It doesn’t seem possible that removing four dams could actually improve water supplies. But that is one potential result of the recently approved deal to remove dams on the Klamath River.

The agreement, announced on April 6 by the U.S. Department of Interior, will likely become the largest dam removal project ever undertaken in the United States. It involves removing four dams owned by PacificCorp on the Klamath River by 2020: Iron Gate, Copco 1 and Copco 2 (all in California) and J.C. Boyle (in Oregon).

One of the unusual facts about these dams is that none serves as a water supply. Instead, they function solely to produce hydroelectric power. But modernizing them to satisfy Federal Energy Regulatory Commission relicensing rules requires a greater investment than their energy output is worth, which is why PacifiCorp supports dam removal.

So, removing the dams does not deprive anyone of a water supply. In reality, it could have the opposite effect. With the dams gone, endangered salmon populations in the Klamath are expected to see a tremendous rebound. This would ease pressure on farmers in the upper river basin, who are often forced to give up water to help salmon runs.

“Absolutely, we’re hopeful that’s the outcome,” said Scott White, executive director of the Klamath Water Users Association , which represents farmers who rely on Klamath water. “That’s definitely a bonus for our irrigators if we don’t have to send as much water downstream, especially in short water years.”

Coho salmon in the Klamath River are listed as threatened under the federal Endangered Species Act. Iron Gate and the Copco dams prevent them from spawning in upriver tributary streams, which are some of the best habitat in the watershed. Instead, they are confined below the dams, where the water is warmer and habitat is relatively poor.

Releasing more water is one of the only ways to fix this, and it usually comes from Upper Klamath Lake, an important source of irrigation water for farmers in the Klamath basin, just over the Oregon line. Those farmers aren’t to blame for the salmon’s decline, but they often pay the price when the fish need more water.

“The only tool that’s presently available is releasing more water,” said Brian Johnson, California director of the conservation group Trout Unlimited . “So having healthier fish populations takes away one of the stresses on their (irrigation) diversions. Dam removal is not the only thing, but it’s the single biggest thing that we can do for salmon and steelhead populations.”

Another stressor is water quality. The dams make water too warm for fish. This also creates enormous algae blooms that make the water harmful to fish and other animals. Removing the dams will eliminate this problem.

If fish are healthy, that means more fishing opportunities, as well. The Klamath is one of the most important salmon-producing streams on the Pacific Coast. But its ability to produce the fish is often severely hampered by poor water quality, blocked access to habitat and inadequate water flows – all of which are related to the dams.

“If we do things like remove dams and improve riparian habitat, then the regulatory pressures on agriculture are lessened,” said Craig Tucker, natural resources policy advocate for the Karuk tribe , one of three Native American tribes that engage in subsistence fishing in the Klamath watershed. “If fish runs are healthy, then we don’t need to beat up on farmers all the time.”

Without the dams, it’s widely expected the Klamath will produce a lot more salmon – as much as an 85 percent improvement, Johnson said. Over time, this may be enough to remove North Coast Coho salmon from the endangered species list. This would not only help water users by clearing a regulatory obstacle to water diversions, but would also help fishermen.

Improved water flows and improved habitat access will also boost the population of Chinook salmon, which are not endangered but are the backbone of commercial fishing in California and Oregon. More fish also means a healthier fishing industry, both in the ocean and on the rivers.

“We think that Klamath dam removal is the single biggest act of salmon restoration to ever happen in North America,” said Tucker. “The healthier the river is, the healthier the fish runs are and the fewer regulatory burdens farmers have to face.”

Matt Weiser is a contributing editor at Water Deeply. Contact him at [email protected] or via Twitter at @matt_weiser .