A flow restored: Fossil Creek before decommissioning of power plants and after. Photo by Nick Berezenko, courtesy of Arizona Public Services

Fossil Creek Unbound

Restored Creek May be National Model

A good environmental deed was done when the full flow of Fossil Creek was recently restored after nearly 100 years of restricted flows. It was the familiar river-and-dam tale told in reverse, this time with power plants decommissioned to restore the flow of a river.

Fossil Creek holds special interest to researchers who view the project as a possible national case study in ecosystem restoration, with results from research useful as dams are decommissioned throughout the nation. (Dam removal is occurring more frequently in the United States, with 145 dams removed since 1999, 65 of them decommissioned in 2004 alone.) The facility is located northwest of Payson, in a remote area between Strawberry and Camp Verde.

The Fossil Creek saga began in 1909 when its waters were diverted by the Fossil Springs Diversion dam to operate a hydroelectric power plant at Childs on the Verde River. In 1916 the Irving plant, on the banks of Fossil Creek, came on line. Time and the river, its waters now reduced, flowed onward. In 1999 Arizona Public Service signed a historic agreement with the Yavapai-Apache Nation and various environmental groups to voluntarily give up its hydropower license.

Even before the turbines were permanently shut down amidst ceremonially fanfare on June 18, work was underway to promote natural conditions along the creek once it was restored to full and unobstructed flow.
Jane Marks of Northern Arizona University examined creek conditions above and below the dam to determine the dam’s effects. She found native fish thriving above the dam in a pristine river with natural flow; the native species were not threatened by non-native fish or crayfish. Conditions differed below the dam: non-native fish, primarily bass and sunfish, were top predators to the disadvantage of the native fish.

Also aquatic insects such as damselflies, mayflies and dragonflies were forced to compete for limited resources below the dam. Due to water diversions that reduce habitat complexity fewer niches exist. Insects and snails living above the dam on the other hand are able to feed on greater amounts of algae and leaf litter and are in turn eaten by the native fish. Emerging from the water the insect life becomes a food source for birds, lizards and frogs that populate the riparian forests.

The study of conditions above and below the dam profiled the extent to which the diversion of most of the creek’s base flow disrupted the river’s ecosystem. Restoring the river’s full flow and removing non-natives to increase the native fish population would likely result in a more productive river.

A group of federal and state agencies undertook the task of eradicating non-native fish to create more favorable conditions for the native species. Native fish were removed and placed in a holding tank while the river was treated with a chemical that poisoned the non-native fish. Native fish were released back into the creek when safe conditions returned. A fish barrier will help prevent the reinvasion of non-native fish from the Verde River.

A unique feature of Fossil Creek that is expected to be enhanced with full river flows is the continual formation of travertine. The waters of Fossil Creek, coming from underground limestone, are calcium carbonate-rich. NAU researcher Abe Springer has characterized over 60 springs feeding into the creek.
Water cascading over cobbles and boulders releases carbon dioxide; calcium carbonate is then deposited in the creek forming travertine dams, waterfalls and deep blue pools similar to those found at Havasu Falls. Rod Parnell of NAU’s Geology Department predicts that a restored flow will increase the number and size of travertine dams. And there will be a biological payoff: NAU biologists say the increased travertine will likely create conditions conducive for the shelter and spawning of native fish.

A question was raised about the sediments behind the dam, whether the restored river would flush the sediments out without harming downriver plants and animals. Any effort to manually remove the sediment would be very costly. Based partly on work by NAU researchers Charlie Schlinger and Steve Monroe, the Federal Energy Regulatory Commission decided to require a 14-foot lowering of the diversion dam, which is slated to occur in 2007, and allow the sediment to naturally disperse downstream during flood events.

Schlinger and his students are investigating the distribution and movement of that sediment both prior and subsequent to lowering of the dam. Follow-up research by Parnell and Marks will study the actual effects of the sediment release on the travertine formation and the life in the river.

With the creek restored the state will be gaining an additional 14 miles of wetland ecosystem valuable for wildlife and creek-side recreation. The creek, which flows at 46 cubic feet per second, is one of the few perennial streams left in Arizona. NAU researcher Marty Lee is working with the U.S. Forest Service to determine appropriate recreation activities for the area that will have minimum impact. Lee also is exploring options to provide stewardship of the Fossil Creek area including the possibility of forming a “Friends of Fossil Creek” group.

NAU’s work thus far has focused on gathering baseline data prior to the return of full flows. Now that flows are restored NAU’s research and monitoring will examine the changes that take place.

The restoration work at Fossil Creek will be the subject of a video documentary produced by NAU’s Stream Ecology and Restoration Group, in collaboration with the Museum of Northern Arizona and Paul Bockhorst Productions. The video will show that the complex environmental issues that challenge researchers at Fossil Creek will likely arise at other such restoration projects. The video will present Fossil Creek as a national case study.

Fossil Creek State of the Watershed Report, a document summarizing available information on the current conditions of the physical, biological and social environment of the Fossil Creek Watershed prior to the decommissioning activities, is being finalized and will be available on the web site, along with other information about NAU’s involvement in the project. Check: http://www.watershed.nau.edu/FossilCreekProject/

The Nina Mason Pulliam Charitable Trust has supported the NAU team’s overall effort in Fossil Creek including research and monitoring activities. The trust also is providing partial support of the documentary video.