Phosphorus is a nutrient important to the growth and reproduction of plants and is considered a pollutant of concern in the Lake Tahoe Region. Nitrogen and phosphorus together support the growth of algae in Lake Tahoe and contribute to the decline in water transparency and adversely affect nearshore aesthetics. Landscape disturbances including impervious surfaces, residential and commercial development, wildfire, and the degradation of stream environment zones (SEZs), can contribute to sediment and nutrient inputs to the lake or its tributaries. Projects such as restoring SEZ and limiting fertilizer use in the Region seek to reduce phosphorous in Lake Tahoe's tributaries. Phosphorous reductions are monitored by partners through the Lake Tahoe Total Maximum Daily Load Program (TMDL). 


Phosphorus load reduction with the target shown in 2019 in light blue.

Evaluation Map

Lake Clarity Tracker Projects

2019 Evaluation

Considerably Better Than Target
Rapid Improvement
View Evaluation

Applicable Standard

WQ35) Reduce total annual phosphorus load to achieve long-term pelagic water quality standards (WQ1 and WQ2) and littoral quality standards (WQ5 and WQ6).

Key Points

  • In 2019, TMDL implementors (CalTrans, CLST, Douglas, El Dorado, NDOT, Placer, Washoe) exceeded their load reduction targets for phosphorus by 75 percent greater than the target.
  • In 2019, approximately 7,500 miles of streets were swept using high-performance sweepers, 29 non-compliant wood stoves were removed or replaced, and nearly seven miles of pedestrian and bicycle routes were constructed.
  • At the September 2020 meeting of the Threshold Update Initiative Stakeholder Working Group, consistent with guidance from the Tahoe Science Advisory Group, the water quality standards related to load reduction were recommended to be removed as threshold standards and retained as Environmental Improvement Program performance measures.

Delivering and Measuring Success

EIP Indicators

Monitoring Programs