At the 7 p.m. Pacific Time reading this evening, the surface elevation of Lake Mead dropped to 1080.18 feet above sea level, surpassing the previous low set last August to mark the lowest the big Colorado River Reservoir has been since it was filled in the 1930s:
The record came as Hoover Dam’s operators ramped up water releases to meet Saturday evening power demands. Current projections call for Mead to continue dropping through June, as continued downstream demand in Arizona, California and Nevada outpace upstream inflows.
It is again worth noting that this is in large part a demand-driving decline in Lake Mead. Water deliveries from the Colorado River’s Upper Basin are meeting that basin’s legal requirements, and in fact this year are projected to be above the minimum legal requirement. But the Lower Basin states have still not come to grips with what has been called a “structural deficit” – higher legal entitlements to water than the river system can provide under these circumstances. That has left the Lower Basin dependent on wet year surpluses. With the drought, those surpluses have evaporated, and 1080.18 is the result.
The previous record was set last August, which broke a record set in 2010. In other words, the reservoir keeps stair-stepping down, what you’d expect from a system in which water use exceeds supply.
There is an argument to be made that an empty Lake Mead is, in fact, the reservoir being used precisely for the purpose for it was built: storage in wet years, for use in dry years (now). The question now is one of risk tolerance: how much more risk are downstream water users willing to tolerate as Mead drops further, and what if any additional steps need be taken to protect the Lower Basin’s “junior users” – those whose water rights will be curtailed (particularly Arizona’s – here are the basics of what happens there should Mead continue to drop) should the lack of surpluses continue.