With decreasing snowpacks and changing precipitation patterns, Washington State seeks ways to conserve, protect, and enhance its water supply. Stream restoration has been viewed as a means to utilize alluvial aquifers for groundwater storage and augment late-season streamflow. However, the relationship between stream restoration and groundwater dynamics is still under investigation. Starting in 2014, several partners including the Washington Department of Ecology (Ecology), Washington Department of Fish and Wildlife (WDFW), the Department of Natural Resources (DNR), the Yakama Nation (YN) and the Kittitas Conservation Trust (KCT) began work to restore Indian Creek, a small tributary of the Teanaway River in central Washington. These partners utilized the method of large wood restoration, or the placement of logs within the stream and across the floodplain, to form pools to enhance fish spawning, promote stream velocity heterogeneity, establish riparian vegetation, and increase groundwater storage and late-season baseflow. However, since wood installation little work has been done to investigate if these restoration goals have been reached.
This study sought to better characterize the Indian Creek alluvial aquifer and discern if any measurable changes in the groundwater dynamics have occurred since stream restoration. Ongoing monitoring occurred on a 1.2-mile reach of Indian Creek equipped with seven piezometers, four of which have been collecting data since 2014 and three of which were installed in October 2018. The newly installed piezometers, as well as slug tests, were used to better characterize aquifer properties. Water level data from the piezometers determined if there were any notable temporal and spatial patterns in the groundwater system that could be associated with stream restoration. The resulting analysis showed little change in water table elevation and groundwater baseflow. There was some increase in groundwater storage volume, but this is likely attributable to other processes and the geologic characteristics of the aquifer. Although the results provide minimal evidence that there are any measurable impacts from stream restoration on groundwater dynamics at Indian Creek, this study provides a strong foundation for continued investigation. Additional monitoring and further analyses are needed to draw a stronger conclusion about the impacts of stream restoration on this particular alluvial aquifer.