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WSP05094
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Last modified
1/26/2010 2:16:55 PM
Creation date
10/12/2006 12:51:40 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8277.600.10
Description
Big Sandy River Unit - Colorado River Salinity Control Program
State
WY
Basin
Colorado Mainstem
Date
2/1/1988
Title
U.S.D.A. Selected Plan - Big Sandy River Unit
Water Supply Pro - Doc Type
Definite Plan Report
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<br />,;', <br /> <br />Irrigation Systems <br /> <br />In making the irrigation system analysis, it became evident that the <br />irrigated acreage in the project area was continually changing. The <br />following Table 2-1 defines the values and definitions of time periods <br />and relationships uaed in this report. <br /> <br />A canal and lateral system analysis was conducted for the historic water <br />record (1960 through 1977 irrigation seasons) on the Eden Valley <br />Irrigation Project. This analysis indicated that 82 percent of the <br />water diverted from the reservoirs is being delivered to the farms. <br /> <br />:, ~ <br /> <br />The average irrigation water required by crops grown in Eden Valley was <br />estimated to be 1.17 acre-feet per acre for the 1960-77 evaluation <br />period. The average irrigated acreage for this period was 14,320 acres. <br />Dividing the irrigation water required by crops by the total water <br />delivered to the farm, an average onfarm irrigation efficiency of <br />35 percent was derived. This indicates the overall project efficiency <br />to be approximately 29 percent. using an 82 percent conveyance <br />efficiency (see Table 2-2). <br /> <br />~ <br /> <br />;i' <br /> <br />" <br /> <br />r:::': <br />, <br />, <br /> <br />,-,'. <br /> <br />The water not used by the irrigated crops (71 percent) can be accounted <br />for by (1) phreatophyte use. including essentially all nonirrigated <br />plants in the project area and along the river to Gasson Bridge, <br />(2) evaporation from reservoirs and ponds, and (3) drainage ditch and <br />deep percolation return flows to the Big Sandy River. <br /> <br />% <br />r,.A <br /> <br />,'" <br /> <br />r1f <br /> <br />f." <br /> <br />It should be noted that the irrigated acreage has expanded with about <br />15,700 acres of the 18.370 water-righted acres being irrigated in 1986. <br />The land use distribution for the 15.700 acres is shown in Table 2-3. <br /> <br />,re'!', <br /> <br />'7- <br /> <br />The historic land use was the basis for the water budget (see Table 2-4 <br />and Figure 2-1A) developed that shows the water requirements for <br />irrigation. This historic evaluation shows a significant change in <br />species of forage grown over the 18-year period. The species of forage <br />presently grown have proven to be the most efficient utilizers of water. <br />Over long periods of time. ranches have selected the species that are <br />adapted to the 90-day growing season. soils, irrigation methods, and to <br />the available water supply. Historic data from USGS and the Eden-Farson <br />Irrigation and Drainage District were utilized in development of <br />Table 2-4. <br /> <br />~ <br /> <br />',-! <br /> <br />n <br />~;'-~ <br /> <br />i'''":: <br />v,,> <br />~\-, <br /> <br />Using the historic water supply and present 15,700 irrigated acres, the <br />present onfarm efficiency is about 39 percent with a project efficiency <br />of 32 percent. In addition. the water and salt budgets (see Table 2-5) <br />show that during the past few years salt contributions were greater than <br />the 1960-77 18-year average. Using the present irrigated acreage and a <br />balanced water budget. the revised annual salt budget would produce a <br />157,570-ton output into the Big Sandy River. Under present conditions, <br />it is estimated that 142.250 tons of salt are a result of irrigation and <br />15,320 tons are a result of runoff, erosion, and natural seeps. If <br />irrigation in the project area were completely eliminated, it is <br />estimated that the contribution of salt from runoff, erosion, and <br />natural seeps would increase to 32,720 tons. The increase from <br /> <br />CJ11:.;1 <br /> <br />~; <br />,.{ <br />~-,f , <br /> <br />2-3 <br />
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