The practical implications for the entire basin of continued overuse in the Lower Basin are real and significant. If Lake Mead drops below 1,025`, the 2007 Interim Guidelines require re-consultation.
From a compact perspective, there is virtually no chance that the Lower Division states or the Interior Secretary could use the 1922 Compact to require a cutback or curtailment of uses in the Upper Basin because of overuse in the Lower Basin. The more likely scenario is that to prevent Lake Mead from dropping below 1,000`, current water users in the Lower Basin would have to conserve or save additional water beyond the 500,000 acre foot cutback required by the Interim Guidelines.
It is possible that the Upper Division states would be asked to provide additional stored water that would be considered “surplus,” but even this option should only be considered as a “last resort.”
Additionally, if (perhaps when) Lake Mead approaches 1,000`, there will be great political pressure for expanded water marketing. Traditionally, the Basin States and water agencies have adamantly opposed efforts to market water between the upper and lower basins.
The best certainty for all users on the Colorado River system is full reservoirs. One method the Basin’s municipalities could use to maintain storage in system reservoirs would be to acquire large amounts of agricultural lands and retiring or changing crops on these lands to reduce water use. But such transfers of water use, even temporarily, would have dramatic impacts on the economy, land use and lifestyles of the basin.
“Flexible water sharing reduces risk in dry times” by Jon Stavney
Basinwide Drought Planning by Eric Kuhn