| Cuenca | Capacidad | Embalsada | Variacion | ||
| Tajo | 11056 | 7434 | (67.24%) | 34 | (0.31%) |
| Guadiana | 9261 | 3962 | (42.78%) | -14 | (-0.15%) |
| Guadalquivir | 8113 | 4044 | (49.85%) | 0 | (0.00%) |
| Ebro | 7642 | 6970 | (91.21%) | 40 | (0.52%) |
| Duero | 7507 | 6647 | (88.54%) | 24 | (0.32%) |
| Miño-Sil | 3030 | 2573 | (84.92%) | 1 | (0.03%) |
| Júcar | 2846 | 1687 | (59.28%) | 6 | (0.21%) |
| Guadalete-Barbate | 1651 | 844 | (51.12%) | -1 | (-0.06%) |
| Med. Andaluza | 1174 | 693 | (59.03%) | 1 | (0.09%) |
| Segura | 1140 | 536 | (47.02%) | 0 | (0.00%) |
| Galicia Costa | 684 | 600 | (87.72%) | -3 | (-0.44%) |
| Cataluña Interna | 677 | 641 | (94.68%) | 1 | (0.15%) |
| Cantabrico Occidental | 518 | 460 | (88.80%) | -5 | (-0.97%) |
| Tinto, Odiel y Piedras | 229 | 183 | (79.91%) | -1 | (-0.44%) |
| Cantabrico Oriental | 73 | 68 | (93.15%) | -2 | (-2.74%) |
| Pais Vasco Interna | 21 | 19 | (90.48%) | 0 | (0.00%) |
