Lake Tahoe, N. America



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 Tahoe Basin
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  Images: Lake Tahoe, California
Tahoe Basin Pilot Project

The Tahoe Basin Region exemplifies how regional ecosystem forecasting increasingly requires cross-disciplinary, cross-institutional collaboration and systematic methods for knowledge sharing to support solutions networks. By choosing a regional planning challenge of national significance as our testbed for cross-disciplinary problem-solving with a range of user groups, we highlight the need to link diverse knowledge, from natural geophysical and biological processes (since the start of the most recent interglacial period to today’s Tahoe residents and visitors), all of which are relevant to understanding Tahoe Basin dynamics.

Key management questions relate to the need for a quantitative perspective on the natural baseline eco-dynamics of the Tahoe Basin, which is critical to assess the influence of human activities on Lake Tahoe and its surrounding watersheds. Scientific knowledge, to be useful for land management, needs to be made available in a format that is easily accessed and understood by decision makers.

Images from Lake Tahoe.

The Tahoe Regional Planning Agency (TRPA) serves as a federally recognized, bi-state level authority for all land-based planning and development in the Lake Tahoe Basin (LTB). By design, TRPA cooperates broadly with 20+ federal, state and local agencies including: Federal Highway Administration, Fish and Wildlife Service, Natural Resources Conservation Service, CalTrans, Lahontan Regional Water Quality Control Board, Nevada Department of Environmental Protection, Nevada DOT, Carson City, Douglas, El Dorado, Placer and Washoe counties, the City of South Lake Tahoe, and a dozen unincorporated towns and the Washoe Tribe, all of whom manage geospatial data and information, as well as real-world assets in the LTB. Sharing these geospatial resources via a common GIS framework is essential to ensure future use of Tahoe science and other knowledge in formulation of Tahoe policy.

A twenty-year planning effort in the Tahoe Region has swung into high gear. The Bureau of Land Management made $300 M. available for Tahoe Basin Restoration (under management of the Tahoe Regional Planning Agency) over the next ten years. Pathway 2007 launched public policy-oriented workshops in January 2005. The University of California (led by UC Davis) in partnership with Sierra Nevada College, the Desert Research Institute, and the Rand Corporation is building a new facility for its Tahoe Environmental Research Center on the North Shore of the Lake, on the Sierra Nevada College campus. Many research groups are already working in this region.

The USGS and universities have a range of science teams working at Lake Tahoe; see the USGS Summary of Geography Research at Tahoe (pdf)

The California Center for Collaborative Policy, a partnership of California State University, Sacramento, McGeorge School of Law, and the University of the Pacific, is leading public participation and policy formulation through the Pathways 2007 initiative for the Lake Tahoe Restoration Project. High public and policy interest in Tahoe regional planning offers an opportunity to highlight the importance of assembling diverse teams to address the need for a better interface between science findings and public policy. Tahoe can be a model for other locations, e.g. Chesapeake Bay, the Everglades, Columbia River Gorge, and the Channel Islands. Efforts toward integrated planning at Tahoe involve TRPA, the Forest Service and many other agencies, USGS, and the dual state collaboration of California and Nevada.

The Tahoe Basin is a complex system. The regional water system in the Tahoe basin controls many of the variables that impact the quality of the natural environment for wild life, human habitation, and natural resources in the basin. Variables include water budget and quality, sediment stability, slope stability, flora and fauna diversity and distribution, etc. Larger categories impacted by these factors include recreation (water sports, winter sports, summer sports, human habitation, etc.), natural hazards (wild fire, landslides, tsunamis etc).

The USGS Integrated Science Plan for the Tahoe Region will recognize that the regional water system, and the variables influenced by basin hydrology, are dynamically linked, both to paleo-geologic events and to future geologic processes through complex interactions defined by the physics, biogeochemistry, and biology of the region. For example, the hydrodynamics in the basin directly influences sediment release and transport, slope stability, and soil structure. Flora, while providing fuel for wild fire, also introduce countervailing feedback in the system by influencing soil structure and water channeling. Because water runs downhill, the entire system is controlled by topography across all scales in the basin, while topography is controlled by geologic events, thus closing many loops in this dynamic system. In populated areas in the Basin, these systems have been transformed dramatically through direct and indirect human interventions in the water cycle.

We chose the Tahoe Basin as our pilot project for six reasons:
  • First, the Tahoe Basin is a significant environmental landmark, now threatened by environmental degradation. Because of its high profile, many people recognize the need to make the right decisions to preserve Lake Tahoe and its environs for future generations

  • Second, while the impacts of human activities in the Tahoe Basin are significant, they have been regionally constrained by the watersheds surrounding the Lake. So the Tahoe Basin provides an ideal testbed for decision support teams and to showcase a method that can later be adapted and applied in other locations.

  • Third, the Tahoe Basin is a region with potential for improved environmental management through increased use and better application of NASA’s Earth Observing Satellite data, e.g. for climate studies, ground cover models, forest health monitoring, analysis of the impacts of development, etc.

  • Fourth, accurate ecological forecasting depends upon translating scientific findings into effective decision-making. Teams representing diverse disciplines and institutions collaborating are a key to effective policy. Scientists and engineers, planners and managers, policy-makers and the public must continue to communicate and collaborate in order to effect constructive policies for Tahoe.

  • Fifth, there is great need to bridge the gap between scientific research and policy/ public outreach in order to integrate all aspects of the effort at Lake Tahoe into a single integrated framework.

  • Finally, the proposed Tahoe Geolibrary aims to become a premier demonstration of public-private participation in technology for sustainable development. With new initiatives for collaboration, such as Pathways 2007 and the Tahoe Geolibrary, TRPA and its collaborators can build a community that will preserve Tahoe over centuries to come.
Lake Tahoe Clearinghouse is an integrated system being assembled so that management can try out alternative hypotheses and sets of decisions in a simulated environment and explore outcomes, intentional or not.

Tahoe is the ideal landmark to showcase a process and decision support framework that can in the future be applied to many regional, cross-disciplinary ecosystem challenges, from coastal management to disaster response.

Tahoe GeoLibrary development led by Tahoe Regional Planning Agency with other partners offers a “collaborative magnet” for a range stakeholders, from scientists to policy-makers, that will contribute to a big picture mapping of cross-disciplinary problem linkages for ecosystem forecasting. As the GeoLibrary grows, its knowledge management and decision support framework will enable new project linkages and collaborative opportunities. The GeoLibrary will not only offer a portal to relevant NASA products, and to USGS research and output from the USGS Integrated Science Plan for the Tahoe Basin (launched January 2005), but also serve a range of decision-makers and collaborative teams.

The first step toward a GeoLibrary is to enlist stakeholders to contribute their knowledge, data, models, and software. Networks of linked processes and models will show co-dependencies and impacts of human interventions. Dynamic visualization of the results of these models, displayed in a format that is quickly, easily understandable, and supports decision-making. The Tahoe Geolibrary’s GIS framework can serve as the foundation for integration and visualization of cross-disciplinary information. Engineering an urbanization computer model that can be manipulated to project how different management scenarios could affect future conditions in the Tahoe Basin requires integration of components into an interactive GIS format that decision makers can use for land use planning — a GIS expert system for scientists, policy-makers and land managers.

Studies of environmental change caused by human activity within the Lake Tahoe Basin have in the past been hampered by lack of knowledge of the natural baseline conditions and lack of knowledge of the magnitude and frequency of catastrophic events that existed before human activity began to impact the basin. Tahoe knowledge mapping for science applications requires that spatial and temporal data be integrated, both to understand the history of this complex region, and for ecological forecasting.

USGS plans to deliver specific information on important hazards, including droughts, floods, earthquakes, landslides, and mudflows over the past 11,000 years, and to investigate the consequences of these events on flora, basin hydrology, fire frequency, bio-productivity, and sediment mobilization in the Tahoe Basin. The USGS will also conduct relevant specialized studies, such as evaluating the probability of earthquake-triggered landslides on the margin of Lake Tahoe under existing structural conditions of the fan-delta system. By developing a basin-wide geologic and geo-hydrologic framework, USGS researchers will support more informed decisions regarding land use issues affecting Lake Tahoe Basin, and show the geologic structures that may impede or enhance ground-water flow and guide other hazard, water, and environmental studies.

The Tahoe Environmental Geographic Information System (TEGIS, cf. Tahoe Regional Planning Authority: TRPA) regional compilations (mixed 1:24K, 1:62.5K, and 1:125K scales) have all been attributed in NADM V4.3. (North American Data Model). Newly available geologic mapping at 1:24K scale for the northern end of the Tahoe Basin by the University of California Santa Barbara and the University of Nevada Reno is being attributed in NADM V4.3 by the USGS team assigned to this task.

The USGS team has already created a prototype expert GIS system in an ESRI ArcGIS geodatabase for generalization of the existing geologic maps of the basin. Using this system, Tahoe geology can be generalized and interpreted for erodability, acid buffering capacity, bio-available calcium, iron, potassium and other nutrients, and geotechnical properties and hazards, as well as traditional geologic attributes, such as formation name, age, and lithology. More work is needed to refine and advance the system from prototype to operational status. Production tools also need to be developed to manage the underlying geodatabase and to evolve the system as new mapping becomes available. The proof-of-concept for this work has recently been demonstrated by the USGS team for the Columbia River Basin Ecosystem Management Project. Preliminary demonstrations in the Tahoe Basin confirm that knowledge of the geologic foundation of the environment is an important tool in land management.

Utilizing newly available 1:24K geology of the northern portion of the Tahoe Basin and the existing TEGIS geology, the USGS team will organize the geology in the North American Geologic Map Data Model in an ESRI geodatabase that contains a geologic expert system for non-geologically trained users. This expert system, as demonstrated for the CRB and preliminarily for the Tahoe Basin, can provide geologic information in a GIS form useful for forest, animal health and habitat, human behavior, geologic hazards, and other land-management issues.

This existing system can be adapted to address general construction and geologic hazards management, evaluating the effectiveness of existing, and guiding the design of future, sampling programs, as well as defining input into site-specific decisions, contributing to forest and animal health, and other applications. The geodatabases assembled will become a valuable adjunct to the ongoing management of the Tahoe Basin. In addition, the tools and techniques developed will be readily transferable to other geologic settings and environmental applications.

Integrating Systems for Decision Support. This system can be adapted to address general construction and geologic hazards management, evaluating the effectiveness of existing, and guiding the design of future sampling programs, defining input into site-specific decisions, contributing to forest and animal health, and other applications. The geodatabases developed in this project can become a valuable adjunct to the ongoing management of the Tahoe Basin. In addition, the tools and techniques developed are readily transferable to other geologic settings and environmental applications. Key tasks are
  • first, to transform the existing Tahoe Basin maps, and other geological data, from their various forms (coverages, shapefiles, spreadsheets, etc.) to a uniform geodatabase format (ESRI) to develop advanced, geologically sophisticated software tools; and
  • second, to deploy an operational, web-accessible digital geologic map of the Tahoe Basin, together with expert system tools that relate its content to ecosystem behavior and choices, of direct use to land managers and policy makers.
Functional capabilities and tools that will result from these tasks include
  • Property Inspector for entry/editing of geological map data, specifically
  • Map Manager for coalescing individual maps into a common geodatabase, and
  • Web Expert integrating webmapping with expert system interpretation

For LAKE TAHOE Resources and Organizations, see the Resources Page.


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