Western Irrigated Agriculture: Methods

Data summaries in the 147 electronic data tables highlight the structural characteristics of western irrigated agriculture across four farm-size classes based on data from USDA's 1998 Farm and Ranch Irrigation Survey (FRIS). Structural characteristics were summarized only for irrigated agriculture within the 17 contiguous Western States for several reasons. First, these States dominate irrigated agriculture in terms of the number of irrigated farms, as well as the extent of irrigated acreage, water use, and value of irrigated farm sales. Second, much of irrigated agriculture in the 31 Eastern States (while economically important regionally) occurs largely as supplemental irrigation, while in many parts of the West, crop production may not be an option without irrigation. In addition, while water reallocation can be a contentious issue across the U.S., it is especially so in the more arid western States.

The four farm-size classes used for this analysis were defined using "total farm sales" from the 1997 Census of Agriculture, carried over to FRIS (by observation). Farm-size classes are defined to be consistent with the ERS farm typology (Hoppe and MacDonald, 2001).

Sampled observations for FRIS were selected from irrigated farms and ranches identified in the 1997 Census of Agriculture (23,567 farm operations across all 50 States, with 6,875 farm operations from the 17 Western States). For a detailed explanation of FRIS sample design characteristics, coverage, statistical methodology, estimation, response rates, and reliability measures, see the NASS website.

Farm-Size Class Definitions Used to Examine Structural Characteristics of Irrigated Agriculture

1/ Farm-size classes were defined using the value of the total farm sales variable from the 1997 Census of Agriculture applied to the 1998 FRIS data (by observation).

2/ Nonfamily corporate farms could not be identified with FRIS data. For more information on the ERS farm typology, see the America's Diverse Family Farms: Assorted Sizes, Types, and Situations (Hoppe and MacDonald, 2001).

For this analysis, three additional data reliability issues deserve some attention. First, for each of the summary data tables, a cell value of "d" indicates "insufficient data for publication." Consistent with NASS/USDA data disclosure requirements for FRIS, summarized data could be published only if the summary statistic was based on five or more represented farms. For most summary tables, the FRIS sample size was more than sufficient across farm-size classes by State to meet this test. Disclosure "d" appears across farm-size classes for only a few summary tables, namely those tables summarizing a statistic for a subtopic area, like pumping (energy) costs by farm-size class for farms using gasoline rather than electricity to power well pumps.

Second, for such key variables as the number of irrigated farms, acres irrigated, and water applied (total and by water source), values by State for the "total" column in the appropriate summary tables are equivalent to values reported in the FRIS report (NASS, 1999) for corresponding State-level summary tables. Thus, the summarized data tables present a farm-size "structural" view of irrigation characteristics reported in the FRIS report.

Third, for all data tables summarizing a weighted-average statistic, coefficient of variation (CV) statistics were computed by farm-size class and by State (and region). Coefficient of variation values were computed as [(standard error of the estimate divided by the estimate) x 100], and reported in the appropriate data tables using * for CV < 25; ** for 25 < CV < 50; *** for 50 < CV < 100; and **** for CV > 100. For most summary tables, CV values across farm-size classes across the Western States were generally less than 25 and most often less than 50, indicating relatively low variability of irrigation characteristics within most farm-size classes.

FRIS Irrigated Farm Numbers by Farm-Size Class, 17 Western States

References

Hoppe, Robert A. and James M. MacDonald (2001). America's Diverse Family Farms: Assorted Sizes, Types, and Situations, Agricultural Information Bulletin, No. 769, Economic Research Service, USDA (May): pp. 8.

National Agricultural Statistics Service (NASS) (1999). Farm and Ranch Irrigation Survey (1998), Vol. 3, Special Studies, Part 1, U.S. Department of Agriculture, Washington, DC.