SHASTA LAKE, Calif. — The federal government is considering enlarging a dam to boost the state’s water supply, which would flood what little land remains above water where a Native American tribe had fished and farmed for centuries.
Nine-tenths of the ancestral land of the Winnemen Wintu was submerged in 1945, when the federal government built a 602-foot dam downstream of their ceremonial and prayer grounds.
Now the U.S. Bureau of Reclamation is considering enlarging Shasta Dam, flooding the remaining 22 miles of rocky, steep canyon shoreline, including two sacred rocks involved in coming-of-age rituals.
‘‘These sacred places help keep the tribe healthy. They help keep it balanced and they help us to heal,’’ said tribal chief Caleen Sisk-Franco. ‘‘There is no replacement. There’s not an option to move it.’’
The desire by the few remaining tribal members to preserve the remnants of their homeland is running headlong into the desires of Central Valley farmers, the main beneficiaries of the federal proposal to enlarge Lake Shasta.
When it was filled to capacity, the lake flooded 46 square miles where tribal leaders say some 20,000 Winnemen Wintu once lived along the McCloud River. Their numbers fell to 395 at the turn of the century, with thousands massacred by western settlers and ravaged by disease during the Gold Rush. Today, the tribe counts 122 enrolled members, about a fifth of whom live in a makeshift village of trailers and a house on 42 acres of private land a few miles from the McCloud River, some 225 miles north of San Francisco.
Lake Shasta is the starting point for the federally run Central Valley Project, a system of 21 reservoirs, canals and aqueducts that funnel water to some 3.2 million acres of farmland and supplies water to about 2 million people.
Supporters say an enlarged lake is needed to meet the needs of California’s growing population. The larger reservoir also would be able to store more cold water, which is needed to help the salmon that used to migrate to cooler water upstream before the dam blocked their path, according to the U.S. Bureau of Reclamation.
The bureau is studying whether to raise the dam by 6 1/2 to 18 1/2 feet, which would enlarge the reservoir by more than a tenth of its current size. That’s enough water to serve the city of Los Angeles for more than year.
‘‘What’s so potentially promising about raising Shasta Dam, all things considered, is an opportunity to provide more storage at a facility that’s already in place,’’ said Ron Ganzfried, a supervisor in the Bureau of Reclamation’s regional planning division.
A higher dam also would provide more hydropower, flood protection along the upper Sacramento River and combat future water shortages expected to come with climate change, according to a recent bureau report.
Although the price tag is steep — with preliminary costs ranging from $531.3 million to $854.9 million — it’s far less than the cost of building a new dam. For example, the state estimates it could cost $3.6 billion to build a reservoir in a valley north of Sacramento that would store roughly the same amount of water as would be added behind a taller Shasta dam.
That makes it an attractive solution for California’s farmers and municipal water agencies whose water supplies have dwindled after two dry winters and a federal court order that greatly reduced water diversions to protect threatened delta fish.
But conservation groups are concerned that swelling of the lower portion of the McCloud River would ruin one of the state’s prized trout streams. They also question whether the additional cold water that would be stored behind a higher Shasta Dam would be saved and released for migrating salmon, as government officials claim.
Instead, environmental groups favor building bypasses for salmon to get them around the dam and into the McCloud River. They also advocate paying farmers and other users to increase water conservation efforts.
‘‘We need to come up with permanent solutions that will increase flexibility and provide what we need for the salmon rather than reinvesting in the very projects that caused the problem,’’ said Mindy McIntyre, a water specialist at the nonprofit Planning and Conservation League.
Federal officials say environmental organizations and the Winnemen Wintu tribe will be consulted as plans move forward over the next few years, but how much sway the tribe — which is not a federally recognized tribe — will have to block the dam project is questionable. Congress must still authorize and fund the project.
Although the tribe is small in number, its ties to the area remain central to preserving its heritage. The rocky shoreline along the McCloud River is where tribal members come at least once a year to celebrate the womanhood of their teenage girls. Medicinal plants are ground on a special rock and traditional prayers are offered.
Across the river, toddlers are introduced to another rock where tribal elders tell their ancestral stories. Both cultural spots could be swamped by the rising water if Shasta Dam is raised.