake is one of the largest bodies of water in west Asia and plays a crucial role in conditioning regional climate. Rapid shrinkage of the lake not only changes climate conditions in northwest Iran, but it also has a transboundary climatic effect on the neighboring countries such as Turkey, Azerbaijan and Armenia. Decreasing the lake’s surface area leads to expansion of salt planes with high albedo and affects the thermal balance of the atmosphere above the lake. Freshly exposed salt planes become new point-sources of toxic slat aerosols into the atmosphere, and can cause serious agricultural and health complications across the region. While enhanced global climate change cannot be ruled out as a contributor to higher evaporation rates at Lake Urmia, it is clear that anthropogenic sources have played a far more significant role in the graduate demise of the largest continental lake in the Middle East. The fate of Lake Urmia and the demand for saving it has increased tension between people and state authorities in a way that an environmental disaster has turned into a national security concern (“The Guardian” September 5, 2011).
Another important aspect of our research is the study of abrupt climate change in the history of the Lake Urmia. Long-term climate data can be used to assess the natural trends in regional climate and their effect on the lake’s water and sedimentary regime. During September of 2012, in collaboration with the Iranian National Institute for Oceanography, we conducted a field campaign in Urmia National Park and collected more than 20 meters of split cores from different locations around the Lake. The preliminary results of our study has revealed possible abrupt variations in past climate condition of the region, but the severity of such variability and its impact on Lake Urmia is the subject of our ongoing investigation.
By: Assistant Professor Ali Pourmand and graduate student Arash Sharifi of the Division of Marine Geology and Geophysics at RSMAS
