From the Getches-Wilkinson Center (Lawrence J. MacDonnell and Anne J. Castle). Click through and read the whole paper. Here’s an excerpt:
To achieve the intended benefit to the Colorado River System, the Upper Basin, and the State of Colorado in particular, the Compact security water must actually make its way to Lake Powell. That is, the water must be moved from its existing place of use or storage and reach Lake Powell when necessary without being diminished by other water users. Absent relatively specialized circumstances, most conserved consumptive use water will require some form of administrative “shepherding” to reach the state line and Lake Powell. Water shepherding here refers to the delivery of a specified volume of conserved consumptive use water from its original place of storage or use to a downstream location without diminishment by other users.
A recent report on Alternative Transfer Methods (ATMs) addresses the issue of Colorado River Compact security and concludes that the ability to shepherd conserved or changed water to Lake Powell is essential. This report reflects the consensus opinion of many knowledgeable water users in Colorado. But existing water law in the Upper Basin states, including in Colorado, presents challenges for protecting Compact security water from diversion and use by others.
This paper explains the basis for the concern about storage levels in Lake Powell and, focusing on Colorado, discusses some of the legal and policy issues involved with moving Compact security water to the reservoir. It offers recommendations for revisions to Colorado law. It considers interstate issues and the management of Compact security water once it reaches Lake Powell. The Technical Appendix provides a more comprehensive discussion of the legal and policy issues.