Identifying key stream restoration variables in an agriculturally impaired Chesapeake Bay watershed

Authors

Julia Portmann, James Madison UniversityFollow

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.

ORCID

https://orcid.org/0000-0002-0190-6192

Date of Graduation

5-12-2022

Semester of Graduation

Spring

Degree Name

Master of Science (MS)

Department

Department of Biology

Second Advisor

Heather P. Griscom

Third Advisor

Christine May

Abstract

The Chesapeake Bay watershed spans several states, supports diverse ecosystems, and is crucial to local economies. However, agricultural practices in this region impair water quality. 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 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, measured canopy cover, algal density, substrate size, and bank height and angle. We identified macroinvertebrates to family and calculated the Chesapeake Basin-wide Index of Biotic Integrity (Chessie B-IBI), diversity, and the Virginia Stream Condition Index (VSCI). We also 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 GIS. 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 additional measures when restoring streams, we can more effectively improve water quality throughout the watershed and thus improve the health of the Chesapeake Bay.