In 2014, TERC established a network of water quality instrument stations at various points on the shoreline around the lake. The program aims to understand the causes of degradation of Lake Tahoe's nearshore and provide the essential data needed to guide restoration and future stewardship.
As of June 2016 there are 7 stations installed around Lake Tahoe, and an additional station on Cascade Lake[DR1] which feeds into Lake Tahoe. Each station consists of a Turner Designs C3 Submersible Fluorometer measuring turbidity, algal concentration, and dissolved organic material, along with a RBRmaestro CTD measuring water temperature, conductivity, lake level, and wave height. An underwater cable supplies power to each station and returns data, which are displayed as near real-time and can be accessed via the internet. TERC aims for a minimum of 12 other stations to be added in the future as additional funding is acquired.
Why are these nearshore data so important? The nearshore is the area of the lake most people come in contact, it is a very ecologically productive area of the lake, and the quality of this area is more likely to impact a visitor's impression of Lake Tahoe. Also unlike the deep portion of the lake, the nearshore is subject to sudden erratic changes in water quality. These changes occur in response to storms, inflows from streams and storm drains, local erosion, or drift from other parts of the lake. Every part of the nearshore responds differently. The Nearshore Network will allow scientists and agencies to better understand the causes of degradation, to better implement projects to mitigate degradation, and to determine appropriate and meaningful threshold standards for nearshore conditions.
Data will also be used to educate the public through the Lake Tahoe In Depth display located at TERC’s Tahoe Science Center and other locations around the basin.
What has been learned so far? To start, we now have baseline data for the instrumented sites to know what "normal" and "extreme" conditions are. The figure to the left shows the distribution of algal concentration from six sites for a winter period shown in blue and a spring period shown in red. The line across each box is the median value recorded. The upper and lower bounds of the boxes represent the 75th and 25th percentiles respectively, and the symbols represent all values outside this range.
At all sites, algal concentration is higher in winter, often by a factor of 2 or 3. Cascade Lake has the highest algal concentration, while the lowest median concentrations in Spring were in Meeks Bay and Dollar Point. The most extreme low values were on the west shore, due in part to cold water upwellings.
Funding for this project (along with access to docks) is being provided through a unique partnership between lakefront property owners, private donors in the Tahoe basin, instrument manufacturers, and TERC. Each donor is supporting the operation of one nearshore sensor for a minimum of four years. Click here if you are interested in supporting TERC's Nearshore Network.