WINDOW ON CLEAR LAKE
Part 3- Fixing the Clear Lake Wetlands
By Jim Steele
Studies have found that the functional loss of wetland ecosystems that historically ring Clear Lake has allowed phosphorus-containing sediments to enter the lake directly. This growing, recycling lakebed nutrient continues to fuel cyanobacteria scum blooms each year. A special sediment-core study on the Clear Lakebed by the US Geological Survey [Richerdson et al, 2008] indicated that the ~1927-38 use of earthmoving equipment in Lake County created a profound impact on the lake. By the time this equipment was used, over half the protective sediment-settling wetlands were already being used for agriculture. In addition, some early activities bypassed the remaining wetlands by building levee systems with horse-drawn landplanes. The die was cast.
The introduction of large equipment allowed for distributing lakeside mining deposits into the lake, the building of roads that upset erosion processes, conducting streambed gravel mining which released interstitial fines [containing phosphorus], and the building of levees to reduce flooding. The changes in sediment-core analysis not only correlated with these large mechanical operations but also with land clearance for farmland within the wetlands, with hillside disturbances within the drainage basin, with logging on surrounding hills, and even with the misuse of pesticides. These combined to add insult to the lake ecosystem.
The natural history of Clear Lake responded to these changes, and evidence includes significant cyanobacterial blooms that can even be seen by satellite cameras. The sediment introduction continues today with the advent of off-road vehicle recreation [ORV] sanctioned on BLM land on Scotts Creek and on thousands of 1920’s failed subdivision parcels called the “paper subdivisions.’ These areas tally up thousands of ORV use-days each year. This result is obvious from turbid runoff to streams following heavy rain. Fun in one misplaced activity can cause a problem elsewhere.
You would think, following the landmark publication prepared for the Lake County Flood Control and Water Conservation District, et al; “The Causes and Control of Algal Blooms in Clear Lake” [Richard and Suchanek (1994)], that there would be a significant effort to monitor and control erosion-causing activity in the basin and restore the sediment-settling wetlands that once protected the entire lake. What happened was the promise of state funds to restore a segment of the original Middle Creek seasonal wetlands. But this process included a clause that allowed only the purchase of wetland property from willing sellers. The Army Corps of Engineers [ACOE] was also tasked with the planning and execution of rehabilitating the wetland, but ACOE dictated that no planning shall begin until all the land is in County hands. Unfortunately, these stipulations were a recipe for delay.
So far, the resulting 20-year restoration delay, plus the difficulty of securing funding along the way, has led to tons of additional sediment entering the lake, adding to the annual recycling of phosphorus already there. Clear Lake has become a high-powered warmwater ecosystem with no limits on nutrients, so future ecosystem stability is unpredictable. But the 1994 report was cautiously optimistic that recovering streams and wetlands would positively impact recovery. How long it will take is uncertain because those time studies were not done. So, what to do now?
Because wetlands are so valuable in intercepting upland runoff, a reset of the original plan for full restoration should be considered. The ACOE plan was thought to secure Federal funding, but the present Federal Administration appears unwilling to fund California projects. Meanwhile, protecting the lake from stormwaters by breaching levees to reflood the seasonal wetland lands with existing historical elevations could help significantly. This would include areas near the mouth of Rodman Slough on County-owned property.
An alternative to immediately breaching the levees is to install equipment to generate lanthanum slurry at the Rodman Slough channel mouth. The equipment automatically regulates the addition of slurry to the stream rather than the lake by sensing the flow and turbidity. The result is harmless phosphorus pebbles locked up from lake recycling processes. Perhaps these alternatives can be reviewed for cost-benefit lake protection while we’re waiting for a bigger fix? Next is part 4, Fixing the Uplands.
