Are Wild and Scenic River Watersheds "Wild"? Assessing Streamflow and Water Quality Beyond the Designated Corridor.

Abstract:

The Wild and Scenic Rivers (WSRs) Act offers the highest level of stream preservation in the United States to select river segments by protecting and enhancing their outstanding values, water quality, and free-flowing condition. However, WSR segments are inescapably influenced by the tributaries, catchments, and watersheds that they drain. Although knowledge of the condition of WSR watersheds is critical in protecting and enhancing WSR values, comprehensive efforts to assess the WSR System have not gone beyond their designated corridors. To address this issue, we developed a method to assess the water quality and hydrologic condition of river segments within the WSR System as well as the streams within their contributing watersheds.

This assessment uses data from the federally maintained Water Quality Portal to analyze total suspended solids, metals, chlorophyll a, Escherichia coli, nutrients, and pH across all WSR watersheds. This inventory of water quality data is used to identify areas within WSR watersheds with good water quality, those with poor water quality, and those that have a lack of water quality data. The assessment also uses daily streamflow data from USGS-maintained stream gauges to develop regression equations that predict natural streamflow magnitude, duration, and frequency for low and high flows. These statistics are then compared to the observed flow measured at gauges within WSR watersheds. We additionally quantify land use, stream modifications, and other land disturbances such as forest fire or urbanization within each WSR watershed to examine whether these factors relate to any departures of WSR flow from reference conditions, or if they have impacts to WSR water quality. For comparison to WSRs, we also compile data across other watersheds using the same methodology to evaluate whether designated WSRs have different watershed characteristics than watersheds without WSRs.