The Siurana: Anatomy of an Extraction

On 27 March the route of my project The Open Shore (La vora oberta) begins. As context, I have synthesised the content of a couple of documented sources, with the aim of bringing this conflict closer to those who are not familiar with it.

The Siurana river is the backbone of the Priorat, so much so that in the territorial reorganisation of the Republic in 1936, it was proposed that the comarca be named “Conca del Siurana”. Yet for almost a century, most of its flow never reaches the sea: a diversion system built in the 1930s redirects its waters towards the Baix Camp (Tarragona). What began as a hydraulic solution has become a territorial conflict that goes far beyond engineering.

The Open Shore (La vora oberta) begins with a journey along the Siurana river, from its source in the Prades Mountains to its confluence with the Ebro. The project addresses the water transfer to Riudecanyes as a territorial and symbolic wound that empties the river’s natural course and turns it into an extracted body. With the support of Terra d’Art / Isabelle Meyer Award 2025.

A long-standing problem

It all began with the Riudecanyes reservoir. Built in 1916 in the Baix Camp, it soon proved insufficient to supply agriculture and the towns of the area — particularly Reus. The solution found was to look to the neighbouring basin: the Siurana, a river that rose in another comarca.

In 1926, the Spanish state approved a project to divert water from the Siurana to Riudecanyes via a 21-kilometre canal and a 9-kilometre tunnel cutting through the sierra that separates the two basins. Work began in 1935. In 1971, the Siurana dam was built to reinforce the system. The result is an interconnected hydraulic system that still operates exactly the same way today: water from the Priorat travels to the Baix Camp.

How much water is actually diverted?

The figures speak for themselves. In a recent measurement at the diversion point, the river was flowing at 304 litres per second. Of that volume, 244 litres — roughly four-fifths — were being diverted out of the basin. Only 60 litres continued along the Siurana’s natural course. At times, barely 10% of the water stays in the river.

The original concession justified the diversion by referring to “surplus water”. But can a river have surplus water if it dries up every summer? Many experts and environmental groups have spent years questioning that definition.

Topograpo: securing water for the villages at the river’s expense

In 1986, Torroja del Priorat, Poboleda, Gratallops and Porrera formed the Topograpo intermunicipal association—its name combines the opening syllables of the four villages—to secure drinking water and irrigation supplies. The contradiction was already plain: communities within the Siurana basin struggled to access water from their own river, held behind a dam designed primarily to feed the Riudecanyes system.

In 2001, the Agència Catalana de l’Aigua, the Riudecanyes irrigators’ association and Topograpo signed an agreement setting aside 200,000 cubic metres a year for these villages: 95,000 for domestic use and 105,000 to irrigate roughly seventy hectares.¹ A network for abstraction, treatment and distribution was built to deliver that allocation.

Officially presented as a safeguard for local supply, the agreement also has a far more contentious reading. Under the protocol, the previous reserve of 200 litres per second of unregulated water for downstream users ceased to apply.² The maintenance flow subsequently implemented fell as low as 20 litres per second.

For critics, Topograpo did not resolve the imbalance so much as formalise it: access to the Priorat’s own water became a negotiated allocation while the transfer to Riudecanyes remained in place. The contradiction lies at the heart of the dispute: as Siurana water crosses the mountains towards the Baix Camp, communities in its own basin rely on a vulnerable supply network to meet their basic needs.

A river in decline

The ecological consequences are visible. The reduction in flow has caused the disappearance of pools and small natural reservoirs that were essential for wildlife. Invasive vegetation has colonised the riverbed. Seasonal floods — necessary to renew the ecosystem — no longer occur with the required frequency. And the Siurana, which historically never dried up completely, now does so regularly every summer.

The minimum ecological flow set by the Agència Catalana de l’Aigua (Catalan Water Agency) is just 20 litres per second — a figure that contrasts sharply with the 200 l/s provided for in the original concession, and which many consider wholly insufficient to keep the river alive.

The trial: who is prosecuting whom

In 2017, around fifty people carried out a symbolic action at the Siurana dam: for a few hours, they returned to the river the water that the diversion system extracts from it every day. It was a peaceful protest. Years later, two of its spokespeople — Andreu Escolà and Anaïs Estrems, from GEPEC-EdC and the Plataforma pel Riu Siurana — are being tried for it.

Those prosecuting them are the Comunitat de Regants del Embassament de Riudecanyes (the private body that manages the public water diverted from the Siurana). The formal charge is unlawful water diversion. The paradox is hard to ignore.

One of the accused describes the situation bluntly: “Justice spends hours prosecuting us while year after year a cross-basin diversion continues that goes against the European Union’s Water Framework Directive.” He adds: “Those who profit from an essential public good tell us we need to be generous. And they say it while drying out our comarca, leaving us without the little water we have, and filling their pockets doing so.”

The trial, which should have been held in June 2023, has now accumulated five postponements. The hearing scheduled for 12 March 2026 was suspended once again and, according to information published by the Plataforma pel Riu Siurana, the new scheduled date is 7 December 2026.

More information in the GEPEC article: El riu Siurana a judici.

The underlying question: water justice?

The Siurana conflict is not merely technical. It is also political and territorial. The Priorat is a comarca with scarce resources and limited institutional influence. The Camp de Tarragona, with greater demographic and economic weight, has historically been able to secure access to a resource that, nonetheless, originates in someone else’s territory.

These kinds of imbalances between river basins are at the centre of the European debate on water governance. Increasingly, water management models prioritise the ecological sustainability of rivers, respect genuine minimum environmental flows, and balance the needs of different territories. The EU’s Water Framework Directive, in fact, establishes clear obligations in this regard — and numerous voices point out that the Siurana diversion systematically breaches them.

Is there a solution?

Yes, or at least there are serious alternatives on the table. The institutional route has already been tried: the Siurana-Riudecanyes Negotiation Table, promoted by the Generalitat, concluded eight sessions without agreement.³ Technical studies, however, point to the reuse of treated wastewater — especially from the Reus sewage treatment plant — as the most viable route to reducing dependence on the diversion. It is estimated that water reclamation could provide between 4 and 6 cubic hectometres per year for irrigation, a volume equivalent to or greater than what is currently extracted from the Siurana. To this should be added improvements in irrigation efficiency and better use of other sources already available in the Camp de Tarragona.

The Siurana conflict is, ultimately, the result of decisions taken almost a century ago that now collide with a new reality: climate change is worsening water scarcity, and what once may have seemed a reasonable exchange between territories now demands an honest reassessment. Until that reassessment arrives, two activists stand before a judge for having done, for a few hours, what nature has been demanding for decades: letting the river flow.

Chronology

• 1916 — The Riudecanyes reservoir is built in the Baix Camp; water arrives in 1919. It soon proves insufficient for Reus and its agriculture.
• 1926–1930 — A project to divert water from the Siurana to Riudecanyes is drawn up and authorised: a canal of around 21 km and a tunnel of around 9 km through the sierra that separates the two basins.
• 1935 — Work begins on enlarging the reservoir and building the diversion canal.
• 1949 — The Siurana–Riudecanyes system enters into operation; the enlarged reservoir begins serving a 120 km² basin.
• 1951 — The diversion canal, designed by Joaquim Blasco, is completed.
• 1971–1972 — The Siurana dam (12 hm³, operational in 1972) is built to reinforce the system.
• 1986 — Torroja del Priorat, Poboleda, Gratallops and Porrera form the Topograpo intermunicipal association.
• 2001 — A cooperation agreement allocates Topograpo 200,000 m³ a year from the Siurana: 95,000 for domestic supply and 105,000 for agricultural use.
• 2017 — Around fifty people symbolically return water to the river for a few hours at the Siurana dam.
• 2023–2026 — The trial of two spokespeople from the Plataforma pel Riu Siurana accumulates five postponements; the new scheduled date is 7 December 2026.

Sources for the hydraulic chronology: official website of the Pantà de Riudecanyes and Viquipèdia / enciclopèdia.cat.

Sources

• Comissió de Comunicació Prioritat. “Siurana, quan el riu sona.” Butlletí Prioritat, nº 2 (Estiu 2025). ISSN 3081-7137 (printed ed.); 3081-7145 (online ed.). https://www.are.na/block/42708928.
• Agència Catalana de l’Aigua. Comissió Ordinària de Desembassament del Riudecanyes. Session no. 15, 24 October 2017. Original document.
• Diputació de Tarragona. Acta de la Junta de Govern de 6 de maig de 2025. Includes the record of the Topograpo intermunicipal association’s establishment, published in DOGC no. 688 on 21 March 1986. Original document.
• GEPEC-EdC. “Entitats socials i ecologistes del Priorat exigeixen que es deixi definitivament de transvasar aigua del riu Siurana.” 30 April 2025; updated 5 May 2025. Original article.
• Molero, Núria. “El Riu Siurana a judici: El judici de defensa del riu Siurana arriba després de quatre ajornaments i tres anys de retard.” GEPEC-EdC. 5 March 2026. https://gepec.cat/el-riu-siurana-a-judici-el-judici-de-defensa-del-riu-siurana-arriba-despres-de-quatre-ajornaments-i-tres-anys-de-retard/.