COLUMBIA--GRAND COULEE DAM (GCDW1)
| Observed | Forecast/Trend Issued: 2026-05-17 09:05 PDT | ||
| Date/Time (PDT) | Pool Height | Date/Time (PDT) | Pool Height |
| 2026-05-17 00:00 | 1259.44 | 2026-05-18 05:00 | 1261.59 |
| 2026-05-16 00:00 | 1258.22 | 2026-05-18 11:00 | 1261.81 |
| 2026-05-15 00:00 | 1257.07 | 2026-05-18 17:00 | 1262.02 |
| 2026-05-14 00:00 | 1256.2 | 2026-05-18 23:00 | 1262.22 |
| 2026-05-13 00:00 | 1255.67 | 2026-05-19 05:00 | 1262.42 |
| 2026-05-12 00:00 | 1255.45 | 2026-05-19 11:00 | 1262.62 |
| 2026-05-11 00:00 | 1254.87 | 2026-05-19 17:00 | 1262.82 |
| 2026-05-10 00:00 | 1254.48 | 2026-05-19 23:00 | 1263.01 |
| 2026-05-09 00:00 | 1253.96 | 2026-05-20 05:00 | 1263.2 |
| 2026-05-08 00:00 | 1253.15 | 2026-05-20 11:00 | 1263.38 |
| 2026-05-07 00:00 | 1251.77 | 2026-05-20 17:00 | 1263.57 |
| 2026-05-20 23:00 | 1263.75 | ||
| 2026-05-21 05:00 | 1263.93 | ||
| 2026-05-21 11:00 | 1264.1 | ||
| 2026-05-21 17:00 | 1264.27 | ||
| 2026-05-21 23:00 | 1264.44 | ||
| 2026-05-22 05:00 | 1264.61 | ||
| 2026-05-22 11:00 | 1264.77 | ||
| 2026-05-22 17:00 | 1264.93 | ||
| 2026-05-22 23:00 | 1265.08 | ||
| 2026-05-23 05:00 | 1265.23 | ||
| 2026-05-23 11:00 | 1265.38 | ||
| 2026-05-23 17:00 | 1265.52 | ||
| 2026-05-23 23:00 | 1265.67 | ||
| 2026-05-24 05:00 | 1265.81 | ||
| 2026-05-24 11:00 | 1265.95 | ||
| 2026-05-24 17:00 | 1266.1 | ||
| 2026-05-24 23:00 | 1266.24 | ||
| 2026-05-25 05:00 | 1266.38 | ||
| 2026-05-25 11:00 | 1266.51 | ||
| 2026-05-25 17:00 | 1266.64 | ||
| 2026-05-25 23:00 | 1266.77 | ||
| 2026-05-26 05:00 | 1266.9 | ||
| 2026-05-26 11:00 | 1267.02 | ||
| 2026-05-26 17:00 | 1267.15 | ||
| 2026-05-26 23:00 | 1267.27 | ||
| 2026-05-27 05:00 | 1267.39 | ||