Bay Nature magazineJuly-September 2003


A History of the Reservoirs of the East Bay

July 1, 2003

There were only a few, small permanent lakes in the East Bay before the coming of engineers; to find anything sizable you would have had to cross the Bay to Lake Merced in San Francisco or Bass Lake in Point Reyes. Yet humans are water-loving animals, says Harvard naturalist Edward O. Wilson in his book Biophilia — hardwired to experience contentment when looking out over bodies of freshwater. Freshwater means fish and, most important of all, enough to drink. In that light it makes sense that some of the most artificial intrusions in our semiarid East Bay parks, the reservoirs, are also among our most popular “natural” attractions.

Only a ten-minute bike ride from north Oakland’s Rockridge BART station is my favorite artificial aquatic retreat: Lake Temescal. The contentment reflex Wilson describes hits me as I stand surveying the small, sublime lake, the first reservoir built in the East Bay. With its ducks, overhanging willows, and well-worn trails, it looks more like Walden Pond in New England than anything you would have found around here 150 years ago. The resemblance is enough to satisfy a nostalgic longing, in many of us immigrants at least, for the less arid, lake- and pond-dotted regions of the world from which we’ve come.

Although engineering and economics lie behind the East Bay’s fabricated lakes, the ecosystems evolving around and within them have taken on lives of their own, displacing some plants, animals, and habitats while favoring others. Some of these changes represent clear ecological loss, mostly of riparian habitat. They also represent habitat gained for animals who’ve lost standing freshwater elsewhere — notably freshwater marshes along the margins of the Bay. But the reservoirs represent something new as well, an evolving ecological innovation still in its early phase.

In 1869, Anthony Chabot gouged out several hillsides inOakland to create Lake Temescal, the East Bay’s first resevoir. (right)No longer a source of drinking water, Lake Temescal today is a verypopular summer swimming hole. Photos courtesy of Bancroft Library,University of California, Berkeley, and Nancy McKay/EBRPD.

It all began here at Temescal 135 years ago when the gritty Canadian-born entrepreneur Anthony Chabot won a contract to supply the small but growing town of Oakland with water. He’d already made his mark by developing a method of blasting gold deposits out of the Sierra Nevada with high-pressure water cannons. The technique made him rich, but it also created millions of tons of tailings that silted up the entire Sacramento River system, altering the hydrology of the Bay for decades. Chabot applied the same technique for Oakland’s new reservoir, but this time he trapped the loosened sediment to make a dam.

In 1869, Temescal Reservoir gave Oakland its first city water supply. But it was an aesthetic and ecological abomination, a gross scar cut out of what had been a lovely, free-flowing creek and meadow. No one seemed to care; in fact there seems to be no record of anyone having noticed the loss. There were plenty of other healthy East Bay creeks in those days. Anyway, locals were in hot pursuit of Progress, and Preservation was not yet on the map.

As the years and decades passed, the scars gouged by Chabot’s water guns smoothed over. Migrating ducks and Canada geese carried seeds in their guts to plant the cocktail of native and exotic rushes and lilies, cattails, and other aquatic plants that have blurred the sharp, unnatural land-water interface. Today the reservoir is a sanctuary of wildlife and space in what would otherwise be an unbroken blanket of north Oakland homes and roads.

Of course the story has just begun. As Temescal and the other Bay Area reservoirs collect sediment behind their dams they become shallower. Birders Dave Quady and Robert Lewis have been leading Christmas counts here for 30 years. In 2002 they and other volunteers counted 83 different species on and around Temescal, from grebes to ring-necked ducks. But as the lake grows shallower, they speculate, the number of diving birds, such as double-crested cormorants, may be declining, while other types of birds that prefer shallow water, such as egrets and herons, are on the rise.

The salmon and steelhead that once lived in this watershed are gone, and few native fish remain. But a number of fish species such as rainbow trout and both channel and white catfish are stocked several times a year to serve the sportfishing community. Other exotics, including redear sunfish, bluegill, and largemouth bass, also now make themselves at home here. The beleaguered Sacramento perch, California’s only native sunfish, is being overrun by exotics in its historic habitat in the Delta and has had to head to the hills for protection. It now finds refuge in Jewel Lake (in Tilden Park) and Briones Reservoir, exotic habitats coming to the rescue of a native fish running from alien invaders in its native habitat downstream.

For half a century, Temescal was used as a secondary source of water for Oakland. But by 1936, the pipes were shut off and the lake shifted identity from water source to recreation site. Today Temescal Regional Recreation Area is one of the most popular units of the East Bay Regional Park District (EBRPD), drawing more than 200,000 visitors every year from surrounding neighborhoods and farther afield, especially in the summer, to picnic, sunbathe, fish, or swim laps.

When Anthony Chabot completed Temescal Dam in 1869, there were 10,000 Oaklanders. Only six years later there were 25,000, and their collective thirst exceeded Temescal’s capacity. Chabot looked south to a large gorge on San Leandro Creek that gathered rains from a watershed of nearly 50 square miles. There he once again turned his sluice hoses on the hillsides and, with the help of as many as 500 Chinese immigrant workers, molded the resulting sediment into a dam. He inundated the gorge with five billion gallons of water, creating Lake Chabot.

Today, Lake Chabot is officially a secondary drinking water source for the East Bay (though no drinking water has been drawn from it since the 1970s); to maintain the water’s purity, no swimming is allowed. But there are several kinds of boats for rent at the Chabot Marina and the reservoir is deservedly one of the Bay Area’s most popular fishing spots. It is kept stocked with rainbow trout, catfish, and bass, while bluegill, crappie, and carp ply the waters without any human assistance. The lake produces some of the biggest trophy bass around.

The ten-and-a-half-mile circumnavigation by foot takes three-plus hours at a good clip, but it’s a lovely and varied hike, passing through oak and bay laurel woodland and chaparral, and skirting the silted-in, marsh-like Honker Bay, where egrets, herons, and red-winged blackbirds hang out. From the trail high above the lake, the Bay is visible, five miles off to the west.

For some migrating birds the freshwater reservoirs constitute welcome corridors offering food, water, and rest on their north-south journeys. But for more land-bound animals, such as the California newt and the red-legged frog, the reservoirs may present significant obstacles to age-old annual migrations. On the other hand, bullfrogs, an alien species from the lake-filled landscapes east of the Rockies, have benefited from the reservoirs, displacing much of the native herpetological fauna.

The most obvious impact of reservoir creation was the obliteration of the habitat — creeks and valleys, meadows and woodlands — that now lie beneath thousands of acre-feet of water. The second most salient biological change was the interruption of the creeks that were the annual migration routes for anadromous fish species like salmon and steelhead. After spawning in the upper reaches of the watersheds, adult salmon would perish by the ton, transferring nutrients from the ocean into the creeks. No more. While some steelhead adapted to life in the reservoirs and the creeks above them, skipping the saltwater phase of their lives and becoming rainbow trout, the salmon were less mutable. Unable to get to their spawning grounds above the dams, they died without reproducing.

The dams also influence the hydrology of the hills and the Bay, altering flow schedules by holding back water in wet winters, and thereby eliminating the floods that used to punctuate the decades with big washouts. Like the uncontrolled fires of past centuries, these floods scoured riparian slopes, making way for different vegetation types and starting a new vegetation succession cycle in the canyons. Incidentally, reservoirs also act as obstacles to the spread of the periodic fires that once characterized the surrounding forest, grassland, and chaparral habitats.

In addition, dams hold back sediment that formerly would have passed into the Bay from the surrounding watersheds in wet winters. While Chabot’s water cannons once overloaded the Bay with Sierran sediment, today, that extra sediment has largely been flushed out the Golden Gate, according to Robin Grossinger of the San Francisco Estuary Institute. He says the Bay now suffers from a sediment deficit keenly felt by engineers trying to restore Bay wetlands.

Reservoirs also affect water quality. Heavy winter rains deposit coliform and other bacteria from upstream sources into reservoirs. That is why swimming is often prohibited early in the spring. Extended exposure to the sun effectively neutralizes the unhealthy microorganisms, and the water leaving reservoirs is generally cleaner than water going into them. By summer, water quality has improved significantly. (Quality is constantly monitored in all of the swimming reservoirs; managers shut them down if there is any doubt about pathogen levels.)

Twenty miles southeast of Lake Chabot, just south of Livermore in the headwaters of the Alameda Creek watershed, sits Lake Del Valle, the biggest, most impressive, and least urban of the EBRPD reservoirs. Unlike Temescal and Chabot, whose rough edges of artificiality have been worn away and replaced by nature’s own designs, Del Valle still looks surreal and as out of place as it is: a huge lake in the middle of typically dry inner Coast Range oak woodland. But spend a truly hot day hiking or biking here, followed by a cool swim, and the juxtaposition becomes pure ecstasy.

Lake Del Valle was created in the early 1960s as a storage and flood control facility by the State Water Project, with recreation as a side benefit. Filled by Arroyo Del Valle, in times of drought the lake is used to supplement supplies in Santa Clara and San Mateo Counties. At such times, the lake releases up to eight inches of water a day and the elevation can fluctuate by up to 25 feet over the course of a year. In his book about the East Bay regional parks, East Bay Out, Malcolm Margolin says that when he watches the Del Valle level drop, he keeps “hoping that this magnificent valley will reappear, intact and magical like the lost city of Atlantis.”

But an awful lot of people like it just the way it is. Last year more than 350,000 visitors came to Del Valle, most of them in the summer. And humans aren’t the only ones. Mountain lions are sighted here every year. They would do fine without a lake, but apparently appreciate the extra raccoons, deer, possums, and birds drawn to the reservoir. And a few years ago a pair of bald eagles nested in the park, the first to grace the area within living memory. The pair has since moved their nest outside the park boundary, but they still fish in the lake and engage in breathtaking courtship and mating displays in the air above.

“Artificial” is such an ambivalent word, denoting both human creativity and lack of authenticity. Our artificial lakes embody both of these extremes. They are beautiful works of human invention as surely as they are out of place. As for their authenticity: enough time makes a native out of anyone or anything.

Back at Lake Temescal, which seems a tame and manageable pond compared to Del Valle, four double-bedded trucks pull into the parking lot and begin to unload 200 tons of sand ground out of Sierra granite, destined for the swimming beach. Looking out over the lake I see grebes, coots, and ruddy ducks swimming near the patch of yellow irises on the east shore. Behind me a lovely (albeit artificial) waterfall gurgles away. Ahh! — there is that Wilsonian contentment rising again in my exotic heart, as unnatural here as those irises or the lake that feeds them. What, I wonder, is the ecological effect of the millions of human contentment reflexes stimulated by these reservoirs? A heightened regard for the natural world? A greater sense of connectedness to the community of organisms that share our watersheds? Or a collective sense that everything is well in our relationship to the rest of the natural world . . . even though it surely is not? I just don’t know. Perhaps I should take another walk around the lake and think about it.

About the Author

Gordy Slack is a freelance writer living in Oakland. He writes an environmental column for California Wild, the quarterly magazine of the California Academy of Sciences, and he is the co-editor of Faith in Science (Routledge, 2001), a collection of interviews with religious scientists.

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