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Park Watch: Secrets of Central Park Lake

Like a magnet, Santa Clara’s 52-acre Central Park draws joggers, dog walkers, families with kids, teens hanging out, sweethearts smooching on benches, and assorted feathered friends that make the walkway that circles the park’s centerpiece lake so messy.

“We work pretty hard to keep the walkways as clean as possible, but we’re at the mercy of the seagulls, ducks, and geese,” says park foreman Mike Gilpatrick. “The [Canada] geese are the worst.”

Lake walkways are power washed every three to four weeks in winter—depending on rainfall—and every two weeks in summer. They are blown or swept clean between times.


Even though it is fun for the kids, feeding the birds is against posted park rules and increases their waste. Birds should eat their normal foods—mainly grasses for geese—rather than be tempted with people food. Ducks get their food from the water.

As well as birds, the lake is home to a few carp and red-eared slider turtles that can be spotted sunning on the smooth stones edging the pool (

Jim Teixeira, city parks and recreation director; Jay Selig, parks supervisor; and Gilpatrick have researched and revealed these secrets of the lake:

Central Park was built in phases between 1965 and 1976, and the lake was built during phase VIII in 1973. The approximately one-acre, two-level lake is cement lined and averages five feet deep, shallower in the upper basin and deeper toward the drain in the lower basin.

The lake holds just under one million gallons, and eventually, recycled water from the South Bay Water Recycling program will be used to fill it. The lake is topped off when the water gets low in dry weather, and the surface is skimmed of debris as needed. Every few years when water is changed in the park’s international swimming pool, the pool water (after the chlorine evaporates) is pumped into the lake. Waste not, want not.

The three aeration fountains in the lake flow 24/7 and are turned off only to clean their filter screens or replace a burned out motor (every five to seven years). The two fountains in the lower lake are free floating but anchored by cables.

The fountains are more than decorative. They circulate and aerate the water, helping to reduce the growth of algae, which turns the chemically untreated water green. In addition, there are four bubbling aerators and a re-circulation pump to move water from the upper to the lower lake.

To further control algae in an environmentally-sound way, the parks department has raised Daphnia in its shop and introduced them into the lake. Daphnia are tiny crustaceans related to brine shrimp but are called “water fleas” because of their swimming style. They the eat algae in the water. Revive (a biological water enhancer made up of bacteria, bacterial enzymes, and nutrients) is added monthly.

In August or September, when the algae is at its worst, the lake is drained by half to two thirds of its volume into the city’s sanitary sewer system. With this timing, the lake sparkles for the September art and wine festival. The last time the bottom sediment was removed, was more than ten years ago. That cleaning took about two months and involved about ten employees.

And you thought keeping your fish tank clean was difficult!

Oh yes, as far as Teixeira knows, no one has ever fallen into the Central Park lake. Been pushed in? That may be another story.


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