Guadiana river · Guadiana Basin · dam built in 1961 · latest official reading: 6 October 2026.
Orellana is currently at 73.4 % of capacity, above normal for the time of year. The week-41 average across 38 years of records is 58.1 %, a difference of +15.3 points.
For context: a year ago it stood at 75.9 % and a month ago at 74.8 %. Against last week’s reading it is essentially flat (+0.0 points).
Blue line: average monthly filling across the whole record, from 1988. The dot marks today’s reading, 73.4 % in October.
With 2,023 weekly readings since 1988, the average pattern of Orellana is clear: it peaks in May at 77.8 % and bottoms out in October at 58.4 %. That 19-point range makes it a reservoir with a moderate annual swing.
The highest reading in the whole series is 100.4 %, on 13 January 1998, and the lowest 12.3 %, on 22 December 1998. 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 808 hm³ of capacity it is the fourth largest of the 39 dams the bulletin tracks in the Guadiana basin, holding 8.5 % of the whole demarcation’s capacity on its own. The basin as a whole is at 72.1 % today, so this reservoir is running closely in line with 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 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.
See the whole demarcation, with all 39 dams the bulletin tracks: Guadiana Basin.
