Climate Change Impacts on Groundwater Recharge in a Low-Mountain Area, Eskasoni First Nation, Nova Scotia, Canada.

In cold regions, snowmelt is an important source of groundwater recharge and spring streamflow. However, in a warming climate the factors governing snowmelt recharge dynamics are expected to change. The amount and timing of groundwater recharge may be altered through changes in air temperature and soil ice content, and the shift from less snow towards more winter rain. While declining snowpacks have been linked to reduced summertime low flows, the impact of a precipitation phase shift on groundwater resources is not well understood. This study investigates whether snowmelt is more effective than rainfall at recharging groundwater under future climate conditions in the Christmas Brook watershed of Eskasoni First Nation, Nova Scotia, Canada (45°57′45″N,60°34′59″W), where the local community relies on groundwater as a potable water source.

We monitored hourly precipitation, snow depth, groundwater level, soil moisture and temperature, and streamflow across three landscape types at differing topographic positions. We used field observations to calibrate the Simultaneous Heat and Water (SHAW) model, a one-dimensional critical zone model that simulates coupled heat, water, and solute transport through canopy, snow, residue, and soil as well as the consideration of freeze-thaw processes. Simulations were run over historical, mid-century, and end-of-century periods to quantify differences in recharge between rain versus snow recharge events under climate change.

Preliminary results indicate snowmelt historically makes up a significant proportion of groundwater recharge. However, the region experiences recharge events year-round from a combination of snowmelt and rainfall. By the year 2100, the simulated snowpack depth declined 40% on average from historical observations. Additionally, the annual number of days with snow cover reduced to around one third of the historical count. Overall, evolutions in snow cover and melt patterns, as well as soil ice content, shifted recharge dynamics in the watershed. The results illustrate the complex mechanisms controlling groundwater recharge in cold regions and the utility of modelling to understand how decreases in snow and increases in rain will impact groundwater resources.