EFFECTS OF WATER TRANSFERS PROJECTED IN THE SPANISH NATIONAL HYDROLOGICAL PLAN ON THE ECOLOGY OF THE LOWER RIVER EBRO (NE SPAIN) AND ITS DELTA

This paper refers to the effects of projected water transfers, envisag ed in the Spanish National Hydrological Plan, on the ecology of the lo wer River Ebro and its delta. Present management strategies, have resu lted in highly eutrophic river water and a salt wedge which runs for m ore than 30 km upstream from the river mouth and its presence has been recorded during most of the year. Some parts of the delta coast are i n regression as most of the inorganic sediments carried by the river a re trapped in the darns. This is also leading to the sinking of the de ltaic plain because subsidence and eustatic sea level rise are not com pensated by new sediments. The high productivity of two bays and the c oastal zone adjacent to the delta is related to influx of freshwater f rom irrigation channels, used in rice cultivation and the river. In th e new National Hydrological Plan, a withdrawal of water upstream from the delta of 2012 hm(3)/year (15% of the mean annual discharge) is pla nned as well as the construction of 49 new reservoirs, mainly for irri gation purposes. A minimum river flow of 100 m(3)/s will be establishe d by the Plan. If the plan is carried through, due to the water abstra ction, forecasts based on ecological studies in the area predict: (1) increased presence of the salt wedge in the final 18 km of the river w ith detrimental effects on river fauna and flora; (2) serious threats to aquaculture and fisheries in the bays; (3) reduction of fish and cr ayfish production in the platform area; (4) further reductions in sedi ment and freshwater inputs to delta; (5) salinization of fields under cultivation; and (6) detrimental side effects on deltaic ecosystems.