The Cupertino Courier

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Reservoir is full, but in no danger of flood

By HUGH BIGGAR

After the recent rains, Stevens Creek Reservoir has filled up like a bathtub, but the Santa Clara Valley Water District says there is no reason to worry about flooding from the reservoir.

"It won't cause flooding," said Mike di Marco, water district spokesman, of the more than 99 percent full reservoir. (The rains have caused basement flooding in San Jose's Rose Garden, though. Since the beginning of March, a clay aquifer in the Newhall neighborhood has trapped water and prevented it from subsiding.)

In Cupertino, the Stevens Creek Reservoir is designed to prevent flooding. Any overflow from the reservoir, which holds 3,138 acre-feet of water, is diverted into a concrete channel known as a spillway. From there it flows down into Stevens Creek and helps replenish ground water in the Santa Clara Valley.

"It's a natural function and cleans up the water," di Marco said of the full reservoir. "All of the rain flushes out the creeks [into the bay] and also draws in steelhead trout."

According to di Marco, the water district's 10 other reservoirs also are 85 percent full or at capacity.

Lexington Reservoir (named for a community it replaced) in Los Gatos has attracted attention after its overflow created a waterfall-like affect. Los Gatos' Vasona Reservoir has also spilled over. The Almaden Reservoir below Mount Umunhum is also expected to overflow. Like Stevens Creek, these reservoir overflows are diverted to spillways, then to creeks, streams and dams.

All the water also helps restock the area's groundwater, which provides about half of Santa Clara County's water.

"Groundwater is an important part of the valley; in fact, it is one of the reasons the reservoirs were built [in the 1930s and 1950s]," di Marco said. "The farmers pumped out the groundwater at such a rate land was subsiding. The water district was created to help collect water and make sure that didn't happen."

As a part of that process, the reservoirs serve as catch basins for all of the rainfall and help prevent flooding.

The more than 40 inches of rain this year, which is slightly above average, would otherwise run off into San Francisco Bay. Instead, much of the water goes to the water district's reservoirs, where it is mixed with imported water and stored, before it is used for ground water recharge or treatment for drinking water.