RGDSS_Historic_CUreport_20040601

• Title: RGDSS - Rio Grande Historic Crop Consumptive Use Analysis
• Description: The documentation is for the Rio Grande Basin Historic Crop Consumptive Use Analysis, developed during the RGDSS implementation for the period 1950 through 2002. It includes 100 percent of the crop consumptive use in the basin for the period. Documentation consists of the final Historic Crop Consumptive Use Analysis Report and supporting appendices.
• Decision Support - Doc Type: Modeling Dataset Documentation
• Date: 6/1/2004
• DSS Category: Consumptive Use
• DSS: Rio Grande
• Basin: Rio Grande
• Contract/PO #: C153863
• Grant Type: Non-Reimbursable
• Bill Number: HB98-1189, SB99-173
• Prepared By: Leonard Rice Engineering

Table 2
1998 Irrigated Acreage by Crop Type
Irri ated Cro T e Acrea e % of Total
Irri ated Meadow 278,760 45
Alfalfa 141,265 23
Small Grains 114,841 18
Potatoes 80,507 13
Vegetables 7,495 1
Total Basin 622,868 100
Colorado Agricultural Statistics (CAS) are county-based, and not provided on a ditch or
well basis. However, to determine supply-limited consumptive use, it is necessary to
associate acreage with surface water and/or ground water sources. The 1998 acreage
estimates were assigned to surface and ground water sources, and therefore were used in
conjunction with the CAS estimates to determine historic (1950 through 2002) acreage by
structure. Table 3 shows a comparison of 1998 irrigated acreage from the RGDSS effort
and 1998 CAS data.
Table 3
Comparison of 1998 RGDSS Irrigated Estimates to 1998 Colorado Agricultural
Statistics (acres)

Crop Type Irrigated Acreage
Assessment CO Agricultural
Statistics
Difference Percent
Difference
Irrigated Meadow 278,760 87,000 191,760 69
Alfalfa 141,265 135,000 6,265 4
Small Grains * 114,841 105,000 9,841 9
Potatoes 80,507 76,900 3,607 4
Vegetables 7,495 N/A N/A N/A
Total 622,868 402,391 211,473 34
* Small Grains include Barley, Oats, and Wheat
There are several reasons for the discrepancies between the irrigated acreage assessment
and the amount reported by the Colorado Agricultural Statistics including:
The CAS estimates are obtained by a random survey of a sample of growers and are
subject to the errors associated with this approach.
The CAS estimates reflect the acres of harvested crop, not the acres of planted crop
defined in the irrigated acreage assessment.
The irrigated meadow category of the CAS estimates reflect only the acreage that was
hayed (had a harvested crop removed from it) and does not include the acreage that
was pastured or grazed.
Colorado Agricultural Statistics (CAS) for potatoes, small grains, and alfalfa were
determined to be an appropriate basis for estimating historic acreage and crop types. On-
C:\Projects\rgdss\finemos_2004\appendA_cropcu_6-2004.doc A-3 of A-10 June 2004