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 were conducted in 2003 and 2004, and a final report was approved, published, and distributed in 2005 that disseminates the information from 2001-02, during the drought.

The report presents a conceptual model of ground-water flow and provides a preliminary assessment of the hydrogeology and ground-water availability in the carbonate aquifer system of Frederick County, Va. Water budgets and effective ground-water recharge are calculated for both the Cedar and Opequon Creek Basins, for 2001-02.

Activities proposed for Fiscal Year 2006 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 2005 efforts were focused on the Stephenson quadrangle, and will focus on the White Hall and Hayfield quadrangles in FY 2006.

• 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).

Ground-Water Flow System

• Continue operation of water-level monitoring network, conducting water-level measurements during high and low water conditions. Water-level data will be archived and published in the USGS annual data report.

• Continue operation of the real-time ground-water-level station in the County.

• Investigate the occurrence and nature of subsurface water-bearing fractures and directional controls on ground-water flow.

• Continue investigation of the apparent ground-water divide in the vicinity of Apple Pie Ridge.

Water Balance

• Continue spring-discharge and miscellaneous streamflow measurements.

• Discharge data will be archived and published in the USGS annual data report.

• Estimate the effective ground-water recharge for the Cedar and Opequon Creek Basins during 2004.

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.