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The Lake Tahoe TMDL is a scientific effort at the forefront of the campaign to return Lake Tahoe water clarity to historic levels. The scale of the TMDL effort signifies the importance of this national treasure; to date the TMDL Program has involved research by nearly 200 scientists and engineers and more than a $10 million investment by the federal government and the states of Nevada and California as well as eight years of cooperation and participation by Tahoe resource management agencies, local governments and the public. In order to better manage the enormous undertaking of the Lake Tahoe TMDL, it was necessary to break the effort into three distinct phases, for which key questions were posed Phase 1 involved the establishment of a comprehensive research program to answer the following questions:
The analysis indicates that the primary pollutants controlling clarity are fine sediment particles and the nutrients phosphorous and nitrogen. Fine sediment particles (FSP) cloud the water while nutrients fuel algal growth. Although each affects the distance that light is able to penetrate into the water column, the analysis indicates FSP, particularly those less than 16 micrometers, appear to be more important than nutrients due to their light scattering effect. The vast majority of FSP entering the Lake are derived from the urban area. Modeling results suggest that a 65% reduction in FSP, accompanied by reductions in nitrogen and phosphorous, are necessary to restore historic clarity within Lake Tahoe.
The Pollutant Reduction Opportunity (PRO) Report [March 2008: 451 Pages - 11 MB ] was a basin-wide analysis which quantified load reductions achievable from implementing various levels of pollutant control efforts. Together the Tech and PRO Reports provide the scientific and technical basis for the development of a recommended implementation strategy capable of achieving the Clarity Challenge. This interim target of 80 feet annual average Secchi disk depth to be achieved within 20 years, is important because scientists may then state with confidence that we have actually reversed the trend in clarity loss and are now moving in the path of restoring Lake Tahoe to its historic clarity. Approximately a 32% load reduction in FSP with accompanying reductions in nitrogen and phosphorous are needed to achieve the Clarity Challenge.
Phase 3, the current phase, represents the transition from the science-based policy formation phases to the implementation and performance evaluation phase. In this phase the recommended strategy will be implemented by local government agencies, as well as state, regional and federal regulatory and land management agencies through their respective programs. Load reduction requirements will be established based on allocations contained in the TMDL document.
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 What's New:
Lake Clarity Crediting Program
Because urban stormwater is the main source and represents the greatest opportunity to resolve the Lake clarity problem, NDEP and the Lahontan Water Board sought to develop a program that would drive accountability and motivate effective action to improve Lake Tahoe clarity. An Environmental Protection Agency (EPA) Targeted Watershed Initiative Grant was used to create the Lake Clarity Crediting Program (Crediting Program).
Through the fall of 2010, NDEP and the Lahontan Water Board will work with local governments and transportation agencies on a non-regulatory basis to test and implement the protocols, tools and methods described in the Handbook. Through the beta-testing we expect to improve the Crediting Program and Handbook to make them more efficient, functional and better able to support targeted efforts to reduce pollutant loading. Funding is being sought to support testing and training for jurisdictions to implement the Handbook. The Handbook will be updated in the Fall of 2010 based on lessons learned and comments received during the beta-test period. At that time, we expect to incorporate the Crediting Program into policies, permits, MOA and codes. Comments or questions on the Crediting Program and Handbook during the beta-test period may be submitted to . |
Best Management Practice Maintenance |
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What's Next:
Draft Lake Tahoe TMDL Peer Review and Final Draft Document Production
In the summer of 2009, a Draft Lake Tahoe TMDL document was sent out to nationally recognized experts in a variety of disciplines for peer review. Please see the Lahontan Water Board's website, where the review request and reviewer comments are posted. Also posted are the documents provided to the peer reviewers, including the Draft Lake Tahoe TMDL document. Please do not submit comments on the document at this time. Lahontan Water Board and NDEP staffs are working with the Lake Tahoe TMDL Scientific Advisor to address the peer review comments; a revised draft is expected to be available for public review and comment in late 2009.
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 Newsletters 02/06 — Lake Tahoe Nutrient & Sediment Total Maximum Daily Load
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