Can Lake Tahoe be saved?
No one knows if we can restore Lake Tahoe’s remarkable water clarity or even what it would take to halt the decline in that clarity. As we described in last week’s article, there has been a fairly steady reduction in water clarity (the distance one can see objects, such as a Secchi Disk, below the surface) since scientific measurements began in 1968. The depth we could see in 1968 was 105 feet, or about 50 percent greater than today’s depth of about 70 feet. The considerable protection efforts by the federal government and California and Nevada since the late ’70s have not yet shown a positive effect in reducing the rate of water quality decline. But Alan Heyvaert, a researcher from UC Davis, has found evidence in the sediments on the lake bottom that the lake has recovered from pollution before. He has taken core samples of the layers of sediment on the floor of the lake which indicate that water quality was likely reduced during the Comstock silver mining boom of the late 1800s, when most of the forests of the Lake Tahoe Basin were clear-cut to provide timber for the mines. When the boom died out and the logging stopped, the forests in the basin grew again, and the soil disturbances healed over time. During the first half of the 20th century, the lake’s water quality and clarity actually improved. Given this evidence, there is hope that we can stop Tahoe’s decline if we can reduce the unnaturally high levels of nutrients and fine sediments that enter the lake due to human disturbances. Tahoe’s current problems began in the 1960s when the popular Squaw Valley Olympics triggered a boom — a sharp rise in urbanization in the Tahoe basin. The construction boom disrupted the watershed’s natural water filtration processes, and the combined effects of soil erosion, nutrient pollution and air pollution caused the decline we have measured since the ’60s. Because watershed restoration efforts to date have not reversed the downward trend of water quality, and because Tahoe is considered a national treasure, state, federal and local governments have committed to a new level of cooperative effort to save the lake from turning green. The Lake Tahoe environmental improvement program is a model for collaboration between public agencies and the private sector to stop the inflow of pollutants into the lake. More than 800 restoration projects are being planned and millions of dollars are being raised to fund this massive, cooperative effort. While experts agree the lake can recover if we greatly reduce pollution, they urge citizens to be patient. We must continue our efforts to repair the soil disturbances of urbanization, so the watershed can recover as it did when the forests grew back in the early 1900s. If we can greatly reduce the amounts of nutrient and fine sediment pollution that reach the lake, Heyvaert’s research indicates that water quality could improve within 20 or 30 years. — Watch for the Enviro Report in the Tahoe Daily Tribune each Wednesday, and tune in to KOLO-TV News Channel 8 Tuesdays at 5 p.m. Next week learn more about how removing snow the right way can make a difference. The Enviro Report is a collaborative effort of the Lake Tahoe Environmental Education Coalition, University of Nevada Cooperative Extension, UC Davis and the U.S. Forest Service. For more information, contact Heather Segale at (775) 832-4138, or log on to http://www.lteec.org or http://www.unce.unr.edu