Déficit de sedimento fluvial a causa de las presas y las extracciones de áridos. Revisión con ejemplos del NE de España

Resumen

Rivers carry sediment almost continuously from headwaters to deposition zones. Dams and gravel mining interrupt such continuity, causing severe damages to downstream fluvial and coastline ecosystems. Sediment deficit is not only an environmental issue, but also a socio-economic problem. Sediment captured by reservoirs reduces their capacity to store water, and infrastructures in rivers and beaches are also strongly affected by lack of sediment. Sediment deficit and its effects are illustrated in this report with examples from NE Spain, focusing on the Ebro River and rivers in the Catalan Coastal Ranges and Eastern Pyrenees. Over the long-term, sound programmes must be definitively implemented to monitor sediment transfer in river systems and changes over time. But, in the meantime, short-term correction steps should be undertaken, including a) for gravel mining, prohibition in strongly unbalanced rivers, especially in reaches downstream of dams, adding of environmental costs into the price of product (aggregate), and exploring alternative sources of aggregate (concrete recycling, reservoir deposits), and b) for regulated rivers, sediment-pass through in reservoirs only during high flows, and mechanical removal from reservoirs together with flushing flows for artificial sediment nourishment downstream, to prevent (or restore) lost of fish habitat and delta regression.