Desalination of seawater cannot replace water shortfalls from the Tajo-Segura transfer, a warning issued as government plans for new watershed schemes take shape. Leaders of major environmental organizations in Spain have cautioned that desalination remains a pollutant-producing option with significant environmental impact and should be restricted to highly specific uses.
The message from Greenpeace’s water coordinator, Julio Barea, stresses that while people must not be left without water, it is unacceptable for desalination facilities to irrigate large crops, golf courses, illegal irrigation, or urban developments. The warning comes as the public debate intensifies over how best to balance supply and conservation.
Teresa Ribera, the third vice-president and minister for Ecological Transition, has explained that the updated Tagus watershed plans aim to identify increasingly large ecological and welfare flows by 2027. These plans are intended to secure more investment in desalination and in irrigation efficiency, while also determining how much water can be retained from transfers.
There are tens of thousands of illegal irrigation systems in Spain
The stance from environmental groups is clear: desalination is not opposed outright, but its large-scale use is. The concern is that too many desalination projects would scale up beyond necessity and impact.
Desalination is considered a last resort and should be deployed sparingly to guarantee drinking water for the population. Authorities are encouraged to exhaust all other means first before relying on desalination as a broad solution.
Water expert and activist Santiago Martín Barajas, spokesman for Ecologists in Action, has called for a halt to further transfers unless irrigation volumes are better allocated to crops in need. The concern is that current allocations do not reflect actual agricultural requirements in the Levante communities and Castilla-La Mancha, which participate in the Tajo-Segura transfer.
Desalination plants are facilities that convert saline or brackish water into sources usable for drinking, industry, and irrigation. The first large project in Spain was built in the 1960s in Lanzarote in the Canary Islands to address water shortages driven by tourism growth.
Spain features abundant rivers and groundwater due to its geography. It hosts many desalination facilities—some of the world’s largest producers of desalinated water—with more than 700 plants distributed mainly across the Canary Islands and the Mediterranean coast.
High CO2 emissions to the atmosphere
In addition to landscape impact along coastlines, ecologists point to the high electricity consumption required by many desalination operations, which leads to substantial carbon dioxide emissions.
Critics note that roughly half of every liter of desalinated seawater can be suitable for drinking and certain uses, while the other half is concentrated brine with a variety of salts and chemical byproducts that can be released into the sea if not properly managed.
The remaining portion of the output consists of brine, which is highly concentrated and involves salts and chemicals used in the process. This brine can pose risks to marine ecosystems when discharged improperly.
The Ecologistas en Acción representative stated that the effects of brine discharges are worse than previously thought, notably impacting Posidonia meadows, a marine plant vital for the reproduction and survival of many fish species.
It would be unacceptable for facilities to run continuously just to desalinate water. Allocations should be limited to specific moments, targeting populations during droughts and under particular water scarcity conditions.
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