From the US Bureau of Reclamation’s April 24-month Colorado River operations plan (pdf):

The April 24-Month Study with an annual release volume from Glen Canyon Dam of 8.23 maf projects a Lake Powell end of water year elevation of 3,662.63 feet. Based on this projected condition and consistent with the provision in Section 6.B.3 of the Interim Guidelines, a shift in Glen Canyon Dam operations to being governed by the Equalization Tier will occur for the remainder of water year 2011. The April 24-Month Study projects a Lake Powell annual release volume of 11.56 maf; however, the projected annual release will be updated each month throughout the remainder of the water year to reflect changing hydrology in order to achieve the operation specified by the Equalization Tier.

Translated: extra water transferred from the Colorado River’s Upper Basin to the Lower Basin this year, a result of a good snowpack in the Rockies. The current forecast calls for Lake Mead to finish the year 21 feet above last year’s elevation.