California uses it's allocation. For a while when there was too much water in the Colorado more was released to California from Lake Mead - this was pre-drought. California and Colorado receive an equal allocation, the balance is distributed between the other States with Nevada getting the least amount of allocation. They've resolved some of this by cleaning hotel water and putting it back into Lake Mead so they get a in and out count [so to speak]. Things worked pretty well til the drought - and don't forget the population has shifted - as millions move out of California to Colorado, Utah, Arizona, etc. the population in California keeps increasing .... may soon increase a LOT more... When we have a flush - that isn't extra water going downstream.
What it really is - is water being sent around the energy-producing turbines of Glen Canyon Dam. This results in smaller releases during the rest of the water year.
A lot of people get confused because we have two separate water years. Glen Canyon water year ends September 30th, Lake Mead doesn't end until December 31st. So you cannot look at them as apples and apples when looking at current data.
Lake Mead is in trouble for many reasons - not the least of which is the drought. The runoff into Mead from the Virgin and other rivers has been down significantly.
People need to remember not all water into Lake Powell comes from the Colorado River - people who say California is stealing our water never take into consideration we have rivers below the Glen Canyon dam feeding into the Colorado below Glen Canyon and into Lake Mead and we have rivers feeding into Lake Mead..
They also ignore in addition to the water sent to Arizona, Nevada and California from Mead we are obligated by international treaty to send 1.5 to Mexico. We've been able to hold some back from Mexico for a variety of reasons, but if they put a call on their water owed we have to send it to them.