This coverage provides the locations and approximate farmed area under center pivot irrigation systems in use in Illinois during the 2012 and 2014 growing seasons. Center pivot irrigation imprints identifiable circular patterns on the landscape which can be visible in aerial images. The USDA collects aerial images during the crop growing season through the National Agricultural Imagery Program (NAIP) and makes them available through the USDA Geospatial Data Gateway. Images collected by the USDA during the 2012 and 2014 growing seasons were used to develop this coverage of center pivot irrigation areas. This was done by digitizing the area under each irrigation system using ArcGIS to plot the maps spatially, and creating a polygon for each individual system. The NAIP images were examined for irrigation patterns, and field boundaries were traced to create an ArcGIS map layer. In reviewing the USDA 2014 data, a QA/QC check indicated a few polygons were omitted from the original 2012 map. This revision includes the 2012 omitted systems and additional pivots identified from USDA images collected during the 2014 growing season. Using aerial photography to identify irrigation systems is limited by the resolution and timing of the photography, and in some cases a system may not have been discernable and may have been missed.

A total of 5,829 center pivot irrigation systems were identified in Illinois during the summer of 2012, representing approximately 553,000 acres of farmland. An additional 826 pivots were in use during the 2014 growing season, bringing the statewide total to 6,656 center pivot systems irrigating approximately 625,000 acres of farmland in 2014. This GIS layer does not include all forms of irrigation employed in Illinois. Alternative irrigation methods include subsurface, lateral-move, solidset, and traveling gun. These types of irrigation systems may cover a significant number of irrigated acres and are not reflected in this coverage.

Funding for developing this coverage was provided in part by the Illinois Department of Natural Resources, Office of Water Resources, under their Water Supply Planning Program. Use of this GIS layer and the map product are protected under the copyright of the University of Illinois, Board of Trustees. Their use and reproduction are bound by the terms of the Illinois State Water Survey Data Use License Agreement. (info@isws.illinois.edu). Data are provided as is. In all cases the Illinois State Water Survey must be credited as the source of the data.