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Groundwater storage to save the coho

Mary Anderson, Redwood Times

Posted: February 23, 2011

The fifth session of the Bureau of Land Management lecture series took place under rainy conditions at the BLM office on Tuesday evening. The four inches of rain that came with the first storm of February brought local water courses up, but by the time September comes, many of the small creeks in the area will be reduced to dry beds and small, isolated pools where young salmonids will be scooped up and eaten by hungry raccoons or die for want of oxygen. In this scenario, coho and even chinook salmon will become extinct in the Mattole watershed. Tasha McKee presented possible options for saving the fish and enhancing the watershed at the BLM office on Shelter Cove Road Tuesday, within shouting distance of the rain-swollen Mattole River. McKee and the Mattole Watershed Council have spent the last decade and more studying and collecting data on the Mattole watershed, searching for the causes of the low flow and looking for ways to return the river and the feeder creeks to a condition that will sustain a healthy population of fish.

Flows in the watershed for nine out of the last 12 years have been the lowest in the 61 years of record keeping in the watershed. Over that period, thousands of young salmonid have died when they became isolated in small shallow pools of water. With 100 percent mortality of the fish due to lack of water, the species will not survive. In 2010, only two adult salmon were found in the system. In the spring, there were only about 100 juveniles seen in Thompson Creek. Of that 100, only two or three are likely to return to spawn the next generation. It is thought a population of 250 adults are needed to maintain the species.

For 20 years, the Mattole Restoration Council (MRC) has been doing its utmost to restore the watershed, but all that work has not taken care of the problem of low flows and the coho are on the brink. The problem is more complicated than originally thought and some of what was done in the past only exacerbated the bad conditions. Logging practices, road building and fire depression changed the nature of the forest. In the 1980s, the thinking was all about sediment and the various agencies supported a program of removing all woody debris from the watercourses. This removed the deep pools that the salmonid need to survive. During high water events in the winter, the river does not provide escape outlets for salmonids and they get swept away. In the late summer, they get trapped in pools and die.

These conditions are compounded by climate change. The dry season has expanded from an average of three months to dry periods of five months. Once the flows go down, there isn’t enough water in the river to meet either the needs of the fish or the humans living along the creeks. To minimize the impact of the human equation, the MRC started its program to encourage everyone taking water out of the streams to store water in tanks and agree not to pump water during the dry months. The nature of climate change means the weather is less predictable and there’s no knowing whether the dry season will be long or short.

McKee and her group have come up with an additional strategy to restore the ability of the watershed to store water in the ground. Clear cuts on Barnum land in the Gibson Creek area have removed a natural “sponge” that used to hold ground water. Water doesn’t soak into the ground, but runs off. Naturally, forest cover stores water underground and released it over time to keep the rivers flowing. It will take a long time to restore that sponge. In the meantime, she is promoting the idea of creating more wetlands along watercourses.

In Oregon, beavers build ponds in river courses, which serve to slow the water down and allow it to seep into the ground where it is stored for release in dry periods. Because of the environmental damage in that state, the beavers were hard pressed to keep their dams from being washed away in high flow events, so the state stepped in and began augmenting the beaver dams to help them survive high flow events. McKee is not proposing that beavers be brought into the area. As far as is known, beavers never inhabited this watershed. She proposes that the MRC construct small dams on watercourses, similar to what a beaver would build, to slow down the water and allow it to soak into the area by the river. Water would be stored along the banks of the creeks to be naturally and slowly released over the dry periods. She is talking about off-stream ponds and wetlands where fish can retreat during high flows and engineered instream ponds that will provide good habitat and connectivity to other instream ponds for migrating fish. Ideally, she hopes that they will be able to create about 90 ponds along the course of the Mattole and its feeder creeks to provide habitat for fish and to enhance the area’s water supply. They will be starting with a couple of small pilot projects and are in the process of getting the permits and funding to do them. They have been getting some support from regulatory agencies and those agencies will be monitoring the pilot projects to see how they work. McKee says that the agencies are concerned about the dams creating blockages. Beaver don’t do that. The beavers build them in such a way that fish are able to get through. McKee says the MRC hopes to emulate the beavers in that way and provide easy access for migrating fish. The agencies are also concerned about bullfrogs and herons that love to eat fish and are attracted to ponds. She thinks that’s a solvable situation.

In Oregon, beavers build ponds in river courses, which serve to slow the water down and allow it to seep into the ground where it is stored for release in dry periods. Because of the environmental damage in that state, the beavers were hard pressed to keep their dams from being washed away in high flow events, so the state stepped in and began augmenting the beaver dams to help them survive high flow events. McKee is not proposing that beavers be brought into the area. As far as is known, beavers never inhabited this watershed. She proposes that the MRC construct small dams on watercourses, similar to what a beaver would build, to slow down the water and allow it to soak into the area by the river. Water would be stored along the banks of the creeks to be naturally and slowly released over the dry periods. She is talking about off-stream ponds and wetlands where fish can retreat during high flows and engineered instream ponds that will provide good habitat and connectivity to other instream ponds for migrating fish. Ideally, she hopes that they will be able to create about 90 ponds along the course of the Mattole and its feeder creeks to provide habitat for fish and to enhance the area’s water supply. They will be starting with a couple of small pilot projects and are in the process of getting the permits and funding to do them. They have been getting some support from regulatory agencies and those agencies will be monitoring the pilot projects to see how they work. McKee says that the agencies are concerned about the dams creating blockages. Beaver don’t do that. The beavers build them in such a way that fish are able to get through. McKee says the MRC hopes to emulate the beavers in that way and provide easy access for migrating fish. The agencies are also concerned about bullfrogs and herons that love to eat fish and are attracted to ponds. She thinks that’s a solvable situation.

”The risks of doing this far outweigh the risks of doing nothing,” she says. She says we can’t count on the longer dry season going away and if something isn’t done, the coho and probably the chinook will go extinct.

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