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. ~ . In'" ..... I:! """ COLORADO RIVER SALINITY CONTROL PROGRAM (continued) The EPA has collected ground water and soil samples in the Lower Las Vegas Valley for a survey of potential hszardous wastes. The magnitude and type of materials in the Las Vegas Wash ground water may influence both the planning and design of salinity and nutrient control features. Evaporation ponds may require more stringent lining requirements if they are expected to concentrate hazardous materials. A report of the findings of the ground water investigations would be provided in a status report that is scheduled for completion in July 1981. The recommended comprehensive water and aolute management plan may be developed in 1981 and provide the basis for a salinity control definite plan report in mid-1982. B. Projects Authorized for Planning Section 203(a)(1) of Public Law 93-320 authorized and directed the Secretary of the Interior to expedite completion of the planning reports on units described in the Secretary's report, "Colorado River Water Quality Improvement Program, February 1972," Section 203(b) (2) and directs the Secretary to undertake research on additional methods of accomplishing the objective of this title, (Title 11 of Public Law 93-320). There are three categories of projects listed under Section 203, (1) irrigation source control, (2) point source control, and (3) diffuse source control. The schedule of reports for projects authorized for investigation is shown on Figure 4. The investigative program for each project is reviewed periodically to accelerate the completion of the reports. A brief description and status of the listed projects follows: 1. Irrigation Source Control Projects Under the Colorado River Water Quality Improvement Program msjor program emphasis for control of irrigation sources is placed on improved irrigation management through an IMS program and improved control of water flow in canals, laterals, and drainage systems through a Water Systems Improvements (WSI) program. Basically, the IMS program is a nonstructural management technique for increasing irrigation water efficiency and reduc- ing salt loading. This is a demonstration-type program based on the concept that the water uaer will take over and operate the program. Under requirements in provisions of Public Law 92-500, this practice is expected to spread to other irrigated areas in the basin. Benefits expected to be derived from IMS irrigation scheduling include increased yields, labor savings, reduced leaching of soi Is, and reduced drainage requirements. The WSI program, on the other hand, involves a structural water man- agement tool for improving water delivery conveyances and, thus, reducing seepage and salinity pickup. The lining of canals and laterals would result in decreased deep percolation losses, thus reducing water contact with highly saline soils, shales, and saline ground waters. 71