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W "-l ~ ~v Irrigation source control would reduce salt loading by improving irrigation practic~s that currently leach salt from marine shales and other saline deposits. The Grand Valley, Lower Gunnison Basin, and McElmo Creek Units in Colotado; the Uinta Basin Unit in Utah; and the Palo Verde Irrigation District Unit in California are irrigation sources under evaluation. Improve~ent of irrigation practices in all of these areas appears viable and couJd reduce the river's salt load by about 1.0 million tons per year. Point source control would remove salt from localized areas such as mineral springs, abandoned oil wells, and geysers. The Paradox Valley, Glenwood- Dotsero, Springs, and Meeker Dome Units in Colorado; LaVerkin Springs and Crystal: Geyser in Utah; Lower Virgin River Unit in Arizona and Nevada; and the Las' Vegas Wash Unit in Nevada are point sources. Currently, a viable control, plan is available only for the Paradox Valley Unit, having the potential to prevent 180,000 tons per year from entering the river system. Diffuse source control would involve watershed management, 1 and treatment, and the' collection and disposal of irrigation return flows. Utah's Dirty Devil and Price-San Rafael Rivers Units and Wyoming's Big Sandy River Unit are identified diffuse sources. Investigations of diffuse source units are underwav which are examining a combination of irrigation improvements, vegetati on and watershed management, and select i ve withdrawal and di sposa 1 of poor' quality streamflow. Assuming that all agriculture source units are successfully implemented, diffuse and point source control units would heed to redu~e the river's salt load by an additional 1.8 million tons per year. In summpry, the CRWQIP goal is to maintain Lower Colorado River salinity levels at or below 1972 historical levels while the Basin States continue to deveJop their compact-apportioned waters. To attain this goal, an estimat~d 2.8 million tons of salt annually must be intercepted before entering the river system by around the turn of the century (1.2 million tons iS'expected to be removed by the Paradox Valley Unit, a point source, and remaining agricultural source units. Alternatives suggested for salinity control in the Colorado River Basin include' (1) augmentation of the Basin water supply, (2) reduction of salt loads by structural measures as well as management alternatives, and (3) curtailment of future water resource development. The feasibility and des i rabi 1 ity of these three sa 1 i nity control a lternat ives are infl uenced by the costs of such actions; e.g., the relative justification from a cost- effectiveness viewpoint, the recognition of compact-apportioned State water rights, and the political and institutional forces surrounding each alter- native. It is recognized that more than economic impacts result from changing salinity, such as fish and wildlife, recreation, and environmental impacts;. While recognizing that many other effects of salinity do exist, the overriding concern addressed here deals with countering pOSSible monetary effects upon direct users of Colorado River water. Potential damages or total penalty costs from adverse salinity conditions can be defined as the sum of direct penalty costs incurred by water users and indirect penalty costs imposed on the economy of the region. IV-5