COLUMBIA--GRAND COULEE DAM (GCDW1)
| Observed | Forecast/Trend Issued: 2026-09-22 08:03 PDT | ||
| Date/Time (PDT) | Pool Height | Date/Time (PDT) | Pool Height |
| 2026-09-23 00:00 | 1284.08 | 2026-09-23 05:00 | 1284.24 |
| 2026-09-22 00:00 | 1283.63 | 2026-09-23 11:00 | 1284.33 |
| 2026-09-21 00:00 | 1283.33 | 2026-09-23 17:00 | 1284.44 |
| 2026-09-20 00:00 | 1283.11 | 2026-09-23 23:00 | 1284.55 |
| 2026-09-19 00:00 | 1282.65 | 2026-09-24 05:00 | 1284.64 |
| 2026-09-18 00:00 | 1282.26 | 2026-09-24 11:00 | 1284.72 |
| 2026-09-17 00:00 | 1281.94 | 2026-09-24 17:00 | 1284.8 |
| 2026-09-16 00:00 | 1280.43 | 2026-09-24 23:00 | 1284.88 |
| 2026-09-15 00:00 | 1280.74 | 2026-09-25 05:00 | 1284.96 |
| 2026-09-14 00:00 | 1280.33 | 2026-09-25 11:00 | 1285.03 |
| 2026-09-13 00:00 | 1279.96 | 2026-09-25 17:00 | 1285.11 |
| 2026-09-25 23:00 | 1285.18 | ||
| 2026-09-26 05:00 | 1285.24 | ||
| 2026-09-26 11:00 | 1285.3 | ||
| 2026-09-26 17:00 | 1285.35 | ||
| 2026-09-26 23:00 | 1285.4 | ||
| 2026-09-27 05:00 | 1285.44 | ||
| 2026-09-27 11:00 | 1285.47 | ||
| 2026-09-27 17:00 | 1285.5 | ||
| 2026-09-27 23:00 | 1285.53 | ||
| 2026-09-28 05:00 | 1285.58 | ||
| 2026-09-28 11:00 | 1285.65 | ||
| 2026-09-28 17:00 | 1285.73 | ||
| 2026-09-28 23:00 | 1285.8 | ||
| 2026-09-29 05:00 | 1285.86 | ||
| 2026-09-29 11:00 | 1285.93 | ||
| 2026-09-29 17:00 | 1285.98 | ||
| 2026-09-29 23:00 | 1285.98 | ||
| 2026-09-30 05:00 | 1285.99 | ||
| 2026-09-30 11:00 | 1285.99 | ||
| 2026-09-30 17:00 | 1286 | ||
| 2026-09-30 23:00 | 1286 | ||
| 2026-10-01 05:00 | 1286.02 | ||
| 2026-10-01 11:00 | 1286.03 | ||
| 2026-10-01 17:00 | 1286.05 | ||
| 2026-10-01 23:00 | 1286.07 | ||
| 2026-10-02 05:00 | 1286.08 | ||