Project Summary:

The overall objectives of the project were to increase the understanding of the impacts of urban growth on water quality in the Exeter River Watershed in the Seacoast region of New Hampshire. The study was designed to monitor long-term changes in biological communities and determine the watershed characteristics that may be responsible for alteration of such communities. The Exeter River Watershed was identified for this study because the river flows within the boundaries of Rockingham County, the fastest growing county in New Hampshire.

The project consisted of a water-quality network with the goal of assessing the environmental quality of streams and its response to changing watershed conditions using benthic-macroinvertebrate data as an indicator. Current stream conditions were documented in undeveloped watersheds and in watersheds that are expected to experience considerable urban growth in the near future. Data were analyzed to enhance our understanding of the extent and amount of urban land-use change that results in impacts to the macroinvertebrate communities and identify those watershed characteristics that correlate with these alterations. A web site will be developed to make watershed characteristics and environmental data collected during the project accessible to decision-makers.

The sampling protocols for the study were based on the Rapid Bioassessment Protocols (RBPs) that were established by the U.S. Environmental Protection Agency. Fifteen monitoring sites were selected to represent an urban gradient throughout the Exeter River Watershed.

Specific conductance, turbidity, nitrite plus nitrate yields, and selected macroinvertebrate community data were significantly correlated with most measures of urbanization used in this study; however, E. coli concentrations and total phosphorus yields were not statistically correlated with most measures of urbanization in this study. The measures of urbanization that had the highest correlations with stream-quality variables were those measures that were associated with the percent of urban land in buffer zones near and upstream of a sampling site. Mean Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa richness showed a response to urbanization in a watershed, indicating that EPT taxa richness may be an appropriate metric to evaluate the effects of urban land use on small streams in this region. Results from this study indicate that the percent of urban land use in buffer zones and the percent of impervious surface in a watershed can be used as indicators of stream quality.