[Arragonis]

From Wikipedia

Lake Mead's water level has three times fallen below the drought level (1125 feet above sea level).[4] From 1953 to 1956, the water level fell from 1,200 to 1,085 feet (370 to 331 m). From 1963 to 1965, the water level fell from 1,205 to 1,090 feet (367 to 330 m). Since 2000 through 2008, the water level has dropped from 1215 to 1095. In 2009 the water level rose slightly, but only due to cool winter temperature and rainfall.

In June of 2010, the lake was at 39 percent of its capacity,[5] and on October 17, 2010, it reached 1,083 ft (330 m), setting a new record low.[6] Arrangements are underway to pipe water from elsewhere in Nevada by 2011, but since the primary raw water intake at Lake Mead could become inoperable as soon as 2010 based on current drought and user projections, Las Vegas could suffer crippling water shortages in the interim.[7] Lake Mead draws a majority of its water from snow melt in the Colorado, Wyoming, and Utah Rocky Mountains. Since 2000 the water level has been dropping at a fairly steady rate due to less than average snowfall. As a result, marinas and boat launch ramps have either needed to be moved to another part of the lake or have closed down completely. The Las Vegas Bay Marina and the Lake Mead Marinas were relocated a few years ago to Hemenway Harbor. Overton Marina has been closed due to low levels in the northern part of the Overton Arm. Government Wash, Las Vegas Bay, and Pearce Ferry boat launch ramps have also been closed. The marinas that remain open include Las Vegas Boat Harbor and Lake Mead Marina all sharing Hemenway Harbor/Horsepower Cove, Callville Bay Marina, Echo Bay Marina, and Temple Bar Marina, along with the Boulder Launch Area (former location of the Lake Mead Marina) and the South Cove launch ramp.[8]

Changing rainfall patterns, natural climate variability, high levels of evaporation, reduced snow melt runoff, and current water use patterns are putting pressure on water management resources at Lake Mead as the population depending on it for water and the Hoover Dam for electricity booms. A 2008 paper in Water Resources Research states that at current usage allocation and projected climate trends, there is a 50% chance that live storage in lakes Mead and Powell will be gone by 2021, and that the reservoir could drop below minimum power pool elevation of 1,050 feet (320 m) as early as 2017.[9][10][11] But, Terry Fulp, manager of the federal bureau office for the lower Colorado, disagreed with the paper, saying that global climate models were not sensitive or refined enough to forecast such effects.

So maybe its natual cycles, maybe its usage from a growing population, maybe its something not fully understood. And hasn't there just been a massive dose of rain in that area from a storm whcih stretched across a large part of the Pacific ?