WSP06290

• File Number: 8277.600.10
• Description: Big Sandy River Unit - Colorado River Salinity Control Program
• State: WY
• Basin: Colorado Mainstem
• Date: 5/1/1986
• Title: U.S.D.A. Selected Plan - Big Sandy River
• Water Supply Pro - Doc Type: Definite Plan Report

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It should be noted that the irrigated acreage has expanded with
about 15,700 acres of the 18,370 water-righted acres being irrigated in
1986. The land use distribution for the 15,700 acres is shown in
table 1-5.

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The historic land use was the basis for the water budget (see
Table 1-2) developed that shows the water requirements for irrigation.
This historic evaluation shows a significant change in species of forage
grown over the 18-year period. The species of forage presently grown
have proven to be the most efficient utilizers of water. Over long
periods of time, ranches have selected the species that are adapted to
the 90-day growing season, soils, irrigation methods, and to the
available water supply, Historic data from USGS and the Eden-Farson
Irrigation and Drainage District were utilized in development of
Table 1-2.

TABLE 1-1

HISTORIC EVALUATION VS. PRESENT CONDITION

Historic
(1960-1977)

Present
(1985)

Water-Righted Acres
Irrigated Acres
Conveyance Efficiency (Percent)
On-farm Efficiency (Percent)
Project Efficiency (Percent)
Annual Salt Load (Tons/Year)
Salt Load from Irrigation (Tons/Year)

18,370
14,3201/
82
35
294/
149, 18ot/
133,86~

18,370
15,700
822/
3~
323/
157,57~/
142,25~

1/ Average irrigated acreage from a low of 11,485 acres in 1961 to a
high of 15,700 acres in 1976,

1/ With an average water supply of 57,620 acre-feet diverted into the
canals and laterals and the on-farm irrigated acres increased from
14,320 to 15,700. The on-farm efficiency has increase to provide a
full water supply to the 15,700 acres.

1/ Under present condition, the system is assumed to be in balance (no
loss to ground water), therefore, outflow will increase from the
historic outflow of 29,580 ac ft to present outflow of 31,430 ac ft.
This increased outflow increases salt loadings to the river by
8,390 tons/year.

4/ Average value for 18-year evaluation.

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Oj~Lto

1-2