WATER-QUALITY RESULTS FROM THREE CHESAPEAKE BAY SHOWCASE WATERSHEDS: MONITORING AND ANALYSIS DESIGNED TO ASSESS AND INFORM RESTORATION

In 2010, the U.S Geological Survey partnered with the U.S. Department of Agriculture to characterize water-quality conditions within three Chesapeake Bay showcase watersheds that were targeted for increased implementation of conservation practices. The Smith Creek watershed is located in Virginia’s Shenandoah Valley and is dominated by cattle and poultry production. The Upper Chester River watershed is located on Maryland’s eastern shore and has heavy row cropping activities. The Conewago Creek watershed is located in southeastern Pennsylvania and is characterized by mixed agricultural activities. A fourth watershed, Difficult Run, located in northern Virginia and characterized by suburban development, was included in this study to contrast the water-quality conditions found in the agricultural showcase watersheds. Water-quality monitoring within each of these watersheds aims to assess the effectiveness of implemented conservation practices and to better inform future management decisions.

Spatial analysis of water-quality monitoring data within the Smith Creek and Upper Chester River watersheds demonstrated differences in stream chemistry that were largely driven by patterns in land-use. In these watersheds, streams draining forested headwaters showed generally dilute chemistry, and made minimal contributions to downstream nutrient and sediment loads. In contrast, streams draining agricultural areas had variable stream chemistry that typically included higher nitrate concentrations.

Calculated nutrient inputs from surrounding land-use and nitrogen isotope data, where available, were used to characterize the dominant sources of nitrate within each watershed. These evaluations indicated that the dominant source of nitrate is likely manure in Smith Creek, inorganic fertilizer within the Upper Chester River, a combination of manure and fertilizer within Conewago Creek, and a mixture of sources that likely include septic system leachate within Difficult Run.

This understanding of spatial patterns in water-quality and of dominant nutrient sources can help target the placement and type of restoration activities within a watershed. Additionally, these comprehensive watershed characterizations can serve as a framework for future water-quality monitoring programs.