Lake Tahoe Is Now in ‘Terminal’ Condition

by Jon D. B.

Lake Tahoe Trouble: “In one 36-hour period, the lake level fell by 1.2 inches due to evaporation,” four-times the annual rate.

Wildfires have devastated much of the Lake Tahoe Basin in 2021. To make matters worse, Lake Tahoe itself is now terminal.

According to the UC Davis Tahoe Environmental Research Center, Lake Tahoe’s water level has fallen at an unprecedented rate over the past week. While recent snowfall was expected to fuel the lake, the famous body of water is now below the “critical rim.”

The center anticipated the fall. But the evaporation has been so intense that Lake Tahoe fell below the rim six days sooner than expected.

“In one 36-hour period, the lake level fell by 1.2 inches due to evaporation,” TERC reveals in a statement for Sierra Sun. “This is almost four times the annual evaporation rate of about 72 inches per year.”

Though wildfires continue to burn California, they are not to blame in this instance. The center cites high winds accompanying the recent show showers as the culprit for “rapid evaporation.”

The startling decrease isn’t over, either, which is why Lake Tahoe is now terminal. Water will continue to fall another 1-to-1.5 inches, the center says, so long as “significant precipitation” does not come. This mere inch equates to about 4-to-6-billion gallons of water per week. That’s enough to meet the daily needs of 48-72 million people.

In other words, “That’s not a drop in the bucket,” TERC adds.

What Does ‘Terminal’ Mean for Lake Tahoe?

Sometimes referred to as an endorheic lake, a terminal lake is one that does not produce outflow to streams and other bodies of water that rely on it.

The mass of Lake Tahoe, one of North America’s largest inland bodies of water, straddles the California-Nevada border. It’s now-terminal nature leaves Pyramid Lake and Walker Lake in danger in Nevada. In California, Mono Lake and the Salton Sea will suffer.

But the most immediate impact is on Lake Tahoe’s own shoreline. Low tide and water levels already have algae deposits rotting on the beaches of the South Shore, Sierra Sun cites. On the North Shore, docks are completely out of the water.

Thankfully, TERC does add that “It is likely that winter will arrive in the next few months and the lake level will rise above the natural rim soon after.”

Things will only return to normal if this winter is a wet one, however. “I the 21/22 winter turns out to be below average, next year the lake will fall below the natural rim much sooner and likely stay there for most of 2022,” the center continues.

What will that look like? Lake Tahoe residents and visitors could expect “many docks and boat ramps [to] be further away from the shoreline.” In addition, “The growth and the washing up of filamentous algae on the very wide beaches will increase.”

Most drastic of all, however, would be “The sill across Emerald Bay [ending] up above the water surface, physically turning Lake Tahoe‘s Emerald Bay into a separate lake, a similar issue that may occur at the mouths of many streams cutting off access to spawning kokanee salmon next fall.”