Integrating the National Hydrography Dataset Into RiverSpill William B. Samuels, David Amstutz, Jonathan Pickus, Rakesh Bahadur The purpose of this project was to analyze the improvement in calculating the fate and transport of waterborne contaminants using the NHD with the RiverSpill modeling tool. The operational version of RiverSpill uses the Enhanced Reach File (ERF1), a 1:500,000-scale stream network. The value of ERF1 was that it contained, on a national scale, mean flow and velocity information that could be updated to reflect real-time conditions. In this pilot study, covering three hydrologic units, NHD was populated with mean flow and velocity values. This pilot data set was integrated into RiverSpill. Comparisons were made between ERF1 and NHD derived results. Introduction RiverSpill is a GIS based system that models the real-time transport of constituents within a river system. RiverSpill calculates time of travel and concentration based on real time stream flow measurements, decay, and dispersion of constituents introduced into surface waters. By selecting a location on a river to introduce a chemical or biological constituent, the model performs the following functions: ● Calculates the downstream distribution of contaminant concentrations and travel time using real-time stream flow data. ● Simulates the behavior of contaminants from instantaneous and continuous point sources. ● Tracks the chemical or biological constituent, under real time flow conditions, to a water supply intake. ● Associates an intake to a water treatment plant. ● Identifies the population served by the water treatment plant. ● Performs upstream tracing (by distance or time) to identify potential sources of contamination Incident Command Information Tool The US Forest Service (USFS), Environmental Protection Agency (EPA), Federal Emergency Management Agency (FEMA), Defense Threat Reduction Agency (DTRA) and the Technical Support Working Group (TSWG) have identified as a high priority, the need for protecting drinking water. An early detection of contamination and the need for information to enable incident commanders to evaluate the risks posed to the public will fulfill this need. For example, the Forest Service manages federally owned watersheds that are sources of drinking water for 3000 towns and cities nation-wide and serve a combined population of 60 million people. Forest Service employees, trained as incident commanders primarily for wildland fires, are tasked to lead the multi-agency responses to other emergencies, such as water contamination incidents, when they occur on federal land and elsewhere as needed. Technical Description RiverSpill is one of three components of the Integrated Water Quality Security System (IWQSS). The IWQSS (see figure 1) provides a comprehensive approach to assessing the consequences of threats to water supplies through its three modules: RiverSpill (source water), Water Treatment Processes (Filtration Plant) and PipelineNet (finished water in the distribution system).