Why heavy rain isn't filling Spain's reservoirs

The debate on rain that fails to fill reservoirs

How can it be explained that water falls for weeks while dams barely rise? This question has circulated for some time, with answers that don't quite align. A video attempts to clarify this using infographics and diagrams, focusing on the path of rainwater to the sea: the conclusion is uncomfortable, as much of that water never reaches storage.

The most repeated explanation points to deforestation. Proponents argue that without vegetation to slow runoff, water slides across the soil, concentrates in ravines, and flows into the sea without recharging rivers or aquifers. The more degraded the land, the less infiltration occurs. This argument is presented as hydrological, yet it is where otherwise dissimilar viewpoints converge.

Why doesn't torrential rain fill the reservoirs?

According to this view, water falling in torrents does not infiltrate; it runs off quickly toward the sea, and dams only retain what arrives via river channels. It's not that reservoirs leak, but that rain enters through unintended paths. Hence, it pours heavily while reserves rise drop by drop.

A more sarcastic version circulating suggests that torrential rains in central Spain are "evaporated by changing climate." The term "changing" is a typo by the author, not a meteorological fact. However, the idea has defenders: if water leaves before reaching the dam, it matters little how much falls.

Evaporation, transfers, and other theories of disappearing water

To evaporation is added another suspicion: that water moves between basins without public declaration. The example given involves two reservoirs in the same area evolving oppositely—one full a few weeks ago, another pitifully low in April—leading to hypotheses of covert transfers to other regions. There is no proof supporting this; it remains conjecture.

This list also includes the idea that reservoirs are emptied intentionally, that gates are peine to reserve water for specific uses, or that current rain is "asymptomatic": it falls but doesn't fill, while simultaneously triggering phone alerts. Those defending this paradox call it doublethink; others respond that water simply trinc its natural course.

Some go further, claiming freshwater entered financial markets and that scarcity benefits those who commercialize it. From there, speaking of the next bubble—worse, they say, than olive oil—is just a step away.

What the data says: reserves rising above 2021 and 2022 levels

Against these theories lies a public record consulted daily: changes in stored water by basin. Here appears a datum contradicting half the discussion. According to observers of this record, reserves continue to grow, surpassing levels from 2021 and 2022. If reservoirs were emptying on their own, these numbers wouldn't add up.

A tricky nuance: according to one participant, information is updated on Tuesdays. Someone checking the panel on Wednesday or Thursday still sees last week's snapshot and might announce drought with seemingly valid reasons, even if false for a couple of days. Calendar lag explains many heated discussions.

The counter-narrative data: double the forest mass

If deforestation were the sole cause, it would clash with an inconvenient figure raised in debate: Spain has double the forest mass compared to 100 years ago. Meaning, the country has more trees today than at the start of the last century, not fewer. This doesn't dismiss runoff issues but complicates blaming the problem solely on lack of forests.

In the thread, both claims are accepted simultaneously without reconciliation.

Groundwater and floods: local accounts

Where models fail, locals speak. In the Henares corridor, an underground water zone covering several towns, a participant asserts that streams previously drying in two or three days have remained wet for six weeks. He notes that pumps continue extracting water even without rain, filtering from the subsurface, something unseen locally before.

Rain distribution is uneven: Galicia and Castilla y León receive the bulk, while the southwest gets little, though conditions improve in Sierra del Segura, source of tributaries. The picture changes depending on the map location. With it, the sense that water behaves unpredictably.

If water evaporates upon falling yet triggers mobile alarms, someone must explain how both fit under the same sky. While clarified, reservoirs keep rising. Curiously, this hasn't closed the debate either.