What: When President Clinton visits Lake Tahoe next week to address the famous lake's environmental woes, UC Davis studies will be at the heart of the two-day talks, July 25-26. For a field tour and demonstration of the research into the lake's environmental problems, media are invited to ride research vessels, witness air-quality testing and see firsthand what plagues the surrounding forest. Prior to the boat trip and demonstrations, journalists are invited to attend a luncheon on the lake and hear a brief overview of the research that has taken place at the lake for nearly 40 years. Also outlined will be problems still ahead and possible solutions. The keynote speaker will be Charles Goldman, director of the UC Davis Tahoe Research Group, considered a leader in environmental research at the lake and in studies of lake ecology internationally. When: Thursday, July 24, at noon. The boat trip will begin at 1 p.m., returning to the dock at approximately 3 p.m. The entire program is expected to end by 4 p.m. Where: The trip begins with lunch and an overview at the Tahoe Yacht Club, 700 North Lake Blvd. (Highway 28) Tahoe City, (916) 581-4700 (map available). Visuals: -- Research divers will bring up samples of rocks covered with algae, one of the most visible signs of increased urbanization because of nutrient pollution. -- Demonstration of the underwater remote-video camera unit, used mostly to observe fish behavior deep in the lake. -- A Secchi disc reading, showing the loss of lake clarity over the years due to human impacts. The depth reading has been averaging about 60 feet, indicating a loss of about one-third of Lake Tahoe's clarity in the last 27 years. -- Unique views of the lake: the clarity of the cobalt blue water as seen from above, the effects of erosion at stream deltas, the patches of gray on the sides of the mountains indicating areas of dead trees. -- A portable air-quality monitoring unit, similar to the permanent ones in the Tahoe basin. Visual demonstration of air pollution, with the filters clogged with tiny particles that may cause human health problems and decrease visibility. -- A brief walk into the forest for examples of its declining health, including overgrowth of pine trees, a comparison of old- and new-growth forest, and the accumulation of dead and dying trees. -- Images of traffic problems: the main road through Tahoe City near the dock site is jammed with cars every afternoon. Background: The UC Davis Tahoe Research Group, http://trg.ucdavis.edu, has been compiling data from the lake for nearly four decades. The group maintains a lakeside research laboratory and a 37-foot custom-built aluminum research boat, the John Le Conte. Both the president and vice president have been invited to see the research facilities on board the John Le Conte. Key participants: -- Charles Goldman, director of the UC Davis Tahoe Research Group and internationally known lake ecologist -- John Reuter, ecologist with the UC Davis Tahoe Research Group and director of the Lake Tahoe Inter-Agency Monitoring Program -- Bob Flocchini, chair of the UC Davis Commission on the Environment, recognized for his air pollution studies -- Michael Barbour, UC Davis professor of environmental horticulture and expert in native California plants