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C. Enhanced absorption capacity of river basin ecosystems as a new component of integrated watershed management

As a starting point to achieving sustainable water resource management in freshwater ecosystems, two fundamental parameters should be assessed and regulated. First, the absorption capacity of ecosystem (or its resistance to change and resilience) in response to anthropogenic impacts should be determined. In the case of Lake Tanganyika, for example, its size, depth, and dynamics of biological productivity possess a very high resistance to nutrient loading, and, in consequence, the symptoms of eutrophication are likely to be limited to urbanised coastal areas for quite a long time. The opposite situation often appears in shallow reservoirs, where an high ratio of catchment to reservoir surface area, and lack of stratification, can amplify the symptoms of eutrophication.

Second, the intensity of the human impact has a two-dimensional character: point source pollution, which can be reduced significantly by technologies, and the degradation of evolutionarily established water and nutrient cycling in the catchment. The traditional approach to river basin management focused on the elimination of flood risk, which often led to the over-engineering of the environment by formation of straight channels, the elimination of land/water ecotones (the riparian zone and floodplain), and the acceleration of water flows. This may reduce water quality by destroying the natural ecosystem structure and processes. The loss of biodiversity and self-purification potential has the additional consequence that the evolutionarily established resistance and resilience of ecosystems against natural disturbances is lost. Because various forms of human impact act in a manner analogous to natural disturbances, the methods of restoration should use ecosystem properties as a management tool, and apply a full range of phytotechnologies.

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