USGS Releases Online Tool for Estimating Atrazine Levels in Streams and Rivers

A new online, interactive tool for estimating atrazine concentrations in streams and rivers is now available. 

The online mapping tool can assist water managers, policy makers, and scientists in several ways, including:

• Understanding where and why pesticides occur in streams.
• Assessing geographic patterns in pesticide stream concentrations at many scales, ranging from the watershed to regional and national;
• Designing efficient and cost-effective monitoring programs and studies; and
• Identifying streams with the greatest likelihood to have concentrations that exceed a water-quality benchmark of potential concern. 

“Assessment and management of pesticides require far more information on concentrations in streams and rivers than we can afford to directly measure for all the places and times of interest,” said Wes Stone, the USGS hydrologist who developed the model.  “For these situations, statistical models can be used to estimate water-quality conditions at unmonitored locations under a range of possible circumstances.” 

The estimates are based on a USGS statistical model — referred to as Watershed Regression for Pesticides (or “WARP”) — which also provides key statistics for each selected stream, including the probability that a pesticide may exceed a water-quality benchmark of potential concern, and a level of confidence and uncertainty associated with each estimate. 

The release for atrazine is the first in a series of statistical models for other pesticides, each of which is based on USGSNational Water-Quality Assessment (NAWQA) monitoring in streams from 1992-2011, agricultural pesticide use, and environmental characteristics, such as soil characteristics, hydrology, and climate.  

Future updates will provide similar mapping and modeling for additional pesticides. Estimates and interactive mapping of pesticides for streams in the U.S. are available at this USGS website. The new website replaces an earlier version of the model for atrazine.