USGS Washington Water Science Center
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YG00FYY - Raging River Temperature and Groundwater/Surface-Water Interactions
Problem - Large, in-channel wood helps create and maintain key elements of aquatic habitat in rivers throughout the Pacific Northwest, but was removed from many rivers during the late Nineteenth and Twentieth Centuries. Present efforts to restore aquatic habitat for endangered and threatened salmonids in the Pacific Northwest often include reintroductions of wood to create and maintain geomorphic and hydraulic complexity, enhance connectivity between the river and floodplain, and stabilize stream banks. High water temperatures are a major water-quality concern within the greater Snohomish River basin for Endangered Species Act-listed salmonids including Chinook salmon and steelhead trout. In order to guide stream restoration efforts in the Raging River watershed, watershed managers need data about the effect of restoration actions on in-stream habitat including the occurrence and availability of cold-water refugia.
Objective - The objective of this study is to collect temperature data to characterize the thermal regime of the Raging River in a reach where wood was introduced in 2009 and an unaltered control reach immediately upstream of it. Temperature data will be collected in summer 2015 during baseflow conditions when the temperature gradient between surface water and groundwater water is greatest. These data will complement contemporaneous monitoring of the 2009 restoration reach by King County, which includes physical surveys of instream habitat and characterization of hyporheic zone processes through solute tracer injections and measurement of hydraulic heads in surface waters and hyporheic-zone waters using shallow mini-piezometers.
Approach - One week of diurnal cycles will be monitored using a fiber-optic distributed temperature sensor at each field site in order to identify consistent temperature anomalies associated with groundwater discharge to the creeks. While the fiber-optic DTS detects cold-water anomalies that, in summer, are associated with groundwater discharge zone, it does not detect losses of surface water to groundwater. In the context of restoring stream habitat for cold-water fishes, however, groundwater discharge zones are the most salient feature of groundwater-surface water interactions.