Investigations by Reclamation began in 1972 as the Littlefield Springs Unit.  The initial approach was to study a series of saline springs along the river at Littlefield Springs near the USGS gauge, "Virgin River at Littlefield, Arizona."  The object of that investigation was to determine the best method of collecting and disposing of the water and returning the freshwater to the river or disposing of the saline water from the springs by evaporation.  This project was strenuously opposed locally because the springs are the only reliable water supply for irrigation at Mesquite, Bunkerville, and Riverside, Nevada, during the summer.  The Littlefield Springs study was, therefore, terminated.

In 1977, another study was started to determine the feasibility of extracting the saline subsurface water flowing under the Virgin River bed downstream of the irrigated area.  Information on surface flows indicated that less salt was leaving the area than was entering.  It was, therefore, postulated that salt was leaving the reach in underflow.  The results of the study found the subsurface water concentration (3,000 mg/L) was too low for collection, extraction, and evaporation.  A concluding report was published in November 1981.

In January 1984, Reclamation reinitiated the Lower Virgin River Unit study to determine if a dual purpose water supply and salinity control project would be feasible.  Saline underflow of the Virgin River would be intercepted by wells and piped 41 miles to the proposed Harry Allen Powerplant where it would be used for cooling water.  The Nevada Power Company proposed to construct the powerplant for a 1997 startup.  The 1,000-megawatt powerplant would need a water supply of about 14,000 af/yr.  In 1987, the investigation was suspended because the schedule for the powerplant construction became uncertain. 

In 1991, the Las Vegas Valley Water District and Reclamation began a cost-shared study to evaluate using the Virgin River as a water supply for Las Vegas.  The objective of the study was to determine the technical, environmental, and institutional feasibility of a dual purpose salinity control and water supply project on the lower Virgin River in Nevada.  The study found the proposal was not cost effective. No project was implemented.