Clear Lake is a large natural warmwater lake with a small dam, a shoreline surrounded by homes with docks, roads built around the waters’ edge, small communities and two cities with hardened street surfaces focusing rain water toward the lake forming the picture today. It’s sometimes a beautiful scene with abundant wildlife including the best fishing in the state and inhabited by several hundred bird species. But it does have some noticeable cyanobacteria blooms during warm periods and this can dampen the lake tourism industry. Has it always been this way as you sometimes hear?
In the past 100 years, over 50 mines in the upper watershed and one significant one on the shoreline at sulfur bank road removed minerals from the earth. Gravel mining for construction extracted significant material from streams but released uncounted tons of sediment and destabilized the streambeds for miles upstream. The channels are still adjusting through bank collapse and bed scour. Later, entrepreneurs developed thousands of lots with road access across the hillsides for sale to second home owners now called the “paper subdivisions.” But this effort failed due to new laws that required water and sewage facilities for new developments. You can today hear sounds of recreational off-roading on public lands and on a good day dozens of motorcycles and other ORV’s cruising the backcountry with many also using the paper subdivision roads. The winter rains which can sometimes be gully washers, bring sediment from the old mines, dirt roads, streets and unstable streambeds toward the lake. Only herculean efforts by the County Resource Conservation Districts and volunteer watershed restoration groups slowed this process down.
Of course the lake itself has also changed in a hundred years of development. To the practiced eye the shoreline of this natural lake doesn’t look as natural any more. Sediment trapping emergent native vegetation along the shore lines has been replaced with retaining walls in many places, sometimes homeowners who like a clean look will pull the shoreline tules and even invasive primrose will replace native plants. The biggest change to the natural processes in the lake might be the filling of natural wetlands to produce more farm land or the dredging of channels to promote boating. The addition of levees in the largest wetland on the lake along Middle Creek funneled the water and sediment flow of several streams directly into the lake rather than settle out before entry.
The buildup of nutrients forming the ecological processes that you studied in school is perhaps a bit too much for human sensitivities when it dies back forming a sulfurous backdrop to the evening barbeque. So, the question of what is causing the cyanobacteria blooms was left to speculation and study lasting over 30 years by the University of California at Davis (UCD) finishing in the 1990’s after many discoveries were made. Perhaps the most important of which was that the sediment from the uplands draining into the lake has significant mineral phosphorus from the volcanic fields surrounding the lake and it was unlocked and released from the lake bottom due to low oxygen conditions during the warm summer months. This key life supporting component along with other abundant natural minerals supporting bacterial, cyanobacteria and phytoplankton begins the strong web of life that is Clear Lake’s natural history story. Unfortunately, the second component of this story is that phosphorus can recycle in the lake year after year without an understanding of how long it remains.
A little more study by UCD along the ecological support system for cyanobacteria is needed to clearly understand key drivers and the best rewilding techniques to bring about conditions before European influence. A little more study by UCD along the ecological support system for cyanobacteria is needed to clearly understand key drivers and the best rewilding techniques to bring about conditions before European influence. This is was what I had envisioned when a “Blue Ribbon Committee” was first formed by our state assembly representative. This welcomed attention by the State was designed to provide a pathway toward a more “healthy” lake ecosystem through public consensus. The technical side of the consensus would be guided by the continued research from UCD and paid by the State. Some of the remaining ecological questions answered by UCD could form the bench mark of local management practices to guide future development on the upland and shoreline of the lake going forward. After all, it was long ago local management decisions that allowed for the uninformed development leading to our odoriferous lake in the first place. So what are those questions that would guide better decision making to a rewilding of the watersheds ecosystems?