Nearshore Turbidity (No Stream Influence)
Turbidity is a measure of water’s clarity, and this standard establishes a goal for the nearshore. The nearshore represents an important socio-economic value because this is where most visitors and residents experience the lake first-hand. Turbidity in the nearshore is influenced by many factors including wave action, algae, and discharge from streams, especially during storms. Projects and programs reduce pollutant and sediment loading to the lake and also are likely to improve nearshore clarity.
Status
Distribution of section average values obtained from individual nearshore clarity circuits at a seven meter depth (23 ft.) completed using equivalent methods since 2001. Survey re listed in chronological order on the x-axis (mm/yyyy format). Survey dates are non-continuous. The blue line follows median values from each circuit represented by quartile boxplots, with whiskers to outermost data points within 1.5 times the interquartile range.
2019 Evaluation
- Status
- At or Somewhat Better Than Target
- Trend
- Little or No Change
- Confidence
- Low
Applicable Standard
WQ4: Turbidity shall not exceed one NTU in shallow waters of the Lake not directly influenced by stream discharges.
Key Points
- Tahoe's nearshore waters, similar to its deep lake waters, are incredibly clear. Scientists have suggested the need to better understand the drivers of nearshore clarity. Recent investment by TRPA and partners has focused on improving our understanding to both target management to improve clarity and identify appropriate goals for nearshore clarity.
- In 2014, UC Davis began deploying a network of sensors that continuously monitor nearshore conditions (chlorophyll, dissolved organic matter, wave height, temperature, conductivity, and dissolved oxygen). Preliminary findings suggest that nearshore clarity is primarily influenced by wind and wave height.
- During high wind events, nearshore sediments are resuspended in the water column, and decrease the clarity of the water, until the wind speed and wave height are reduced.