Determination of groundwater recharge and residence time in the Itasca moraine area, north-central Minnesota : a hydrogeochemical approach

Abstract

The Itasca moraine, because of its size and relief, is suspected to influence the groundwater flow regime of north-central Minnesota by serving as a major recharge area driving regional flow. This study uses hydrogeochemistry to determine the spatial distribution of recharge and discharge areas in the context of previously-defined glacial landform assemblages. The chemical evolution of groundwater along a flowpath results in a difference in the chemistry of juvenile and evolved waters. The effects of topography on flow systems become apparent in the spatial analysis of juvenile and evolved chemistries. Topography influences the development of oxidizing zones and local flow systems which, in turn, affect the groundwater chemistry. The broad, flat outwash plain south of the moraine is found to be an area of high recharge, the hummocky stagnation complex an area of moderate recharge, and the low-lying, undulating till plain north of the moraine an area of discharge.