What it means
In Arizona, “Tier 1” is not a ranking. It is the first level of shortage on the Colorado River, declared by the federal government when Lake Mead, the reservoir behind Hoover Dam, is projected to sit too low. Each tier means a bigger cut to the water Arizona takes from the river, and that water reaches Scottsdale through the CAP canal. “We’re in Tier 1 again” is how locals say the river is still short; “Tier 2” is how they say it got worse.
For Scottsdale the stakes are high because the river is its biggest source. About two-thirds of the city’s drinking water is Colorado River water, as the Scottsdale Water guide explains. So far the city’s own supply has been protected, because the CAP’s priority system pushes the first cuts onto farms in Pinal County. But the tiers drive the city’s drought planning, and in 2023 they set off the most controversial water decision in its history.
Where you’ll meet it
In headlines every August, when the next year’s tier is announced; in the city’s drought and water-supply pages; in the Arizona water law guide; at the Xeriscape Garden, where the response is planted; and in every story about Rio Verde Foothills.
Where the words came from
The vocabulary is federal. In 2007 the seven Colorado River states and the Interior Department adopted interim guidelines for sharing shortages on Lake Mead, with cuts that grow as the lake falls past set elevations. The first trigger is 1,075 feet, the projected level on January 1 of the coming year; below that comes Tier 1. Lower thresholds bring Tier 2 (split into 2a and 2b) and Tier 3. In 2019 the lower-basin states added the Drought Contingency Plan, which made the cuts deeper and earlier; Arizona’s version was finalized in February 2019 by a steering committee of about 40 water professionals.
For a decade the tiers were theory. Then, in August 2021, the Bureau of Reclamation declared the river’s first-ever shortage, a Tier 1 for 2022. Arizona lost 512,000 acre-feet, about 30 percent of the CAP’s normal supply. The next August brought Tier 2a for 2023, a cut of 592,000 acre-feet. Conditions eased back to Tier 1 for 2024, 2025 and 2026, but the state has not left shortage since it entered.
The acre-foot entry translates those numbers: 512,000 acre-feet is roughly 167 billion gallons, or a year’s water for about 1.5 million Valley households.
What it is not
A Colorado River tier is not a Scottsdale drought stage. The tier is a federal cut to Arizona; the stage is the city’s response. And neither is the same as the local weather: the river’s problem is snow in the Rockies, not rain in Scottsdale.
The fine print
Scottsdale’s Drought Management Plan, updated in spring 2021, has four stages, each more restrictive. The city declared Stage 1 in 2022, in step with the first federal shortage. One Stage 1 provision ended sales of hauled water to customers outside the city, and on January 1, 2023, that cut off the water haulers serving Rio Verde Foothills, an unincorporated community next door. A 2023 state law and a station run by EPCOR, opened January 1, 2026, restored a supply; the unincorporated county guide covers how the community is governed.
The lake itself has not recovered. The city put Lake Mead at about 1,039 feet in August 2026, close to the record low of 1,040.58 feet set on July 28, 2022. For 2026 the city says Tier 1 does not reduce its municipal supply.
The bigger question is the rulebook. The 2007 guidelines and the Drought Contingency Plan expire on December 31, 2026. The Bureau of Reclamation issued a draft environmental impact statement on January 9, 2026; Arizona, California and Nevada submitted a joint short-term proposal on May 1; and the final environmental impact statement came out in July 2026. The new rules begin in 2027. How deep they cut Arizona, and whether municipal water like Scottsdale’s stays protected, is the Valley’s largest unanswered water question.