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Change in Irrigated Acres, 1982-1997

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Description

This bar map shows changes in the acreage under irrigation for Farm Production Regions. The map includes irrigated cropland and irrigated pastureland. Each region contains 4 bars showing the increase or decrease in acres for the following periods: 1982-1987; 1987-1992; 1992- 1997; 1982-1997. The length of each bar is proportional to the number of acres it represents. There were 67.5 million acres of irrigated land in 1997. Continued and prolonged droughts may lead to concerns about surface and groundwater withdrawals in irrigation growth areas. This may lead to water supply issues in areas where it has not been of major concern in the past.

Cautions for this Product:
This map does not show the amount of acres currently under irrigation. This map does not show change in irrigation for land uses other than cropland and pastureland. Data are not collected on Federal land. Data are not available for Alaska or the Pacific Basin.


Sources

Source: National Resources Inventory, 1997
Distributor: USDA-NRCS-RIAD
Reliability:
NRI sample data are generally reliable at the 95% confidence interval for state and certain broad substate area analyses. Generally, analyses that aggregate data points by smaller geographic areas and/or more specific criteria result in fewer data points for each aggregation and therefore less reliable estimates. NRI maps reflect national patterns rather than site- specific information.

Layers

Aggregate Layer: Farm Production Regions
Other Layers Displayed: State

Definitions

Cropland:
A Land cover/use category that includes areas used for the production of adapted crops for harvest. Two subcategories of cropland are recognized: cultivated and noncultivated. Cultivated cropland comprises land in row crops or close-grown crops and also other cultivated cropland, for example, hayland or pastureland that is in a rotation with row or close-grown crops. Noncultivated cropland includes permanent hayland and horticultural cropland. [NRI-97]

Irrigated land:
Land that shows evidence of being irrigated during the year of the inventory or during two or more years out of the last four years. Water is supplied to crops by ditches, pipes, or other conduits. Water spreading is not considered irrigation; it is recorded as a conservation practice. [NRI-97]

Pastureland and Native Pasture:
A Land Cover/Use category of land managed primarily for the production of introduced or native forage plants for livestock grazing. Pastureland may consist of a single species in a pure stand, a grass mixture or a grass-legume mixture. Management usually consists of cultural treatments-fertilization, weed control, reseeding, or renovation and control of grazing. (For the NRI, includes land that has a vegetative cover of grasses, legumes, and/or forbs, regardless of whether or not it is being grazed by livestock.) [NRI-97]

Product Information

Product ID: 5115
Production Date: 12/14/00
Product Type: Map

For additional information contact the Resources Inventory and Assessment Division. Please include the Product ID you are inquiring about. nri@wdc.usda.gov or 1400 Independence Avenue SW - P.O. Box 2890 - Washington D.C. 20013. If you use our analysis products, please be aware of our disclaimer.