In recent days, the precipitation has spread again over much of Spain and has left accumulations exceeding 150 liters per square meter in points of the Valencian interior. However, the latest official balance still shows a loss of stored water: the reservoirs hold 37,107 cubic hectometers, although they maintain a much better situation than a year ago and than the average of the last decade.
The rains recorded during August have still not managed to reverse the seasonal decline of Spanish reservoirs. The latest photograph published by the Ministry for Ecological Transition places the water reserve at 66.2% of its capacity, with 37,107 cubic hectometers stored.
In one week, 997 cubic hectometers were lost, equivalent to 1.8% of the total capacity. The drop occurred despite the fact that the precipitation significantly affected the Mediterranean slope and, to a lesser extent, the Atlantic.
There is an important nuance. This balance corresponds to August 18, so it still does not incorporate the subsequent rains recorded in Spain. We will have to wait for the next national data from the Ministry to know if the latest episodes have been sufficient to slow down or stop the decline.
The rains have returned, but the reservoirs continue to lose water
The change compared to the beginning of August is clear. On August 4, the reservoirs stored 39,016 cubic hectometers and were at 69.6%. A week later, they had dropped to 68%, with 38,103 cubic hectometers. On August 18, they were already at 37,107 cubic hectometers and 66.2%.
In just two weeks, therefore, the reserves have lost 1,909 cubic hectometers and 3.4 percentage points of capacity.
The evolution prolongs the usual summer trend. At the end of July, specifically on the 28th, Spain still held 39,985 cubic hectometers, 71.3% of the total capacity. Since then, the stored volume has decreased by 2,878 cubic hectometers.
The latest precipitation has indeed been much more significant than that recorded at the beginning of the month. AEMET points out that between August 12 and 18 it rained in most of the Peninsula and more than 10 liters per square meter were exceeded in numerous points of the north and the eastern half.
The episode was especially intense in the interior of the Comunitat Valenciana, where more than 150 liters per square meter were exceeded. Among the main observatories, AEMET recorded 19 liters at the Málaga airport, 18 at Valencia, 14 in Cuenca, 13 in Daroca, 11 in Ciudad Real, and 10 in Oviedo.
Spain has much more water than a year ago
The drop in August does not mean that Spain is in a worse situation than in recent years. It is precisely the opposite.
The 37,107 cubic hectometers stored in the latest official balance exceed the 34,738 cubic hectometers recorded in the same week of the previous year. The difference is around 2,370 cubic hectometers.
The distance is even greater compared to the average of the last ten years for this time, which stands at 28,481 cubic hectometers. Spain currently has about 8,600 cubic hectometers more than that average.
The reason lies in what happened during the entire hydrological year. According to AEMET, between October 1, 2025, and August 18, 2026, an average of 625 liters per square meter had accumulated in Spain, approximately 7% more than normal for that period.
The distribution has not been uniform either. The accumulated precipitation is above normal values in much of the Peninsula, especially in the southern half. The main exceptions appear in part of the Cantabrian coast, between Asturias and Navarra, Burgos, Teruel, and southern Almería.
The reservoirs with the most and least reserves
The differences between basins remain significant. The highest percentages appear in the internal basins of the Basque Country, with 81%, the internal basins of Catalonia, with 79.9%, Guadalete-Barbate, with 79.2%, Guadiana, with 75%, and Guadalquivir, with 74.6%.
At the opposite end is the Segura, at 54%, followed by the Júcar, at 56.4%; the Ebro, at 59.2%; Galicia Costa, at 59.9%; and the Tagus, at 60.7%.
The data for the Segura is particularly significant because it continues to be the basin with the lowest percentage of stored water among the major demarcations recorded by the Ministry. Nevertheless, its current 616 cubic hectometers practically double the 340 cubic hectometers that marks the average of the last ten years for this week.
The contrast is also very strong in Andalusia. The Guadalquivir holds 5,991 cubic hectometers, compared to 3,826 a year ago and 3,108 on average over the last decade. Guadalete-Barbate stores 1,307 cubic hectometers, when a year earlier it had 756.
An extremely dry summer after a rainy hydrological year
The apparent contradiction between still high reserves and their rapid decline over the last few weeks has another element: July was extremely dry.
AEMET estimates that in July 2026, an average of barely 4.3 liters per square meter fell in mainland Spain, 26% of the usual value. It was the driest July in the historical series, which began in 1961.
The storms in August have changed that pattern in certain areas, but a recovery in the national reservoir balance is still not evident. The latest data continues to show a decline and the most recent rains are not yet incorporated.
The next update will allow us to check if the episodes of the second half of August manage to break that trend or simply slow down the loss of reserves typical of summer.