Initial Lake Tahoe water clarity study findings promising after Caldor Fire
Special to the Sierra Sun
The League to Save Lake Tahoe is studying its initial findings in a study to analyze the impacts of the Caldor Fire on the lake.
The Tahoe Science Advisory Council launched a rapid response scientific study to gather samples of smoke and ashfall from the Caldor Fire.
The project was funded by The League with additional support provided by the Tahoe Regional Planning Agency, the state of California and Nevada and the Tahoe Fund.
It included real-time data gathering into changes in algae growth, the presence of clarity-diminishing particles, and other ecological dynamics at play in the lake.
According to The League, some of the nutrient and bacterial analysis are still being processed at the lab, courtesy of South Tahoe Public Utility District, but they do have some findings to share.
Pipe Keepers with The League sampled and tested stormwater during the late October storm.
“During the height of the storm (afternoon of Sunday, Oct. 24) we had 14 Pipe Keepers volunteers and several staff sampling and testing stormwater at 25 sites, including 16 stormwater pipes and eight stream sites that drain the areas burned by the Caldor Fire,” said Chris Joseph, communications manager for The League, in an email to the Tribune.
“Overall, turbidity (a measure of the particles suspended/cloudiness in the water) and water quality was not out of the ordinary for an intense storm – i.e. slightly to moderately elevated – which in the context of the recent fire, is good news,” Joseph continued. “The lower the turbidity, the lesser the impact on Lake Tahoe’s water quality and clarity.”
They did observe flood conditions, fast moving water and visual signs of erosion that are common with the “first flood event.”
Joseph said the storm’s impacts on the lake could have been far worse without improvements to stormwater infrastructure over the past years. It would have been concerning if they had seen debris flows on burned slopes.
Volunteers and staff collected samples from several sites along the Upper Truckee River. Those results, from sites along the river’s flow from Christmas Valley down to the U.S. Highway 50 bridge by the Hangar, illustrate the natural filtration function of Tahoe’s rivers, marshes, meadows and wetlands.
According to Joseph, the Lahontan Water Quality Control Board’s standard for Lake Tahoe turbidity is 3 Nephelometric Turbidity units or lower.
- Beginning in Christmas Valley, turbidity readings were some of the highest (41.7NTU), which is logical given proximity to steep, burned slopes.
- Turbidity readings decline as the Upper Truckee River moves through Washoe Meadows (19.8NTU) and Elks Club (13.4NTU), down to 4.4 NTU at the airport.
- Urban stormwater entering the UTR bumps turbidity up to 16.3 NTU near the southern end of Sierra Tract (around Lodi Ave), and all the way up to 41.9 NTU at the U.S. 50 bridge over the river. Note how large of an impact urban runoff has on water quality.
“Interestingly, with the swollen UTR flows, the pilot channels in the Upper Truckee Marsh, which were recently rehabilitated by the California Tahoe Conservancy as part of their marsh restoration project, had flow for the first time,” Joseph said. ”That’s a cool milestone in bringing the marsh back to its natural, functioning state – which provides tons of wildlife habitat and even more filtration for water flowing to the lake.”
While initial results are positive, the lake did not get out of the fire unscathed.
“The Lake did receive some sediment loading (clarity-degrading runoff) from the storm,” Joseph said. “There are other impact; things like ash fall, long term impacts to soils, as well as plant and tree growth (and therefore animal life) in burned areas, smoke effects, and more. Though several of those things aren’t in the water, they do impact the Lake.”
Research the League is funding through the University of Nevada, Reno, Desert Research Institute and UC Davis Tahoe Environmental Research Center will give them a better understanding of some of those long-term impacts.
The League is continuing regular, long-term water sampling and monitoring efforts, especially for areas impacted by the Caldor Fire to check for impacts.
Anyone who wants to participate can get involved by emailing firstname.lastname@example.org.
Laney Griffo is a staff writer for the Tahoe Daily Tribune, a sister publication of the Sierra Sun
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Last month, during the storm driven by an atmospheric river, the League to Save Lake Tahoe’s staff and Pipe Keepers citizen scientist volunteers collected stormwater samples, made qualitative visual observations, and took quantitative measurements of…