The first-ever comprehensive publication of decades of research on the Lake Tahoe watershed's air, water quality, forests and economy is being released to the public today. The 1,200-page Watershed Assessment report -- developed by the U.S. Forest Service in response to President Clinton's 1997 visit -- reflects unprecedented collaboration among Tahoe researchers. The document will help guide future scientific work at the lake to allow for informed policy decisions to restore and preserve the lake. The following news tips highlight some of the findings by the University of California, Davis; University of Nevada, Reno; Desert Research Institute; and USDA Forest Service scientists. ----------------------------------------------------------- * Is there a clear future for Lake Tahoe? * Looking below the surface at Lake Tahoe * Prehistoric Tahoe basin ecosystem smokier, but healthier * What kind of water runs into Lake Tahoe? * In catastrophic blazes, does Lake Tahoe clarity suffer? * Moving toward water-quality improvements at Tahoe * Experimental watershed * Impact of combustion products on Tahoe wildlife * Atmospheric pollutants * Bark beetle strategy * Mapping Tahoe's geological history * Linking science to management * Adaptive management * Land management in the Tahoe basin ----------------------------------------------------------- IS THERE A CLEAR FUTURE FOR LAKE TAHOE? Should the current annual clarity loss continue in Lake Tahoe, by 2030 the lake will lose 66 feet of clarity, estimate UC Davis Tahoe Research Group scientists. That means that the point where the Secchi disk -- a white, dinner plate-shaped device dropped into the lake to measure clarity -- would be seen when placed into Tahoe would be at 39.6 feet, compared with a depth of 66 feet in the late 1990s. The murkiness would be accompanied by a change in color from the famous cobalt blue to green, related to algal growth, estimated by the scientists to be increasing at a rate greater than 5 percent annually -- resulting in a clarity decline of one foot per year. Led by limnology professor Charles Goldman, UC Davis scientists studying the lake since 1962 can now show that factors including urbanization, habitat destruction, air pollution and soil erosion have interacted to degrade the Tahoe basin's air and water quality, landscape and streams. Yet, the researchers point out in the Lake Tahoe Watershed Assessment report, some of the same features that maintained the exceptional water quality historically now threaten its future. "We now know that once nutrients enter the lake, they remain in the water, and can be recycled for decades. As a consequence, these pollutants accumulate over time and contribute to Lake Tahoe's progressive decline," says John Reuter, associate research ecologist and director of the Lake Tahoe Interagency Monitoring Program, a multi-agency monitoring and research effort formed to understand the effects of watershed and atmospheric processes on the water quality of Lake Tahoe. "The ability of Lake Tahoe to dilute nutrient and sediment inputs to levels where they have no significant effect on lake water quality has been lost." Contacts: John Reuter, (530) 304-1473, jereuter@ucdavis.edu; Lisa Klionsky, News Service, (530) 752-9841, lrklionsky@ucdavis.edu. LOOKING BELOW THE SURFACE AT LAKE TAHOE When UC Davis scientists probe Lake Tahoe to learn more about what's clouding its clarity, they look at the "neighborhoods," or microscopic organisms, beneath the surface -- tiny plants known as phytoplankton or algae. These algae are at the base of the aquatic food web and are very responsive to physical and chemical changes in the aquatic environment. UC Davis researchers have found and report in the Watershed Assessment that long-term data on such algae show a change in community composition and biodiversity towards a more eutrophic environment, one that is rich in nutrients, and thus algal growth. And if those nutrients -- nitrogen and phosphorus -- continue coming into the lake at their current rate, the Tahoe Research Group scientists foresee phytoplankton growth and diversification and expansion of different species of phytoplankton. "The current assemblage of flora and fauna in Lake Tahoe is largely the result of human influence in the Tahoe basin," the scientists report in the assessment. However, based on changes in the lake since the late 1800s when clear-cut logging flourished in the basin and sediments clogged the lake, it appears the lake can respond to watershed restoration, so that the human influence contributing today to the lake's higher nutrient level may be reversible. Contacts: Charles Goldman, crgoldman@ucdavis.edu; John Reuter, (530) 304-1473, jereuter@ucdavis.edu; Lisa Klionsky, News Service, (530) 752-9841, lrklionsky@ucdavis.edu. PREHISTORIC TAHOE BASIN ECOSYSTEM SMOKIER, BUT HEALTHIER The relatively good, smoke-free air found during the summer at Lake Tahoe is actually something of an artificial phenomenon, caused by years of fire suppression in the Tahoe Basin, say UC Davis air-quality researchers. But in fact, the prehistoric Tahoe watershed was at times a rather smoky place in which fires burned at low intensity during summer and fall, say Tom Cahill and Steve Cliff, who contributed to the Watershed Assessment report. "The recent conditions are an aberration, achieved by putting out naturally occurring fires," says Cahill, a professor emeritus. In fact, catastrophic fires today cause more damage, including acutely worse air quality, than did historic small but frequent wildfires that tended to burn relatively low to the ground, not reaching treetops. "Every square foot of the forest of the basin used to burn every 30 years," Cahill says. And, interestingly, according to a model developed by Cahill and postdoctoral researcher Cliff, those historical summer wildfires would not have reduced visibility below the current standards. By comparison, prescribed fires burning 125 acres a day during the fall would significantly violate human health-based air-quality standards for particulate matter and visibility thresholds, the researchers say. The researchers conclude that prescribed burns for forest health are best conducted when ventilation is good -- which typically occurs during summer daytime hours. The finding may interest forest managers who have hoped to conduct more intensive forest management during spring and fall when fire danger and Tahoe tourism are lower. Still, Cahill and Cliff say more study is needed of the air-quality implications of fire in the Tahoe basin. Contacts: Tom Cahill, (530) 752-1120, tacahill@ucdavis.edu; Steve Cliff, (530) 752-1120, sscliff@ucdavis.edu; Lisa Klionsky, News Service, (530) 752-9841, lrklionsky@ucdavis.edu. WHAT KIND OF WATER RUNS INTO LAKE TAHOE? Water running into Lake Tahoe -- from streams, storms, and even from groundwater -- brings with it more than what might meet the eye. The water brings nutrients and sediment, including nitrogen and phosphorus, all important contributors to the water's decreasing clarity. For the Lake Tahoe Watershed Assessment report, UC Davis' Tahoe Research Group studied what sorts of water inputs into the lake bring which amounts of nitrogen and phosphorus. Knowing more about the contributions can help in the quest for improved water clarity in the lake -- in part by future policy that might be developed to prevent the flow of nutrients and sediment in the first place. In the Watershed Assessment, the researchers report that more than half the nitrogen ending up in the lake during a year comes from atmospheric deposits on the lake's surface, and that direct runoff -- runoff from the more urban areas that flows directly to the lake -- groundwater and streams contribute between 10 percent and 20 percent each. For phosphorus, the researchers found that direct runoff provides 35 percent, streams, 30 percent and the atmosphere, 25 to 30 percent. The researchers note that the direct relationship between dissolved phosphorus and algal growth is of particular concern. Contacts: John Reuter, (530) 304-1473, jereuter@ucdavis.edu; Lisa Klionsky, News Service, (530) 752-9841, lrklionsky@ucdavis.edu. IN CATASTROPHIC BLAZES, DOES LAKE TAHOE CLARITY SUFFER? Not only are catastrophic modern forest fires damaging to forests, they also may contribute to the increasing algal growth of Lake Tahoe, which in turn diminishes its clarity. Nitrogen is stored in a tree's leaves; when trees burn completely in a devastating forest fire, there's a good chance that nitrogen ends up in the lake, say Tom Cahill and Steve Cliff, contributors to the Watershed Assessment report and air-quality researchers with UC Davis. "Ground-based, low-intensity prehistoric forest fires didn't release a lot of nitrates into the air, which is one of the factors that cause the lake to become green, whereas today, nitrate emissions are part of high-intensity, crowning fires. Additionally, modern wildfires have huge updraft plumes that can carry wood ash and phosphorus into the lake," also degrading the lake, Cahill says. Even though air-quality studies have yet to determine the specific sources of the phosphorus and nitrogen, in-basin wood smoke as well as road dust are thought to be significant sources of atmospheric phosphorus. "Further study of the links between sources, transport, chemical transformation and deposition to the surface of Lake Tahoe will be necessary to complete integrated management models," Cahill and Cliff conclude in their chapter of the Watershed Assessment. Contacts: Tom Cahill, (530) 752-1120, tacahill@ucdavis.edu; Steve Cliff, (530) 752-1120, sscliff@ucdavis.edu; Lisa Klionsky, News Service, (530) 752-9841, lrklionsky@ucdavis.edu. MOVING TOWARD WATER-QUALITY IMPROVEMENTS AT TAHOE To improve or protect the quality of Lake Tahoe's water and ultimately its clarity, what are known as best management practices (BMPs) are undertaken. Some of these practices are required by regulatory agencies as conditions for new construction projects; however, retrofitting existing development for water-quality treatments presents the largest challenge. Examples include lining of ditches with rock, using natural or restored vegetation to remove sediment and nutrients for urban runoff, and installing sediment traps and basins to remove sediment from runoff. Still, UC Davis and UNR researchers suggest in the Watershed Assessment that more research on the effectiveness of those practices is needed for the unique, mountainous conditions in the Tahoe basin. "Current levels of funding for research and monitoring in the areas of best management practices effectiveness, source identification and control and treatment of runoff in the Tahoe basin is inadequate to meet the demands," of management, the researchers say in the report. The researchers suggest working with the water resource, regulatory and planning agencies at Lake Tahoe to develop a priority or ranking system to select BMPs or other restoration projects -- with consideration given to those that reduce nutrient and sediment input into the lake. Contacts: John Reuter, (530) 304-1473, jereuter@ucdavis.edu; Lisa Klionsky, News Service, (530) 752-9841, lrklionsky@ucdavis.edu. EXPERIMENTAL WATERSHED Under the direction of environmental and resource science department chairman Watkins "Wally" Miller, researchers at UNR have secured an EPSCOR grant to establish an experimental watershed at Lake Tahoe. In conjunction with scientists from TRPA and the Forest Service, Nevada researchers hope to continue to unlock questions concerning sources of declining water clarity in the lake. Potential sites for the experimental watershed include Incline Creek and Tunnel Creek. "This program allows you to have a watershed so that if someone wants to try something, you try it, and you set it up as a research project, and you find out whether it works or not," Miller said. "Having an experimental watershed up there, having lots of instrumentation and people at the site on a regular basis, is going to be a really good thing." Miller said he envisions the site to serve as "complement" to water-clarity work being done at Lake Tahoe by the UC Davis Tahoe Research Group. "It's just another effort to more effectively integrate all the programs at Lake Tahoe," Miller said. Contacts: Watkins "Wally" Miller, UNR, (775) 784-4773; John Trent, UNR News Service, (775) 784-1582. IMPACT OF COMBUSTION PRODUCTS ON TAHOE WILDLIFE Glenn Miller, director of the University of Nevada's Center for Environmental Sciences and Engineering, has several ongoing studies into the impact of combustion products, particularly PAH (polycyclic aromatic hydrocarbons) on Lake Tahoe's wildlife. PAH is toxic to wildlife, and even the new generation of quieter, fuel-injected engines that comply with TRPA's 1999 ban of certain engines on the lake do not fully burn PAH, Miller said. PAH is a large hydrocarbon molecule that is soluble in fat but not water, and can enter fish via their gills and become incorporated in their bodies. PAH molecules are sensitive to sunlight, which causes a photochemical reaction rendering them highly toxic even in minute quantities, Miller said. It remains unknown whether concentrations of PAH molecules in recreational lakes are sufficiently high to harm fish and other aquatic life, Miller said. "In the next five years, we will all have a better idea of what the ecological and human impact of these substances are, and they will be regulated appropriately," Miller said. Contacts: Glenn Miller, UNR, (775) 784-4108; John Trent, UNR News Service, (775) 784-1582. ATMOSPHERIC POLLUTANTS Alan Gertler, head of the university's atmospheric sciences program and a research professor at the Desert Research Institute, completed a summer 1999 study that sought to quantify which pollutants are the most significant atmospheric nitrogen sources for both the forest and the lake in the Tahoe basin. Gertler and university graduate student Leland Tarnay found that during the summer months alone, the amount of nitric acid and ammonia absorbed by the lake is equivalent to what other studies have estimated go into the lake in a year. Gertler's study is a key first step in ultimately answering the question of the origin of Tahoe basin air pollution -- is it carried in the atmosphere from Sacramento or the Bay Area, or is it generated in the basin itself? Contacts: Alan Gertler, UNR, (775) 674-7061; John Trent, UNR News Service, (775) 784-1582. BARK BEETLE STRATEGY Gary Blomquist, university biochemistry professor, has studied bark beetle behavior and has worked with the U.S. Forest Service and the Nevada Division of Forestry on new strategies to ward off the attacks of the insect, which can kill great stands of coniferous trees. Trees felled by the rice-sized insects become dangerous fuels for wildfire. Contacts: Gary Blomquist, UNR, (775) 784-4104; John Trent, UNR News Service, (775) 784-1582. MAPPING TAHOE'S GEOLOGICAL HISTORY Richard Schweikert, chairman of the university's geological sciences department, geology professor Mary Lahren, Steve Wesnousky, director of the university's Center for Neotectonic Studies, and geology professor Robert Karlin have performed research to better map the ground under Tahoe and define weather patterns dating back thousands of years. Contacts: Richard Schweikert, UNR, (775) 784-6901; John Trent, UNR News Service, (775) 784-1582. LINKING SCIENCE TO MANAGEMENT Now that the Watershed Assessment is completed, what is to be done with it? How is it to be used? Five interagency working groups will begin meeting soon with the assessment report authors to address key findings. From these meetings, next steps for regulatory agencies will be defined. Contact: Linda Massey, USDA Forest Service Public Affairs, (530) 573-2688. ADAPTIVE MANAGEMENT Watershed Assessment report authors recommend that adaptive management be the strategy for getting additional information, reviewing data and making decisions about future restorative actions. What is the adaptive management process? How does it work? Why is it the best strategy? Contacts: Chris Knopp, USDA Forest Service, (530) 573-2600. LAND MANAGEMENT IN THE TAHOE BASIN The Desert Research Institute's John Tracy is conducting two studies to better understand the impact of the land-management system tool known as Individual Parcel Evaluation System. He is working with the U.S. Geological Survey and the Tahoe Regional Planning Agency to determine this parcel development system's anticipated impact on property values and its anticipated impact on sediment loading. "For the first time, what we've tried to do is tie an indicator of socioeconomic health (property values) to an indicator of environmental health (sediment loading in watersheds)," Tracy said. Contacts: John Tracy, DRI, (775) 673-7300; John Trent, UNR News Service, (775) 784-1582.