The demolition and removal of four hydroelectric dams on the Klamath River is now complete. Last month, the Klamath River Renewal Corporation’s (KRRC) lead construction contractor, Kiewit, demobilized its equipment and work crews from the former dam sites, marking the effective end of construction.
The physical work of removing the dams may be done, but the impacts to the river and the fishery are not. We need to be clear-eyed about this concern and confront the situation.
Klamath Water Users Association (KWUA) is a nonprofit organization whose mission is to preserve and enhance the viability of irrigated agriculture in the Klamath Basin, for the benefit of current and future generations. Dam removal is a contentious subject with a complicated history, but the fact is that KWUA honored a commitment to remain neutral on the issue.
As with all environmental restoration efforts, KWUA remains supportive of increasing and improving fish habitat, on the simple premise that such projects 1) do not create additional regulatory burdens on agriculture, and 2) effectively help recover threatened and endangered fish populations and trust resources.
As the focus on the river shifts from dam removal to restoration, KWUA’s position is unchanged. But we are concerned about continued impacts to fish and the long-term recovery of fish stocks in the Klamath River. More importantly, we remain concerned about whether farmers and ranchers will be called upon to provide – or regulated to require – mitigation of such negative impacts.
KWUA’s specific concerns revolve around the one thing still remaining from the dams – sediment. Hundreds of thousands of tons of fine, organic sediment that had accumulated behind the dams over decades and now have been deposited in the mainstem of Klamath River through the reservoir drawdown and dam removal process.
A large release of sediment most recently occurred during removal of the cofferdam at Iron Gate at the end of September, causing a temporary crash in dissolved oxygen levels in the river. Fortunately, unlike the similar event at the end of August, there were no reports of dead fish downstream, just thick, muddy water.
Significant amounts of sediment continued to be released from the former reservoir through September and the first half of October. Provisional data, which was publicly available before recently being pulled from the U.S. Geological Survey’s website, indicated that more than 80,000 tons of sediment flowed out of Iron Gate in September alone. Much of this sediment – mostly decayed algae that had accumulated in the hydroelectric reservoirs during their existence – was carried out to the Pacific Ocean and deposited somewhere on the continental shelf. But initial data also supports what we know anecdotally – a massive amount of sediment has been deposited in the Klamath River downstream of Iron Gate.
Data submitted by KRRC’s contractors to the Federal Energy Regulatory Commission indicate that between the start of dam removal process in January and the end of October, over one million tons of sediment were released from the former dam sites. Roughly ten percent of this volume – around 100,000 tons – has been deposited in the river’s mainstem between Iron Gate and Seiad Valley.
Downstream landowners and county representatives have expressed concern over this sediment in terms of the presence of heavy metals, like arsenic and mercury, and the potential risk to health and human safety. Those concerns are legitimate and deserve respect.
For farmers and ranchers of the Klamath Project, whose water supply has been severely reduced over the last three decades for the sake of salmon, the concerns with the sediment are tied to its existing and future impacts to fish.
According to monitoring data collected this past year, the initial release of sediment during the reservoir drawdown process last winter destroyed the salmon redds in the mainstem reach of the Klamath River below Iron Gate Dam. That loss meant the effective failure of a large portion of the wild fall-run Chinook that returned last year to the Klamath River to spawn.
While the number of fish that hatch and survive to maturity varies each year, the natural lifecycle of fall-run Chinook salmon means that there are generally only five age-classes of fish in the population. So when an event like dam removal prevents an age-class from successfully reproducing the entire population is affected.
The full magnitude of the harm to fall-run Chinook from dam removal process won’t be fully known until 2027 or 2028, when the fish born in 2023 would be expected to return to the river as adults. But for a population that is widely reported as already struggling, the cumulative impact could be severe.
Looking forward, the sediment will continue to pose the risk of smothering salmon redds and killing juvenile salmon so long as it remains in the river.
The impacts to salmon are not just limited to their redds being destroyed. Sediment from the hydroelectric reservoirs has been and looks to continue to be a primary driver of fish disease in the Klamath River.
Since the early 2000s, coinciding with the adoption of flow requirements under the Endangered Species Act, scientists have documented a dramatic increase in the prevalence and rate of infection of the parasite Ceratonova shasta in juvenile salmon in the Klamath River downstream of Iron Gate Dam. C. shasta is a disease that attacks the intestinal tracts of fish, causing hemorrhaging and in severe cases, death.
The increase in the disease has been attributed in part to the prevalence of fine, organic sediment released from the hydroelectric reservoirs. This sediment is an ideal habitat and food source for the microscopic worm that serves as a host for the parasite. (The basic cycle with C. shasta is the worms release spores that infect juvenile fish, and when infected adult fish return to spawn, they release spores that infect the worms, restarting the process.)
By providing consistently high flows in the Klamath River, even during periods of drought, Upper Klamath Lake was prevented from filling and spilling, thus eliminating the types of “flushing flows” that historically scoured this sediment from the river. Due to managed river flows post-2000, the sediment built up in the river channel downstream of Iron Gate Dam. Under this flow regime, worm populations and C. shasta proliferated.
Following the draining of the reservoirs, researchers initially found lower numbers of the worms that cause C. shasta, suggesting that the sediment released from the dam sites had somehow disrupted populations. But as the summer progressed, the worms quickly and extensively recolonized the new sediment in the river. As a result, contrary to expectations, this year’s monitoring showed C. shasta spore counts matching recent years.
In the long-term, when this sediment has finally been flushed from the system, it is plausible that C. shasta will be less of a problem. But until that occurs, this disease is likely to continue to impact coho and Chinook salmon, slowing recovery of these stocks in the wake of dam removal.
The recent reports of adult Chinook spawning above the former dams, including tributaries in Oregon, may reinforce concerns with the sediment in the river below the dam sites. While hundreds of fish have recently been seen above the dam sites, typically thousands of fish spawn in the mainstem, particularly the reach from Iron Gate to the confluence of the Shasta River.
So far this fall, the river below Iron Gate has been too clouded by sediment to observe any redds and only ten adult carcasses – a proxy for the annual run size and potential spawning success – have been found in that reach. The average for this time of year would be around 1,000 carcasses. Similarly drastic declines of spawning adult Chinook have been observed in Bogus Creek, immediately below Iron Gate Dam.
KWUA has recently joined with the Yurok Tribe, Karuk Tribe, and the Klamath Tribes in supporting restoration work throughout the Klamath Basin. As projects move forward and restoration occurs, it is critical that the sediment left in the river in the wake of dam removal not be overlooked or forgotten.
The federal and state regulatory agencies responsible for overseeing dam removal need to ensure that KRRC addresses the sediment remaining in the river, now and likely for years to come. As these agencies repeatedly promised in the lead-up to dam removal, releasing more water from Upper Klamath Lake is not an option for dealing with this sediment. KRRC and the supporters of dam removal will need to come up with other physical, mechanical, or biological solutions.
Nor is acceptable to allow the continued impacts from this sediment to somehow warrant additional legal protections for fish or other regulatory burdens on farmers and ranchers in the Klamath Project. That would also violate an explicit promise made by federal and state agencies in advance of dam removal.
Now that the debate surrounding removal of the dams is over, it’s time to confront the remaining and continuing impacts to the Klamath River and the heavy work needed to now clean it.