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Davis, California

Thursday, May 23, 2024

Breakthrough study to ensure fish safety under water dams


On Oct. 15, BioScience Advance Access published a study conducted by UC Davis associate research scientist Joshua H. Viers, UC Davis fish biology professor Peter Moyle and U.S. geological survey research scientist Theodore Grantham. This study resulted in a method to ensure the safety of endangered fish by ensuring sufficient water flow under California water dams.

Due to the drought in California, water dam owners are reluctant to ensure sufficient water flow underneath their dams.

The motivation for the study began with the researchers’ concern for the rapid decline in fish populations.

“Eighty percent of fish endemic to California are facing extinction within the next 100 years if something does not change,” Grantham said.

Grantham also explained that the problem of declining fish population has existed for quite a while, but finding a conceivable solution was still complicated.

In an article written by Grantham and Moyle on the California WaterBlog, they found their clear start to fix the problem.

The WaterBlog article states, “[the screening process] provides a scientific basis for dam operators, natural resource managers, and policymakers to perform water ‘triage’ — setting management priorities for dams requiring the most urgent attention.”

The screening process they developed has already shown success. Out of the 753 dams the researchers had screened so far, about 25 percent have been categorized as dams with insufficient water flow. With over 3,000 dams in California, the percentage of unsafe dam operations is only more likely to grow.

Though the framework to check fish safety was just recently invented, according to Moyle, dam owners have been neglecting fish safety for decades. In May 2000, the Putah Creek Council, City of Davis and UC Davis filed a lawsuit against the Solano County Water Agency and the Solano Irrigation District for mismanagement of the creek. The court ruled in the plaintiffs’ favor.

Moyle pointed out that native fish are doing much better since then.

According to Moyle, once these kinds of cases are brought to court, it is almost impossible to lose.

“If a dam is disrupting flow under the dam, they are breaking the law,” Moyle said.

Section 5937 in the California Fish and Game Code explicitly states, “The owner of any dam shall allow sufficient water at all times to pass through a fishway, or in the absence of a fishway, allow sufficient water to pass over, around or through the dam, to keep in good condition any fish that may be planted or exist below the dam.”

The problem, Grantham said, is that no one is enforcing this law due to lack of funding and resources. It is not until someone or some organization brings awareness to the problem and takes it to court that sufficient water flow is restored beneath dams.

Because of this, Grantham pointed out, cases where dams that are not as well-known and most likely in worse shape are not being brought to court. The next line of action is for environmentalist organizations to take this framework and screen every dam — and if those responsible are not providing sufficient water flow under the dam, the environmentalists must take action to protect fish populations.

The researchers have already begun to rank the different dams based upon how endangered the fish population residing and migrating under the dam is, the size of the dam – that is, height and reservoir capacity – and the degree of flow alteration.

Not only would the future screenings reveal whether a particular dam is harming fish, but they could also provide the answer to a bigger issue Grantham is concerned with.

“We hope the information gathered can prioritize future studies and [allow us to] see how the dams can be modified to be less harmful to downstream fish communities,” Grantham said.

Already, UC Davis is taking more of a stand in support of providing greater flow of water to the fish — not only from the perspective of the researchers and professors, but also a significant portion of the students as well. One of the student clubs invested in improving the conservation and sustainability of fishery resources and advancing fisheries is the American Fisheries Society.

Jesus Vargas, a member of the AFS and a fourth-year wildlife, fish and conservation biology major, commented on the importance of this study and others like it in an email.

“These studies are essential to discover the minimum habitat and resources necessary for them to sustain healthy population sizes. With these studies, we can create and regulate dam flows based on the type of flows necessary for the fish to thrive,” Vargas said.

Vargas also explained that certain fish require different water flow rates, which complicate how much water flow to release from the dam.

“The more information we have on what the fishes need, the better we can adjust the flows; any other habitat and resource adjustments that must be made can also be taken into account,” Vargas said.

Researchers hope a compromise can be made to better conserve native fish populations.

“[This study] is a place to start; It is not an end,” Moyle said.

Photo by Stephen Volpi



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