In the Sierra Nevada’s Highland Lakes, midway between Lake Tahoe and Yosemite Park and over 8,000 feet above sea level, a 150-mile journey begins. About 100 miles below, part of the Mokelumne River branches off through a reservoir, aqueducts, pipes, taps, human bodies, tubs, more pipes, and garden hoses into San Francisco Bay. But up here, where the lodgepole and whitebark pines mix with red firs, where willows grow along the lakes and the riverbank, the industrial uses of the river seem a world away.
Surrounded on three sides by the granite peaks of the Carson-Iceberg Wilderness, the paired Highland Lakes punctuate the headwaters of the Mokelumne River. In summer, the grassy flats along the lakes produce a bouquet of water buttercup, scarlet gilia, monkeyflower, paintbrush, and many others. Belding’s ground squirrels, chipmunks, black bear, and mule deer forage; wolverine, California spotted owl, and goshawk live among the conifers. The lakes and river have both rainbow and introduced brown trout; on their banks spotted sandpipers and dusky flycatchers breed. In early spring, the entire bowl will be covered by 20 feet of snow, the quiet broken only by an occasional raven or Clark’s nutcracker.
“This is just an amazing place,” said Amador County resident Pete Bell, vice president of the Pine Grove, California–based Foothill Conservancy. “Yosemite has nothing on the Mokelumne River Canyon.”
Below Highland Lakes, the river winds about 10 miles into the 10-acre Hermit Valley at 7,000 feet, and from there sweeps northward along the southern border of the Mokelumne Wilderness. It flows down a steep granite canyon, churning up whitewater fit for only the most expert of rafters. The gorge is accessible at a few points but no trails parallel it. “Every half mile the river runs into these granite shoulders of mountains, does a horseshoe, and runs into another mountain,” said Bell. “You can hike on the shoulders and look down on old growth — 250 acres of red fir, with mixed conifer and pines lower down. You can walk through whole forests of trees four feet in diameter.”
By the time the river reaches Salt Springs reservoir at 4,000 feet, 27 miles downriver from Highland Lakes, it has wound its way through habitat for a range of rare animals — from pine marten, Yosemite toad, and mountain yellow-legged frog to the American dipper, an aquatic songbird favored by John Muir.
The Mokelumne watershed’s 575 square miles in the Sierra Nevada, enclosed on the north by Squaw Ridge and the south by the Pacific Grade Summit, encompass most of the 105,000-acre Mokelumne Wilderness. Much of the rest is within the Stanislaus and Eldorado National Forests, where cattle occasionally graze in watershed pasturelands.
But Pacific Gas and Electric (PG&E) has also claimed parts of the high country watershed. From 7,500 down to 900 feet, it runs a series of flumes and tunnels attached to more than a dozen dams, six diversions, and two reservoirs, the larger one at Salt Springs. The plumbing carries the water high and drops it to capture energy. As dams do, these have disrupted seasonal flows and trapped silt; in an October 2001 federal relicensing agreement for four power plants, PG&E agreed to remove three dams and improve flows for local fauna. In a joint power authority with local water agencies and three county governments, the East Bay Municipal Utility District (EBMUD) has also sought to acquire all PG&E’s Mokelumne facilities.
PG&E was not the first to claim Salt Springs.
“According to the archaeologists, Indians excavated pools immediately below the springs,” said Bell. “They traded the salt for obsidian. This whole canyon was a trade route for Miwok on the west slope, Washoe and Paiutes on the east.”
Downstream of Salt Springs Reservoir, the Mokelumne flows through mixed conifer, oak, madrone, and Pacific yew woodlands, down Devil’s Nose Canyon in Amador County. Between 4,000 and 3,000 feet the river enters a patchwork of national forest and private property. By 1999, much of the area’s timberland belonged to lumber giant Sierra Pacific Industries. “Over the years, they aggressively bought out just about every timber operation up here,” said Bell. “They’re doing a lot of clear-cutting, filing harvest plans so quickly no one can follow them. It could really load the river with silt and herbicides.”
With the joint authority, EBMUD “is trying to do a comprehensive review to protect the watershed,” said EBMUD environmental specialist Eileen Fanelli. “We are concerned about erosion, herbicides, and nutrient increases in the water.”
When the Mokelumne winds down to below 3,000 feet, it enters logged-over former gold-mining country west of Highway 49, with its younger mixed conifers and blue oak woodlands. At the 2,300-foot-high Tiger Creek juncture, it leaves the national forest, with the landscape gradually adding scattered chaparral. At about 700 feet, the river runs into the Pardee Dam, a few miles southwest of Jackson, population 3,000.
EBMUD, which secured water rights to the river in the early 1920s, built the dam across a deep valley here; the concrete wall towers 358 feet above the riverbed, turning the valley into a “lake” with 37 miles of shoreline. The reservoir supplies water to more than 1.2 million people in 22 East Bay cities from San Lorenzo to Crockett, including Oakland and Berkeley. At full capacity, it can hold about 200,000 acre-feet of water, enough for about 10 months of use. (An acre-foot, about 326,000 gallons, would flood an acre one foot deep.)
During an average year, when the watershed produces more than 741,000 acre-feet of water, EBMUD’s typical 232,000-acre-feet diversion amounts to more than one-quarter of the river (Amador County and Jackson Valley can take about 11,000 more acre-feet). EBMUD’s take remains roughly constant; during wet winters, which can generate more than twice the average flow, a larger proportion of the river will escape diversion. But of course the proportion drastically decreases during a drought, defined as two consecutive years with under 500,000 acre-feet of precipitation. When the Pardee Reservoir is low, EBMUD will let it fill to ensure its water supplies.
The “Southwest Fork of the Mokelumne,” as Amador
County locals sarcastically call it, begins with the Mokelumne aqueducts at the reservoir. The three six-foot-wide steel aqueducts carry the southwest fork across the Central Valley to Walnut Creek, more than 80 miles away. Gravity alone will move up to 202 million gallons a day for the trip. With all three aqueducts open and the station’s pumping plants running, EBMUD can move 325 million gallons. For all water treatment and pumping, including over the East Bay hills, the agency requires about 95,000 megawatts of energy, said EBMUD spokesman Charles Hardy — enough to power about 95 million homes.
From Walnut Creek, the water goes either to a treatment plant in Orinda or to three East Bay reservoirs, where it takes on local runoff before reaching two treatment plants. Together, the reservoirs can hold enough water to supply locals for four to six months. From the treatment plants, which add chloramine and fluoride, the river flows through more than 3,944 miles of distribution pipes and 164 neighborhood reservoirs — and on to businesses and households for drinking, cooking, bathing, washing, gardening, and industrial use.
The tap is not the endpoint. Some water returns to the earth, via lawns and gardens — or as recycled wastewater sprinkled on golf courses or highway medians. Industrial water becomes industrial effluent. Household water usually takes a trip through sink drains or human bodies, enters the sewer system, flows to a wastewater treatment facility, and then enters San Francisco Bay.
From back up at the Pardee Dam, the remaining free river lurches towards the Bay on its own, with a few obstacles remaining. After about 10 miles of altered flow, the river brushes past the 1860s-era Penn Mine. The mine, infamous for its toxic copper, zinc and cadmium legacy, completely sterilized the river after a 1943 “cleanup” flushing, and used to discharge an average of 23 million gallons of hazardous waste annually after EBMUD tried a “quick-and-dirty” remediation in 1977, said Bill Jennings of the Stockton-based Committee to Save the Mokelumne. Before the $10 million mine cleanup in 1986, massive fish kills regularly occurred just below the mine, said Jennings.
Other structural problems remain. Just below the mine, the river pools behind the 38 year-old Camanche Dam, which holds flows from wet winters for release during dry seasons.
Situated above thousands of Lodi-area homes and businesses, the dam breaks the cycle of an ancient flood plain. “The floods have stopped, thus removing the annual process that built incredibly rich soil in the valley,” said Bell. “The whole Central Valley was essentially a flood plain.”
The dams have also blocked the downstream flow of gravel, which makes good spawning beds for salmon and trout. Much of the gravel has since been mined; what remains is piling up behind the dams. Since 1992, EBMUD has regularly spread imported gravel below Camanche Dam, encouraging some salmon recovery.
But fish also need water and access to spawning grounds. During wet years before 1998, EBMUD was required to release a minimum of 13,500 acre-feet of Camanche Reservoir water downstream — beyond the amount reserved for farms — but only a 5,400 acre-foot trickle in dry years.
In the 1980s, successive drought years made it difficult for fish to make it up from the San Francisco Bay Delta, and the Mokelumne “was almost written off as a river” by sport fishermen, said outdoor writer Dan Bacher, who’s covered its fisheries for the Fish Sniffer online magazine. After an expensive 10-year battle, EBMUD agreed in 1998 to release from 34,000 to 85,000 acre-feet. But the spring salmon run has long since disappeared; the Pardee Dam cut off its spawning habitat — probably riffle pools at elevations of 3,000 to 5,000 feet. Lack of cool water downstream also discourages steelhead from making the migration; but much of their prime habitat had also been cut off by the Pardee Dam. Fall-run salmon, a tiny portion of whose historical spawning habitat was below the Camanche Dam, have made a comeback. State Department of Fish and Game biologists trap them, extract their eggs, and hatch them at a hatchery below Camanche Dam. But when it was built, Camanche Reservoir removed 95% of the habitat for a fall run of 60,000 to 80,000 salmon, and for thousands of steelhead, said Jennings.
Below the dam, as foothills give way to flat farmland of the Central Valley, levees and channels guide the much-reduced river down about 25 miles to Lodi, population 57,000. Native animals like river otter and beaver still live in the lower river.
At Lodi, the river pools behind Woodbridge Dam, which diverts 77,000 more acre-feet to vineyards and orchards, leaving behind “at times hardly a rivulet, sometimes hard ground,” said Jennings. This is the last major diversion before the Mokelumne drains into the lower San Joaquin River about 15 miles southeast of Antioch. At the confluence, state and federal pumps suck most of the remaining Mokelumne to the Delta for export to Southern California. The San Joaquin wanders through the Delta, past individual farmers “who put their own straws in the water,” said Jennings. Eventually, the San Joaquin meanders into the Sacramento River, flows through Carquinez Strait, enters San Pablo Bay — and carries the remaining Mokelumne into the tides of San Francisco Bay.