Tracer experiments have been used to study the exchanges of channel waters with groundwater in streams and their impacts on ecosystem function and water quality are well documented (Bencala & Walters, 1983; Mulholland et al., 1997). However, these experiments are much more difficult in larger rivers due to higher flows which would require very large masses of tracer and beds that are harder to reach from the water surface. It is not well understood how large rivers interact with adjacent aquifers. This research, which is focused on the Columbia River near the Hanford Site in eastern Washington, aims to determine whether large scale geologic units or finer scale river bed sediment units more strongly influence the locations of preferential groundwater exchange sites on the river bed. Ultimately, we will address this question by collecting extensive geophysical datasets (using FloaTEM) concurrently with hydrometric and radon data just above the river bed and near the surface to identify groundwater inflows. This work builds on a previous project which conducted surveys along the shorelines, primarily from a canoe, and used anomalies in temperature and electrical conductivity (EC) to identify locations of groundwater inflows (Conner, 2019). I will discuss the results of the first field campaign of this project, which was conducted in February 2021. We used Campbell sensors on a weighted tether behind a jet boat to measure EC and temperature just above the river bed and near the water surface. Water samples were collected and analyzed for radon focusing on regions where potential groundwater inflows were identified. There were more temperature and EC anomalies along the eastern shoreline than on the western shoreline where the Hanford site is located. Many of the anomalies on the eastern shoreline were seen at topographic low points. Though further data collection efforts and analysis are needed, we believe that this difference is caused by irrigation on the eastern shoreline.Ìý