Appraisal of the Northern Shenandoah Valley
Carbonate Aquifer System,
Frederick County, Virginia

OBJECTIVE

The objective of this study is to better characterize the carbonate aquifer system in the Northern Shenandoah Valley and provide relevant hydrogeologic information that can be used to guide the development and management of this important water resource.

APPROACH

This study will be carried out as four major work elements to include (1) Hydrogeologic Framework, (2) Ground-Water Flow System, (3) Water Balance, and (4) Water Quality. The study will be completed in three and one-half years and began in October 2000.  During Federal FY 2001 field reconnaissance was conducted, and existing geologic, hydrologic, and associated information was collected, organized, and evaluated. Limited field data-collection activities began in FY 2001, were expanded in FY 2002, and will continue in FY2003. Data analyses will be completed in 2003, and a final report will be produced in FY 2004. Continued monitoring and further investigation of specific water management issues will likely be carried out thereafter.

Activities proposed for Fiscal Year 2003 are as follows:

Hydrogeologic Framework

• Continue geologic evaluation of major formations, with descriptions of folds, faults, and prominent jointing. Randall Orndorff and David Weary of the USGS Geologic Division are conducting this effort on a 7 1/2-minute quadrangle basis. During FY 2002 efforts were focused on the Winchester quadrangle, and will focus on the Inwood quadrangle in FY 2003.

• Continue to field locate sinkholes and springs with GPS, enter into a geospatial database, and describe their position and relation to geologic and hydrologic features (conducted in cooperation with Randall Orndorff and David Weary of the USGS Geologic Division).

• Finalize the hydrogeologic framework for the study area.

Ground-Water Flow System

• Continue operation of water-level monitoring network, conducting water-level measurements during high and low water conditions to provide information for a generalized water-table map.

• Initiate investigation of the occurrence and nature of subsurface water-bearing fractures by the application of advanced geophysical logging methods.

• Initiate characterization of the ground-water-flow system by the use of environmental tracer and ground-water age-dating techniques.

• Analyze and interpret data collected to date.

Water Balance

• Estimate/calculate components of the water balance using data collected to date.

• Continue spring discharge and miscellaneous stream measurements.

• Analyze and interpret data collected to date.

Stream Gaging

• Continue operation of stream gages on Cedar Creek and Opequon Creek. Discharge data will be archived and published in the USGS annual data report.

RELEVANCE AND BENEFITS

Work on this project will contribute to the knowledge of water resources in the carbonate aquifers of Frederick County and the northern Shenandoah Valley of Virginia. The study will set the framework for further investigation of fundamental processes controlling the occurrence and movement of water in the carbonate aquifer system. Over the long term, information from this study will be incorporated with current and past investigations in neighboring states to increase our knowledge of the hydrogeologic controls on ground-water flow in the karst terrain of the Middle Atlantic States.