Matthew Johnson
Geological Research at the IGS

IGS Miscellaneous Map: Near-surface Groundwater Recharge in Indiana

Status Start Date End Date Locations
completed Oct 1, 2015 Dec 31, 2016 All Counties
Director: Sally Letsinger
Other Researchers: Matthew Johnson, Kevin Russell, Deborah DeChurch
Issue: As the transport of most potential groundwater contaminants from the surface to the water table occur in the aqueous phase, recharge represents a significant control on aquifer sensitivity to contamination. In support of that idea, multiple studies have hypothesized that the key to understanding aquifer sensitivity relies on a reliable estimation of recharge.
Objective: Develop a conceptual model of the physical factors and processes that control groundwater recharge in Indiana, and devise an objective measure of recharge over the landscape. Develop a statewide assessment of aquifer sensitivity to near-surface contamination based on the relationship of recharge to migration of contaminants through the unsaturated zone.
Approach: The proportion of baseflow to runoff in stream hydrographs (n=189), determined using a local-minimums approach with a recession slope test, was used as the measure of recharge in this study. A multiple regression model was developed to spatially distribute recharge point values to continuous estimates. Partial correlation coefficients were used to identify and rank the most statistically influential (p=0.001) independent variables in the study domain, as follows: the elevation of the near-surface water table, the proportion of sand in the subsurface (as determined by lithologic logs of water-well records), and the thickness of near-surface clay. Other factors that appear to explain the spatial distribution of recharge include: the cumulative upstream area occupied by water bodies (streams, lakes, ponds), the density of wetland areas, and the cumulative upstream area occupied by forest.
Products: A map in the IGS miscellaneous map series showing the estimated rate of near-surface groundwater recharge in Indiana.
Benefits: A statewide groundwater recharge map can be reinterpreted for the purpose of assessing aquifer sensitivity to near-surface contamination.

Map of Indiana showing near-surface aquifer recharge

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