CLEARLAKE OAKS >> This winter’s seemingly endless river of storms and above-average rainfall has sent an unusually high amount of sediment-laden runoff into Clear Lake, especially in the Northshore area.
The amount of this new sedimentation is difficult for even local lake experts to estimate but it’s probable that after five years of drought, this season’s exceptional rainfall has sent more sediments into the lake than in the last few drought years combined.
This silt and sediment increase has negative effects on the lake and other water bodies, according to local environmental activist Chuck Lamb of Clearlake Oaks.
“It’s the most common pollutant in rivers, lakes and reservoirs,” Lamb said. “Natural erosion produces 30 percent of the total sediment flow.”
The other 70 percent comes from human uses of the land around the lake and the creeks, streams and runoff that feed into it.
However, a Lake County official who did not want to be identified because the person had not been cleared to comment publicly, had a different take, saying sedimentation has no negative effects on the lake. The official said this is because there are two earthquake fault lines that straddle the lakeshore.
These faults have created a “geological phenomenon” in which the bottom of the lake is being “pulled down” at roughly the same rate as new sediment is deposited, the official said, adding that this makes Clear Lake “extremely special” among lakes in the world.
Sediments are solid material that are carried by creeks, streams and runoff from nearby land into the lake. They include sand, gravel, pebbles, dirt and agricultural debris. Sediments may also contain harmful agents, including fertilizers, pesticides and in Lake County, the highly toxic heavy metals mercury, arsenic and antimony.
During storms, sediments are readily visible in streams as dirty, brown or cloudy water. Once in Clear Lake, the sediments settle to the bottom.
The amount of sediment in a stream, river or creek can be measured but it requires expensive, specialized equipment and water samples must be taken over time, as streamflow rises and drops during storms, according to the U.S. Geological Survey (USGS).
“We’re a rural county so we don’t get the (financial) support that more populated counties get,” the official said.
According to Lamb, negative effects of increased sedimentation include preventing animals from seeing food in the murky water, inhibiting growth of aquatic vegetation and disrupting the natural food chain by destroying habitats for fish, wildlife and plants.
Lamb and his wife, Holly Harris, also an environmental activist, have advised the East Regional Town Hall (EaRTH) on lake sedimentation issues. EaRTH is an advisory board to the Lake County Board of Supervisors and District 3 Supervisor Jim Steele.
Increased lake sediments also have economic consequences, including increasing the cost of drinking water that’s taken from the lake. It also reduces recreational benefits of the lake that, in turn, can reduce tourism and hurt the economy, Lamb said.
“All of the problems sedimentation causes will continue to have a negative effect on our lake until such time as the county, cities and property owners do something to mitigate the man-made contribution,” Lamb added.
Northshore problem
The Northshore of the lake, east of Highway 20 from Clearlake Oaks to Lucerne, is a particular problem because the steep slopes and the land above them provide much of the lake’s sedimentation and offer short, easy routes into Clear Lake.
One of the main conduits for sediment-laden runoff to flow into the lake from the Clearlake Oaks area is Schindler Creek, where sediment buildup affects fish populations, including the Clear Lake hitch, a large minnow found only in the Clear Lake basin.
Other sources, according to Lamb, include illegal activities such as off-road vehicles (ORV), dumping of garbage and marijuana grows.
Still other sources are runoff from Highway 20, dirt roads, firebreaks, trails, natural erosion, mudslides and loose, disturbed soils on slopes, especially during storms, Lamb said.
He added that there are a number of actions that can be taken to reduce sediment flow into the lake. These include:
—- Clearlake, Lakeport and the county need stricter requirements for getting permits for projects that will disturb the soil. They also need to mandate best management practices (BMPs) to ensure soil runoff is mitigated.
—- Better education of property owners about the negative effects of sediment runoff into the lake.
—- Code enforcement agencies should address existing conditions on properties that have sediment runoff, both before and after problems occur.
—- Better BMPs by CalTrans along the northshore corridor of Highway 20.
Perhaps the primary problem area where lake sediment comes from in the east region of the county is what’s called the Paper Subdivision in the hills above Clearlake Oaks. It gets its name from the fact that it’s a subdivision on paper only.
This is because the approximately 300 lots are not developable individually for a variety of reasons, including small size, unusual configurations and steep slopes. Despite this, the lots keep getting sold and resold.
Two years ago, the Board of Supervisors adopted a management plan to address the Paper Subdivision problems, including erosion and sediment runoff that reaches the lake. Lamb and Harris helped develop the plan.
Ultimately, the plan’s goal is for the county to acquire the lots and turn them into a regional hiking trails park. Most of the lots are along Mountain View Road, which is more like a wide dirt trail, blocked at several points by landslides.
There is also a plan in place to restore wetlands, which help to filter sediments. This is a more environmentally friendly plan than the proposal to dredge that came up in the past.
“Dredging the lake is completely off the table forever,” the county official said, adding, “The lake is really, really healthy”
Asked if there is a point when lake sedimentation will reach a “critical mass,” especially if Lake County has a few more years in a row of average or high rainfall, Lamb replied, “Yikes. Good question.”
However, the unnamed county official, who is familiar with lake and water issues, said, “It’s not ever going to be a problem. People should be more concerned about Mt. Konocti erupting.”
Carolyn Ruttan, Invasive Species Program Coordinator with Lake County Water Resources, refused to answer any questions about the sedimentation issue in the lake when contacted by telephone Wednesday.
