Because groundwater continuously discharges to the stream, providing a baseflow even when there is limited rainfall. This is normal. But when a stream goes dry every year, something must be happening. Changes in the groundwater system, for example due to pumping groundwater wells near a stream, can alter the exchange of water between the stream and the aquifer. In particular, winter snow droughts (Dierauer et al. 2018; 2019) and summer droughts can lead to extreme summer low flows. The photograph shows Bertrand Creek in the Lower Fraser Valley in late summer 2018. Bertrand Creek provides critical habitat for the Nooksack Dace, and endangered fish species. Local residents around our field site at Otter Park in Langley have noticed that the stream has recently begun to run dry during the summer. What is causing this?

Dr. Diana Allen (Professor) in the Department of Earth Sciences is leading several projects that aim to build understanding of how the interactions between groundwater systems and streams are influenced by pumping and drought. In collaboration with partner agencies, April Gullacher (MSc student) is developing groundwater drought indicators that can be applied in drought response decision-making in the Province of BC. She will evaluate these indicators in the Okanagan Basin and map how susceptible different types of aquifer-stream systems are to drought. Adam Mitton (MSc student) is beginning Phase 3 of a multi-year field study at Otter Park to explore linkages between instream flow conditions (streamflow, groundwater exchanges, streambed temperature, streambed morphology, water chemistry) and aquatic communities (benthic invertebrates). Stephanie Hunter (PhD student) is using tree ring widths as a proxy for groundwater levels to extend the historical records further back in time, with the goal of studying how the magnitude and timing of droughts in the Southern Interior of BC have changed over time.  The reconstructions will also be analyzed for evidence of the underlying mechanisms for these droughts, such as climate oscillations like the El Niño Southern Oscillation and the Pacific Decadal Oscillation.  This information about past droughts can be utilized in water management to help prepare the region for future drought conditions.

The various research projects are funded by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canadian Mountain Network, the BC Ministry of Forests, Lands, Natural Resource Operations & Rural Development (FLNR) and the BC Ministry of Environment.