Section 301(b) of the Colorado River Basin Project Act (43 U.S.C. 1521(b)U.S. Code — Title 43, Section 1521(b)View official source on GovInfo) is amended to read as follows: (b) In times of shortage or reduction of main stream Colorado River water for the Central Arizona Project, as determined by the Secretary, all diversions from the Colorado River for consumptive use by the States of Arizona, California, and Nevada shall be reduced on a pro-rata basis relative to their base annual apportionments, without preference to present perfected rights..