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Dominant Cropland Irrigation Water Source, 1992

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This shaded polygon map shows the dominant water source for irrigated cropland for each 8-digit hydrologic unit. Water sources are categorized by 1) Well, 2) Pond, Lake, or Reservoir, 3) Stream, Ditch, or Canal, 4) Lagoon or Wastewater (not tailwater), and 5) a combination of water sources. The dominant water source is defined as the water source that is the most common in that hydrologic unit. Areas with 95% or more Federal area are shown as gray. Areas without irrigated cropland are left white.

Cautions for this Product:
In many areas shown on this map as irrigated, non- irrigated cropland may be more common than any type of irrigated cropland. The total amount of irrigated cropland may be small. Irrigation of land uses other than cropland is not included. Data are not collected on Federal land. Data are not available for Alaska, and the Pacific Basin. Data for Puerto Rico and the U.S. Virgin Islands are shown by 6-digit hydrologic unit.


Source: National Resources Inventory, 1997
Distributor: USDA-NRCS-RIAD
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.


Aggregate Layer: 8 Digit Hydrologic Unit Areas with Federal Land
Other Layers Displayed: States, Rivers


An artificial waterway used for irrigation. [NRI- 97]

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]

A long, narrow trench or furrow dug in the ground, as for irrigation. [NRI-97]

Hydrologic units:
A hierarchical system developed by the U.S. Geological Survey that divides the United States and the Caribbean into 21 major regions, 222 subregions, 352 accounting units, and further subdivided into 2,150 cataloging units that delineate river basins having drainage areas usually greater than 700 square miles. [USGS]

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]

Lagoon - waste treatment:
An impoundment made by excavation or earthfill for biological treatment of animal or other agricultural waste. [NHCP]

An inland body of water (fresh or salt) of considerable size occupying a basin or hollow on the earth's surface, and which may or may not have a current or single direction of flow. [ASCE- "Nomenclature for Hydraulics"]

A flow of water in a channel or bed, as a brook, rivulet, or small river. [NRI-97]

A hole drilled or bored into the earth providing access to water. [NRI-97]

Product Information

Product ID: 5950
Production Date: 2/8/01
Product Type: Map

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