Assessing future climate change impacts on groundwater recharge in Minnesota

Abstract

• Minnesota recharge will decrease despite increased precipitation, due to increased ET. • Soil moisture availability can limit ET increase and consequently recharge decrease. • Changes in runoff can modulate recharge response to climate. • Less frozen ground in warmer future can reapportion spring runoff to recharge. Although the northern Laurentian Great Lakes region is projected to undergo major climate changes, it has had a paucity of future groundwater recharge studies. We used the state of Minnesota (USA) as a testbed to understand how recharge will respond to changing climate in upper mid-latitude, low-elevation temperate settings. Not only can this inform water resource management, but it can help probe difficult-to-predict sign changes in recharge in temperate zones, as well as the under-studied land-surface processes controlling them. Our study implemented the Community Land Model with ensemble outputs from five climate models under two emissions scenarios (RCP8.5 and RCP4.5) to investigate future changes in recharge for 2026–2055 relative to the baseline historical period of 1976–2005. We found that despite quite consistent projections of higher precipitation (P) and some local occurrences of increased recharge, state-average recharge will mostly decline or remain about the same due to warming-induced evapotranspiration (ET) increases. However, our simulations showed that several processes serve to buffer recharge decreases. In drier ecoregions in the west, soil moisture limitations start to constrain evapotranspiration, thus curbing reductions in recharge. These regions also include higher historical surface runoff due to its runoff-prone soils, and because much of future reductions in net atmospheric inputs (P-ET) are partitioned to lower this runoff instead of recharge, decreases in recharge are further modulated. Statewide warming also lessens frozen ground coverage, reapportioning early spring runoff of snowmelt to infiltration and recharge. Our results demonstrate that in addition to precipitation change and warming, moisture feedbacks on ET and the influence of hydrogeological properties and frozen ground dynamics on runoff must be considered when quantifying climate change impacts on recharge in temperate zones.