City addresses Atascadero Lake annual summertime algae
Submitted by the City of Atascadero
–Each summer when warm weather begins, naturally occurring algae affect the waters of Atascadero Lake and generates comments and concerns from local residents. First and foremost, the City of Atascadero assures the community that the water in Atascadero Lake isn’t toxic, is safe for human contact and there is no environmental hazard associated with it. Thankfully, the types of algae found in Atascadero Lake are not the more infamous and dangerous blue green algae, which is not truly an alga but is a type of bacteria.
It is also important to note that all activities and actions the city undertakes that affect Atascadero Lake must comply with, as well as be permitted by, various State and local regulatory and licensing agencies including the Department of Fish and Wildlife and the State Water Resources Control Board.
Atascadero Lake is not a true, natural “lake,” but is a landlocked shallow basin and man-made pond with no natural spring or water source that routinely replenishes its water supply. The natural basin that became Atascadero Lake was originally a seasonal wetland that dried up each year until the lake was excavated and enlarged to become Atascadero Lake. Given these constraints, the lake is highly susceptible to massive quantities of weed growth and resultant algae blooms. A major contributing factor for the extensive aquatic plant growth and therefore the algae is the nutrient level supplied to the lake. These nutrients come from many sources including fertilizers, sediment, leaves, grass clippings, as well as droppings from duck and other wildlife. Most of the nutrients are from direct runoff that flows from nearby lawns and pastures.
Atascadero Creek is the Lake’s primary water source, with approximately 100-acre feet per year being diverted during high flow times from the creek into the lake, as allowed by the City’s Water Diversion Permit. Another factor to the lake’s algae growth comes from Atascadero Creek, which contains additional nutrients contributing to the lake’s plant and algae growth. As the creek is the primary water source, it is extremely difficult to keep those elements from also affecting the water quality of the lake, as the amount of herbicide and chemicals it would require to have an algae-free lake would be far too high to ensure a safe water environment.
However, addressing water quality and algae growth in Atascadero Lake has always been and always will be an important and ongoing effort. The city has employed and continues to explore various other methods to address the lake’s algae issues and has implemented long-term algae management strategies, which involve the use of non-toxic aquatic dye, and supplements, hydrologic and algae level studies and biological and botanical resources surveys. The management plan focuses on prevention and provides options for addressing algae blooms that do develop. In addition, the city has performed preventative measures to help stop massive weed and plant growth that would promote algae in open waters. Another regularly scheduled supplementary application of the approved dye and probiotic algae preventative treatment was completed by city staff this week.
The city has implemented and will continue additional measures as needed to help manage algae blooms. The city’s application for the Algae and Aquatic Weed Control Permit has been approved and issued, which will allow the city the option to use a collection of algaecide and aquatic herbicide treatments in addition to the pond dye and probiotic supplements. Recognizing certain health and safety concerns, the city uses herbicides and algaecides as sparingly as possible, only after other preventative measures are in place and then only upon receipt of all the appropriate permits and approvals by the necessary regulatory agencies. Furthermore, the lake’s water conditions are monitored, sampled and tested; both routinely and as needed on a more frequent basis, as current conditions may dictate.
In recent years, the Friends of Atascadero Lake installed and maintains an additional water supply pipeline from a nearby private well, which helps to supplement the City’s Creek Pipeline water supply and to keep the lake’s water level from shrinking as rapidly as usual during our typical hot summer months. In 2017, the Friends of Atascadero Lake also commissioned a water aeration system that oxygenates the Lake and helps to improve water circulation. The City of Atascadero values its partnership and will continue to work closely with the Friends of Atascadero Lake and the members of the community to address the lake’s water quality, algae growth and other concerns.
