Abstract

Preferential groundwater discharge zones are critical to a wide range of surface water habitat and water quality processes, but they can be difficult to characterize due to strong spatial variability in flux rate and high attenuation of natural temperature signals. As such, passive heat-as-a-tracer methods employing Vertical Temperature Profiler data are often ill-suited for quantifying vertical discharge flux rates due to a combination of inadequate sensor distribution and resolution paired with analytical modeling methods based on diurnal signals only. Using data from a site of contaminant-loaded groundwater discharge to the Quashnet River on Cape Cod, Massachusetts, USA, we demonstrate how coupled improvements in instrumentation and parameter estimation methods can largely alleviate these issues. Consequently, more accurate groundwater flux estimates, including temporal variations, are now possible at sites of strong discharge using passive heat-as-a-tracer methods.