Hyman-Rabeler Paper Examines Climate Change and Groundwater Recharge

Climate change is affecting countless natural systems in ways we are only beginning to understand, and Staff Water Resources Engineer Katrina Hyman-Rabeler’s recently published master’s thesis is an important addition to the growing body of research on how our shifting climate is impacting groundwater recharge. 

Hyman-Rabeler and Steven P. Loheide II published their research paper “Drivers of Variation in Winter and Spring Groundwater Recharge: Impacts of Midwinter Melt Events and Subsequent Freezeback,” in Water Resources Research Volume 59, Issue 1. This paper summarizes the first half of Hyman-Rabeler’s master’s research in water resources engineering from the University of Wisconsin-Madison. She’s hoping to complete the follow-up paper, which focused on modeling these processes, soon. 

Thanks to climate change, midwinter snow melt events are becoming increasingly common in many areas. Hyman-Rabeler and Loheide analyzed the impact of thawing and refreezing events on groundwater recharge. Without insulating snow, bare ground can freeze more deeply and prevent surface water from reaching and recharging aquifers. Very little research has been done on this issue, and Hyman-Rabeler and Loheide’s study is an important step toward understanding how warmer winters will affect the water resources on which we all depend.

“It feels great to finally get this research out in the world,” Hyman-Rabeler says. “My hope is that this study, combined with the modeling companion paper, increases people’s awareness of winter and vadose zone (the unsaturated area between groundwater and the surface) processes, two areas that are often underappreciated.”

Conceptual model of how midwinter melt and subsequent freezeback events can create nearly impermeable frozen soil, reducing infiltration and groundwater recharge and increasing overland flow in subsequent melt events. (a) Snowmelt from midwinter melt events can infiltrate and cause discrete recharge events when soil is minimally frozen and has low moisture content. (b) Midwinter melt events can also increase soil moisture content and leave the ground exposed to subsequent cold periods, or freezeback events, creating a deep soil freeze. (c) In subsequent snowmelt events, the nearly impermeable frozen soil layer can reduce infiltration and recharge and increase overland flow.

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