The contribution of sediments from the entire Ebro basin, vital management for the Delta
The Study Commission on the Protection of the Ebro Delta, held as every month in the Parliament of Catalonia, once again put on the table the need for solid sediment management to guarantee the survival of the Ebro Delta. With this, there are already three sessions that have provided the vision of experts and professionals from the academic world in relation to the problem of regression and subsidence (sinking) suffered by the Delta.
Álvaro Arasa, geologist and member of the EbreRecerca Group, and César González, doctor in fluid mechanics and professor at the Department of Science at the University of Zaragoza, participated in yesterday's commission.
Arasa explained how the Delta is currently being "deconstructed", with a clear setback, with problems of subsidence, regression of the delta front and generating a "skeletal" coast, with a river that transports very few sediments. The geologist explained that the Ribarroja reservoir would accumulate some 30 million tons of sediment, while Mequinenza would have up to 280 million tons of mud. «But to give continuity to the Ebro Delta we must not only consider the sediments. This is insufficient. We must consider the entire basin », he valued. For Arasa this also occurs by the "Dutch method", with up to 22 kilometers of sand offshore. However, the Ebro does not have these resources, although the sand is accumulating in the Fangar bay (where the year 2024 has projected a dredging by the Generalitat) and at the Cuerno point.
The sea level can have a minimum rise in 2100 of 0.43 meters, and a maximum of 0.84. “The only way to avoid it is to go up the platform and for that you need fine sediments. I bet on contributing sediments from the whole of the Ebro Basin in a domino effect, which go down systematically, by the colmateo method. It would be necessary to lower the sludge during the months of rice cultivation, "explained Arasa.
For his part, César González warned that the drainage of the Mequinenza and Ribarroja de Ebro funds should be reviewed and he warned of the presence of cracks in the Mequinenza reservoir. A dangerous situation in terms of public safety totally avoidable.
The scientist has carried out, commissioned by the Sediments Association, a report on the problem of the bottom gates of the Mequinenza and Ribarroja de Ebro reservoirs. «The panorama of the Ebro Delta is somewhat bleak. We have many dams built, others in the pipeline, also irrigation, and the withdrawal of flows is also dramatic for a delta, and the possible threat of a transfer, in addition, of course, to climate change. Inaction leads to the disappearance of the Delta as we know it," he said.
But in order to properly manage the sediments, for the doctor it is first necessary to check that the bottom drains of the reservoirs work properly, which, in his opinion, in Mequinenza and Ribarroja they do not. “They are surely clogged, and the tests that are carried out are empty. It would be good if the CHE asked for tests of real operation». The scientist also valued that the solid ecological flow of a river is calculable and manageable "but it is a matter of will."