Lake Tahoe Interagency Monitoring Program Since 1979 the Tahoe Research Group has led the effort to provide monitoring data for lake water quality, tributary water quality and the nature of compounds deposited directly to the lake surface by rain, snow, and dry fallout at Lake Tahoe. The group first identified and has documented for more than fifteen years the growth in algae production and decrease in lake transparency as the population in the Tahoe basin has increased. Erosion Modeling In cooperation with the UC Davis Department of Civil and Environmental Engineering, this project is investigating erosion from natural and disturbed hill slopes and other topographic conditions in the Tahoe Basin. The model we have developed allows for the study of erosion at small (30m x 30m) as well as large scale (watershed) levels. Lake Tahoe Nutrient Cycling Study One of the major research goals of the TRG is to construct a mathematical model which relates land use to nutrient input and water clarity at Lake Tahoe. This issue is of national interest as evidenced by the inclusion of Lake Tahoe water quality as a separate item in the original U.S. Clean Water Act. The use of predictive models based on our understanding of the lake, in association with models constructed from our long-term monitoring data base, will allow us to build a model to predict future water quality conditions based on various nutrient loading scenarios. Lake Tahoe Marina Dredging Study Dredging and new marina construction has long been a controversial issue at Lake Tahoe because of its potential negative impact on the lake's water quality. At the request of the California Regional Water Quality Control Board, we are conducting a comprehensive study of the short-term, long-term and cumulative impacts of dredging on Lake Tahoe water quality; best management practices for dredging and disposal of dredge spoils; and other potential environmental impacts. Major objectives are 1) to establish the relationship between the nutrient content in the marina sediment and the overall impacts of dredging, and 2) to determine the most effective approach to dredging while reducing water quality impacts as much as possible. California Lake Water Quality Study Many lakes and reservoirs in California are experiencing increased development and urbanization within its watershed. The California Regional Water Quality Control Board and the Tahoe Regional Planning Agency have requested studies to be done at a variety of water bodies, including Fallen Leaf Lake and Upper and Lower Echo Lakes, to 1) determine current water quality, 2) measure concentrations of U.S. EPA priority pollutant metals in the lake and its major tributary, 3) investigate recently reported taste and odor problems, and 4) recommend changes to water quality plans based on the results of this study. Northern Nevada Lakes and Reservoirs Water Quality Study This study was conducted in cooperation with the Nevada Division of Environmental Protection and the Tahoe Regional Planning Agency. Many water bodies in Northern Nevada fulfill vital functions as both natural ecosystems with important aquatic and wildlife habitat and recreational sites. A study of water quality characteristics of four lakes and reservoirs was commissioned as a follow-up to a similar study the TRG did in 1989. Sierra Nevada Gold Streams Mercury Project This project examines mercury in the food (in trout and several aquatic invertebrates) in foothill rivers and streams. This area has been home to mercury-utilizing gold mining in the past, as well as current high intensity gold mining activities like suction dredging, which typically expose buried historic mercury. As an alternative to water-based assessments of pollutant loading and exposure, we have developed field and lab techniques that use indicator species of aquatic organisms to measure field exposure to mercury in various streams. Pyramid Lake Research Project A terminal lake with no outflow, Pyramid Lake in Nevada is the largest saline lake in North America and part of the Pyramid Lake Paiute Indian Reservation. A diversion dam on the Truckee River severely impacted productive fisheries for two species which have supported the Paiute Tribe for thousands of years. Upstream urbanization of the Reno metropolitan area has led to an increase of nutrients and other wastes discharged into the Truckee River as wastewater and agricultural runoff. Funded by the EPA, we are conducting a major water quality study of Pyramid Lake. Lake Tahoe Fisheries Habitat Enhancement Project The California Tahoe Conservancy funded this project to test experimental fish habitat structures in the deep waters of Lake Tahoe. Using SCUBA, sonar and direct observations from the Tahoe Research Group's underwater Remote Observation Vehicle, data will be collected on the effectiveness of structures designed and installed by the TRG on spawning habits and shelters for important native and sport fish in Lake Tahoe. This project serves as the beginning of a more comprehensive effort by the TRG to assist basin agencies in restoring degraded nearshore habitat. Ski Run Water Quality Treatment Project In 1989 the TRG was requested by the California Department of Justice to participate in the South Lake Tahoe Redevelopment Project as water quality consultants. We numerically modeled the nutrient and sediment trapping potential of a combined detention basin design and linear wetland. From this work we were able to recommend the best operating schedule to comply with Tahoe basin regulatory requirements. Recently we were hired by the city of South Lake Tahoe to conduct the water quality monitoring of this project. Our tasks include analysis of groundwater and surface water quality, construction of numerical nutrient budgets, and other evaluations. Lake Tahoe Sediment Core Study Bottom sediments of lakes act as reservoirs of history, and can be used to document not only the history of the lake itself but also of the surrounding watershed. Chemical and biological analyses of deep sediment cores taken from Tahoe provide us with 1) qualitative measures of sedimentation rates over the years, 2) the major component for nutrient loss in the formation of the lake's nutrient budget, and 3) a record to evaluate the impacts of previous land disturbances and urbanization within the Tahoe Basin.