Bonneville Dam & Lake on Columbia River

September 2026

Day of Month	Inflow kcfs	Total Outflow kcfs	Generation Flow kcfs	Spill kcfs	Midnight Reservoir Elevation	Average Forebay Elevation	Average Tailwater Elevation	Average Head feet	Project Average Tailwater	2nd Powerhouse Flow kcfs
1	86.30	90.30	75.20	2.80	75.60	75.70	9.30	66.40	9.20	72.70
2	92.10	88.10	73.30	2.40	76.00	75.80	9.10	66.70	9.00	61.00
3	89.70	86.70	72.00	2.30	76.40	76.00	8.90	67.10	8.80	53.50
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TOT
AVG	89.37	88.37	73.50	2.50	76.00	75.83	9.10	66.73	9.00	62.40

MAX	92.10	90.30	75.20	2.80	76.40	76.00	9.30	67.10	9.20	72.70
MIN	86.30	86.70	72.00	2.30	75.60	75.70	8.90	66.40	8.80	53.50