Water shortage declarations on the Colorado River trigger mandatory water delivery reductions to Lower Basin states (Arizona, Nevada, California) and Mexico. The severity of cuts depends on Lake Mead elevation levels.

Shortage Tiers

• Tier 1 (below 1,075 ft): Arizona loses 512,000 acre-feet, Nevada loses 21,000 acre-feet, Mexico loses 80,000 acre-feet annually.
• Tier 2 (below 1,050 ft): Deeper cuts - Arizona loses 592,000 acre-feet, Nevada loses 25,000 acre-feet, Mexico loses 104,000 acre-feet.
• Tier 3 (below 1,025 ft): Most severe - Arizona loses 720,000 acre-feet, Nevada loses 30,000 acre-feet, Mexico loses 150,000 acre-feet.

These reductions primarily affect agricultural users, though municipal supplies may be impacted during severe shortages. California, which holds senior water rights, is protected from cuts until more extreme conditions occur.