That long, painful drip-drip-drip of “when will we have Lower Colorado River shortage?” has been pushed out again, with a new set of modeling runs from the U.S. Bureau of Reclamation putting the odds at one in five in 2017 and 50-50 by 2018.
Hidden in that “one in five” next year is some good news. Things would be substantially worse (maybe a one in three chance of 2017 shortage) but for some conservation actions by the Central Arizona Water Conservation District (the agency that runs the Central Arizona Project) and the Southern Nevada Water Authority (Las Vegas) that have the effect of leaving significant water in Lake Mead over the next year. Without those steps, the chances of shortage in 2017 would be substantially higher, according to the Bureau’s modeling team. This is good news, showing that the various system conservation efforts are beginning to have measurable impact. Here’s the full table of modeling results:
There’s another important caveat. The water conservation efforts modeled here only include those Arizona and Nevada water managers were sure enough about to include in their preliminary 2016 water use planning orders. There are more conservation efforts afoot that could further prop up Lake Mead, reducing the chance of shortfall. The scenarios here are conservative. But you also can see that under the current scenarios, the underlying risk remains – water use downstream of the big Colorado River reservoir remains higher than inflows. The system remains out of balance.
What does “Colorado River shortage” mean?
For details on what happens in “shortage”, see here. Basically, Arizona absorbs the major hit which will for some time bite primarily at the Central Arizona ag sector.
For some historical context, I’ve cleaned up my regular Mead-Powell historical storage graphic. Total storage in the two big Colorado River reservoirs will end the 2015 “water year” (the end September) at a historic low, lower than at any time since they began filling Powell in the 1960s:
But what are the chances of flooding?
If you really want to feel optimistic, look at the second to the last row. It shows a one in 50 chance that by 2019 we’ll have the reservoirs full enough for “Surplus – Flood Control”. That would be really bad for sales of my upcoming book, but maybe a second volume focused on flood control ops?