Water transfers within Spain, especially schemes like the Tajo-Segura, look precarious in the near term due to climate change, rising drought frequency, and the substantial costs tied to moving water. This conclusion comes from a study by three scholars from the University of Zaragoza, published in Estudios sobre la Economía Española under the title Status and perspectives of water resources in Spain.
Built on the finding that Spain faces the most severe drought-related damage in the European Union because of global warming, the study projects a drop in available water in the Duero and Tagus basins by 14% to 25%, with outcomes tied to future CO2 emission levels.
Climate change will reduce water availability in the Duero and Tagus by 14% to 25%
The authors, José Albiac, Encarna Esteban, and Safa Baccour, note that the Ebro basin is the only one with sufficient flow to support inter-basin transfers. The Duero and Tagus basins still exhibit notable flows, yet water available for transfer is constrained by the Albufeira Convention, which requires Portugal to maintain minimum flows of 3,800 hm3 in the Duero and 2,700 hm3 in the Tagus.
There is not enough water to transfer
After meeting these obligations, there is little room left for inter-basin transfers, and the outlook for future transfers grows tighter as droughts become more frequent and intense. Transfers threaten to limit future economic growth in regions that rely on water and risk harming ecosystems through reduced river flows.
Increasing drought conditions make transfers more difficult, and growing demand for water by agencies further complicates planning.
When assessing the idea of transferring water from the Ebro, the study shows that allocations should target basins facing greater scarcity, such as Júcar, Segura, the Andalusian Mediterranean, and the Guadalquivir. Yet, the cost challenge is real: transfer costs exceed the price of seawater desalination in nearby regions, making transfers economically sensible only in limited scenarios, such as moving around 200 m3 to Castellón and Valencia, but not to Alicante.
In fact, moving water from the Ebro to the Segura, or to the Andalusian Mediterranean and Guadalquivir basins, proves expensive, with transfer costs approaching or exceeding one euro per cubic meter. In parts of the Júcar basin, reducing subsurface extraction for less profitable crops could offer an alternative to turbanned transfers.
“These transfers favor basins where user groups expand water extraction in an uncontrolled manner.”
José Albiac of the University of Zaragoza emphasizes that any inter-basin transfer should be assessed against its social benefits for both the sending and receiving basins, since transfers can diminish the overall social payoff if not managed carefully.
Who benefits from transfers?
The study concludes that large-scale inter-basin transfers are not the best path to sustainable water management. They tend to benefit basins where water use expands in an uncontrolled way, while harming watersheds that sustain more prudent resource use and environmental flows. Irrigation expansion without proper oversight has caused serious environmental damage, whereas basins that achieve greater sustainability may see their resources strained by transfers.
Writers in the report advocate for institutional collaboration as a key strategy for managing water more effectively. They point to the Júcar basin as an example of robust economic and environmental outcomes that can emerge from coordinated governance.
Despite the need for better institutional cooperation in Spain, water withdrawals from basins continue to rise. Observers note that political decisions often prioritize expanding water supply over protecting water resources and ecological flows. A cited example is the political controversy surrounding wells in Doñana and the broader issue of groundwater management.
The study identifies irrigation expansion as a major driver of water stress. Controlling overexploitation of aquifers across basins and reallocating water among sectors could help stabilize water resources and safeguard environmental flows for downstream ecosystems.
As part of the analysis, the researchers present a cautious stance toward inter-basin transfers and stress the importance of aligning transfers with broader social and environmental benefits across the affected basins.
The study references a detailed examination of these issues and highlights the need for ongoing assessment of water policy measures in Spain. The researchers stress that collaborative governance, careful allocation, and stronger protection of environmental flows are essential to long-term resilience.
Notes on broader implications: the pressure on water resources across Spain is a complex interplay of climate risk, regulatory frameworks, and economic incentives. A comprehensive strategy will require balancing immediate water needs with the health of rivers, wetlands, and dependent communities.
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End of summary.