WSP03164

• Author: USFWS
• Title: Management Plan for Endangered Fishes in the Yampa River Basin - Volume II -Appendices - USFWS - 09-01-2004

002328

August 23, 2000

page 3

Maximum consumptive use of these crops is only achieved with a full water supply. Consumptive
irrigation requirement (ClR) at Dixon, or that amount needed in excess of rainfall to produce a crop, was
determined by Trelease et al. (1970), as modified by Pochop, et al. (1992) to be 22.78 inches (1.9 feet)
for alfalfa and 20.96 inches (1.75 feet) for pasture grass (or grass hay). Modifications to these numbers
to include mountain meadow hay were developed for the Green River Basin Water Plan. For this type
of hay, it has been determined that the irrigated lands above Baggs would experience 19.59 inches (1.63
feet) of annual CIR. For purposes of depletion estimation, the following distribution was used: lands
above Baggs were represented by 89 percent mountain meadow hay and 11 percent alfalfa. with lands
below Baggs represented by 89 percent pasture grass/grass hay and II percent alfalfa. From irrigated
lands mapping, there exist 11,571 acres above Baggs and 4,358 acres below Baggs.

Under the cropping and irrigated lands percentages given above, the total crop-weighted CIR would be
as follows:

_._.----.f!:()J1________~IJP_"~_!3J!gg~____.__!lelow_l!aggs._._._ _____

Total

Grass Acres 10,298 3,879
Meadow/Grass CIR. ft. 1.63 1.75
Grass Total ClR. AF 16,786 6,788
Alfalfa Acres 1,273 479
Alfalfa CIR. ft. 1.9 1.9
Total Alfalfa CIR, AF 2,419 910
Total CIR, AF 19,205 7,698

14,194

23,574

1,755

3,329

26,903

These CIR calculations equate on a crop-weighted basis to 1.66 feet of CIR above Baggs and 1.77 feet
below Baggs. Estimates of actual agricultural depletions (and review of irrigation diversion records)
have shown less depletion than full CIR would dictate, which is to be expected. Estimates of
agricultural depletion, based on studies prepared for High Savery Reservoir (Bums and McDonnell,
ibid.), indicate the basin to currently receive about a 75 percent supply without storage. Current
agricultural depletions are therefore estimated to be 20.050 acre-feet per year. It is recognized that in
practice full CIR is usually not achievable unless fields are flat and irrigation timing is precise.
Nonetheless, full CIR values provide a reasonable calculation of the needs and demands of the aggregate
irrigation in the basin.

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Appendix C - Technical Memoranda from Colorado and Wyoming

C-7