Work to diagnosis the sources of contamination in Lake San Marcos is underway. Downpours in the region this week aided ecologists trying to collect data during rain events. (Photo credit: Teri Figueroa)
LAKE SAN MARCOS — Scientists are closer to figuring out just why Lake San Marcos is sometimes swimming in noxious algae blooms — and that means the problem is closer to getting cleaned up.
The lake is contaminated with nutrients — nitrogen and phosphorous — that reduce oxygen levels and fuel the growth of algae in the water. The blooms have plagued the private 80-acre lake for years, and in 2010 led to a public and private effort to study the problem and come up with solutions.
Since then ecologists have been collecting data in and around the lake to figure out where the contamination is coming from.
Last week, they held a community meeting to talk about their work. More than 100 residents showed up, eager for any sign of progress.
“We are developing a very good understanding of what is happening to the lake,” project consultant Dan Johnson told the gathering.
The Lake San Marcos cleanup project is a joint effort by groups including the city of San Marcos, the Vallecitos Water District and the lake’s new owner, Pino Vitti.
The project is unique in that it isn’t driven by the Regional Water Quality Control Board, which has the teeth to set rules and run the show. Instead, it’s a collaborative effort to come up with suggested solutions and then seek an OK from the water board.
“I do think we will see Lake San Marcos brought back to healthy condition without having to resort to a top-down enforcement approach,” said David Gibson, the regional water board’s executive officer.
The lake — technically, it’s an “impoundment” — was formed in 1946 when the San Marcos Creek was first dammed and is the centerpiece of a neighborhood of roughly 2,400 homes. The creek watershed stretches as far east as Escondido foothills east of Interstate 15 and includes most of the city of San Marcos.
In recent years, both the lake and creek have been listed as “impaired water bodies” under the federal Clean Water Act.
Investigative work to determine the source — most likely, it’s multiple sources — of the extra nutrients in the lake is nearly done.
The data will be used to craft computer models to zero in on the sources of pollution. Johnson told the crowd Wednesday that one working theory is that groundwater plays a role, as do former farms and dairies in the area.
But the work has been slow.
Part of the data collection has been hampered by the state’s historic drought, which has meant few rainy days in which research teams can take samples. As it turned out this week, Mother Nature provided a bit of rain, and the data collectors were out day and night, even as their colleagues were meeting with community members.
The team hopes to get at least two more rainstorms in the coming months. They plan to create a computer model of the lake by May.
Also adding to the holdup: the federal government shutdown last year, which led to a six-month delay in the Environmental Protection Agency’s release of a key watershed model for the area.