“Many of the world’s saline lakes are shrinking at alarming rates, reducing waterbird habitat and economic benefits while threatening human health.”
So begins a recent report in Nature Geoscience.
Saline lakes, also known as salt lakes, are landlocked bodies of water with a concentration of dissolved minerals several times higher than in freshwater lakes, sometimes even higher than in the ocean. The largest in the world is the Caspian Sea, but other well known saline lakes include the Dead Sea and the Great Salt Lake. Two dozen of the world’s most important saline lakes are shown in Figure 1. The larger blue dots indicate those that formerly had a surface area larger than 250 square kilometers (larger than a circular lake about 18 miles across).
Wayne Wurtsbaugh and his associates looked at the volume of water in 6 saline lakes. The sample is loaded towards the United States, but includes two in Central Asia:
- The Aral Sea (Kazakhstan and Uzbekistan)
- The Dead Sea (Israel, Jordan, and Palestine)
- The Great Salt Lake (Utah, United States)
- Lake Urmia (Iran)
- Owens Lake (California, United States)
- Walker Lake (Nevada, United States)
Figure 2 shows the loss of water in the 6 lakes over time, with some lakes going back to 1875. Every one of them has experienced a dramatic loss.
The Dead Sea has experienced the lowest percentage loss, the reason being that it is a very deep lake (Maximum depth 978 ft.) Despite that fact, the surface of the lake has dropped 28 feet, and it has been divided in two. (Wikipedia 2018b, Wurtsbaugh et al, 2017).
Starting in 1913, the streams that fed Owens Lake in California were diverted to provide water to Los Angeles. (See my post on California’s water supply, here. For movie buffs, this is also the subject of the famous movie Chinatown.) The lake has been almost completely drained, and is now mostly a dry lake (salt flat). (Wikipedia 2018c)
Perhaps the “poster child” for what can happen to dry lakes is the Aral Sea. Formerly one of the largest lakes in the world, with a surface area of 26,300 square miles (almost the size of Lake Superior), water diversion has turned it into several small lakes, plus a whole lot of dry lake bed (salt flat). Figure 2 shows the Aral Sea in 2014, with the gray line showing the former extent of the lake. (Micklin 2007, Wikipedia 2018a, NASA 2014)
The demise of these lakes has not been caused primarily by a decline in precipitation, but rather by diversion of water for human consumption. In some cases, the consumption has been to provide potable water for large population, as in the case with Owens Lake and Los Angeles. In other cases, it has been to provide irrigation water for crops, as in the case with the Aral Sea.
Many aquatic species live in saline lakes, and the lake’s demise obviously devastates them. In addition, the survival of many species of migratory birds depends on an unbroken chain of places they can stop and refuel on their long journeys. Break the chain in even one place, and their survival is threatened. Saline lakes are one of the places birds stop during migration, and draining the lakes threatens to break the chain.
In addition, when saline lakes are emptied, what remains behind is a fine, salty dust that is laced with heavy metals and pesticide residue that drained into the lake over many years. It is picked up by the wind and blown for miles. Posts in this blog have discussed the health threats represented by airborne particulates, and the damage done by this salty dust has been well documented around the Aral Sea. Aerial photographs revealed salt plumes extending as much as 500 km. (310 miles) from the lake. It is considered an essential factor in the region’s high incidence of both acute and chronic illness. (Micklin 2007)
Of these lakes, the 2 with the highest percentage of remaining water are the Dead Sea and the Great Salt Lake. Wurtsburgh et al conclude that the key to conserving these lakes is to provide the river inflow needed to restore and sustain them. Otherwise, these once important lakes will remain (become) nothing but a choking dust in the wind.
Micklin, Philip. 2007. The Aral Sea Disaster. Annual Review of Earth and Planetary Sciences. 35:47-72. Available online at http://www.annualreviews.org/action/doSearch?SeriesKey=earth&AllField=Micklin&startPage=&ContribAuthorStored=Micklin%2C%20Philip.NASA. 2014.
NASA. 2014. ”The Aral Sea Loses Its Eastern Lobe.” Earth Observatory. Downloaded 2018-01-04 from https://earthobservatory.nasa.gov/IOTD/view.php?id=84437.
Wikipedia. 2018a. “Aral Sea.” Wikipedia. Viewed online 2018-01-04 at https://en.wikipedia.org/wiki/Aral_Sea.
Wikipedia. 2018b. “Dead Sea.” Wikipedia. Viewed online 2018-01-04 at https://en.wikipedia.org/wiki/Dead_Sea.
Wikiepedia. 2018c. “Owens Lake.” Wikipedia. Viewed online 2018-01-04 at https://en.wikipedia.org/wiki/Owens_Lake.
Wurtsbaugh, Wayne, Craig Miller, Sarah Null, Justin DeRose, Peter Wilcock, Maura Hahnenberger, Frank Howe, and Johnnie Moore. 2017. Nature Geoscience, Vol 10. DOI: 10.1038/NGEO3052. Available online at www.nature.com/naturegeoscience.