Impact of Changing Frozen Ground Regimes on Groundwater Recharge

Abstract:

Development of seasonal snowpack leads to groundwater recharge associated with spring snowmelt, which often accounts for a large percentage of annual groundwater recharge in northern latitudes. In a warming climate, mid-winter snowmelts are expected to become more common, which may shift a portion of this recharge to earlier in the year. However, loss of snow cover can also change the soil thermal regime because snow acts as an insulating layer. In the absence of snow, cold periods occurring after mid-winter melts have the potential to freeze soils, reduce infiltration capacity, and ultimately increase runoff and decrease groundwater recharge during subsequent melt events. In this study, we examine how variations in the soil thermal regime, specifically mid-winter snowmelt events, alter groundwater recharge.

Using publicly available groundwater, soil temperature, and climate records from sites throughout the Midwest, we estimate winter and spring groundwater recharge using the water table fluctuation method. Conducting multivariate statistical analysis at various temporal scales, we investigate the relationships between groundwater recharge, winter precipitation, the soil thermal regime, and other variables. We demonstrate relationships between soil temperature, soil moisture, mid-winter snowmelts, and groundwater recharge, indicating that frozen ground plays a significant role in determining the partitioning between groundwater recharge and runoff. Results suggest freeze and thaw cycles alter groundwater recharge, but the effect is sensitive to many factors, including soil texture and the magnitude and temporal sequence of events. Understanding the multifaceted feedbacks between frozen ground, infiltration, snow cover, and groundwater recharge is critical for predicting the ways in which groundwater resources will be affected by climate variability in the future.