November 10, 2017

Lake Urmia in Iran – a dying salt lake

Lake Urmia in Iran—once the world’s second-largest salt lake—was still eight times the size of Germany’s Lake Constance 15 years ago. EOC research shows that the lake has shrunk to a tenth of its original area. This development also threatens the nearby UNESCO biosphere reserve, home to bird populations like flamingos and pelicans.

Spatiotemporal changes in Lake Urmia’s surface water cover between 2003 and 2016

This dramatic decline is attributed to the massive construction of dams, excessive water extraction for agriculture, and pronounced drought in recent years. The drying up of the lake exposes huge salt flats that are a threat to the environment, agriculture, and the health of the population in the region. The wind picks up and disburses the dry salt particles, which seriously contaminate both agricultural and natural surfaces when they are deposited. In addition to salt, noxious substances have also accumulated in the lake from agriculture runoff over the years. They, too, are exposed as the lake dries out and can be caught up and distributed by the wind.

In 2003 Lake Urmia with its ca. 4250 km² had eight times the area of Lake Constance. Systematic analysis of global water surfaces at EOC shows that the lake had shrunk to about 10% of its original area by 2015, when just under 500 km² of the shallow lake was permanently covered with water. EOC obtains these data from Global WaterPack, a record of the daily fluctuations in the extent of water surfaces. The time-series analysis is based on data recorded by the MODIS sensor on the US satellites Terra and Aqua. This data product, developed by EOC scientists, makes possible daily monitoring of the global water body over the last 16 years at a spatial resolution of 250 metres. The depletion of Lake Urmia has already been reported in a number of science publications. But studies to date have only shown the size of the lake surface at discrete dates within a year, or as a mean value over longer periods, whereas there are strong seasonal variations. With Global WaterPack the drying out of the lake in its seasonal and spatial dynamics can be studied in detail. How does the lake react to natural fluctuations in rainfall and snowmelt? How much of the diverted water actually enters the lake? Do restoration measures have a long-term effect? These and other questions can be addressed in the future with the help of Global WaterPack.

The drying out of Lake Urmia and the resulting problems have been increasingly tackled in recent years in the context of local, national and international initiatives and programmes. Improved water management plays an important role in making lake regeneration possible and limiting the damage that has already occurred (UNDP, 2017). Information products based on earth observation technology, like Global WaterPack, can provide a valuable basis for planning. The first positive effects of the measures that have now been taken can already be seen in the data for 2016.