Aragón river · Ebro Basin · dam built in 1959 · latest official reading: 6 October 2026.
Yesa is currently at 13.9 % of capacity, below normal for the time of year. The week-41 average across 38 years of records is 26.5 %, a difference of −12.6 points.
For context: a year ago it stood at 18.8 % and a month ago at 27.1 %. Against last week’s reading it is falling fast (−2.7 points).
Blue line: average monthly filling across the whole record, from 1988. The dot marks today’s reading, 13.9 % in October.
With 2,023 weekly readings since 1988, the average pattern of Yesa is clear: it peaks in May at 82.9 % and bottoms out in October at 28.6 %. That 54-point range makes it a reservoir with a very wide annual swing — almost half the pool between its best and worst month.
The highest reading in the whole series is 96.6 %, on 11 June 2013, and the lowest 8.5 %, on 7 November 1995. 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 447 hm³ of capacity it is the fourth largest of the 76 dams the bulletin tracks in the Ebro basin, holding 5.7 % of the whole demarcation’s capacity on its own. The basin as a whole is at 45.4 % today, so this reservoir is running below 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 76 dams the bulletin tracks: Ebro Basin.
