Study reveals Whychus Creek warming

Reintroduction of salmon and steelhead runs to Whychus Creek has been a long-term goal since the fish were eradicated by dam construction in the 1960s. In addition to the passage of fish around the dams, another long-known impediment is that Whychus Creek has serious seasonal waterflow and temperature problems in the reach nearest Sisters.

What hasn't been well known however - until discovered by a recent Oregon State University study - is that temperatures during historic salmon and steelhead spawning times could be too warm to successfully sustain the fish reintroduction efforts that have already begun.

According to Lesley Jones, Water Quality Specialist for the Upper Deschutes Watershed Council (UDWC), "Nobody had looked at January to May against a potential future steelhead spawning standard of 13 degrees (Celsius). What we found is that, if that standard were in place, the creek wouldn't meet that standard from Sisters on down."

Everyone knew that summer flows were too low and temperatures too high, but the high temperatures in winter and spring were a bit of a surprise. As a result, the UDWC is interested in exploring how this issue could affect Whychus Creek restoration strategies.

As it happens, there are two potential temperature standards. The spawning standard of 13 degrees Celsius (about 54 degrees Fahrenheit) is one, and the other is the salmon and trout rearing and migration standard of 18 degrees C (about 64 degrees F). Whychus Creek could have problems with both.

Although the salmon and steelhead restoration efforts that started in 2007 could be stymied by water temperatures in Whychus Creek, Ryan Houston, Executive Director of the UDWC, explains, "Steelhead trout are very resilient fish, well adapted to tough conditions. Although the high summer temperatures are a well known problem, we don't know whether the winter and spring temperatures discussed in the OSU study will matter to the fish."

Jones also commented, "Prior to their extirpation, the steelhead populations in Whychus Creek are approximated to be one thousand. At that time, water was being diverted and water temperatures were likely warm. So, current conditions are likely to sustain the reintroduced steelhead despite the warm water temperatures."

Over the past three years, the UDWC has co-hosted an undergraduate internship with OSU-Cascades to monitor temperatures along the entire length of Whychus Creek from the Cascade crest to the creek's mouth where it empties into the Deschutes River 40 miles downstream. The creek's watershed drains approximately 178,000 acres (278 square miles). To no one's surprise, the creek is in distress most everywhere below the irrigation diversions a few miles south of Sisters.

Some of the irrigation diversions have been in use since 1895 and siphon off nearly 90 percent of the water during the warmest months of the year. Further, irrigation begins in April, during a natural low-water period, before the snowmelt fully augments the stream capacity. Despite these daunting challenges, multiple agencies are cooperating to deal with the problem. For example, says Jones, "We are supporting the Deschutes River Conservancy's work with water users to move water back into the stream."

Stream bank habitat restoration is another major effort that is being undertaken both north and south of Sisters by the UDWC and Wolftree, a science education organization. Three other projects currently in the works also hope to further mitigate the elevated temperatures.

One upgrade, at the site of the irrigation diversions, would help screen out fish from water headed into the irrigation systems and improve flow management. Two others, farther downstream, would physically alter the course of the creek to "reconnect" the stream flow to the groundwater and floodplain at Camp Polk Preserve and Rimrock Ranch. Together, the projects would help rehabilitate approximately three miles of Whychus Creek in the highly stressed mid-reaches below Sisters.

Beginning this spring, the UDWC will work with the Deschutes Land Trust to implement a plan to reroute the streambed on its Camp Polk Meadow Preserve to reconstruct the natural meandering flow. The natural streambed was destroyed in the 1960s when the U.S. Army Corps of Engineers gouged out artificially straight channels to keep the creek from flooding the surrounding land.

Mike Riehle, a fisheries biologist with the U.S. Forest Service, said, "The springs at Camp Polk - for whatever reason - seem to be more nutrient-rich than other springs in the area. The meadow complex associated with the springs was probably a spawning hot spot, historically."

The Land Trust would like to see the creek flowing out across its floodplain again. "If the creek is connected to its floodplain and groundwater, it helps lower the temperature of the water," said Jones. When a large meadow, such as Camp Polk, is fully saturated with water, it acts as a giant reservoir, and that accomplishes two things.

First, this residual water acts to stabilize the rate of water flow when precipitation declines in the summer months. Second, the mass of water saturating the soil system is "connected" to the underground water, which typically has temperatures ranging far below that of the surface water, often around 7-11 degrees C (45-52 degrees F).

Jones stressed the importance of cold groundwater entering Whychus Creek in that it may "offer refuge to the fish during periods of low flow and high temperatures...explaining why steelhead were able to have sustainable populations in the past despite challenging conditions." She also expressed concern over development of destination resorts "as a threat to the spring water contribution due to increased groundwater withdrawals."

Regarding steelhead sensitivity to warmer water conditions, Riehle said, "It's not an on-off threshold, but the incidence of fish mortality due to disease and fungus increases as the temperature gets above 13 degrees C."

So, despite the complexity of the issue, the temperature problem is being attacked from several angles by multiple organizations. While, at first glance, the new findings of the OSU study might appear to be a setback, Jones and others are taking it in stride. As Jones explains, "There are always a lot of unanswered questions in watershed restoration, and Whychus Creek is certainly no exception. We'll keep working to help assemble a clearer picture of what needs to be done to help Whychus Creek."