Wednesday June 18, 2025
CalMatters —
Lake Tahoe’s iconic blue waters were the third murkiest on record last year and the worst they’ve been in several years, according to data from scientists who have studied the lake for decades.
Clarity of the alpine lake — measured by dropping a white disk into the water and noting when it disappears from sight — is a signal of its overall health. Tiny particles are major culprits of reduced clarity, including the sediment and other pollutants that wash into the lake from runoff and air pollution and the plankton that grow in its waters.
Researchers with UC Davis’ Tahoe Environmental Research Center reported today that the average murkiness in 2024 was exceeded only in 2021, when fires blanketed the lake in smoke and ash, and in 2017, when the lake was clouded by sediment-laden runoff during a near-record wet year.
The report says that clarity levels are “highly variable and generally not improving,” and recommends that “future research should focus on examining the nature of the particles that affect water clarity.”