INTRODUCTORY COMMENTS      This document is intended as an update for research, monitoring and modeling being conducted at Lake Tahoe by faculty, staff and students at the University of California, Davis. This continues our series of annual progress reports first published in 1998. The document is intended to inform scientists, environmental managers, elected officials and the public of our progress in efforts to help understand and protect Lake Tahoe. The project summaries herein represent new or updated investigations over the past year, or recent material not previously presented.      The contributions included in this Progress Report do not represent the entire level of effort that UC Davis is involved with at Lake Tahoe. Rather, these are the contributions that are ready for dissemination at this time. Through its significant financial support for part of the UC Davis participation in the Lake Tahoe Interagency Monitoring Program (LTIMP), its efforts to build a state-of-the-art research and educational facility, and other activities, the UC Davis administration continues to support the research, education and public service aspects of our work.      Researchers from a number of UC Davis groups have come together to provide Basin agencies with the information needed for science-based decision-making. These include the Tahoe Research Group, Department of Civil and Environmental Engineering, Center for Ecological Health Research, Delta Group, John Muir Institute for the Environment, Department of Environmental Horticulture, Department of Plant Pathology and the Department of Land, Air and Water Resources. In particular, we acknowledge the Center for Ecological Health Research (CEHR), which has provided graduate student support for many Tahoe-based projects over the years. Indeed, the interdisciplinary focus of the CEHR has helped our multi-investigator approach to research at Lake Tahoe.      We continue to develop research collaborations with scientists outside of UC Davis. Contributions included in this document resulting from these collaborations include: Joaquim Losada (University of Girona, Spain), who has worked tirelessly on the Clarity Model; Simon Hook from the Jet Propulsion Lab (Pasadena), who is using Tahoe to validate high-tech remote imaging devices; Robert Coats, a hydrologic consulting scientist with Hydroikos (San Rafael, CA), who worked with the TRG in the mid-1970s and who is still involved in stream data analysis; Jim Oris and colleagues (Miami University, Oxford, OH), who are leading a multidisciplinary team on indicators of aquatic health; Glenn Miller from the University of Nevada at Reno, with whom we have worked for many years on the issue of exhaust products from marine engines; and Pirjo S. Huovinen at the University of Jyvaskyla, Finland, who studied the effects of UV-B light on Lake Tahoe phytoplankton.      All the reports presented below are centered on a theme of applied research; i.e., what do we need to know to assist in the restoration of the Lake Tahoe ecosystem. The findings represent a broad range from completed and peer-viewed to a work-in-progress. Readers are encouraged to contact specific authors before citing their work. As the works-in-progress continue and additional information is collected, certain conclusions could be subject to modification. For further information please contact: John E. Reuter, Tahoe Research Group, University of California, Davis. (530) 304-1473, fax (530) 753-8407, jereuter@ucdavis.edu Charles R. Goldman, Tahoe Research Group, University of California, Davis. (530) 752-1557, fax (530) 752-3350, crgoldman@ucdavis.edu