Alan Heyvaert

Cleaning up the lake shore

Historically, water quality has been tracked at the center of Lake Tahoe.Now Alan Heyvaert, Interim Director of the Center for Watersheds and Environmental Sustainability at the Desert Research Institute (DRI), is collaborating with other researchers to investigate how pollutants are affecting water quality in the near shore area.

“A lot of people never get out into the middle of the lake, but many people swim and kayak in the water or hike along the lake shore,” Heyvaert said. “They experience the near shore more directly than the middle of the lake.”

It’s also where most pollutants enter the lake through stream inflows and urban runoff. Pollutants like fine particulates concern Lake Tahoe’s scientists because they affect water quality and clarity. Fine particulate sediments also contribute nutrients to the lake, which in turn can nurture algae growth and diminish lake clarity.

“You see a lot of changes and hear about changes in the near shore,” Heyvaert said. “But we’ve never quantified these changes in an integrated way.”

Heyvaert has been researching water quality and watershed management at Lake Tahoe for 20 years. Part of this research contributed to the development of the Lake Tahoe Total Maximum Daily Load (TMDL), a guideline listing how much pollution can enter the lake before affecting its water quality. Nevada state management and environmental agencies approved the TMDL in 2011.
He found that urban stormwater contributes more than two-thirds of the fine sediments and about a third of the total phosphorus to the lake.

Fine particulates can be washed into storm drains and culverts from impervious surfaces like parking lots and roads as well as from compacted and disturbed areas. These often discharge directly into
the lake.

“In the winter we also put out sand for traction,” Heyvaert said. “This gets ground up over time by traffic and then gets washed off with the storm runoff.”

Now that state agencies are trying to implement the TMDL’s recommendations, Heyvaert is investigating management and treatment methods that will control pollutant loading from the urbanized watersheds.

“You have fewer problems downstream if you implement best management practices near the point of origin,” he said. “Other useful practices include things like street sweeping to remove fine
particles from road surfaces and management of road shoulders to prevent erosion. Most recently, we’ve been investigating the relationship between urban areas and their nearshore environments,
which are at significant risk of change due to urban runoff, invasive species, and warmer temperatures.”

Researchers are collaborating with Tahoe Basin agencies to implement an integrated nearshore program that will identify problems early and track progress as management actions are implemented.

As a paleolimnologist, Heyvaert has studied various historical changes at the lake and how its ecosystem has recovered from previous disturbances such as logging. The human impacts at Lake Tahoe are now more permanent than they have been in the past.

“With urbanization our effects are chronic and we’re not leaving anytime soon,” Heyvaert said. “These detrimental effects persist and we have to find ways to manage the impact. If we can’t do it at a place like Lake Tahoe where the qualities are so unique and visible, we’ll have a hard time doing it anywhere else in the world.”