A trade deal is brewing between major southern California water agencies to help restock a major reservoir on the drought-stricken Colorado River and meet federal demands to cut back use.

San Diego, Los Angeles and Imperial Valley are the major players trying something that’s never been done before using a water trading agreement inked 20 years ago as a guiding light. Under the proposal, San Diego is going to give up some of its Colorado River water it fought so hard to secure so more can be saved in the larger river system. But instead, it would lean on supplies from northern California, a source that was virtually unavailable to the region due to drought just last year.