A CONDUCTIVITY AND DISSOLVED OXYGEN SUITE FOR IDENTIFYING SURFACE WATER-GROUNDWATER INTERACTIONS

Surface water-groundwater interactions are critical for overall stream health, but identifying the locations of these interactions often requires expensive or intensive field equipment. Moreover, field sampling is often site-specific and identification at multiple locations along a stream reach is limited. Streamlining the identification of surface water-groundwater interactions along a stream reach is a necessary step to large scale restoration projects, particularly in ungauged or unstudied areas. Here, we used a preliminary solute mass balance approach to efficiently estimate the magnitude of downstream surface water-groundwater interactions. We injected an in-stream saline tracer and simultaneously monitored for conductivity and dissolved oxygen adjacent to the stream channel using several groundwater monitoring wells. We then quantified the magnitude of surface water present in groundwater flow paths using a solute mass balance approach. Dissolved oxygen was then used as a proxy for conductivity to identify the location of downstream surface water-groundwater interactions and to quantify the magnitude of surface water present in groundwater flow paths. Results from this study can be used in watershed restoration projects or site assessments as a way to identify the locations of key flow paths that benefit overall stream function.