A profound reduction in the Colorado River water earmarked for Arizona’s crops has at last triggered the rationing that irrigation farmers have dreaded. The Tier 1 shortage will prompt a 512,000-acre-foot reduction in Arizona’s Colorado River deliveries.

That amounts to about 30% of Central Arizona Project’s normal supply. Extrapolating from University of Arizona studies, it will result in a decrease of about $100 million in farmgate sales, and much more if the indirect effects are fully factored in.