COLUMBIA--GRAND COULEE DAM (GCDW1)
| Observed | Forecast/Trend Issued: 2026-05-26 16:26 PDT | ||
| Date/Time (PDT) | Pool Height | Date/Time (PDT) | Pool Height |
| 2026-05-27 00:00 | 1268.13 | 2026-05-27 11:00 | 1268.25 |
| 2026-05-26 00:00 | 1267.39 | 2026-05-27 17:00 | 1268.28 |
| 2026-05-25 00:00 | 1266.66 | 2026-05-27 23:00 | 1268.3 |
| 2026-05-24 00:00 | 1265.46 | 2026-05-28 05:00 | 1268.33 |
| 2026-05-23 00:00 | 1264.92 | 2026-05-28 11:00 | 1268.35 |
| 2026-05-22 00:00 | 1264.36 | 2026-05-28 17:00 | 1268.38 |
| 2026-05-21 00:00 | 1263.6 | 2026-05-28 23:00 | 1268.4 |
| 2026-05-20 00:00 | 1262.87 | 2026-05-29 05:00 | 1268.43 |
| 2026-05-19 00:00 | 1262.35 | 2026-05-29 11:00 | 1268.47 |
| 2026-05-18 00:00 | 1261.14 | 2026-05-29 17:00 | 1268.53 |
| 2026-05-17 00:00 | 1259.44 | 2026-05-29 23:00 | 1268.6 |
| 2026-05-30 05:00 | 1268.7 | ||
| 2026-05-30 11:00 | 1268.81 | ||
| 2026-05-30 17:00 | 1268.95 | ||
| 2026-05-30 23:00 | 1269.11 | ||
| 2026-05-31 05:00 | 1269.29 | ||
| 2026-05-31 11:00 | 1269.49 | ||
| 2026-05-31 17:00 | 1269.72 | ||
| 2026-05-31 23:00 | 1269.96 | ||
| 2026-06-01 05:00 | 1270.23 | ||
| 2026-06-01 11:00 | 1270.5 | ||
| 2026-06-01 17:00 | 1270.8 | ||
| 2026-06-01 23:00 | 1271.09 | ||
| 2026-06-02 05:00 | 1271.4 | ||
| 2026-06-02 11:00 | 1271.71 | ||
| 2026-06-02 17:00 | 1272.02 | ||
| 2026-06-02 23:00 | 1272.33 | ||
| 2026-06-03 05:00 | 1272.63 | ||
| 2026-06-03 11:00 | 1272.94 | ||
| 2026-06-03 17:00 | 1273.24 | ||
| 2026-06-03 23:00 | 1273.53 | ||
| 2026-06-04 05:00 | 1273.82 | ||
| 2026-06-04 11:00 | 1274.1 | ||
| 2026-06-04 17:00 | 1274.37 | ||
| 2026-06-04 23:00 | 1274.64 | ||
| 2026-06-05 05:00 | 1274.9 | ||