The Bureau of Reclamation’s monthly forecast, out this morning (pdf), contains some very good news for Lake Mead and its water users in California, Nevada, and Arizona. But there is a huge caveat.
the good news
As it stood in early March, the snowpack in the Rockies was enough to send a big slug of extra water into Lake Powell during the spring-summer runoff. That would push Powell high enough to send a big slug of bonus water downstream, the result of operating rules intended to try to keep the reservoirs roughly in balance. If the forecast holds, Mead would rise 27 feet this year.
the huge caveat
Note those weasel words – “if the forecast holds”. It probably won’t. The Upper Basin’s version of the report (pdf) includes these words in big bold type:
It should be noted that since the March final forecast was issued on March 2, 2017, the Colorado Basin River Forecast Center Ensemble Streamflow Prediction indicates a decrease in the forecasted inflow. It is unlikely that the March final forecasted inflow will be sustained in the April final forecast. The April 24-Month Study projections are used to determine whether there is an adjustment to equalization or balancing under the Interim Guidelines governing Lake Powell releases for the remainder of water year 2017.
It’s not the March forecast that matters, it’s the April one. So the dry spring is taking a bite out of Lake Mead’s hope.