Watersheds with a High Potential for Pesticide and Nitrogen Leaching
Source: Natural Resources Conservation Service
Map Description:
This map depicts the top 400 watersheds with a high potential for pesticde and nitrogen leaching. Three maps of leaching indicators were overlaid to identify which watersheds have the greatest potential for combinations of water pollution sources. Watersheds identified as having a high potential for more than one pollution source (pesticides, nitrogen, or soil) would have a high priority for implementation of conservation programs. The top 400 watersheds (about 20%) were selected from each of the seven contributing maps as watersheds with a high potential for chemical or soil loss from farm fields.

A variety of algorithms were used to create watershed values, generating a variety of units (pounds per watershed, index scores per watershed, etc.). To facilitate comparisons among the maps, the classes shown in each map were based on a consistent set of watershed rankings. The 200 watersheds with the highest scores are shown with the darkest color. The next highest 200 watersheds are shown with a slightly lighter color, and so on.

Taken from a poster presentation at the 52nd Annual SWCS Conference (July 1997), "Potential Priority Watersheds for Protection of Water Quality from Nonpoint Sources Related to Agriculture" by R.L. Kellogg, S. Wallace, K. Alt, and D.W. Goss. Revised October 1997.

Cautions for this Product:
Analyses do not show which watersheds will have water quality impairments related to agricultural production. The simulation models estimate soil loss, chemical loss, or vulnerability indexes for conditions at the edge of the field and the bottom of the root zone. Not included in the indicators are dynamics of fate and transport from the farm field to a water body. Dilution from runoff and recharge on noncropland areas in the watershed will also reduce the potential for actual water quality impairments.

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