The reservoir water reserve continues to fall in Spain despite the latest rains

The accumulated rainfall deficit in Spain is of such a caliber that the latest rainfall, although abundant and widespread, does not manage to reverse the worrying drought situation experienced by several basins of the country. In fact, instead of increasing, in the last week the reservoir water reserve of the whole of Spain has fallen again. Specifically, 0.2% compared to the previous week, according to data from the hydrological bulletin of the Ministry for Ecological Transition released on Tuesday.

Nine consecutive weeks of decline have accumulated these reserves. You have to go back to the bulletin of March 28, 2023 to find an increase, which was only 0.1%. At that time, the Spanish water reserve was at 51.7% of its capacity; now it is down to 47.5%.

The normal thing at this time of year is that the water accumulated in the reservoirs of Spain was increasing, which would help to spend in better conditions the dry summer that is expected. But the lack of rain in February, March and, especially, April have meant that stocks have fallen uninterruptedly for more than two months.

"The rainfall of the last few days is a very valuable contribution of moisture for the soils, which are currently much drier than normal for this time of year," explains Rubén del Campo, spokesman for Aemet (State Meteorological Agency). "In addition, as the skies are cloudier and the air humidity is high, evaporation is lower and this helps in some way for vegetation to reduce its water stress to some extent," he adds.

Del Campo, however, stressed that "rainfall has not yet been noticed in the reservoir water." "The water outputs of the reservoirs have exceeded the inflows," so the reserve has fallen again this week. The best way to understand the situation is to compare the current reserves (that 47.5%) with those of the average of the last decade: 68.4%. That is, the reservoir water is 20.9 points below the average of the decade.

By basins, the one that is in a more complicated situation is that of the Guadalquivir, where reserves are at 23.8%, which is 38.4 points below the average of the last 10 years (which for this week of the year is 62.2%). It is followed by the internal basins of Catalonia (with 25.6%, 59.9 points less than the average of the last two decades) and that of the Guadiana (31.8%, 30.1 percentage points less).

Rainfall deficit

In these three basins is where the rainfall deficit of recent months, even years, is most accentuated. Although the final stretch of May has been rainy, the month will close within the threshold of normality. Del Campo explains that "from day 1 to day 28, 50 liters per square meter have already fallen, a figure approximate to the normal value of the full month, which is 57 liters per square meter." Beyond this month, spring can already be considered "very dry". And if you go back even further, to the beginning of the hydrological year, on October 1, the situation is more dramatic. "Since the beginning of the hydrological year, rainfall is around 27% below normal," says the Aemet spokesman. "We are, therefore, facing one of the eight driest hydrological years to date since 1961."

Drought

Experts usually speak of three types of drought, which are different although they are related: meteorological (rainfall deficit), agricultural (deficit of moisture in the soil) and hydrological (deficit in water reserves, such as reservoirs). Normally, the meteorological drought is the main trigger of the rest, that is, the lack of rain. And Spain has been dragging that deficit for more than a year.

Therefore, the respite caused by the abundant rains of recent days (which are expected to last for the rest of the week and the next), is not enough to get a good part of the country out of the complicated situation in which it is. To measure the magnitude of the problem, it is best to go to the latest monthly report on the situation of drought and scarcity prepared by the Ministry for Ecological Transition. In the last of these reports, which is based on the data as of April 30, 2023, it was stated that 36.3% of the country's territory was on alert or emergency due to a short-term water shortage.

This indicator takes into account several measurements (such as storage volumes in reservoirs or flows...) and is used to determine problems that may arise for supply, such as irrigation and supply to populations. There are four scenarios of short-term shortages: normality, pre-alert, alert and emergency. At the beginning of May, 19.6% of the national territory was in an "emergency" situation and 16.7% was on "alert".

Again, the most complex situation is experienced in the basins of the Guadalquivir and in the internal ones of Catalonia. In the case of the Guadalquivir, 82.3% of the surface supplied by the waters of this basin is in an emergency scenario, which affects a population of 730,231 people. In this basin, the water used for irrigation has already been reduced by almost 90% compared to the rights granted to farmers.

In the case of Catalonia, since the beginning of May there are 495 municipalities (where more than 6.5 million people live) in an exceptional situation due to drought. This implies the implementation of limitations in agriculture and industry and the prohibition of the use of drinking water for irrigation of parks and public and private green areas, among other measures.

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