Groundwater recharge in formerly glaciated terrain: Exploring the relationship between frost dynamics, precipitation, and snowmelt in a Northeastern Minnesota deranged drainage basin

Abstract

Sustainable groundwater management relies on an accurate understanding of groundwater recharge rates and mechanisms. In formerly glaciated regions, the timing and quantification of groundwater recharge is complicated by low-permeability glacial tills and the presence of seasonally-frozen ground. In Northeastern Minnesota, remnant tile drainage further complicates groundwater recharge dynamics in current and abandoned agricultural systems. This study examined the relationship between precipitation, snowmelt, frost dynamics, and shallow groundwater processes through continuous monitoring of groundwater levels, soil water content, and soil temperature. Additionally, water sources and pathways throughout the system were identified using δ18O and δ2H from soil water, groundwater, precipitation, and streamflow. My observations revealed a relatively dynamic shallow groundwater system in a low-relief, glacial-till agricultural field in Northeastern Minnesota. Lateral subsurface flow and depression-focused recharge played a large role in redistributing groundwater throughout the system. Recharge events were greatest during the fall and spring snowmelt periods. It is likely that multiple recharge mechanisms are active at the site throughout the year and that these mechanisms vary seasonally and spatially. Frost dynamics, lateral flow, and tile drainage ultimately complicated the system response to snowmelt and thus more research is needed to assess how each of these components influence shallow groundwater processes in formerly glaciated regions.