The U.S. Bureau of Reclamation’s key August forecast, out today (pdf),projects that there will be enough water in the Colorado River system next year to release a bonus pulse of 770,000 acre feet of water from Lake Powell down to lake Mead above and beyond the legal requirements of the Colorado River Compact. But even with that extra water, Lake Mead is projected to fall another five feet during 2015, flirting with levels that could trigger the Lower Colorado River Basin’s first formal shortage declaration in 2016.

How could this be? The Lower Basin is getting extra water above and beyond its minimum legal entitlement, yet Lake Mead keeps dropping?

It’s simple, really. The U.S. Supreme Court’s 1963 Arizona v. California decision effectively allocates more paper water than there is wet water in the system, (click here for the wonky explanation of the mistake, and the fact that folks kinda knew at the time it was a mistake but ignored it) and as long as each of the Lower Basin states keeps using its full entitlement, Mead will keep dropping unless a giant climatic wet spell delivers magic extra water.

See also “hookers and blow on the lower Colorado“.