Fifteenmile Creek

An infiltration basin. Creek water is diverted into the basin from the left and pumped through an underground pipe system into a deep basalt well to the right. The water is stored in the well until summer, when it is pumped back into the creek, thereby increasing summer flow and dropping creek temperatures.

A pilot project could prove key to the future health of Wasco County’s Fifteenmile Creek, which originates in Mt. Hood National Forest above Dufur and joins the Columbia River just east of The Dalles. The project will test an underground water storage system designed to increase water flow and decrease water temperature in the creek, benefiting fish and area farmers alike.

The Fifteenmile Watershed Council has secured two grants from the Oregon Watershed Enhancement Board (OWEB) and a third through Oregon Water Resources Department (OWRD) to move forward on a pilot project to provide more water in Fifteenmile Creek in summer by storing some of the creek’s winter and spring flow underground.

“Fifteenmile Creek often exceeds lethal temperatures to aquatic species, harming steelhead and other fish as well as threatening the water source for irrigators and their businesses, when flows are low,” said Abbie Forrest of the Fifteenmile Watershed Council. “This project will benefit both farmers and fish in our basin and we are glad that OWEB and OWRD understood the need for this project.”

The project will be located approximately six miles upstream from Dufur, which is south of The Dalles in Wasco County.

Surface flows in Fifteenmile Creek are over-allocated in summer months. Over-allocation is a term to describe the water available instream versus the irrigation water demand for surface water diversion. Fifteenmile Creek is over-allocated, meaning there (typically) would not be enough water left instream if all water right holders were to use their legal water right the full length of the summer/irrigation season.

Watermaster Bob Wood “regulates back” (or reduces use for more junior water right holders) users based on water right priority dates to meet minimum flow needs. This is called the right of prior appropriation. During high spring flows, ample water is typically available to meet water rights and user demands. When streamflows decrease throughout the summer, there is less water instream than the certificated water rights.

With low water levels come hotter stream temperatures, which harms or kills salmon and trout that are spawning, rearing or migrating in the creek — including mid-Columbia steelhead, listed as threatened by the federal Endangered Species Act. Stream temperatures in lower reaches frequently exceed 65 degrees during late summer months, and have exceeded lethal thresholds in certain reaches, according to the grant application.

The Fifeteenmile Creek Watershed Council is partnering with the Wasco County Soil and Water Conservation District, which completed two studies that both determined it is feasible to divert cool water from Fifteenmile Creek during winter and spring when flows are higher, store it underground and return it in summer when flows are low.

The new funding allows the council and partners to:

• Construct a small-scale pilot project to test the underground water storage idea;

• Identify an owner and operator for the project long term, including potentially a special district;

• Identify funding for the project’s long-term operations and maintenance;

• Create initial designs for the diversion;

• Design a treatment system to ensure diverted water meets water quality standards.

Other fish species that will benefit from the project include Pacific lamprey, cutthroat trout and more. Additional project partners include Oregon Department of Agriculture, Oregon Water Resources Department and the Oregon Department of Fish and Wildlife.

“The council has been seeking solutions to summer temperatures and low flows for over a decade,” said Shilah Olson, district manager of Wasco SWCD. “They are a model for collaborative conservation and there have been a lot of thoughtful conversations leading up to this point. The district looks forward to helping the council implement these grants and move the project from concept to reality.”

Wasco SWCD is providing match funding to support the project through their local tax base.

About the Fifteenmile Watershed Council

Fifteenmile Creek Watershed is a 373 square mile (238,720 acre) drainage area mostly in northern Wasco County. The City of Dufur, in the center of the watershed, encompasses 730 acres. The Fifteenmile Watershed Council was formed on March 19, 1997. The council is made up of many landowners, agencies and partners that are focused on managing irrigation needs with fish needs.

About the Wasco SWCD

Wasco County SWCD was formed by a consolidation of three districts on June 10, 1973 (originally created in 1942). Conservation Districts are local units of government consisting of a seven-member, locally-elected board of directors. Through partnerships with organizations and public agencies, the district promotes a locally led, cooperative approach to natural resource conservation.