It’s a great unit for dealing with lots of water though. Talk x billion gallons vs xxx million gallons and people glaze over. A m3 is too small, but the entire Colorado compact is only like 17 km3. The analogous km2-meter might work, but it’s still huge.

The acre-foot is a nice manageable size. Plus if you know you’ve got 160 acres planted, and you need 6 in of water over everything, it’s pretty easy figure the volume to request