The Tahoe Research Group has released its annual average transparency data for Lake Tahoe, showing that 1998 is the second worst year for the Sierra lake's clarity. The clarity depth of 66 feet is the second worst year after 1997 for Tahoe since the intensive sequence of frequent and long-term measurements was established in the mid-1960s, says Charles Goldman, director of the research group and a UC Davis limnology professor. Goldman notes that in 1997, the lake had slightly lower transparency than in 1998. The transparency measurements are made from aboard the UC Davis research vessel the John Le Conte about 35 times a year using the reliable Secchi disc, which resembles a white dinner plate. Poor viewing conditions related to wave height or cloud cover are eliminated to provide the average annual transparency, which varies considerably from month to month depending upon algal growth and suspended fine sediments. With sediment and nutrients such as phosphorus associated with urbanization flowing into the Tahoe basin, algal growth has increased at between 5 percent and 5.5 percent per year, Goldman reports. The U.S. Environmental Protection Agency has provided the research group with funding to develop a water clarity model, which should make it possible to predict future transparency conditions in the lake under various management strategies. Goldman and John Reuter, a UC Davis researcher and director of the Tahoe Interagency Monitoring Program, released the clarity findings this week to various state and federal agencies during a research symposium held in the Tahoe basin.