Cañizares et al. (2025) Los problemas estructurales del Trasvase Tajo-Segura y sus efectos en las superficies cultivables del sureste español

Identification

• Journal: Boletín de la Asociación de Geógrafos Españoles
• Year: 2025
• Date: 2025-11-25
• Authors: Antonio Oliva Cañizares, Jorge Olcina Cantos
• DOI: 10.21138/bage.3490

Research Groups

• Instituto Interuniversitario de Geografía, Universidad de Alicante (Spain).
• Departamento de Análisis Geográfico Regional y Geografía Física, Universidad de Alicante (Spain).

Short Summary

This study identifies structural planning errors in the Tagus-Segura Transfer (ATS) and utilizes high-resolution GIS mapping to demonstrate that actual cultivated land in the Vega Baja del Segura is significantly lower than official estimates. The findings suggest that current water deficits can be managed through non-conventional resources and realistic land-use planning rather than relying on obsolete transfer projections.

Objective

• To identify the structural problems of the Tagus-Segura Transfer (ATS) originating from its design phase.
• To map the real cultivated, uncultivated, and abandoned land areas in the Vega Baja del Segura.
• To recalculate water allocations and demands based on actual irrigated hectares to propose sustainable hydrological planning under climate change.

Study Configuration

• Spatial Scale: Regional scale focusing on the Vega Baja del Segura region (Alicante, Spain), covering 957.2 km².
• Temporal Scale: Historical analysis of planning data from 1933 and 1969, with land-use mapping focused on the year 2022 and transfer data spanning 1979–2022.

Methodology and Data

• Models used: GIS-based photointerpretation and spatial analysis (QGIS 3.26.2); mathematical proportionality models for water demand recalculation.
• Data sources:
  • Historical planning documents: 1933 National Hydraulic Works Plan (PNOH) and the 1969 ATS Preliminary Draft.
  • Cartography: PNOA orthophotos (2022) from the National Geographic Institute (IGN) and Valencian Cartographic Institute (ICV).
  • Hydrological data: Segura Hydrographic Confederation (CHS), Tagus Hydrographic Confederation (CHT), and the Central Syndicate of Irrigators of the Tagus-Segura Aqueduct (SCRATS).
  • Climate data: State Meteorological Agency (AEMET) and CEDEX reports.

Main Results

• Structural Planning Errors: The 1933 and 1969 plans used overestimated precipitation data (1000–1500 mm/year vs. actual 700–900 mm/year at the Tagus headwaters) and underestimated population growth (1.4 million projected for 2010 vs. 2.03 million actual in 2023).
• Transfer Deficit: The average volume transferred (1979–2022) is 308 hm³/year, which is only 51.3% of the 600 hm³/year projected for the first phase.
• Land Use Discrepancy: GIS mapping identified 34,169.6 ha of cultivable land in the study area, significantly less than the 54,543 ha reported by SCRATS.
• Cultivation Status: Of the actual cultivable area, 25,690 ha (75.2%) is currently cultivated, while 8,479.6 ha (24.8%) is abandoned or uncultivated.
• Water Demand Recalculation: The actual demand for the identified area is 118.2 hm³/year. Given the available resources of 73.9 hm³/year, there is a deficit of 58.4 hm³/year, which the authors argue can be covered by the Torrevieja desalination plant (expandable to 120 hm³/year) and wastewater reuse.

Contributions

• Provides a high-precision cartographic update of actual irrigated vs. abandoned land, correcting long-standing official overestimations.
• Critically evaluates the obsolescence of the 1969 ATS Preliminary Draft in the context of current climate change and anthropogenic warming.
• Proposes a transition from the "old hydraulic policy" of inter-basin transfers to a sustainable "multi-source" model integrating desalination, reclaimed wastewater, and rainwater harvesting to ensure regional water security.

Funding

• The authors declare no specific funding projects or reference codes in the provided text. The research was conducted through the University of Alicante.

Citation

@article{Cañizares2025Los,
  author = {Cañizares, Antonio Oliva and Cantos, Jorge Olcina},
  title = {Los problemas estructurales del Trasvase Tajo-Segura y sus efectos en las superficies cultivables del sureste español},
  journal = {Boletín de la Asociación de Geógrafos Españoles},
  year = {2025},
  doi = {10.21138/bage.3490},
  url = {https://doi.org/10.21138/bage.3490}
}

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