Identifying Key Stream Restoration Variables in an Agriculturally Impaired Chesapeake Bay Watershed
Faculty Advisor Name
Bruce Wiggins
Department
Department of Biology
Description
The Chesapeake Bay watershed spans several states, supports diverse ecosystems, and is crucial to local economies. However, land use in the region can be harmful to water quality. Agriculture, particularly livestock pastures with access to waterways, is one of the most prevalent land use types. The Smith Creek watershed, within the Shenandoah Valley, was designated a showcase watershed in 2010 by the United States Department of Agriculture to demonstrate the efficacy of implementing stream restoration projects. We sampled fifteen farms ranging from unrestored to thirty-six years since restoration. At each site, we conducted a kick-net survey for macroinvertebrates, which were later identified to family level. Using these data, we then calculated the Chesapeake Basin-wide Index of Biotic Integrity (Chessie B-IBI), diversity, and the Virginia Stream Condition Index (VSCI). At each site, we also measured canopy cover, algal density, substrate size (median=D50, 90th percentile=D90), and bank erosion using bank height and angle to quantify in-stream habitat. Using geographic information systems, we calculated the percent pasture, cropland, and forest within 10 and 100 meters (m) of the stream on the property and throughout the watershed, as well as road density at each scale. Using single and multiple linear regressions, we identified several metrics that predicted healthy macroinvertebrate communities. We found that the Chessie B-IBI and VSCI were significantly predicted by increasing time since restoration (p=0.03, R2=0.333; p=0.02, R2=0.400), as was diversity with D90 substrate size (p=0.02, R2=0.383). The Chessie B-IBI was best predicted by the combination of increasing time since restoration and D90 together (p=0.003, R2=0.599). Diversity was best predicted by decreasing road density within 10 m of a stream in the watershed and increasing D90 (p=0.002, R2=0.617). The VSCI was significantly predicted by increasing time since restoration, cropland within 10 m of the stream on the property, road density within 100 m on the property, and decreasing road density within 10 m of the stream on the property (p=0.0001, R2=0.868). Allowing streams time to recover after restoration implementation was the most important factor for improving water quality. However, since seriously impaired sites may require immediate restoration, understanding the natural stream habitat will maximize the likelihood of conducting a successful restoration project. For instance, habitats with inherently larger substrates are likely to respond more quickly to restoration. By taking these measures when restoring streams, we can more effectively improve water quality throughout the watershed and thus improve the health of the Chesapeake Bay.
Identifying Key Stream Restoration Variables in an Agriculturally Impaired Chesapeake Bay Watershed
The Chesapeake Bay watershed spans several states, supports diverse ecosystems, and is crucial to local economies. However, land use in the region can be harmful to water quality. Agriculture, particularly livestock pastures with access to waterways, is one of the most prevalent land use types. The Smith Creek watershed, within the Shenandoah Valley, was designated a showcase watershed in 2010 by the United States Department of Agriculture to demonstrate the efficacy of implementing stream restoration projects. We sampled fifteen farms ranging from unrestored to thirty-six years since restoration. At each site, we conducted a kick-net survey for macroinvertebrates, which were later identified to family level. Using these data, we then calculated the Chesapeake Basin-wide Index of Biotic Integrity (Chessie B-IBI), diversity, and the Virginia Stream Condition Index (VSCI). At each site, we also measured canopy cover, algal density, substrate size (median=D50, 90th percentile=D90), and bank erosion using bank height and angle to quantify in-stream habitat. Using geographic information systems, we calculated the percent pasture, cropland, and forest within 10 and 100 meters (m) of the stream on the property and throughout the watershed, as well as road density at each scale. Using single and multiple linear regressions, we identified several metrics that predicted healthy macroinvertebrate communities. We found that the Chessie B-IBI and VSCI were significantly predicted by increasing time since restoration (p=0.03, R2=0.333; p=0.02, R2=0.400), as was diversity with D90 substrate size (p=0.02, R2=0.383). The Chessie B-IBI was best predicted by the combination of increasing time since restoration and D90 together (p=0.003, R2=0.599). Diversity was best predicted by decreasing road density within 10 m of a stream in the watershed and increasing D90 (p=0.002, R2=0.617). The VSCI was significantly predicted by increasing time since restoration, cropland within 10 m of the stream on the property, road density within 100 m on the property, and decreasing road density within 10 m of the stream on the property (p=0.0001, R2=0.868). Allowing streams time to recover after restoration implementation was the most important factor for improving water quality. However, since seriously impaired sites may require immediate restoration, understanding the natural stream habitat will maximize the likelihood of conducting a successful restoration project. For instance, habitats with inherently larger substrates are likely to respond more quickly to restoration. By taking these measures when restoring streams, we can more effectively improve water quality throughout the watershed and thus improve the health of the Chesapeake Bay.
