SEASONAL, INTERANNUAL, AND SPATIAL PATTERNS OF GROUNDWATER TEMPERATURES IN NOVA SCOTIA, CANADA

Groundwater temperature is often a critical determinant of groundwater quality, subsurface energy potential, and the health of groundwater-dependent ecosystems; however, the spatiotemporal variability of groundwater temperature remains poorly understood. For example, changes in climate, land cover, and geology are known to exert influence on groundwater thermal regimes, yet there is considerable disagreement in the literature regarding the relative future warming of aquifers vs. surface water bodies and the associated vulnerability for groundwater-dependent ecosystems. Few studies have considered interannual groundwater temperature dynamics and how these are influenced by atmospheric regimes, land cover, and geology.

In this study, we present 10+ years of groundwater temperature time series from 10 monitoring wells in Nova Scotia, Canada for differing land cover types, geology, and groundwater systems. We consider the relationship between air and aquifer thermal regimes at seasonal and interannual time scales by performing dynamic harmonic regression as well as longer term trend analysis. The results vary widely among sites and indicate that groundwater temperature is damped and lagged compared to air temperatures on both seasonal and interannual timescales. It was found that the long-term trend in the aquifers is warming; however, the rate of long-term aquifer warming is strongly dependent on aquifer depth, land cover, and geology. Results will be interpreted in the context of the thermal sensitivity of groundwater-dominated streams and well as groundwater-sourced thermal refuges for cold-water species.