Podcast Summary: Qué sabemos de los embalses

Podcast: Más de uno
Host: Carlos Alsina (Onda Cero)
Date: February 17, 2026

Overview

This episode of Más de uno, with Carlos Alsina, dives humorously and informatively into Spain's reservoirs ("embalses"): how they function, their history, management, safety protocols, and the nation's fascination with them—especially in light of the heavy rains filling up reservoirs across the country. Alsina is joined by expert guests: Prof. Francisco Bueno (hydraulic engineering professor at the University of Burgos) and David Galán (safety coordinator for Canal de Isabel II).

Key Discussion Points & Insights

1. La obsesión popular con los embalses y el tiempo

• [00:04–01:24]
  • The episode opens with Alsina and Jorge joking about how Spaniards—especially men—are compulsively checking the status of water reservoirs, while others obsessively follow the weather.
  • Notable quote:

    “Decía... Las mujeres tenéis en favoritos la página de la AEMET... Y los hombres lo que consultamos de forma incluso compulsiva a veces, el estado de los embalses. Es mi caso.”
    —B (Jorge) [00:26]

2. España y el inesperado récord de lluvias

• [01:36–02:53]
  • There’s been a historic weekly increase in water reserves: 5,634 hm³ in one week—the most since records exist.
  • The heavy rains have filled reservoirs to the brim, causing controlled discharges.

3. Derribando mitos: ¿De cuándo son las presas españolas?

• [02:54–04:22]
  • Many in Spain still associate the mass building of reservoirs with Francoist Spain, thanks in part to NO-DO archival footage, but major hydraulic infrastructure plans began in the 1920s under Primo de Rivera and the Second Republic.

4. La presa de Montejaque: una infraestructura ‘fantasma’

• [04:22–06:29]
  • The Montejaque dam (Málaga), built in 1924 to generate electricity, notoriously never held water—until now.
  • Its location—on porous, limestone ground—always led it to "lose" water... but this year’s rains filled it for the first time, forcing its ancient spillways (aliviaderos) and siphons to be used.
  • Notable quote:

    “Por primera vez... han tenido que utilizar los aliviaderos... ¡no los habían utilizado nunca!”
    —B (Jorge) [06:07]

5. ¿Qué es un sifón en una presa?

• [06:35–07:34]
  • Francisco Bueno explains: Siphons are a rare type of spillway, operating only when water rises above maximum levels. Only three such siphons are functioning in Spain, all in old dams.
  • Notable quote:

    “Funcionan como los sifones de nuestros cuartos de baño. Es un tipo de aliviadero”
    —Prof. Francisco Bueno [06:52]

6. Diferencia entre presa, embalse y pantano

• [08:22–09:32]
  • Presa: The wall that contains or regulates water.
  • Embalse: The body of stored water.
  • Pantano: Natural wetland; the term is imprecise for reservoirs, but colloquially used.
  • Notable quote:

    “La presa regula, el embalse almacena el agua... Pantano indica otra cosa.”
    —Prof. Bueno [08:57/09:11]

7. España como ‘potencia’ de embalses

• [09:37–10:53]
  • Spain & California: Economies with semi-arid climates that have become dependent on reservoirs.
  • Without dams, Spain would only use 8% of its water; with them, up to 40% is regulated and usable.

8. Historia de las presas en España y su ingeniería

• [10:53–14:40]
  • Existing Roman dams (Proserpina, Cornalbo) are still functional.
  • Types: Dams made of earth/material ("materiales sueltos") vs. masonry/concrete ("de fábrica").
  • Complexity: Reservoir engineering is one of the most demanding disciplines, especially regarding pressure management and safety.
  • Risk Classification: Dams classified by potential downstream danger (Types A, B, C).
  • Notable quote:

    “La presa es difícil que se rompa, pero por si acaso, simulamos que se rompe y vemos qué pasa aguas abajo.”
    —Prof. Bueno [13:07]

9. Seguridad y mantenimiento

• [14:40–15:54]
  • Maintenance investments in Spain are not at ideal standards, though the risk of failure is low. The profession has called for more funding for safety.

10. Belleza y formas de las presas

• [15:31–16:57]
  • Iconic examples: Aldeadávila (Salamanca), Almendra; some are works of art, harmoniously integrated with the landscape.
  • Shapes: Arched dams are more efficient and safe with less material.

11. Gestión y regulación de las presas

• [16:57–18:24]
  • Management is divided among hydrological confederations (state-run, especially for large dams) and concessionaries (city halls, companies).
  • Notable quote:

    “Quien tiene el control general... son las confederaciones hidrográficas”
    —Prof. Bueno [17:18]

12. Seguridad en la operación: experiencia del Canal de Isabel II

• [19:21–22:39]
  • David Galán details monitoring protocols for Madrid’s 15 large dams.
    • Operation and maintenance plans
    • Auscultation plans for detecting movement, deformation, and leaks (“filtraciones”), both automated and manual.
    • Four maintenance checks per year for bottom outlets and spillways.
  • Sediment issues: Not a big issue in Madrid (granite geology), but a problem in Mediterranean basins and other countries (e.g., Morocco).

13. Niveles y cifras actuales (Feb 2026)

• [23:46–24:11]
  • Madrid’s reservoirs are at 87% of total storage—effectively 100% for February—thanks to record rainfall, with “resguardos” (safety margins) kept for flood control.
  • Notable quote:

    “Estamos al 87%... pero al 100% de la capacidad efectiva para el mes de febrero porque necesitamos un volumen de resguardo para laminar las avenidas.”
    —David Galán [23:46]

14. La gestión de años intensos de lluvias

• [24:11–25:13]
  • For infrastructure managers, a winter of continuous storms is challenging but ultimately satisfying seeing reservoirs fill up safely.
  • Water consumed vs. received: Madrid gets about as much rainfall contribution this year as its annual water consumption.

15. Filtraciones: inevitables pero controlables

• [25:27–26:29]
  • “Filtraciones” through the dam and foundations are normal, monitored, and factor into safety plans.
  • Engineers measure, correlate with levels, and act if rates increase.

16. Presas favoritas

• [26:29–27:05]
  • Both guests agree: Aldeadávila is Spain’s (and among the world’s) most beautiful, especially for its integration into the Duero landscape.
  • In Madrid: the Atazar Dam is highlighted and beloved by those who operate it.

17. La vocación académica

• [27:05–27:51]
  • Professor Bueno teaches hydraulics and environmental engineering, noting an increased interest among students lately.

Memorable Quotes

• Jorge [00:26]:
  “Estoy viciadísimo, muy enganchado a esto [los datos de los embalses].”

• Prof. Francisco Bueno [06:52]:
  “Los sifones de la presa de Monte Jaque funcionan como los sifones de nuestros cuartos de baño. Es un tipo de aliviadero.”

• Prof. Bueno [09:11]:
  “A mí la palabra pantano personalmente nunca me ha gustado... Un pantano es una especie de humedad natural... en el momento en que hay presas son embalses artificiales.”

• Prof. Bueno [13:07]:
  “La presa es difícil que se rompa, pero por si acaso... simulamos que se rompe y vemos qué es lo que pasa aguas abajo.”

• David Galán [20:55]:
  “Tenemos dos planes: de operación y mantenimiento y el de auscultación. Auscultamos la presa, verificamos su comportamiento y estamos tranquilos cuando hay una avenida.”

• David Galán [23:46]:
  “Estamos al 87% de la capacidad... pero al 100% de la capacidad efectiva para el mes de febrero porque necesitamos un volumen de resguardo para laminar las avenidas.”

• David Galán [26:33]:
  “La presa Aldea Dávila es maravillosa... es un arco gravedad integrado perfectamente en el terreno y con el paso del tiempo parece una presa natural.”

Timestamps of Key Segments

• Obsesión digital con los embalses y el tiempo [00:04–01:24]
• Montejaque: la presa fantasma [04:22–06:29]
• Diferencias: presa, embalse, pantano [08:22–09:32]
• Historia y tipos de presas en España [10:53–14:40]
• Gestión y regulación centralizada [16:57–18:24]
• Seguridad: monitorización y mantenimiento (David Galán) [19:21–22:39]
• Cifras actuales, margen de resguardo por lluvias [23:46–24:11]
• Filtraciones y cómo se gestionan [25:27–26:29]
• Presas más hermosas seleccionadas por los expertos [26:29–27:05]

Conclusion

The episode brilliantly weaves together technical expertise, historical curiosities, and relatable humor to shed light on why reservoirs are so crucial for Spain, how they’re built and managed, and which ones are worth a visit. It’s a celebration of the often-unseen infrastructures that make modern life—and safe drinking water—possible.