When the U.S. Bureau of Reclamation announced last month that the country’s largest reservoir, Lake Mead, had fallen to its lowest-ever level at 1,074ft (327m), the question many asked was: How will it affect one of California’s primary drinking sources?

After all, some 19 million Californians, nearly half the state’s population, receive some part of their water from the Colorado River, which flows into the 80-year-old reservoir created by Hoover Dam outside Las Vegas.