Clear Lake, the largest natural lake in California and the heart of Lake County, is far more than that: it is the oldest natural lake in North America, with 68 square miles of surface area and an average depth of 26 feet; among the world’s most productive fresh water ecosystems; and a regional, national and planetary treasure.

It’s not unusual for warm, shallow, nutrient-rich lakes to support large populations of fish, birds and mammals of many different species, but bodies of water like this are ordinarily quite ephemeral, lasting only a few hundred or thousands of years before transforming first to marsh and then to meadow.

What makes Clear Lake unique are tectonic forces that have deepened its bed at approximately the same pace as sedimentation has accumulated: sediment cores show that a lake has existed continually at this location for at least 450,000 years and possibly as much as 2.5 million years.

Although the lake and its watershed offer a paradise for wildlife and abundant agricultural and recreational opportunities, the region also faces serious problems. Clear Lake has been subject to algal blooms for much of the past century, and was listed as impaired for excess nutrients under the federal Clean Water Act in 1986.

Like most other watersheds in the region, numerous abandoned mercury mines in the basin, especially the Sulphur Bank Mine Superfund site, have led to significant mercury contamination. Although water clarity improved noticeably beginning in the 1990s, noxious “blooms” of cyanobacteria (commonly called “blue green algae”) have been intermittent since 2009.

Devastating wildfires in 2015, 2016, 2017 and 2018 have denuded the hills surrounding the lake and increased the phosphorus-rich sediment delivery that encourages rampant growth of “algae” and invasive aquatic weeds, while simultaneously reducing the tax base, increasing the demand for services and therefore limiting the capacity of local government to address these issues.

What to do? The Central Valley Regional Water Quality Control Board, charged with developing a recovery plan, has held periodic workshops that offered little besides recommendations to extend compliance deadlines.

Then in 2017 Assemblywoman Cecilia Aguiar-Curry, D-Winters, whose district includes all of Lake County, sponsored Assembly Bill 707 to create a Blue Ribbon Committee charged with developing strategies to clean up the lake and revitalize the local economies that depend on it.

The committee is chaired by the Secretary of Natural Resources and includes representatives from local government, UC Davis, the Water Board, Lake County tribes, and spokespersons for economic development, agricultural, environmental and public water supply constituencies. The legislation also included $2 million for research and formulation of a stewardship plan, and prospects for an additional $5 million in upcoming water bond funding.

The committee held its first organizational meeting in Upper Lake on Oct. 10, 2018, followed by a series of three stakeholder workshops on Oct. 24. The facilitators acknowledged that the first task was to assemble and coordinate the numerous studies that have been conducted on the lake in the past and are continuing on an ongoing basis, and to use this data set to create a model of what a healthy lake looks like, while avoiding any temptation to base that model on deep, cold bodies of water such as Lake Tahoe.

They appeared surprised at the number of local residents who participated and by both their commitment to Clear Lake and their breadth of knowledge, while many of the participants appeared equally surprised that the focus of the group seemed to be as much on the economic revitalization of Lake County as on the ecological well-being of the lake itself. Although these subjects are admittedly closely connected, it was apparent that mission creep could become a serious issue as the committee’s mandate evolved.

The second committee meeting, on Dec. 20, was preceded by a tour of the Middle Creek Flood Damage Reduction and Ecosystem Restoration Project site: this project, first proposed in the 1990s, is widely acknowledged to be the single most effective action available to improve watershed health and Clear Lake water quality.

By breaching antiquated levees that “reclaimed” 1600 acres of wetlands for agriculture in the 1930s and ’40s, and by restoring the natural contours and hydrological functions of the area, the project will intercept much of the nutrient-laden sediments that currently trigger rampant growth of weeds and “algae.”

The project also will restore wildlife habitat, improve breeding and rearing conditions for the threatened Clear Lake Hitch, and provide significant recreational opportunities. Both the Water Board and a 1994 Environmental Protection Agency study have prioritized restoration of the area — the largest single damaged wetland on the lake — as the number one target for improving water quality and restoring an impaired ecosystem, and in February 2019 $15 million in state funding was procured to allow the county to purchase the remaining private properties within its boundaries.

Six additional meetings followed in 2019, several preceded by site visits, along with six meetings of a Technical Subcommittee chaired by committee members but primarily composed of outside experts. The year concluded with preparation of an annual report to the governor and consideration of a formal letter of support for the prompt realization of the Middle Creek Project.

Priorities for 2020 include creating a model of the upper watershed; implementing a basin-wide monitoring strategy; conducting a bathymetric survey of Clear Lake; reviewing existing programs and Best Management Practices; and assessing public perceptions, attitudes, and knowledge gaps about the lake and water quality generally.

At this writing a 2020 meeting schedule was expected soon; schedules, agendas, and much additional information is available at the BRC website, http://resources.ca.gov/clear-lake/.

— Victoria Brandon is the president of the board of directors of Tuleyome. Tuleyome is a 501(c)(3) nonprofit conservation organization based in Woodland. For more information go to www.tuleyome.org.

Crossposted from the Davis Enterprise

Published online on February 11, 2020 | Printed in the February 12, 2020 edition on page A3