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<br />Gunnison River. (That ponion of the Lower Gunnison Basin Unit served by the Uncompahgre <br />Project has been investigated in a separate study.) <br /> <br />Reclamation studied off-farm salinity contributions from saline springs and seepage from unlined <br />canals and laterals. Areas nonh of Delta and southeast of Hotchkiss contribute large amounts of salt. <br />The total off-farm salt contribution from the Nonh Fork area was estimated to be approximately <br />148,000 tons per year. <br /> <br />~ <br />C,n <br />o <br />"-l <br /> <br />Emphasis was placed on identifying and quantifying off-farm sources of salinity and formulating <br />alternative solutions to diminish the salt loading to the river system. Preliminary findings indicated <br />that selective lining of canals and laterals and winter water replacement might be viable; however, a . <br />more detailed study showed the cost of these improvements prohibitive. <br /> <br />Lower Virgin River <br /> <br />This unit is located along the lower Virgin River in nonheastem Clark County, Nevada, and <br />nonhwestem Mohave County, Arizona. The unit includes natural saline springs averaging 2,900 <br />mg/L near Littlefield, Arizona, and 3,500 acres of irrigated land along the Virgin River between the <br />springs and Lake Mead. <br /> <br />Investigations by Reclamation began in 1972 as the Littlefield Springs Unit. The initial approach was <br />to study a series of saline springs along the river at Littlefield Springs near the USGS gauge, "Virgin <br />River at Littlefield, Arizona." The object of that investigation was to determine the best method of <br />collecting and disposing of the water and returning the freshwater to the river or disposing of the . <br />saline water from the springs by evaporation. This project was strenuously opposed locally because <br />the springs are the only reliable water supply for irrigation at Mesquite, Bun.k:erville, and Riverside, <br />Nevada, during the summer. The Littlefield Springs study was, therefore, terminated. <br /> <br />In 1977, another study was started to determine the feasibility of extracting the saline subsurface <br />water flowing under the Virgin River bed downstream of the irrigated area. Information on surface <br />flows indicated that less salt was leaving the area than was entering. It was, therefore, postulated that <br />salt was leaving the reach in underflow. The results of the study found the subsurface water <br />concentration (3,000 mglL) was too low for collection, extraction, and evaporation. A concluding <br />repon was published in November 1981. <br /> <br />In January 1984, Reclamation reinitiated the Lower Virgin River Unit study to determine if a dual <br />purpose water supply and salinity control project would be feasible. Saline underflow of the Virgin <br />River would be intercepted by wells and piped 41 miles to the proposed Harry Allen Powerplant <br />where it would be used for cooling water. The Nevada Power Company proposed to construct the <br />powerplant for a 1997 startup. The I,OOO-megawart powerplant would need a water supply of about <br />14,000 acre-feet per year. In 1987, the investigation was suspended because the schedule for the <br />powerplant construction became uncenain. <br /> <br />In 1991, the Las Vegas Valley Water District and Reclamation began a cost-shared study to evaluate <br />using the Virgin River as a water supply for Las Vegas. The objective of the study was to determine <br />the technical, environmental, and institutional feasibility of a dual purpose salinity control and water <br /> <br />31 <br />