Clear Lake

WINDOW ON CLEAR LAKE
Part 4- Fixing the Clear Lake Uplands
By Jim Steele

The upland terrestrial ecosystem boundary is defined as the 450-square-mile watershed area that collects rainfall feeding Clear Lake. Within this ecosystem are the mountains and soils, with streams draining, flooding, and shaping the landform. Competing for space and nutrients are the many plant and animal species common to the inner coastal range of California. Some of these species have disappeared since the arrival of western settlers, and some have been introduced from other ecosystems. Historically, annual flooding and receding waters replenish the plants with new soil and recharge the groundwater. The meandering channels in the lower elevations run into wetlands that capture any remaining sediments before the water enters the lake. Wildlife abounded in these slow-moving waters, seeking their lowest level.

When western settlers saw the few areas that didn’t flood annually, this drier area was increased by adding levees to bypass wetlands and straighten streams for agriculture and housing. Removing the stream meander meant the water would flow off the land faster, reducing flooding. But it also reduced the population of the floodplain-adapted minnow common in this environment. The threatened “Clear Lake Hitch” was listed in 2023 under the California Endangered Species Act because of habitat alteration.

Bypassing the wetlands resulted in the removal of the sediment-settling area and also reduced wetland wildlife populations. As sediment-laden water entered the lake, cyanobacteria scum blooms became more common because they are very competitive in nutrient-rich, low-oxygen environments. The new thinking is to restore the wetlands and regain their water-filtering powers.

However, restoring wetlands is expensive and requires millions of dollars for planning, land acquisition, and reshaping the landform. It’s quite an investment and a good goal, so unless the incoming sediments from land-use disturbance are significantly reduced, any expensively renewed wetland will quickly fill in. Looking upslope should be a priority step in reducing sedimentation to both the lake and restored wetlands.

What are the offending upland sediment producers? Arguments with finger-pointing and no self-admission of blame have been common. Agriculture in all its forms is the usual suspect, but poor road construction, drainage, and slope disturbance are more likely. Leading the slope disturbance category is Off-Road Vehicle [ORV] use. In Lake County, many areas of the hillsides are made accessible to ORV’s by roads established by failed subdivision projects and are uncontrolled. Adding to this are many ORV activity-permitted areas within US Forest Service lands in the watershed. But the largest ORV park, with thousands of annual use days, is on BLM land adjoining Scotts Creek. The pathway for this erosion is directly to the lake, bypassing the Middle Creek seasonal wetland complex. Restoring the wetland and removing the bypass levees without fixing this upland sedimentation problem will result in reducing the wetland’s filtering capacity after only a few years.

Several things can reduce the upland sediment input. The USFS and BLM Agencies have other public lands that do not drain to the lake, and moving the ground-disturbing activities to areas outside the watershed boundary is the best approach. After that, the large surface area of the BLM ORV Park would require land stabilization and replanting. The area along Scotts Creek would also benefit from bank stabilization structures. Scotts Creek now has braided water channels indicating a large amount of erosion moving through the system. Passing this sediment slowly downstream using check dams will reduce the impact on downstream areas such as Scotts Valley, where nearby housing is vulnerable to flooding. Picking the right standards of repair will be important. Scotts Valley used to be a meandering valley subject to annual flooding, and housing requires changes compatible with protections.

Of course, all of the sediment-producing activities within the Clear Lake basin should be mitigated. But the largest low-hanging fruit, consistent with recommendations from decades of studies on the lake, is found in the Scotts Creek drainage and the Middle Creek wetland. It should be noted, however, that none of the past studies measured large-storm impacts, such as the 1955 or 1964 atmospheric storms that occurred in the Eel River basin. It is these potential storm levels that should serve as the benchmark for the sediment mitigation measures in the Clear Lake Watershed. Fixing Clear Lake depends on a community of agencies, tribes, and the public recognizing, monitoring, and repairing problems across all three ecosystems to meet proper standards and protect the future. With a new three-ecosystem understanding, Clear Lake can be restored and made clear again.

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.

WINDOW ON CLEAR LAKE
Part 2- Fixing Clear Lake
by Jim Steele

The days are getting longer; the sun’s angle is higher in the sky, and sunlight will penetrate the water rather than be reflected off the surface. When the length of the day and light penetration are long enough, a photo compensation point is reached, and single-celled algae will grow and reproduce. That is a good thing for aquatic wildlife. The base of the food chain will feed zooplankton, which are food for small aquatic insects, which feed small fish, and so forth up to larger fish and a great many birds. The cycle of life will soon have the energy it needs to renew. But sometimes things go awry, and people report a cyanobacteria bloom before noticing all the beautiful birds and wildlife.

Algae and flowering plants are the primary producers of oxygen through photosynthesis and create a notable surplus needed by advanced life forms, certainly humans. Algae are technically not flowering plants but instead reproduce by cloning and other simple methods. Single-cell algae are roughly divided into two groups: the primitive forms with simple cell organization are called prokaryotes, such as blue-green algae (cyanobacteria), and those with more complex cell organization are called eukaryotes. The prokaryotes were probably the first life forms three billion years ago. The oxygen produced by these early life forms changed the atmosphere, oceans, and even lakes, making conditions favorable for the development of advanced eukaryotic species. Basically, primitive prokaryotic cyanobacteria thrive in low-oxygen environments, but the eukaryotic phytoplankton thrive in higher-oxygen environments and form the base of the food chain up through all the eukaryotic plants and wildlife.

What causes a loss of lake oxygen to favor primitive cyanobacteria and stink up the lake? Nutrients from soil erosion, fertilizing, highway organics such as oil, and roadkill wash into the lake, creating a nutrient broth. This causes algal types, aquatic rooted plants, zooplankton, insects, and aquatic wildlife to flourish at each trophic level. Is Green good, right? But the large biomass of life in the lake steadily increases during the summer, depending on nutrient availability, all of which need 24 hours of oxygen to thrive.

Oxygen saturation in the water column from daily photosynthesis and winds must last all night, or the primitive cyanobacteria can become competitive in low-oxygen [anoxic] environments. Low-oxygen-tolerant fish species can also die from anoxia and decompose. Decomposing biomass requires additional oxygen, compounding the problem. If enough plants, animals, and decaying material demand oxygen that isn’t available, a sudden mass die-off can cascade, usually just before dawn after a long night. Sometimes, residents will wake to notice cyanobacteria, fish floating, and the smell of decomposing material in what might seem like a sudden event but actually took most of the summer to develop. In the case of nutrients, an extreme level can sometimes take years to build in the lake and have this effect.

The annual dominance of cyanobacteria and accompanying fish kills was studied by major agencies and universities for several decades, most notably U.C. Davis, which published the “Causes and Control of Algal Blooms in Clear Lake [Richerson, Suchanek, Why, 1994].” This publication used data beginning in 1970 [until the report date] and recommended controlling upland sediment and rehabilitating floodplains and wetlands. It further notes that reducing phosphorus in lakebed sediments is an effective strategy to speed recovery.

A new study by U.C. Davis, under a Blue-Ribbon local panel strategy sponsored by Assemblyperson Aguiar-Curry, uses an Engineering approach to the lake. This effort focused on robotic monitoring of lake parameters and later monitored the testing of proposed fixes by outside companies. Among the studies are algae capture and removal, and microbubble and oxygen infusion techniques to temporarily reduce anoxia, thereby benefiting cyanobacteria. These methods add little to permanently balance the problem-causing nutrients in the lake.

But another test approach, more aligned with the 1994 report, locks up the recycling lake-nutrient phosphorus into pebble form using lanthanum/bentonite-clay slurry infusions onto the lakebed. This last approach promises to reduce the level of phosphorus nutrients available to the lake ecosystem. But only if the outside introduction of this nutrient to the lake is also significantly reduced.

When cyanobacteria have the low-oxygen advantage, and the exploding population takes up phosphorus in the lake, they float to the lake surface to gain a sunlight advantage and drift downwind, driven by westerly breezes toward the lower arms of the lake. Here they die and concentrate the phosphorus as a result. By treating these key areas, a significant amount of recycled phosphorus can be locked up using the lanthanum treatments. Yes, the high phosphorus levels fueling cyanobacteria blooms can be reversed.

Next is Part 3, fixing the wetlands.

WINDOW ON CLEAR LAKE: Fixing Clear Lake is a 4-part series.

Part 1: Three ecosystems must work together by Jim Steele

On this 4^th of July and the 250th anniversary of our country’s founding, I sat on the shores of Clear Lake waiting for the fireworks display presented by the Clear Lake Oaks Business Association. It’s really a great event, but one must ignore the cyanobacteria-painted green water and the smell of dead fish littering the lake edge. The shoreline was strewn with carcasses of decaying Threadfin Shad and Carp. What’s interesting about this annual phenomenon is that it’s not unusual or unexpected in such a nutrient-rich warm-water lake full of introduced species from different climes. It has happened in similar lakes all over the world. But Clear Lake has all the attributes that make it a lake very sensitive to nutrient overabundance. After decades of science-based studies to determine the causes, these are now well known. So, what is the problem and can it be fixed?

The answer is yes to fixing, but first the problem. Ecosystems are described as naturally distinct biological and physical systems. As is the case for most freshwater lakes, the Clear Lake ecosystem requires the supporting function of a wetland ecosystem that settles out nutrient-laden sediments before they enter the lake. Complementing this function is a stable upland terrestrial ecosystem that contributes minimal amounts of sediment through several streams into the hundreds of acres of wetlands historically edging the lake. Recent history has not treated this three-ecosystem supporting formula very well.

Clear Lake is our largest natural freshwater lake in California, and lakebed drilling-core studies indicate the lake’s basin received aboriginal settlers thousands of years ago without much change until the last one hundred years. Recognizable changes in the mud cores were correlated to the advent of heavy equipment in the early 1900s from road building, altered streambanks, mineral mining, and they also marked the loss of wetlands to agriculture and housing. Other data-rich lake and watershed studies indicated that tons of sediment would flow off terrestrial uplands during major storms that were restrained by levees, bypassing the settling influence of remaining wetlands. These results stem from past uninformed decisions by policymakers who needed better information. That better information is available now.

Permissive land stewardship allows thousands of off-road vehicle users each year to access the hills and other areas of the lake basin. This sediment-disturbing activity is defended as needed for outdoor equipment use activists. The sediments move downstream past wetlands because of levee protection for housing and agriculture. Once the past decision to remove wetlands as a settling basin was discovered as a mistake, a long process to restore a portion of the wetlands began. But recovering a wetland proved more cumbersome than first imagined, and the project has stalled for over 20 years. During this 20-year delay, additional tons of sediment have entered the lake, forming a large island near Rodman Slough. The delay was not known to add to the problem at the time.

Studies reveal that the lakebed sediments contain nutrient components such as phosphorus that are released annually from the warm-water, low-oxygen environment of the lake bottom. Aiding the release is a sweep of Konocti winds across the lake, which often reach velocities supporting a bottom-stirring Langmuir Circulation. This corkscrewing suspension of bottom silts makes phosphorus available to primitive single-cell cyanobacteria, thereby fueling a scum bloom. The newest revelation is that this lakebed phosphorus component accumulates over the years, and this built-up amount recycles annually from the lakebed, thus creating more and more a cyanobacteria-dominated lake during warm weather.

All three ecosystems, the lake, wetland, and upland terrestrial, have become compromised by past uninformed policy decisions. Now with better information, what can be done? First, additional delays are not an option. The trick is to begin restoring the function of all ecosystems at the same time. Since each system has its own peculiarities, the methods must differ. Reducing the total lake nutrient is the common goal. Next is Part 2, fixing the lake.