Finding a Formula for a Clean Lake : Westlake: Caretakers of tranquil residential waterway struggle to keep algae and evaporation in check. A third well may be needed, they say.

Westlake Village resident Ben Schulman constantly tinkers with the formula for serenity on Westlake Lake.

Kill too much algae and light will cause weeds on the lake floor to sprout as much as six inches a day. Let the algae grow, and within days a green carpet will grow thick enough to prevent a duck from getting its feet wet crossing the lake.

“We’ve got some very difficult problems to deal with, both technically and financially,” explained Schulman, president of the Westlake Lake Property Assn. “And we’re devoting almost all of our time to solving them.”

In addition to the ever-regenerating algae, Schulman said the artificial lake’s engineers have struggled daily to keep it full, despite losing up to 1,000 gallons each minute to evaporation in the summer heat.

So far, Schulman said, they have been able to refill the lake fast enough to conceal the problem from the nearly 1,200 residents who gaze out at it every day.

The 150-acre lake, which straddles the border between Ventura and Los Angeles counties, remains a scene of tranquillity, where it is common to spy a blue heron in flight or a sailboat gliding gently along in the breeze.

Residents such as William Murphy say the beauty of the lake is a cure for the discomfort of summer swelter.

“In front of my house it may be summer, but in back of my house it’s always fall,” he said, the water lapping up against his deck. “You always feel a little bit cooler when you’re looking out at the lake.”

It has not, however, been a summer of calm for Schulman.

Normally, the water that fills the lake comes from the drainage of ground water in 18 square miles surrounding the lake. When the runoff is slow, engineers compensate by tapping into two wells that collect water from an aquifer.

Heavy rainfall two years ago provided enough runoff to keep the lake full for the entire summer, and the wells didn’t operate all season.

This year, the wells began pumping during the first week in June and have not stopped. Even with water from the aquifer, the pumps are barely keeping pace.

The lake loses water in three ways: Evaporation, if unchecked, will drop the lake’s surface five feet during the hottest summer months. Neighboring Westlake Golf Course, by virtue of a 30-year-old agreement, siphons off as much as 400 gallons a minute to irrigate its greens.

And each day, a smaller amount is pushed over a 450-foot-long dam at the east end of the lake.

To keep up with the water loss, Schulman and members of the lake’s water management committee have begun to talk about building a third well.

“We’re trying to improve the efficiency of the two wells we’ve got, to get it to pull more water from the aquifer,” Schulman said. “But now we have to consider a third well, which is a pretty expensive proposition.”

Money for such a project would come from the yearly dues that residents around the lake are assessed. Schulman declined to say how much residents pay for lake upkeep. “You get what you pay for, and this is a beautiful lake,” he said.

Few realize the effort it takes to keep the lake beautiful.

“I really don’t know that much about the maintenance of the lake,” said Irving Wasserman, who lives on the island in the middle of the water. “I see them out there chopping away at the algae all the time, but that’s about all.”

Algae, Schulman’s other main concern, is a problem at many lakes.

Last year on Lake Sherwood, algae grew with abandon. Dead layers of the brownish-green plant filled the air with an odor described by residents as “sewage-like.”

On Westlake Lake, William Murphy said, the plant has at times grown so thick that residents have had a hard time maneuvering boats through it.

“Especially in the summer, it grows like crazy,” he said.

Crosby Fentress, chairman of the property association’s water management committee, explained that the algae feeds on dead weeds that have accumulated at the bottom in layers as thick as two feet.

And, he said, the reclaimed water frequently used to irrigate nearby neighborhoods drains into the lake. That water’s nutrients help the algae grow even faster.

“You can’t eliminate it 100%,” Fentress said. “You just have to try to keep it under control.”

To do that, the property association purchased a $45,000 harvester machine, which chops the algae and sucks it off the surface of the lake.

Also, Schulman said, the caretakers use chemicals in small doses to address the problem.

“When the lake was new, they used enough chemicals to keep it like a swimming pool,” Schulman said. “But they learned that if the lake surface was too clear, the light would speed up the growth of weeds at the bottom.

“It was a no-win situation,” he said. “So now we steer away from using a lot of chemicals.”

Bill Hanson, who for many years worked as the lake’s engineer, called lake management a balancing act.

“Really, it’s a scientific process,” said Hanson, a chemical engineer. “If you manage it well, you end up with something really terrific.”

Lake Woes

Westlake Lake, which straddles the border between L.A. and Ventura counties, is facing summertime woes: an ever-regenerating carpet of algae and rapid evaporation, which leads to a struggle to keep the man-made lake full.