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Hyporheic Cooling with Implications for Support of Fish Habitat in the Willamette Valley, Oregon
Citation:
Faulkner, Bart, Reneej Brooks, AND Ken Forshay. Hyporheic Cooling with Implications for Support of Fish Habitat in the Willamette Valley, Oregon. National Ground Water Association conference, Portland, Oregon, September 08 - 09, 2016.
Impact/Purpose:
Riparian restoration activities are being conducted across the US. It is of interest to quantify the ecosystem services benefits that they may offer. In this work, we monitored temperature data, coupled with characterization of groundwater movement in the hyporheic zone of a section of the Willamette River, Oregon, that is undergoing a variety of restoration activities. Our results show that restoration activities, such as revetment removal, may result in geomorphic changes that could reduce temperature in similar large river ecosystems. The mechanism of cooling is enhancement of hyporheic flow and the heat dissipation that it offers. This information is potentially valuable to restoration planners for protection of cold water refuges beneficial to salmonid species and the organisms which depend on them and the environment created in restored riparian zones.
Description:
It has been hypothesized that groundwater flow which originates from a river and then returns to it could result in a temperature buffering benefit, resulting from dissipation of heat during porous media flow. We installed 50 monitoring wells in a geomorphologically active area along the Willamette River in order to characterize wet and dry season hyporheic flow patterns. The wells were instrumented with pressure transducers with temperature logging, so that we could calibrate groundwater flow models. The sampling network was dense enough so that we could monitor the temperature and stable isotopic variation along individual groundwater pathlines. In one case we observed a temperature decrease of over 6 degrees Celsius along a distance of about 600 m, over a period of about 3 years. In observations along other pathlines we observed considerably lower temperature decreases, but still notable. This presentation will examine some of the possible mechanisms for the temperature decreases and the possible effect of seasonal shifts in flow vectors along hyporheic pathlines.