INVESTIGATING THE GEOLOGIC, HYDROLOGIC, AND ANTHROPOGENIC CONTROLS ON THE NORTH, MIDDLE, AND SOUTH RIVERS OF THE SHENANDOAH VALLEY, VA

The chemistry of stream and river waters are generally controlled by the local geology, climate, hydrology, and anthropogenic influences. We are examining the influences that these controls have on the North, Middle, and South Rivers, located in Augusta and Rockingham County, Virginia within the Shenandoah Valley. The controlling geology for these rivers are Paleozoic sandstones, shales, limestones, and dolomites. The land use is primarily agricultural with some forested woodlands and developed/urban areas. These streams are further chemically influenced by three Wastewater Treatment Facilities (WWTF) in the cities of Mt. Crawford, Verona, and Waynesboro, Virginia.

Samples have been collected from the North, Middle, and South Rivers from the headwaters and periodically downstream until they all join to form the South Fork of the Shenandoah River. Standard field sampling methods were used to analyzed pH, specific conductance, alkalinity, and temperature. Samples were then filtered and preserved and later analyzed in the lab for major cations and anions using a Varian AA 240 Atomic Absorption Spectrometer and a Dionex DX-120 Ion Chromatograph. As interpreted from Piper diagrams, most of the samples are classified as Ca + Mg, Na + K, HCO3, Cl + SO₄.

Preliminary analysis of data show that the total dissolved solids and carbonate mineral saturation indices generally increased from upstream to downstream, indicating that the rivers are maturing with respect to the local geology in a downstream direction. All three rivers show a spike in Cl^- and SO₄^2- concentrations immediately downstream of the WWTF’s as a result of high concentrations of these ions in the treated effluent. Further sampling and data analysis for this project will target issues of seasonality to these trends and whether or not we can develop an analytical method to detect the presence and persistence of pharmaceuticals/hormones in these waterways.