A combination of fresh precipitation and a resurgence in the population of zooplankton has Lake Tahoe appearing bluer than it has since the 1980s, according to UC Davis researchers who measure the lake’s water clarity levels.

The Keep Tahoe Blue crowd has something to celebrate, as Lake Tahoe is not only still blue, but is actually more blue. The water is technically not “blue,” but blueness is a sign of the water’s clearness. As Keep Tahoe Blue explains themselves (and Keep Tahoe Blue is an actual nonprofit organization, not just a popular bumper sticker), “The surface of Lake Tahoe is blue in part because it’s reflecting the sky,” and “Water as crystal clear as Tahoe’s absorbs red light, leaving the rich blue color that we all see.”

And in the wake of the epic volume of precipitation that fell on the area this winter, NBC Bay Area reports that the latest measurements show that Lake Tahoe is clearer than it’s been since the 1980s. That assessment comes from the UC Davis Tahoe Environmental Research Center (TERC), which released their annual Lake Tahoe clarity report on Monday.

“For the last five months of 2022, Lake Tahoe was the clearest it has been since the 1980s,” TERC says in their report topline. “That is due in part to a resurgence of the lake’s native zooplankton. They’ve provided a natural clean-up crew to help restore the lake’s famous blue waters.”

TERC has been measuring the clarity of the water for years using a surprisingly low-tech (but effective) method. They drop a 10-inch white disk called a Secchi disk into the water, and then measure how deep the disk can go into the water while remaining visible.

The precipitation has been a factor in the increase in blueness effect, but tiny microscopic animals called zooplankton are believed to be playing a bigger role in the improvement. Zooplankton gobble up silt, clay, and soot that can affect the water’s visibility levels.

“Other factors are known to influence year-to-year changes in clarity,” TERC explains in their report. “These include the magnitude of the runoff, the warming of the lake surface and the depth to which the lake mixes in the previous winter. The report examined all these factors and concluded that only the change in the zooplankton community could account for the magnitude of this year’s change.”

This year’s “average clarity depth” was 80.6 feet, the best it’s been in decades. Thoug TERC notes that “The states of California and Nevada, which share a border at Lake Tahoe, are actively working to restore lake clarity to its historic 97.4 feet.”    

Related: Tahoe Sees Second-Snowiest Winter on Record; Snow Buries Ski Lifts in Sierras [SFist]

Image: cropbot via Wikimedia Commons