Feature: Spain's Ebro Transfer - a major turnaround
Bigger than flamingos
(Author: Saren Starbridge)
No one was willing to be seen as anti-flamingo, but the potential for disaster, as researchers and campaigners recognised, was considerably larger than a flock of big pink birds.
Deltas are ephemeral landforms and the Ebro delta requires an estimated 1.3 to 2 million cubic metres of sediment per year just to maintain its current condition. Existing dams had already reduced the amount of sediment carried by the river.
Further dam building would cause irreversible erosion damage and, by diminishing the flow of fresh water nutrients, could kill off or severely reduce the important sardine fishery. Scientific research showed that for every cubic metre of Ebro water that failed to reach the Mediterranean, an estimated 200 kilograms less of sardines could be fished from those waters.
In addition, the proposed infrastructure works would affect riparian forests and other habitats, threaten the survival of the endangered Iberian lynx and release a flood of problems including fish migration, protection of endemic fish species and the spread of feral fish and other aquatic organisms between river basins.
Water quality was another issue. A healthy river system has a natural flushing cycle: during periods of high rainfall, the increased flow washes out algal growth and pollutants built up in drier times when the river flows more slowly. Wouldn't increasing the volume of water in the receiving basins flush them out and improve the water quality in those rivers?
The theory may look promising, but a case study of an earlier transfer from Spain's Tajo River into the Segura basin shows severe degradation in both the donor and receiver basins. Since the works, proposed in 1933, were completed in 1973, water demands and fertiliser and pesticide use have increased in the Segura basin while reduced flow in the Tajo means the river is unable to keep pace with effluents pouring in from the Madrid industrial and urban centre.
The Segura, which was to benefit from the transfer, now has the dubious distinction of being known as the most polluted river in Spain, and possibly in Europe. The middle Tagus is also known as one of the most polluted rivers in Europe, unfit even to provide water for irrigation.
