Global Map of Irrigation Areas

United States of America

According to agricultural census data collected by the National Agricultural Statistics Service (NASS) of the United States Department of Agriculture (USDA) the irrigated area in the conterminous US (including Alaska and Hawaii but excluding the islands of Puerto Rico, Guam, Virgin Islands and Northern Marianna Islands) was 55 311 236 acres in 2002 [US01], 56 289 172 acres in 1997 [US02] and 49 404 030 acres in 1992 [US03]. However, the water use estimate reports of the United States Geological Survey (USGS) reported a larger extent of irrigated areas. In these reports irrigated areas was reported to be about 57 900 000 acres in 1995 [US04] and 61 900 000 acres in year 2000 [US05]. All these figures relate to the area actually used for irrigation in the year of the census, the area equipped for irrigation is larger. So the Natural Resources Conservation Service (NRCS) of USDA estimated the area irrigated in 1997 or in at east two of the four years before at 67 500 000 acres [US06].

No information could be found on area equipped for irrigation on a sub-national level. Area equipped for irrigation was therefore estimated on a county-level by first combining the inventories of USDA and USGS on irrigated area per county in years 1995, 1997, 2000 and 2002. The maximum value of irrigated area per county reported for these years was derived and assumed to represent the area equipped for irrigation. For the outlying territories of the United States similar statistics provided by USDA and USGS as part of the census reports were used as long as they were available. For some counties all the inventories reported "no data". Then area equipped for irrigation was set to the value as reported by the agricultural census 1987 and published by Battaglin and Goolsby, 1994 [US07]. Since this inventory also reported statistics for units below the county-level it was used for downscaling of area equipped for irrigation in sub-county statistical units. Irrigated areas per federal state (or territory) computed by summarizing irrigated areas per county as reported by the different inventories is listed in the table below. Irrigated area per county as used for the update of the map adds up to 27 951 503 ha and is documented in this table.

A national land cover data set on a 30 m resolution [US08] was used to assign irrigated areas to specific cells within the sub-national units of the conterminous United States. Irrigated area of the sub-national units was equally distributed over all cells classified as orchards and vineyards (value 61), row crops (value 82), small grains (value 83) or fallow (value 84). If the sum of these cropland areas was smaller than the total irrigated area per sub-national unit, the remaining area was assigned to cells classified as pasture and hay (value 81). This appeared in the majority of the sub-national units in the states of Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oregon, Utah, Washington and Wyoming and in some sub-national units located in the states of Arkansas, Florida, Massachusetts, Missouri, Montana, Nebraska and Texas.

References

[US01] A.M. Veneman, J.J. Jen and R.R. Bosecker (2004): 2002 Census of Agriculture, Volume 1, Geographic Area Series, National Agricultural Statistics Service (NASS) of the United States Department of Agriculture (USDA), downloaded from http://www.nass.usda.gov/census/ in January 2005.
[US02] D. Glickman, M. Gonzalez and D.M. Bay (1999): 1997 Census of Agriculture, Volume 1, Geographic Area Series, National Agricultural Statistics Service (NASS) of the United States Department of Agriculture (USDA), downloaded from http://www.nass.usda.gov/census/ in January 2005.
[US03] R.H. Brown, D.J. Barram, E.M. Ehrlich and H.A. Scarr (1994): 1992 Census of Agriculture, Volume 1, Geographic Area Series, National Agricultural Statistics Service (NASS) of the United States Department of Agriculture (USDA), downloaded from http://www.nass.usda.gov/census/ in January 2005.
[US04] W.B. Solley, R.R. Pierce and H.A. Perlman (1998): Estimated Use of Water in the United States 1995, United States Geological Survey (USGS), downloaded from http://water.usgs.gov/watuse/ in January 2005.
[US05] S.S. Hutson, N.L. Barber, J.F. Kenny, K.S. Linsey, D.S. Lumia and M.A. Maupin (2004): Estimated Use of Water in the United States in 2000, USGS Circular 1268, downloaded from http://water.usgs.gov/watuse/ in January 2005.
[US06] Natural Resources Conservation Service (NRCS) (2005): National Resources Inventory 1997, map: 'Acres of Irrigated Land 1997’, NCRS, USDA, downloaded from http://www.nrcs.usda.gov/technical/land/meta/m5297.html in January 2005.
[US07] W.A. Battaglin and D.A. Goolsby (1994): Estimates of land in agricultural production in counties in the conterminous United States as reported in the 1987 Census of Agriculture, USGS, downloaded from http://water.usgs.gov/GIS/dsdl/ag_land.e00.gz in January 2005.
[US08] U.S. Geological Survey (USGS) and U.S. Environmental Protection Agency (USEPA) (1999): National Land Cover Data (NLCD), downloaded from http://landcover.usgs.gov/natllandcover.asp in January 2005.
[US09] National Oceanic and Atmospheric Administration (NOAA) Coastal Services Center (2004): Main Eight Hawaiian Islands Land Cover, downloaded from http://www.csc.noaa.gov/crs/lca/hawaii.html in February 2005.
[US10] R. Latifovic, Z. Zhu, J. Cihlar, J. Beaubien, R. Fraser (2003): The Land Cover Map for North America in the Year 2000, map version 2, GLC2000 database, European Commision Joint Research Centre, downloaded from http://www.gvm.jrc.it/glc2000 in January 2005.
[US11] E.H. Helmer, O. Ramos, T. del M. López, M. Quinones, W. Diaz (2002): Mapping the forest type and land cover of Puerto Rico, a component of the Caribbean biodiversity hotspot. Caribbean Journal of Science 38, (3/4), 165-183.

Distribution of irrigated area in United States of America by Federal state or outlying territory.