spanish fork
nephi irrigation system
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    project summary
    The proposed action for the SFN System provides for an enclosed pipeline and various associated facilities. The proposed aqueduct would deliver Bonneville Unit and SVP water to the Wasatch Front areas of southern Utah County, from Springville to Santaquin, and Bonneville Unit water to the Mona and Nephi areas of eastern Juab County. The SFN System would also deliver water to Utah Lake for exchange with Jordanelle Reservoir.
    Agricultural Acreage Served

    The SFN System will deliver Bonneville Unit water to approximately 75,570 acres of agricultural land in southern Utah and eastern Juab counties. The Secretary of the Interior has certified these lands as being arable, and they are situated where they can receive water from SFN System facilities. The table below contains the distribution of these lands by area. The lands to be served with SVP water from the Main Conveyance Aqueduct are in southern Utah County.



    Irrigation Water

    The SFN System would provide 73,100 acre-feet of irrigation water, which consists of Bonneville Unit water from Strawberry Reservoir and return flow fro Bonneville Unit water use collected in Mona Reservoir.
    The irrigation water would be delivered to water applicants in southern Utah and eastern Juab Counties under contract with the CUWCD.

    The amounts of Bonneville Unit water provided to each agricultural area annually is based on the crop needs minus the existing water supply and allowable shortages. The SFN System water supply for each area is shown in this table.

    M&I Water

    M&I water needs in southern Utah County were determined for the communities of Mapleton, Springville, Elk Ridge, Woodland Hills, Payson, Salem, Santaquin, Spanish Fork, Goshen, and Genola. The State of Utah projects the populationof these communities and the surrounding unincorporated areas to increase from 60,350 in 1994 to 175,900 in 2035. This will increase the M&I water demand from 21,850 acre-feet in 1994 to an estimated 51,200 acre-feet in 2035. The projected per capita use rate for 2035 was based on 0.25 acre-feet for new urban development.

    The 29,350 acre-foot increase in M&I water need would be met by 8,800 acre-feet from existing community-owned water supplies, 9,350 acre-feet from conversion of agricultural water, and 11,200 acre-feet of M&I water from the SFN System.
    Instream Flow and Utah Lake

    In addition to the irrigation and M&I water needs cited previously, the SFN System would provide and average of 21,300 acre-feet per year of Bonneville Unit water for direct delivery to Utah Lake through the Spanish Fork River. This includes 17,000 acre-feet of Bonneville Unit water for instream flow maintenance in Sixth Water Creek and Diamond Fork Creek, which would then flow into Utah Lake.

    Return flow from water delivered by the SFN System would provide and additonal 20,700 acre-feet of water per year to Utah Lake. Combined, these amounts would provide an average 40,700 acre-feet per year to Utah Lake, which will assist in stabilizing its water level.
    SFN System Facilities

    The proposed action includes the Main Conveyance Aqueduct,
    The Main Conveyance Aqueduct would be a pipeline running through southern Utah County and into eastern Juab County, delivering Bonneville Unit water along the route as far as the Nephi area. The aqueduct would receive Strawberry Reservoir water from the Diamond Fork System at the confluence of the Spanish Fork River and Diamond Fork Creek and transport it to agricultural areas of southern Utah County and eastern Juab County. In its initial reaches, the aqueduct would have capacity to convey Bonneville Unit water plus a portion of the water developed by the SVP for southern Utah County. The 43.6-mile long Main Conveyance Aqueduct has been divided into eight pipeline sections for administration of construction and operation.

    From its beginning at the confluence of Diamond Fork Creek with the Spanish Fork River, the proposed Main Conveyance Aqueduct would be constructed down Spanish Fork Canyon on the north side of the highway, primarily on highway right-of-way. About a mile past the esisting SVP diversion dam, the aqueduct would cross under the highway, railroad tracks, and Spanish Fork River, and then follow the general alignment of the High Line Canal. Between Salem and Santaquin the aqueduct would replace portions of the High Line Canal.

    From Santaquin, the aqueduct would continue southerly along the east side of the valley into Juab County. In Juab County, the aqueduct would continue along Interstate 15 (I-15) to Nephi, then skirt around Nephi on the west, and end about 3.5 miles south of Nephi.

    The proposed aqueduct has been sized to deliver SVP water in addition to Bonneville Unit water, which would have several advantages. The High Line Canal, which currently delivers SVP water, needs renovation to improve its reliability and efficiency. Using the proposed aqueduct for SVP deliveries would avoid the costly renovation. Conveying SVP water in a pipeline provides quicker response to water orders. Finally, delivering SVP and Bonneville Unit water from common turnouts would contribute to efficient local water distribution.

    The design capacity of the proposed Main Conveyance Aqueduct through Spanish Fork Canyon would be 510 cfs, the same as the Diamond Fork Pipeline. The rest of the proposed aqueduct was sized using local streamflows as part of the irrigation supply, and using local irrigation wells to provide water in the peak use month of July, thereby minimizing the required capacity of the aqueduct.