Supply Driven — best recovery potential
Releases follow the 3-year rolling average of natural flow. Highest median ending elevation — but a floor that can bite in back-to-back dry years.
Supply Driven is the simplest of the DEIS plans, and in some ways the most honest. The rule is: release 65% of the 3-year rolling average natural inflow, with a 4.7 MAF/yr floor and a 12 MAF/yr ceiling. In good years the lake lets out more. In dry years it lets out less. This mimics how wild rivers behave — supply-driven, not demand-driven.
Lake Powell elevation under the driest decade on record. The median line shows the most likely path. The worst-10% line shows the bottom 10% of bad-luck futures.
The scorecard
We tested this plan the same way we test every plan. We used inflows from the last ten years — the driest decade on record. We ran 2,000 Monte Carlo trials for 40 years. The starting point and inflows stay the same. Only the operating rule changes.
| Year mark | Median ending | Worst 10% floor | Grade |
|---|---|---|---|
| 10 years | 3629.7 ft | 3435.7 ft | B |
| 20 years | 3668 ft | 3434.4 ft | A |
| 40 years | 3677.6 ft | 3432.8 ft | A |
Strengths
- Highest 40-year median ending elevation of any plan we tested (3,678 ft). In normal-to-good years, the lake recovers strongly.
- Simple rule. Easier to explain, check, and defend than multi-tier or two-signal plans.
- Follows the actual supply. In dry decades it tightens releases on its own. In wet decades it lets the system breathe.
Weaknesses
- The 4.7 MAF/yr minimum release floor can force water out of Powell in back-to-back dry years when releases should arguably be lower. This drags the worst 10% floor down to 3,433 ft — well below the 3,490 ft minimum power pool.
- The 4.7 MAF floor is a political promise to Lower Basin users, not a water-science need. It is the reason this plan only earns a B at 10 years.
- Releases swing a lot from year to year. Downstream users have to plan around changing deliveries, which has its own costs.
Verdict
Supply Driven is one of our two top picks, along with Max Operational Flexibility. SD wins on recovery: the highest median elevation at every long year mark, with bad-luck endings that still land above MOF's. In plain terms, this is the plan that actually fills the lake back up. The tradeoff is downside exposure — the 4.7 MAF/yr release floor forces water out in back-to-back dry years, which drags the worst-case floor below minimum power pool. Back this one if you want the lake to fill back up; back Max Operational Flexibility if worst-case protection is your top priority. If both are blocked, Enhanced Coordination is the safe fallback.
See all plans side by side in the head-to-head verdict, or read about why the real problem isn't drought — it's math.