The Tahoe Regional Planning Agency (TRPA) was established in the late 1960s to protect Lake Tahoe from extensive development. The agency's efforts have preserved the lake's beauty, once described by Mark Twain as "the fairest picture the whole earth affords." However, Lake Tahoe now faces new threats.
A recent report from UC Davis Tahoe Environmental Research Center shows that while winter clarity is improving, summer clarity is declining. TRPA is collaborating with the Tahoe Science Advisory Council to investigate factors affecting lake clarity, including extreme weather, warming temperatures, aquatic invasive species, and wildfire smoke. The agency continues to focus on strategies to restore clarity, which was nearly 100 feet when measurements began in the late 1960s.
Historically, plans for a city comparable to San Francisco threatened the region before TRPA's intervention led to protective measures and environmental standards. Despite these efforts, Lake Tahoe lost about one foot of clarity annually for three decades until stabilizing in the 2000s. Over the past 20 years, average year-round clarity has been around 69 feet.
Scientists attribute this loss of clarity to fine sediment from erosion and pollutants such as nitrogen and phosphorus contributing to algae growth. In response, TRPA and other agencies adopted the Clarity Challenge in 2011. This science-based plan aims for a 100-foot clarity goal by 2076 through initiatives like erosion control projects and stormwater treatment systems.