Role of Watershed and BMP Modeling Tools in Facilitating Watershed Planning, Development of Tmdls, and Formulation of An Implementation Strategy for Pollutant Reduction

Lake Tahoe is a designated Outstanding National Resource Waterbody, an international attraction for millions of tourists and recreationalists each year, and home to some 90,000 full and part-time residents. Over the past 39 years, the clarity of this ultra-oligotrophic lake has declined on average by 0.72 feet each year, with ultra-fine sediments (<15 μm) and algal particles causing much of the clarity loss. Reversing this trend is the focus of those research agencies in the Lake Tahoe Basin charged with coordinating the development of a TMDL (total maximum daily load). More than $1 billion in funding from the federal, state and local governments, as well as the private sector, is pouring into the watershed to improve the Lake Tahoe environment. For this reason, a premium has been placed on developing a suite of stateof-the-science tools to assess management activities, as well as identifying and developing innovative management solutions. The modeling tools under development by a large assembly agency and research cooperators include a detailed, land-use based watershed model for assisting in the calculation of TMDLs and a detailed BMP pollutant load reduction model for supporting implementation planning. These models were developed to assess and prioritize a wide range of management options and provide decision makers and stakeholders with the information necessary to make informed decisions related to the most efficient placement of management practices in the Basin. In addition to the use of the models for watershed assessment and planning, the modeling tools are being developed to support the development of a viable nonpoint-nonpoint source trading program that focuses on urban runoff and protected forest lands. The models are intended to be operational at the watershed, sub-watershed and project scales. These tools will help inform stakeholders on how to use market mechanisms like water quality trading, with time schedules, and the most appropriate way to allocate the nearly $100 million per year in funds for environmental restoration. This paper and presentation will outline how the modeling tools have been used to support TMDL calculations, implementation planning, and development of a water quality trading framework to maximize the efficient allocation and use of resources to solve and prevent water quality problems in the Lake Tahoe Basin.