From InkStain (John Fleck):
Lake Powell is ending May with a surface elevation above 3,596 feet above sea level, four feet above the projection when the month began. That’s an extra 400,000 acre feet of water. Lake Mead, less dependent on weather and more dependent on releases from upstream, is nevertheless a foot above its projections, an elevation above 1,076.
The result is a forecast of more than 5 million acre feet of April-July runoff into Lake Powell, up from a forecast of just 3 million acre feet just a month ago. That is still well below the long term mean of just above 7 maf for April through July, but given the slim margins facing water managers right now the bonus water provides a crucial boost.
Before the storms hit, the Bureau of Reclamation forecast showed Lake Powell flirting with a key elevation threshold – elevation 3,575 come Jan. 1. The 2007 reservoir operation guidelines set that as a trigger point that would require water managers to hold more water upstream and reduce deliveries to Lake Mead. That would have meant a lot less water being sent downstream to Lake Mead beginning in October, setting off a cascade of decisions that could have triggered a shortage declaration in the Lower Basin as early as next Jan. 1…
With an extra 4 feet of water in Powell as of today, and more likely because of our “miracle May”, a 2016 shortage is looking far less likely, though we won’t know for sure until the next round of model results come out after the first of the month. My back-of-the-envelope calculations suggest we’re still at risk of a 2017 shortage declaration, but the risk of one in 2016 has dropped dramatically.
More Colorado River Basin coverage here.