Change in Irrigated Cropland, 1992-1997
Description
This dot density map shows change in irrigated
cropland between 1992 and 1997. Dots are
aggregated by and placed randomly within 8-digit
hydrologic units. Each red dot indicates a
2,500 acre decrease in the amount of irrigated
cropland between 1992 and 1997, while each blue
dot indicates a 2,500 acre increase in irrigated
cropland. This shows where there has been
increased and decreased demand on water supplies
for agricultural purposes. Areas with 95% or
more Federal area are shaded gray. There was a
total increase of 2,932,600 acres, a total
decrease of 3,123,100 acres. The net decrease
for the U.S. was 190,500 acres.
Cautions for this Product:
This map may not be used to determine site-
specific information. Within an 8-digit
hydrologic unit, dot counts represent acreage
totals correctly plus or minus one dot to
account for remainders. Data are not collected
on Federal land. Data are not available for
Alaska or the Pacific Basin. Data for Puerto
Rico and the U.S. Virgin Islands are aggregated
by 6-digit hydrologic unit. Irrigation data are
only collected from cropland and pastureland.
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:
Cross of State with 8 Digit Hydrologic Units and
Federal Land
Other Layers Displayed:
States, Rivers
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:
5300
Production Date:
1/27/00
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.
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