California's two largest reservoirs at 'critically low' levels

Los Angeles Mayor Eric Garcetti on Tuesday announced watering restrictions for Los Angeles Department of Water and Power customers amid a deepening drought. 

According to this week's report from the US Drought Monitor, California's two largest reservoirs - Shasta Lake and Lake Oroville - are at "critically low levels" at the point of the year they should be the highest. 

This week, Shasta Lake is only at 40% of its total capacity, the lowest it has ever been at the start of May since record-keeping began in 1977. Further south, Lake Oroville is at 55% of its capacity, which is 70% of where it should be around this time on average.

California depends on storms and wintertime precipitation to build up snowpack in the Sierra Nevada, which then gradually melts during the spring and replenishes reservoirs.

But record dry conditions have strained the system, lowering reservoir levels, and the State Water Project — which gets its water from the Sacramento-San Joaquin River Delta — has estimated it will be capable of delivering only about 5% of its usual allocation, for the second consecutive year.

In Southern California, water district officials announced unprecedented water restrictions last week, demanding businesses and residents in parts of Los Angeles, Ventura and San Bernardino counties to cut outdoor watering to one day a week beginning June 1.

Scientists say this boom-and-bust cycle is driven by climate change that will be marked by longer, more severe droughts. A study from earlier this year found the U.S. West was in the middle of a megadrought that is now the driest in at least 1,200 years.