From InkStain (John Fleck):
One of the innovations in the 2007 shortage sharing agreement among the federal government and the seven basin states was the creation of “Intentionally Created Surplus” water management widget, a tool to free Lower Colorado River Basin water users from the tyranny of “use it or lose it”. Its purpose, according to the decision document that created it (pdf), was to “minimize the likelihood and severity of potential future shortages” by allowing water users to bank unused water in Lake Mead:
ICS may be created through projects that create water system efficiency or extraordinary conservation or tributary conservation or the importation of nonColorado River System water into the Mainstream. ICS is consistent with the concept that entities may take actions to augment storage of water in the lower Colorado River Basin.
The 2007 agreement anticipated use of things like fallowing, desalination and canal lining to create ICS credits.
One of the big ICS users has been the Metropolitan Water District of Southern California, which by the end of 2012 had banked 489,389 acre feet of ICS credits in Lake Mead. But with drought hitting California and Met in a big way, in 2013 the agency began taking its banked water out, withdrawing 93,858 acre feet in 2013 and another 331,965 of ICS water in 2014.
This is a smart water management tool, allowing MWD to build some resilience by saving water now in order to consume it later. But it offers zero overall net basin water conservation over longer time frames – water conserved in one year is simply used in a later year. ICS simply moves water in time. That 331,965 acre feet Met took out last year above and beyond its normal allocation is five feet of elevation it put in in previous years and withdrew in 2014.
ICS is a cool tool, but the only thing that will keep Lake Mead from dropping is a new class of policy tool that would allow conserved water to stay in the reservoir for good.
More 2007 Shortage Sharing Agreement coverage here.