Before the time of land alterations and groundwater pumping, California’s central and backcountry valleys were rich in wetlands and meandering stream systems that drained the mountains and foothills toward the ocean. Nestled within the inner coastal mountains to the west is the geologic marvel lake that has stayed the same depth for millennia as erosion processes tried to fill it. This sixty square mile depression formed between volcanic mountains slumped slowly as a deep underground fault block slid lower.
Clear Lake waters sit in this bowl, which is characteristic of natural lakes but different because it never became a meadow. As rains fall in the four hundred and fifty square mile catchment of slopes draining toward the lake and filling the streams and lake to overflowing, silt settles where tules quiet the water, building a natural levee. Behind this low bench, trapped water continued to widen the tules’ wetland domain basin.
The seasonal and perennial wetlands formed along these streams and lake are home to one of the most diverse ecosystems in the world. The myriad of niches formed by changes in soil type, water depth, nutrient exchange, and energy flux allow species adapted to each environment to live side by side and sometimes be hunted by overseeing top predators. True to the lake’s gentle sloping edge, tules like rush and cattails dominate the shallow shoreline, providing refuge for native fish, hunting grounds for the diverse shore birds adapted to wading, dipping, floating, and small mammals that can speed through the water for a meal. Hundreds of perennial and seasonal birds hunt and nest near fossorial mammals and herptiles who themselves only have eyes for prey. In these shoreline wetlands, newly hatched fish like split tail, chi, and perch feed on the smallest members of the food web and escape top tropic-level predators for the moment.
The story of Clear Lake is tied to these historically immense wetlands as nutrient-rich sediments settle out before they can fuel a runaway cyanobacteria cycle. As wetland areas grow or recede in comparison to the erosion processes of the surrounding hills, so the lake responds. Rather than fires and earthquakes pushing the envelope’s balance, today, humans have accelerated the processes. Erosion has increased with land disturbance, stream channel straightening, gravel mining, levee building, and stream crossing support structures.
However, wetlands have also declined due to shoreline buttresses, stream channeling, stream exit dredging, wetland farming, levee containment, and tulle removal. Back in the early 1970’s as cyanobacteria blooms in the lake were a problem stretching back decades, and erosion was thought as the only culprit; the Department of Fish and Game released a 95% loss in wetlands study that underscored another component important to the lake’s ecology. The balance of wetlands to incoming sediments was the traditional gatekeeper, but both were out of balance, and now so was the lake. Unfortunately, fixing that balance is not the only problem on the table. After excess nutrients enter the lake, they can recycle there until they are either lost downstream or locked up in a geologic and chemical process. Benchmarks for improvement have not yet been developed.
The engineering prowess that moved the earth, farmed land, and channeled and pumped water is now needed to restore what took millions of years to produce such a marvel of nature. However, recovery, as measured against reduced cyanobacteria blooms, may not happen within a lifetime unless a careful account of the restoration process is kept. Satellite studies show sediment coming in through water-basin streams predominated in the Middle Creek watershed. Still, it was clearly not the only source, and other stream inputs may keep the blooms going on their own. With wisdom brought by a new dawn, it’s become time to start the process of recovering the whole watershed in earnest.
The millions of dollars and two decades of focus toward restoring the Middle Creek wetland is clearly a worthy keystone endeavor that will again support floodplain fish, reduce major sediment input, and increase wetland species. Reversing the mistake of building levees to dry a wetland was an expensive lesson, but a future based on understanding important lake processes is getting brighter. As people embrace living with the land again and improvements continue to be made basin-wide, Clear Lake will someday again regain its nutrient balance.
