A look at karst topography

How does nitrogen get in the streams of the Shenandoah Valley?

Spout Run watershed was a case study in this FOSR 2013 report from Clarke County, Virginia which indicates that springs located near fields or areas where biosolids have been applied have higher Nitrate concentrations than those springs located in areas where biosolids have not been applied.

Download the full report in PDF

This study was conducted by Friends of the Shenandoah River with cooperation of Clarke County and the willingness of landowners who gave access to the springs. Funds for the study were granted to Alison Teetor by the 2013 Citizen Water Quality Monitoring Grant Program, from the Virginia Department of Environmental Quality, and from the Chesapeake Bay Restoration Fund. Chemical analyses were conducted by Karen Andersen and Molly Smith. Ben Sawyer performed GIS measurements and helped with hydrologic analyses. John Young USGS Leetown, WV loaned a stream flow meter. Richard Marzolf helped write this report.

Excerpt:

Spout Run is a type example of a karst watershed in Clarke County in the Shenandoah Valley. Its drainage basin of 21.4 square miles is entirely karst (carbonate); with characteristic fracture zones, frequent sinks and springs and fewer surface streams than the adjacent less permeable metamorphic and siliciclastic formations. Flow from springs is nearly a direct connection to the ground water; that is, ground water, emerging to the surface in spring flow, accounts for up to ca. 80% of the stream flow. Precipitation infiltrates rapidly with only 2- 4% of rainfall appearing as runoff, and, depending on vegetation and season, up to 70% of rainfall is returned to the atmosphere by evapotranspiration. The upshot of this hydrogeological configuration is that base flow is sustained and flood peaks are muted. The central purpose of the study was to examine the role of ground-water transport of nutrient constituents of biosolids when they were applied to lands near springs. A general finding of the chemical analyses was that changes through time were minor in any one spring; while the differences were observed to be among the various springs. Generally the nitrogen concentration was higher in spring flow from springs proximal to biosolid application areas. Total Kjeldahl nitrogen (organic), ammonia and nitrite concentrations were below the limit of detection.