15 reservoirs with a combined capacity of 579 hm³ · latest official reading: 6 October 2026
The Cantabrian demarcation is currently at 57.5 % of capacity, about normal for the time of year. The week-41 average across 38 years of records is 62.2 %, a difference of −4.7 points.
For context: a year ago it stood at 63.2 % and a month ago at 64.6 %. Against last week’s reading it is falling fast (−1.7 points).
Blue line: average monthly filling for the whole demarcation since 1988. The dot marks today’s reading, 57.5 % in October.
With 2,020 weeks of record since 1988, the average pattern of the Cantabrian demarcation is clear: it peaks in May at 85.1 % and bottoms out in October at 61.9 %. That 23-point range makes it a markedly seasonal demarcation, with a demanding irrigation season.
The highest reading in the whole series is 94.8 %, on 5 June 2018, and the lowest 40.9 %, on 21 September 1999. Comparing today against those two extremes says more than the bare percentage: 50 % is comfortable in a demarcation that rarely tops 60 %, and worrying in one that usually reaches summer full.
By capacity it is the 13th demarcation of the 14 covered by the hydrological bulletin: its 579 hm³ account for 1.0 % of everything Spain can store in mainland reservoirs. Today it holds 333 hm³.
The 15 dams the hydrological bulletin tracks in the Cantabrian demarcation, sorted by capacity. Linked names have their own page with the full record.
| Reservoir | Capacity (hm³) | Volume (hm³) | Fill | Δ week | Use |
|---|---|---|---|---|---|
| Salime | 238 | 99 | 41.6 % | −2.5 | Hydropower |
| Doiras | 97 | 71 | 73.2 % | −1.0 | Hydropower |
| Arbón | 41 | 37 | 90.2 % | +0.0 | Hydropower |
| Añarbe | 38 | 21 | 55.3 % | −2.6 | Irrigation / supply |
| Tanes | 34 | 20 | 58.8 % | −5.9 | Irrigation / supply |
| Barca, La | 29 | 23 | 79.3 % | +8.7 | Hydropower |
| Alsa - Mediajo | 22 | 18 | 81.8 % | −4.5 | Hydropower |
| Ordunte | 22 | 11 | 50.0 % | −4.5 | Irrigation / supply |
| Cohilla, La | 12 | 2 | 16.7 % | +0.0 | Hydropower |
| Ibai-Eder | 11 | 7 | 63.6 % | +0.0 | Irrigation / supply |
| Urkulu | 10 | 8 | 80.0 % | +0.0 | Irrigation / supply |
| Alfilorios | 8 | 3 | 37.5 % | +0.0 | Irrigation / supply |
| Ibiur | 8 | 6 | 75.0 % | +0.0 | Irrigation / supply |
| San Antón | 5 | 4 | 80.0 % | +0.0 | Irrigation / supply |
| Rioseco | 4 | 3 | 75.0 % | +0.0 | Irrigation / supply |
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The figures on this page come from the official MITECO reservoir archive, the same database behind Spain’s weekly hydrological bulletin. The bulletin covers every mainland reservoir above 5 hm³ of capacity and is published every Tuesday with Monday’s reading.
The latest reading here is from 6 October 2026, and the comparison series starts in 1988. Nothing is estimated, interpolated or forecast: the percentage is stored volume divided by the usable capacity the bulletin itself assigns to the dam. Historical averages are computed over the same calendar week in every previous year, the only fair comparison in a system with such marked seasonality.
National summary and reservoir search on Reservoirs of Spain.
