Mono Lake
Mono Lake in California, which is about a half an hour drive from the entrance of Yosemite National Park, is an incredibly unique area in North America. Would you believe that it's at least 760,000 years old, possibly around one million years old, making it one of the oldest lakes in the western hemisphere? Absolutely incredible!
Scientists have been able to date the lake to at least 760,000 years ago by dating an ash layer to the Long Valley eruption. However, sediments below the ash layer suggest that Mono Lake could actually be the remnant of a much older lake that also covered parts of Nevada and Utah. At its height, Mono Lake was about 900 ft deep. It sits in part of the Mono Basin, which was formed over the last five million years, and has no outlet to the ocean; this lack of an outlet causes high levels of salt to accumulate in the lake, making the water more alkaline.
However, now the lake is about 158 ft deep at its deepest point and averages about 56 ft deep. This is in part due to Los Angeles diverting the tributary streams that fed into Mono Lake to the south instead to meet the water demand in the city. The diversion began in 1941 and, coupled with evaporation, Mono Lake had dropped 25 vertical feet by 1962. As the volume of the lake decreased, the salinity increased, robbing ecosystems of their freshwater source. Algae, which is at the bottom of the food chain, had a decreased photosynthetic rate; brine shrimp saw a drop in their reproductive abilities.
As the water level continued to drop, the lake bed became exposed in some areas, introducing particulate matter into the atmosphere and violating the Clean Air Act. The tufa structures, which you see in all of these photos, also became exposed. Thankfully, a committee was formed in 1978 to fight for the conservation and restoration of the lake. This committee partnered with the Audubon Society in a court battle to protect Mono Lake through public state trust laws.
Eventually this lead to a two-thirds decrease in water diversions from Mono Lake in order to allow the water levels to recover to a more acceptable level. And on September 28, 1994, an order was issued to protect Mono Lake and its tributaries. The goal is to restore the lake level to 6,392 ft above sea level. In 1941 it was 6,417 ft above sea level and in 2013 it was around 6,381 ft. Recent droughts have slowed down this goal, but thanks to the persistence of the Mono Lake Committee, we still have a lake to visit.
As you walk down the path to the lake, ambling past the sage brush, you'll encounter signs indicating the lake's water levels at certain points in recent time. This is how you really grasp just how much diverting the tributaries affected the lake. Alkali flies aside (they are harmless, I promise!), Mono Lake offers a change of pace from nearby Yosemite and some space for reflection and silent (or loud) awe.
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