When researching places to visit during our California road trip, I happened across an area called Mono Lake. Just off the main highway into Yosemite National Park, I thought it might make for a quick stop along the way. The area wasn’t especially well sign-posted from the main road, but as we wound our way down to the lake shore, we could see a parking area and short boardwalk along the edge of the water.
The edge of the lake was dotted with tufa, rock like structures that formed in the lake. Beneath the lake a series of calcium-rich springs flow up through the lake, and the calcium bonds to carbonates in the lake water forming calcium carbonate, a type of limestone. Over time the calcium carbonate builds up gradually forming the tufa. The process is similar to that which forms stalactites and stalagmites, but tufa can form much faster, sometimes growing inches in just a few days.
What makes this location so unique is that because of changes in the water level, many of the tufa that formed under the water are now exposed. The lake catchment provides water for Los Angeles and from 1941 the Los Angeles Department of Water and Power started taking significant volumes of water from the streams that feed the lake causing the lake level to lower. Between 1941 and the early 1980’s the lake level dropped 45 vertical feet, loosing half of its volume and doubling in salinity.
From the mid-seventies, the impacts of the lower lake levels and increased salinity were studied and a non-profit citizens group was formed to try and protect the lake and the unique ecosystem. Eventually in 1994 the State Water Board modified the licenses which stipulate how much water can be diverted from the feeder streams ensuring that the lake level will slowly be allowed to increase.
Even with the slowly increasing lake levels, the water has an unusual composition, being about two and a half times saltier than the ocean and with a high level of alkalinity (pH 10). The unusual composition of this lake is because Mono Lake doesn’t have an outlet stream, so although water flows into the lake, it only leaves through evaporation, and as the water evaporates the salts and minerals that flow into the lake get more concentrated over time. These conditions make the lake inhospitable for fish, but provide the perfect conditions for brine shrimp and alkali flies which in turn provide food for over 300 species of resident and migrant birds.
We both found the area absolutely fascinating and the Mono Lake Committee had done such a great job of explaining the unique geology, human and natural history in the area.