Water Resources Research Act Program

Details for Project ID 2020KY051B

Geophysical imaging of ridgetop wetland-perched groundwater systems

Institute: Kentucky
Year Established: 2020 Start Date: 2020-02-27 End Date: 2021-02-25
Total Federal Funds: $4,789 Total Non-Federal Funds: $9,934

Principal Investigators: Dr. Jonathan Malzone

Project Summary: Ridgetop wetland-perched groundwater systems in eastern Kentucky are a type of geographically isolated wetland that locally stores groundwater at high elevation and offers both upland and lowland water supply during droughts. These systems operate in the Daniel Boone National Forest by collecting winter-spring rainfall that infiltrates and collects on top of an impermeable clay unit found on certain ridgetops, creating a local perched aquifer. During the spring and summer the stored groundwater is utilized by upland forest vegetation during drought and the aquifer slowly leaks to the lowlands. Leakage to lowlands provides headwater seeps that generally run in the spring and after storm events until the groundwater storage is depleted. Hydrological field research by the investigators has shown that ridgetop groundwater depletion varies significantly between ridgetops, indicating that the leakage and storage potentials of systems differ. In essence, the quantity of groundwater storage and the pathways it takes to lowlands on different ridges are unknown, which makes prediction of drought impact and forest management spatially complex. We propose here to use traditional coring and electrical resistivity imaging to map the subsurface structure of four ridgetop wetland-perched groundwater systems of varying hydrology in eastern Kentucky in order to clearly map the storage potential and likely pathways that water takes to the lowlands. Particular attention will be paid to bedrock topography and clay boundary heterogeneity. The general approach includes hydrological monitoring of groundwater levels on ridgetops, sparse sediment coring to bedrock, and using an AGI SuperSting R1 electrical resistivity instrument to make a 3-D model of the subsurface structure. Interpretation of the models will be aided by the physical sediment cores and hydrological data. Expected results include the identification and quantification of preferential flow conduits that groundwater takes to lowlands. This may include breaks in impermeable layers, bedrock slopes, bedrock troughs, or changes in lithology. Such results have the potential of quantifying how ridgetop groundwater storage will vary and aid in the prediction of drought impacts in eastern Kentucky forests and streams. For example, wetlands with more leakage will supply lowland headwaters during drought periods, but will have less upland storage to support forest vegetation. On the other hand, aquifers with less leakage will have longer groundwater storage to supply upland forest vegetation through drought. Finally, these models will be used in future research to create accurate water budgets of these systems.