HYDROLOGIC CHARACTERIZATION OF SINKHOLES IN AGRICULTURAL SETTINGS

Soils in karst terranes have very high agricultural productivity and often support both hayland/pasture-based and row crop production systems. Broad, shallow sinkholes, frequently found in karst regions, are commonly utilized for agriculture, and are thus subject to application of fertilizers, including animal manures and biosolids. Because sinkholes are often hydrologically connected to aquifers, fertilizer application within sinkholes may have an adverse impact on groundwater quality in karst systems. However, there is little information on how to manage surface application of fertilizers to minimize contamination of karst groundwater.

The primary objective of this study is to characterize the hydrology and contamination potential of sinkholes in agricultural settings. The first task involves physical characterization of sinkholes at the Kentland Experimental Farm, Whitethorne, VA. The characterization is being conducted using a combination of Electrical Resistivity Tomography (ERT) and soil mapping. ERT, a geophysical tool, allows remote detection and modeling of subsurface features such as locations of pinnacles, mud-filled fractures, saturated zones, air-filled voids, solutional channels, and the bedrock-soil interface. Preliminary results show clear resolution of the bedrock-soil interface and reveal a bedrock surface that is an exaggerated approximation of surface topography with the addition of irregularities such as small sinks and pinnacles. The ERT and soil data will then allow accurate placement and installation of hydrological monitoring instrumentation designed to sample groundwater and agricultural contaminants as they move through a heterogeneous sinkhole environment.