Reduce Dissolved Inorganic Nitrogen Loads
Nitrogen is a nutrient important to the growth and reproduction of plants, and it is considered a pollutant of concern in the Lake Tahoe Region. Nitrogen and phosphorus together support the growth of algae in Lake Tahoe. Free-floating algae occur throughout Lake Tahoe and contribute to the decline in water transparency and attached algae coat rocks in the nearshore, adversely affecting nearshore aesthetics. Landscape disturbances including, but not limited to, impervious road and parking lot surfaces, residential and commercial development, wildfire, and the degradation of stream environment zones, can contribute to sediment and nutrient inputs to the lake or its tributaries. Weather variations and their effects on stream hydrology (particularly the extremes of droughts and floods), and long-term climate change are considered among the most important environmental drivers of tributary runoff.
2023 Evaluation
- Status
- Insufficient Data to Determine Status or No Target Established
- Trend
- Insufficient Data to Determine Trend
- Confidence
- Not available
Applicable Standard
WQ41: The most stringent of the three dissolved inorganic nitrogen load reduction targets shall apply:
i. Reduce dissolved inorganic nitrogen loads to pelagic and littoral Lake Tahoe from: a) surface runoff by approximately 50 percent of the 1973-81 annual average, b) groundwater approximately 30 percent of the 1973-81 annual average, and c) atmospheric sources approximately 20 percent of the 1973-81 annual average.
ii. Reduce dissolved inorganic nitrogen loading to Lake Tahoe from all sources by 25 percent of the 1973-81 annual average.
iii. To achieve littoral water quality standards (WQ5 and WQ6).
Key Points
- The status of the standard is assessed as "insufficient data" because the monitoring programs assess total nitrogen load, and do not directly quantify dissolved inorganic nitrogen load.
- 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.
About the Threshold
Rationale Details
- Insufficient Data to Determine Status or No Target Established.
- Insufficient Data to Determine Trend.
Confidence Details
- N/A
- N/A
- N/A
Additional Figures and Resources
No photos available.
No documents available.