The Shasta Dam: Engineering marvel needn’t be an environmental disaster

(NOTE: This Op-Ed by CalTrout Conservation Direction Curtis Knight originally ran in the Redding Record-Searchlight)

When Shasta Dam was finally completed, it was an engineering wonder — one that provided flood control to the Central Valley, power to its communities, and water to the Central Valley Project’s irrigators.

Unfortunately, the effects weren’t all positive.

The day the gates closed, as much as 75 percent of California’s prime salmon and steelhead spawning habitat disappeared. The winter-run chinook salmon — the only winter-run chinook in the world — lost access to the cold, spring-fed waters of the McCloud, where it evolved.

A hatchery was built to mitigate the salmon habitat losses, but new research tells us the hatchery may be hurting the salmon more than it’s helping them, degrading wild fish genetics and driving “boom and bust” population cycles common to monocultures.

Meanwhile, the flows in the Sacramento River below the dam were managed for water deliveries, not fish. Further downstream, the river was channelized, eliminating the floodplains — which we’re now learning are essential habitat for juvenile salmon.

In other words, Shasta Dam was good for part of the state, but a disaster for salmon, steelhead and other fish.

The dam, of course, is not coming down. In fact, it may even be raised. With anadromous fish populations a fraction of their historic, pre-dam numbers — and the salmon populations subject to wild oscillations — the problem isn’t one of nostalgia. It’s one of optimization.

In the presence of Shasta Dam, how do we protect and restore salmon and other wild fish stocks?

Restore Floodplains

Recent groundbreaking studies in the Knaggs Ranch area of the Yolo Bypass (conducted in part by CalTrout Central Region manager Jacob Katz) show us that a single-minded focus on riverine spawning habitat is misplaced.

Spawning habitat is wonderful, but it appears that floodplains — which once covered huge swaths of the Central Valley — are vital rearing habitat for juvenile salmon and steelhead. In recent trials performed in rice fields, salmon grew several times faster than the juvenile fish left in the Sacramento’s main channel.

In fact, researchers recorded growth rates of up to 1.5 mm per day — some of the fastest ever recorded in freshwater. When it comes to salmon smolt survival in the ocean, size is everything.

Happily, to leverage floodplain growth, we don’t need to revert the entire Central Valley to a marsh. Studies suggest that flooded rice fields provide excellent rearing habitat.

And many growers already flood their fields to rot rice stubble. And yes, opening up floodplains also offers flood protection to downstream communities.

In other words, more study is needed, but we’re working toward a solution that’s good for everyone — especially fish and farmers.

Mimic Natural Flows

Current flow regimes below Shasta Dam are based on archaic, outmoded models that harm both fish and do little to benefit downstream water users.

For example, Lake Shasta is drawn down every fall to make room for winter flooding, yet when winter precipitation doesn’t come, we’re suddenly short of water.

New models suggest it doesn’t have to be that way. In fact, a modification to Shasta Dam’s spillway would deliver a sizable increase in water holding capacity.

In addition, flows that better mimic natural flow cycles will benefit the Sacramento’s fisheries. For example, natural flows often ramped up quickly but fell slowly. Today, flows are often ramped down quite rapidly, resulting in stranding issues for juvenile fish, which live in the margins of the river.

Better flow management is needed.

Protect Wild Strongholds

While many of the Central Valley tributaries to the Sacramento River have been destroyed or dewatered, some remain strongholds for salmon and steelhead, including Mill Creek, Deer Creek and Butte Creek.

Since new tributaries aren’t being created, it’s imperative we protect those that remain.

That’s also why the restoration of Battle Creek is so important. Simply put, we’ll never get back what was lost above Shasta Dam, so it’s critical to protect what’s left below it.

A Promising Vision

Shasta Dam is clearly an engineering marvel. It’s our mission to see that it doesn’t become a larger environmental disaster.

Its impacts on California’s fisheries have already been sizable. But we believe proper management and a little vision — like the very promising restoration of wetlands and floodplain rearing habitat — mean future generations of Californians won’t view Shasta Dam as the engineering marvel that killed California’s once-abundant salmon and steelhead fisheries.

Curtis Knight is conservation director of CalTrout.