The theories and methods of lake-watershed ecosystem management (LWEM)

Lakes and their watersheds provide important habitat for human beings. In recent years, with the growing problem of lake eutrophication in China and other countries, the importance of integrated management of ecosystems, environmental resources, and social systems within the watershed have been highlighted. Studies have shown that lakes and their watersheds should be viewed as a holistic system from a management perspective. Based on surveys about watershed ecosystem management, management definitions and principles are presented in this paper. Further, the differences between traditional water environmental protection, integrated watershed management and watershed ecosystem management are analyzed. Ecosystem ecology, watershed ecology, ecosystem health and the watershed approach are considered to be the fundamental theories for lake-watershed ecosystem management (LWEM). Ecosystem approach and watershed analysis are taken as the methodological basis for LWEM. In light of previous studies on ecosystem management, a practical process for LWEM is given in this paper. It consists of six steps. The first is scoping of object, area and stakeholders. Second, fundamental data collection and analysis and primary judgment of ecological issues are performed. The third step is goal setting, including operational goals. Fourth, systems in the lake-watershed ecosystem are synthesized, including ecosystem dynamics modeling of lake and the watershed (EDMLW) and scenario analysis and assessment. Next, integrated assessment of the lake-watershed ecosystem, in which ecosystem health and integrity are taken as indictors for assessing ecosystem structure, is performed; ecosystem service is valued to reflect ecosystem function and ecological capacity is measured as a token of supporting capacity of the ecosystems. Adaptive management is the last step in the process, including the formulation of collaborative action and rules, optimal selection of actions and preferential sites, implementation and enforcement, and monitoring, evaluation and feedback. Three core issues are identified for LWEM; uncertainties and obstacles in the process, the effects of land use/cover change to the aquatic ecosystems, and the linkage between social and ecological systems.