A longtime water conservation advocate says Arizona and the other Lower Colorado River Basin states need to cut their water use more and faster.

Sustainable Waters president Brian Richter says Arizona, California, and Nevada need to slash total water use by 18% from their 2000-2018 average to bring Lakes Mead and Powell into a long-term state of balance, the Arizona Daily Star reports. He says the decrease would push the river’s falling reservoirs into sustainability.