An ecological assessment of aquifer-stream connectivity in a groundwater dependent stream

The ecological roles of groundwater are rarely properly addressed in water management due to a lack of understanding of the mechanisms influencing river ecosystems and inadequate methods to assess potential impacts of activities like groundwater pumping. Here, a hydroecological field study was undertaken in Bertrand Creek, South Coast region of British Columbia, to characterize aquifer-stream exchanges, their drivers, how they influence aquatic habitat and macroinvertebrates, and to develop a method to assess potential groundwater pumping impacts. Data collected from May to October from 2018 to 2020 showed declining groundwater levels in response to hotter and drier conditions, but groundwater discharge was sufficient for streamflow to persist downstream. In 2020, groundwater cooled the stream and maintained habitat conditions that allowed macroinvertebrates to survive the summer. Habitat models built with these data were integrated with an analytical streamflow depletion model to produce a tool for assessing the ecological impacts of groundwater pumping.