Our big wet May looks to have all but eliminated the possibility of a Lower Colorado River Basin shortage in 2016, and it now looks like a better than 50-50 chance we won’t have one in 2017 either, according to the U.S. Bureau of Reclamation’s monthly outlook, published this afternoon (pdf).
A shortage is triggered if Mead drops below a surface elevation of 1,075 feet above sea level on Jan. 1. Details here on the criteria and timing of shortage declaration – it doesn’t happen simply when it hits 1,075, but rather when it starts a new year at 1,075. The latest forecast calls for Mead to be at 1,081.58 on Jan. 1, 2016, and 1,077.59 on Jan. 1, 2017.
There are still big problems, but May’s amazing weather appears to have put them off for a bit. The forecast suggests that, based on current inflows from upstream, Lake Mead is just gonna keep on dropping. They call it the “structural deficit“, a formula that allocates more water to downstream users (California, Nevada, and Arizona) during a “normal” year than flows in from upstream. But “normal” really involves a range of possible inflows, and the big May means some bonus water in Mead over the next 18 months.
Lake Powell is now forecast to end the 2015 with a surface elevation 15 feet higher and 1.3 million acre feet fuller than forecast a month ago, according to the U.S. Bureau of Reclamation’s monthly outlook, published this afternoon (pdf). We’ll have a more detailed probability calculation later this week, but this significantly reduces the chance of a Lower Colorado River