WY2026 Risk Explorer
Adjust the April–July inflow scenario and release policy. Watch the Powell elevation trajectory and breach probability update in real time.
Fan chart trajectories shown at most-probable inflow. P(breach) is directly simulated for AOP × all scenarios and all policies × most-probable; other combinations are estimated via hazard-ratio scaling.
Policy Comparison — Most-Probable Inflow
Rows show each release policy at the same (most-probable) inflow. Delivery and breach probabilities shown; delta is from AOP baseline.
| Policy | P(Breach) — MP | Delivery (KAF/yr) | Delivery Δ vs. AOP | Powell P50 Sep 30 (ft) |
|---|---|---|---|---|
| Current AOP | 44.2% | 4,350 | — | 3,491.6 |
| Conserve When Low | 18.9% | 4,161 | −189 KAF (−4.3%) | 3,495.2 |
| Threshold Adaptive | 3.6% | 4,041 | −309 KAF (−7.1%) | 3,499.0 |
How to Read This
The shaded bands show the distribution of modeled outcomes across 200 Monte Carlo draws. The P10 line means 10% of model runs fell below that elevation — a bad-luck year. The P90 line means 90% of runs fell below it. The P50 (median) is the solid teal line: half the draws are above and half below. Wide bands mean high uncertainty; narrow bands mean the outcome is more tightly constrained.
Glen Canyon Dam (Powell) loses hydropower generation capacity when reservoir elevation falls below 3,490 ft. Below that level, turbines cannot produce power for the grid. Hoover Dam (Mead) faces an analogous threshold at 1,050 ft. Power pool breach does not mean dam failure — it means the roughly 4,000 MW of combined hydro capacity becomes unavailable to the regional grid, forcing expensive thermal substitution.
The three inflow scenarios span the realistic envelope for April–July unregulated inflow to Powell. Optimistic reflects wet La Niña or above-normal snowpack years (similar to 2023). Most Probable reflects the BOR March 2026 median forecast. Pessimistic reflects dry years at or below the 10th historical percentile. Because inflow enters as a stochastic process with uncertainty, the fan chart widens over time under all scenarios.
The fan chart trajectories update to reflect the selected release policy at most-probable inflow. The P(breach) statistic is adjusted for the selected inflow scenario using a hazard-ratio scaling (pre-computed from the full 200×3 simulation). When a non-AOP policy and non-MP scenario are both selected, P(breach) combines both adjustments multiplicatively — but this combined value is an estimate, not a directly simulated result. Only the AOP policy × each scenario and all policies × most-probable scenario were explicitly simulated; all other combinations are interpolated. The trajectory itself remains at most-probable inflow in those cases — indicated by the banner above the chart.