National Water-Quality Assessment (NAWQA) Program
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The pesticide use maps provided on this web site show the geographic distribution of estimated average annual pesticide use intensity. Use intensity rates are expressed as the average pounds applied per square mile of agricultural land in a county. The area of mapped agricultural land for each county was obtained from an enhanced version of the 1992 USGS National Land Cover Data (NLCD). The key limitations of the data used to produce these maps include the following: (1) use coefficients for each crop are averages for each state and consequently do not reflect the local variability of pesticide management practices found within states and counties, (2) pesticide use estimates represent typical use patterns for the five year period surrounding each particular year shown on the maps, (3) pesticide use coefficients were not available for all states where a pesticide may have been applied to agricultural land, and and such areas are not included, (4) county crop acreages are form the Census of Agriculture and may not represent all crop acreage because of Census nondisclosure rules, and (5) agricultural land area used to calculate the pesticide use intensity and display the data was derived from 30-meter satellite remote sensing data that may over estimate or underestimate the actual agricultural land area. The maps are not intended for reliably making local-scale estimates of pesticide use, such as estimates for a specific individual county level. Please refer to Method for Estimating Pesticide Use for a detailed discussion of how the pesticide use data were developed. Each set of maps identified below by Census year includes a description of specific data sources and methods applied to make the maps.
U.S. Department of the Interior | U.S. Geological Survey
URL: http://water.usgs.gov
Page Contact Information: nawqa_whq@usgs.gov
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