| Cuenca | Capacidad | Embalsada | Variación | ||
| Tajo | 11056 | 9488 | (85.82%) | 107 | (0.97%) |
| Guadiana | 9538 | 6750 | (70.76%) | 28 | (0.29%) |
| Guadalquivir | 8028 | 4916 | (61.24%) | 16 | (0.20%) |
| Ebro | 7802 | 6922 | (88.71%) | 27 | (0.35%) |
| Duero | 7602 | 6974 | (91.73%) | 88 | (1.16%) |
| Miño-Sil | 3030 | 2577 | (85.05%) | 11 | (0.36%) |
| Júcar | 2846 | 1810 | (63.60%) | 7 | (0.25%) |
| Guadalete-Barbate | 1651 | 912 | (55.24%) | -2 | (-0.12%) |
| Med. Andaluza | 1174 | 669 | (56.98%) | 12 | (1.02%) |
| Segura | 1140 | 335 | (29.39%) | 0 | (0.00%) |
| Galicia Costa | 684 | 571 | (83.48%) | -5 | (-0.73%) |
| Cataluña Interna | 677 | 497 | (73.41%) | 20 | (2.95%) |
| Cantábrico Occidental | 490 | 426 | (86.94%) | -1 | (-0.20%) |
| Tinto, Odiel y Piedras | 229 | 211 | (92.14%) | 1 | (0.44%) |
| Cantábrico Oriental | 73 | 65 | (89.04%) | 1 | (1.37%) |
| País Vasco Interna | 21 | 21 | (100.00%) | 0 | (0.00%) |
