Water Quality in the Future Alcolea Reservoir (Odiel River, SW Spain): A Clear Example of the Inappropriate Management of Water Resources in Spain

The Odiel River is located in southwestern Spain; the greater portion of its basin is composed of materials from the Iberian Pyrite Belt (IBP), an area with numerous massive sulfide deposits that have been highly exploited since the third millennium BC. As sulfides come into contact with the atmosphere due to mining activity, oxidation occurs, generating a highly toxic acidic leachate with large concentrations of sulfates and metals, a process which is known as acid mine drainage (AMD). As a result, the Odiel River and most of its tributaries are severely contaminated. The construction of two large dams in the Odiel River basin is planned. The most advanced project is that of the Alcolea reservoir, with a storage capacity of 274 hm³, whose construction has already begun, with a total budget of around €164 million. There are reasonable doubts about the final quality of the reservoir water, as this dam will regulate a river with a mean pH close to 3.5 and large concentrations of toxic elements. This paper analyzes the data of water quality in the Alcolea reservoir. The results show that the reservoir water will be acidic and not useful at all, although more specific studies are necessary to obtain the exact estimation of its hydrochemical characteristics. It seems unwise to start building the dam, which requires a large economic investment and will have a vast environmental impact, without first conducting these studies. This proves that water management in Spain is still based on political motivation rather than on technical criteria and good management of natural and economic resources.