Skip to main content
U.S. flag

An official website of the United States government

Interactive Map: GIS-based landscape analysis to identify sources of endocrine disrupting chemicals

December 9, 2017

About this tool

Wastewater discharges to surface waters from wastewater treatment facilities (WWTFs), although treated and within compliance of regulations, has the potential to contribute unregulated endocrine disrupting chemicals. A geospatial model for the Shenandoah River watershed was developed to visualize the typical contributions of treated effluent into Shenandoah River watershed streams using WWTF outfall locations and discharge data (average daily 2015 flows), the National Hydrologic Dataset Version 2 (NHDPlus V2, USGS and EPA 2012) stream network, and USGS streamgages.

View of the Shenandoah River
Shenandoah River watershed.

For each river segment in the watershed, the model returns the estimated percent of wastewater present in the river (the percent of accumulated wastewater, ACCWW%) during mean-annual or mean-August (low flow) streamflow conditions and for two scenarios of wastewater discharge:

  • Maximum facility-capacity permitted wastewater discharges (design flow)
  • 2015 average-annual wastewater discharges

ACCWW% was calculated using Python scripting, NHDPlus network connectivity attributes, and the NHDPlus Enhanced Runoff Method modeled streamflow values available for every stream segment representing mean 1971-2000 flows. For each NHDPlus stream segment, the accumulated wastewater upstream was divided by the NHDPlus EROM modeled streamflow for the segment as follows:

ACCWW (%) = (sum of upstream wastewater inputs / Total streamflow for river segment)*100