Zújar river · Guadiana Basin · dam built in 1990 · latest official reading: 6 October 2026.
La Serena is currently at 81.7 % of capacity, far above normal for the time of year. The week-41 average across 36 years of records is 46.4 %, a difference of +35.3 points.
For context: a year ago it stood at 62.1 % and a month ago at 82.9 %. Against last week’s reading it is essentially flat (+0.0 points).
Blue line: average monthly filling across the whole record, from 1990. The dot marks today’s reading, 81.7 % in October.
With 1,913 weekly readings since 1990, the average pattern of La Serena is clear: it peaks in April at 56.4 % and bottoms out in October at 45.8 %. That 11-point range makes it a very stable reservoir through the year, as hydropower pools and very large dams tend to be.
The highest reading in the whole series is 100.9 %, on 13 January 1998, and the lowest 0.0 %, on 13 February 1990. Comparing today against those two extremes says more than the bare percentage: 50 % is good news in a pool that rarely tops 60 %, and bad news in one that is usually full.
At 3,219 hm³ of capacity it is the largest of the 39 dams the bulletin tracks in the Guadiana basin, holding 33.7 % of the whole demarcation’s capacity on its own. The basin as a whole is at 72.1 % today, so this reservoir is running above the basin as a whole.
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 1990. 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.
See the whole demarcation, with all 39 dams the bulletin tracks: Guadiana Basin.
