We have know this for more than 140 years [0].
I strongly recommend that everyone living in the western United States read at least the introduction[1] to Beyond the Hundredth Meridian[2]. The introduction is more relevant now than it was when it was written 67 years ago, itself 75 years after the publication of Lands of the Arid Region.
Previously:
https://news.ycombinator.com/item?id=27910098
https://news.ycombinator.com/item?id=18098899
https://news.ycombinator.com/item?id=26964166
0. https://pubs.usgs.gov/unnumbered/70039240/report.pdf LANDS OF THE ARID REGION John Wesley Powell 1878
1. https://erenow.net/modern/beyond-the-hundredth-meridian/1.ph... Bernard DeVoto 1954
2. Beyond the Hundredth Meridian: John Wesley Powell and the Second Opening of the West ISBN:9780140159943 Wallace Stegner 1954