Water management and wise use of wetlands: enhancing productivity

Abstract

Lakes and reservoirs are affected by human interventions mainly by eutrophication. Changes in morphology are less common, although siltation and local alterations to the riparian zone can result from urbanisation,marina construction and deforestation. In lakes and particularly reservoirs used for water supply and power generation, rapid drawdown can occur that damages riparian vegetation and fish populations. It is unlikely that any of these changes will be reversed for many centuries and it may be anticipated that the pace of river and lake modification will intensify in the coming years in response both to the economic imperatives of development and to global warming. This means that fisheries that are already affected negatively by heavy fishing will be placed under increasing pressure by environmental degradation. They can respond to this in two ways. Inland fish can disappear as a resource for human diets and food fisheries will be replaced by recreational or conservationist goals, as has already happened in much of Europe. Alternatively fisheries will continue but in a very different manner from the present day, with much reduced catches from a relatively restricted spectrum of species. If fisheries are to continue to provide appreciable quantities of valuable protein food some form of intensification of management will have to occur. This paper reviews some of the techniques that are already current in some rivers as candidates for wider use in mitigating the impacts of human development on rivers.