- Kathleen Scavone
- Posted On
The Living Landscape: Magnificent Clear Lake
LAKE COUNTY, Calif. – Clear Lake is set like a jewel in Lake County.
The Mayacamas Mountains are to the east, and Clear Lake, at nearly 70 square miles, is the largest natural lake wholly within California.
Believed to be the oldest lake in North America, Clear Lake is about a half million years old.
Clear Lake sprawls across the landscape diagonally, with two arms at the narrows pointing southeast.
Mount Konocti, a dormant volcano resting on the Pacific Ring of Fire, emerges on the shoreline across the narrows, rising to 4,305 feet.
Clear Lake and Mount Konocti, two distinct and indivisible landscape features of Lake County contain vast stores of mythology, history and exquisite beauty.
Here at Clear Lake there is something for everyone: fishing, boating, kayaking, bird-watching, hiking and scientific discoveries galore.
To quote the magazine of the California Academy of Sciences, "Dead lakes are clear ..."
Clear Lake, never truly clear, since it is shallow and eutrophic, was, however, once more clear than it is now. Clear Lake has an average depth of 27 feet.
Our lake's problems began back in the 1920s. Then, construction development, agriculture practices, along with dwindling wetlands and the removal of the once-prolific tule plants, were the causes of the lake's diminishing clarity over time.
These practices removed the natural filtration structures of the lake and allowed excess nutrients from farms, vineyards.
Once, there were close to 9,000 acres of wetlands adjoining the lake, then the wetlands were decreased to 2,000 acres.
Steps are being taken by groups such as the Lake County Land Trust to reclaim valuable wetlands, like Rodman Slough.
Ecology-minded farmers are using lake-friendly farming practices to aid in the lake's water quality as well.
After European settlers arrived around 1840, lands near the lake were cleared for farming. The farming practices of the time caused sediments to wash into the lake, allowing the nutrient level in the lake to rise.
The geologic basin into which Clear Lake sits, the Clear Lake basin, is an extensively studied basin – one of the most studied in the state of California.
Reports from the University of California at Davis show that the lake's unique filtering system controls how much mercury from old mines enters the food chain.
According to local archaeologist Dr. John Parker, in some 1930s geology publications, "It was indicated that that there was a landslide at the north end of Blue Lakes which blocked and backed up the Clear Lake outlet channel causing the shift to the Cache Creek outlet."
He continues, "Yes there is a landslide there ... however it is not old enough to have caused the shift in Clear Lake’s outflow. The US Geological Survey has determined that the landslide is several hundred years (or thousand years) more recent than the change in outflow (which occurred approximately 12,000 years ago). It is likely that Clear Lake flowed out the Blue Lake canyon to the Russian River several times during its 500,000 plus years lifetime. It is also likely that its outlet channel that direction flowed through the Scott’s Creek Canyon a few times (rather than Tule Lake). In addition to the current Cache Creek outlet (which also was probably used many times over the millennia), geologic evidence suggests that the lake flowed past Lower Lake down the canyon by Hidden Valley Lake and drained out Putah Creek a few times."
Greg Giusti recently delivered a lecture entitled, "What Do We Know About Clear Lake?" at the Clear Lake State Park Visitor Center as part of the Summer Speaker Series sponsored by Clear Lake State Park's Interpretive Association.
Giusti recently retired as Lake and Mendocino County director and advisor for forests and wildland ecology, and holds a master’s degree in ecology from San Francisco State University.
He is a specialist in forest management, wildlife management, vertebrate pest management, wetlands, watersheds, fisheries and freshwater ecology.
Giusti discussed the long association our lake has had with humans, spanning back thousands of years to include the Pomo and Miwok peoples, on up to the pioneers who lived around the lake, and finally, today's recreational uses of the lake by fishermen and other sports and nature enthusiasts.
UC Davis mud core samples from the lake prove that there were once forests much like Cobb Mountain's.
Then, when the ice sheets receded the area became oak-dominated. With the abundance of food, such as fish, grizzly bear, elk and deer, the lake has historically attracted people.
Another interesting facet of Giusti's talk included a NASA image which depicts the abundant phosphorus in the soils adjacent to our lake. This picture delineated where the hotspots for improving the lake are located.
To improve the lake's water quality we need to limit the loss of tule reeds and improve roads as the erosion of the roads harms our lake, and enforce shoreline and stormwater ordinances.
Kathleen Scavone, M.A., is a retired educator, potter, writer and author of “Anderson Marsh State Historic Park: A Walking History, Prehistory, Flora, and Fauna Tour of a California State Park” and “Native Americans of Lake County.” She also formerly wrote for NASA and JPL as one of their “Solar System Ambassadors.” She was selected “Lake County Teacher of the Year, 1998-99” by the Lake County Office of Education, and chosen as one of 10 state finalists the same year by the California Department of Education.