Integrated environmental management of current reservoirs and regulated rivers

At present, it is a common practice to identify reservoirs as the cause of negative effects on the regulated reaches of rivers. Reservoirs and regulated rivers maintain a close unidirectional relationship, downstream, so that the management of a reser-voir, in addition to conditioning its own ecological characteristics, also determines the organization, operation and possibilities of the regulated river ecosystem. Within Spain, the four main environmental problems affecting the reservoir-regulated river system are the alteration of flow regimes, the eutrophication, the interruption of sediment transport and the increasing practice of introducing exotic species. It is possible to continue to draw an indefinite list of the concerns in measuring and criticizing the impacts of reservoirs on rivers, even proposing the demolition of dams, but it is also possible to think about the strategic value of reservoirs in guaran-teeing availability of water and the preservation of the standards of living obtained as a result, and to therefore promote an environmental management program to reduce the negative impacts upon the rivers. The options for controlling levels and flows offered by almost any dam, together with the inclusion in the operating program of each reservoir of a set of environ-mental goals for the reservoir itself and for the downstream regulated river, is an area of application within limnology which has not been as propagated as it should have been. Many myths have still to be demolished –although perhaps no as many as there are dams proposed- and there is considerable margin for the improvement of regulated rivers. The environmental mana