Colorful aerial view of part of the Lee Vining Creek delta with winding blue waterways green and yellow vegetation, and a bright blue-green Mono Lake.

Water Chemistry

Strange water, strange towers

Mono Lake contains chlorides, carbonates, and sulfates—a chloride-carbonate-sulfate “triple water” lake. It is alkaline, with a pH of 9.8, and almost three times as salty as the ocean. At 6392 feet above sea level it will be slightly more than twice as salty as the ocean.

“The waters are clear and very heavy. When still, it looks like oil, it is so thick, and it is not easily disturbed. The water feels slippery to the touch and will wash grease from the hands, even when cold, more readily than common hot water and soap. I washed some woolens in it, and it was easier and quicker than any “suds” I ever saw. . . I took a bath in the lake; one swims very easily in the heavy water, but it feels slippery on the skin and smarts the eyes.”

–William Brewer, California Geological Survey, 1863

No way out

Why is Mono Lake water so salty? Mountains surround Mono Lake forming a closed hydrological basin–water flows into the lake, but it doesn’t flow out. The only way for water to leave Mono Lake is through evaporation. Four vertical feet of water can evaporate off of Mono Lake during the course of a year, and without fresh water streams to replace the evaporated water there would be no lake. Freshwater streams and underwater springs have brought trace amounts of minerals into Mono over the eons. Because the lake has no outlet, it is naturally saline. An estimated 280 million tons of solids are dissolved within the lake, and it is 2-3 times saltier than the ocean depending on its water level fluctuation over the years. Periodic eruptions of volcanic ash have also added considerably to Mono’s chemical mix.

The salinity of the lake is approximately 81 g/l. The Outstanding National Resource Water designation requires that the salinity be maintained under 85 g/l (the concentration of Mono Lake in May, 1996 and November, 1975). The average salinity levels ranged from 42 g/l to 99 g/l since 1913. Under a full-diversion scenario, the average salinity would have been approximately 133 g/l. Click here for an analysis of mineral quality.

Great Basin chemistry

As with most lakes, Mono Lake has a chemistry unique in all the world. Within Mono’s waters are dissolved sodium salts of chlorides, carbonates and sulfates (Mono Lake has a lot of salt and baking soda in it). In contrast, the Great Salt Lake contains abundant chloride but relatively no carbonates. Mono Lake is also rich in borate and potassium (boron concentrations among the highest ever recorded for a lake). Mono is one of the few remaining inland lakes in the Great Basin, a large geographical region with no outlet to the ocean. Mono Lake, Great Salt Lake in Utah, and Lake Abert in Oregon are the last few large hyper saline lakes in the Great Basin that host productive ecosystems and large numbers of migrating birds.

A soap to be reckoned with

High concentrations of carbonates in Mono Lake make it very alkaline. The pH of Mono Lake is approximately 10 (this measure of alkalinity is roughly equivalent to household glass cleaner). Because of this high alkalinity, Mono Lake water tastes bitter and feels slippery. Some observers of Mono Lake water claim it feels and behaves a lot like soapy water (sulfates and carbonates are a factor). William Brewer no doubt found this to be the case; however, you may not wish to repeat Mr. Brewer’s laundry experiment–Mono Lake water has a high enough pH to deteriorate clothing and footwear after repeated soakings.

A chemical jigsaw puzzle

For as much as we understand about Mono Lake’s chemistry, there is still much that we do not. Temperature, wind, climatic variations, underwater springs, and even biological activity can affect Mono Lake’s chemistry at different depths, locations and seasons. We are only just beginning to understand the more subtle changes in the lake’s chemistry. A USGS scientist who had been studying Mono Lake chemistry for many years once remarked, “Every year there are new surprises.” With such a unique chemical signature, Mono Lake will no doubt continue to provoke scientific study.

Learn More

Top photo courtesy of Rick Kattelmann.