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Lake Tahoe Water Quality Improvement Programs

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Lake Tahoe Total Maximum Daily Load

Lake Tahoe's clarity is world-renowned and well-documented. The lake has experienced a decline in water clarity since the late 1960s. A plan to reverse this decline and restore deep-water clarity to historic levels—known as the Lake Tahoe Total Maximum Daily Load (TMDL)—was adopted by the states of California and Nevada, and approved by EPA on August 17, 2011. Prior to approving the TMDL, EPA consulted with the Washoe Tribe of Nevada.

The Lake Tahoe TMDL's implementation plan guides restoration efforts for a number of sources of pollutants responsible for the clarity decline. The plan calls for fine sediment, phosphorus, and nitrogen pollutant load reduction projects to be implemented by state departments of transportation and local municipalities, land and stream resource management agencies, and air quality regulators.

The TMDL and its Implementation Plan resulted from a 10-year development effort funded by state and federal agencies. Both the scientific research and stakeholder input that underpin the final restoration plan are among the most advanced ever applied to a TMDL since passage of the Clean Water Act in 1972.

The Lake Tahoe TMDL:
  • identified the relative amounts of fine sediment, phosphorus, and nitrogen going into Lake Tahoe from major pollutant sources;
  • calculated the load reductions needed from the four largest sources (urban and forest stormwater runoff, stream channel erosion, and atmospheric deposition) to achieve both the TMDL numeric and interim (Clarity Challenge) targets of 97.4 and 78 feet (29.7 and 24 meters) respectively; and
  • details a strategy to achieve pollutant load reductions needed to restore clarity.

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Management Actions Taken

  • Established the Clarity Challenge, an interim goal to achieve 78 feet of clarity within 15-20 years.
  • Developed urban stormwater tools, including a hydrologic load reduction simulation model to aid in developing and selecting alternative project design scenarios, as well as rapid assessment methodologies to help jurisdictions determine the relative condition of stormwater controls and to prioritize and evaluate maintenance activities.
  • Developed protocols and methods facilitating the consistent estimation and tracking of progress toward achieving restoration goals.
  • Developed a TMDL Management System to incorporate new monitoring, scientific and research information and ensure that continual improvement and adaptive management occurs throughout implementation of the Lake Tahoe TMDL.

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Implementing the TMDL

Graph of Lake Tahoe Secchi Depth Annual Averages, Future TMDS Goals, and Select Historic Events, 1968-PresentClick to EnlargeThe Lahontan Regional Water Quality Control Board and the Nevada Division of Environmental Protection (NV DEP) are the two state regulatory agencies that oversee implementation of this TMDL. These two agencies may enact policy and regulations based on the TMDL’s analysis and key scientific findings. Each agency uses its regulatory authority and non-regulatory programs (see funding section below) to ensure that the performance objectives specified in this TMDL are achieved.

Achieving the interim Clarity Challenge—pollutant load reductions expected to improve Secchi disk visibility depth by nearly 10 feet—necessitates substantial reductions from all pollutant source categories, particularly urban stormwater runoff. The Lake Tahoe TMDL has blazed new ground by developing a comprehensive method for estimating, tracking and reporting progress from on-the-ground pollution control activities. Urban stormwater jurisdictions are expected to prioritize and implement needed load reductions at the catchment or neighborhood scale, as well as to verify and obtain credit for these activities through the Lake Clarity Crediting Program. Tracking protocols and performance measures are in place or under development for the other source categories, facilitating the assessment of progress toward meeting load reduction goals and enabling greater transparency and accountability for the expenditures of public funds.

Secchi Disk: A flat, circular disk with high-contrast black and white paint alternating to increase visibility attached to a measuring cable.Example of a Secchi Disk.The following is a representative list of practices and treatment options that responsible parties might use to meet the Clarity Challenge load reductions by 2026, and ultimately achieve the TMDL by 2076. Many of these practices are already in use by responsible parties, and an enhanced level of effort may further reduce sediment and nutrient discharges to Lake Tahoe. In the future, technological advances may add other actions to the list. This list is not intended to be final. Implementing agencies may select other actions to achieve required load reductions. Please refer to the Lake Tahoe TMDL Section 11.3 for more discussion on implementation.

  • Stabilize and re-vegetate road shoulders and eroding slopes
  • Implement an aggressive street sweeping program with high-efficiency street sweepers
  • Upgrade/enhance fertilizer/turf management practices to reduce nutrient application
  • Remove impervious ground cover (to increase water infiltration)
  • Apply advanced deicing strategies (to reduce or eliminate abrasive application) Upgrade/increase/enhance infrastructure operation and maintenance
  • Redirect runoff for additional treatment
  • Install and maintain infiltration systems
  • Install and maintain detention basins
  • Install and maintain sand filters
  • Control retail fertilizer sales within the Tahoe Basin (watershed)
  • Recommend landscaping practices that reduce movement of nutrients
  • Install and maintain wet basins / infiltration basins
  • Install and maintain constructed wetlands
  • Install and maintain filters in stormwater vaults
  • Pump stormwater to more suitable treatment locations
  • Put gravel on unpaved roads and pave dirt roads at access points
  • Reduce residential wood burning with incentive programs
  • Mulch and revegetate ski runs
  • Decommission and re-contour some existing dirt roads and trails
  • Implement stream restoration projects and reconnect floodplains
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The Lake Clarity Crediting Program establishes the framework that connects on-the-ground actions to the goal of restoring Lake Tahoe clarity. It defines a comprehensive and consistent accounting system to track pollutant load reductions from urban stormwater. The Crediting Program aligns policies with ongoing implementation to ensure accountability and motivate effective action to improve the lake’s clarity.

Slideshow: TMDL & Stormwater Accounting

To ensure that implementation proceeds efficiently, the Lake Tahoe TMDL Program established an adaptive management system -- a formal process to enable programmatic and/or policy adjustments as needed. Adjustments may be triggered by changing political or economic environments, new scientific findings, input from TMDL stakeholders, or unforeseen future conditions caused by climatic, geologic or wildfire events. The TMDL Online Interface is the central hub for information on the Lake Tahoe TMDL Program and the TMDL Management System.

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Environmental Improvement Program (EIP)

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The Tahoe Regional Planning Agency (TRPA) launched the Environmental Improvement Program (EIP) in an effort to better implement its Regional Plan, and highlighted it at the Presidential Forum at Lake Tahoe in 1997. Recognizing that capital investments, research, and monitoring were essential components of the Regional Plan, the EIP has invested over $2 billion in capital projects, research, and monitoring in the Tahoe Basin. The EIP includes hundreds of specific projects and programs undertaken by more than 50 funding partners, including federal, state, and local agencies and the private sector. The projects have been focused on improving air, water, and scenic quality, forest health, fish and wildlife, and public access to the lake and other recreation areas. The prime directive of the EIP is to move the Tahoe Basin closer to attaining these environmental goals. The EIP Project Tracker provides information on EIP projects and expenditures, funding sources, and performance, as well as an annually-updated list of projects slated for implementation in the next five years.

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Nearshore Protection

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In response to nearshore degradation, a multiagency partnership including the Lahontan Regional Water Board, Nevada DEP, TRPA, and EPA collaborated with the foremost experts on Lake Tahoe’s nearshore environment to produce the Lake Tahoe Nearshore Evaluation and Monitoring Framework (PDF)(410 pp, 25 MB, About PDF) (October 2013), and to develop the Lake Tahoe Nearshore Water Quality Protection Plan (PDF)(15 pp, 883 K, About PDF) (June 2014), which includes the following elements:

  • Continue implementing programs that benefit nearshore environmental quality (such as the Lake Tahoe TMDL and the TRPA Regional Plan).
  • Establish and implement an integrated nearshore monitoring plan to track change in the nearshore environment and track pollutant inputs to nearshore waters.
  • Evaluate localized “hotspots” where nearshore change has been documented, and assess causes of observed degradation.
  • Investigate climate change influence on nearshore water quality.
  • Assess the need for revised or new water quality standards to protect nearshore water quality.

The partnership is now implementing a Nearshore Resource Allocation Plan to guide future research and monitoring.

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