COLUMBIA--GRAND COULEE DAM (GCDW1)
| Observed | Forecast/Trend Issued: 2026-05-10 13:58 PDT | ||
| Date/Time (PDT) | Pool Height | Date/Time (PDT) | Pool Height |
| 2026-05-10 00:00 | 1254.48 | 2026-05-10 23:00 | 1254.89 |
| 2026-05-09 00:00 | 1253.96 | 2026-05-11 05:00 | 1254.93 |
| 2026-05-08 00:00 | 1253.15 | 2026-05-11 11:00 | 1254.99 |
| 2026-05-07 00:00 | 1251.77 | 2026-05-11 17:00 | 1255.07 |
| 2026-05-06 00:00 | 1251.31 | 2026-05-11 23:00 | 1255.17 |
| 2026-05-05 00:00 | 1251.5 | 2026-05-12 05:00 | 1255.3 |
| 2026-05-04 00:00 | 1251.59 | 2026-05-12 11:00 | 1255.45 |
| 2026-05-03 00:00 | 1251.72 | 2026-05-12 17:00 | 1255.61 |
| 2026-05-02 00:00 | 1252.49 | 2026-05-12 23:00 | 1255.79 |
| 2026-05-01 00:00 | 1253.35 | 2026-05-13 05:00 | 1255.98 |
| 2026-04-30 00:00 | 1253.93 | 2026-05-13 11:00 | 1256.17 |
| 2026-05-13 17:00 | 1256.37 | ||
| 2026-05-13 23:00 | 1256.57 | ||
| 2026-05-14 05:00 | 1256.79 | ||
| 2026-05-14 11:00 | 1257 | ||
| 2026-05-14 17:00 | 1257.22 | ||
| 2026-05-14 23:00 | 1257.45 | ||
| 2026-05-15 05:00 | 1257.68 | ||
| 2026-05-15 11:00 | 1257.92 | ||
| 2026-05-15 17:00 | 1258.16 | ||
| 2026-05-15 23:00 | 1258.42 | ||
| 2026-05-16 05:00 | 1258.68 | ||
| 2026-05-16 11:00 | 1258.96 | ||
| 2026-05-16 17:00 | 1259.24 | ||
| 2026-05-16 23:00 | 1259.53 | ||
| 2026-05-17 05:00 | 1259.82 | ||
| 2026-05-17 11:00 | 1260.12 | ||
| 2026-05-17 17:00 | 1260.4 | ||
| 2026-05-17 23:00 | 1260.69 | ||
| 2026-05-18 05:00 | 1260.97 | ||
| 2026-05-18 11:00 | 1261.24 | ||
| 2026-05-18 17:00 | 1261.5 | ||
| 2026-05-18 23:00 | 1261.76 | ||
| 2026-05-19 05:00 | 1262.01 | ||
| 2026-05-19 11:00 | 1262.26 | ||
| 2026-05-19 17:00 | 1262.52 | ||
| 2026-05-19 23:00 | 1262.78 | ||
| 2026-05-20 05:00 | 1263.05 | ||