5 Management of Aquatic Resources in Large Catchments: Recognizing Interactions Between Ecosystem Connectivity and Environmental Disturbance J.A. STANFORD AND J.V. WARD Abstract Management within catchment basins must be approached with an empiri- cally based understanding of the natural connectivity and variability of structural and functional properties of riverine ecosystems. Rivers are four- dimensional environments involving processes that connect upstream-down- stream, channel-hyporheic (groundwater), and channel-floodplain (riparian) zones or patches, and these differ temporally. Natural and human distur- bances, including biotic feedback (such as predation, parasitism, and other food web dynamics), interact to determine the most probable biophysical state of the catchment ecosystem. Human disturbances can be quantitatively determined by deviations from an observed biophysical state (baseline), but usually this requires long-term ecological data sets. A case history of the Flathead River-Lake system in Montana (USA) and British Columbia (Can- ada) is summarized to illustrate how disturbances interact at the catchment level of organization. Owing to the natural complexities of catchment eco- systems and the cumulative effects of human disturbances, the rationale and logistics of obtaining long-term data often seem intractable and excessively expensive. The naive alternative is to derive and implement simplistic pro- cedures that are agency specific and often result in management actions that interfere with each other. We argue that integrated management at the catch- ment level is needed and propose some simple principles, beginning with broader based collegiate training for prospective managers. Key words. Ecosystem, river, catchment, drainage basin, management, dis- turbance, natural resources, watershed, Flathead River, Montana. Introduction Professor Noel Hynes first synthesized the concept of ecological connectiv- ity in the context of river systems in his Baldi Lecture at the 19th Congress 91 R. J. Naiman (ed.), Watershed Management © Springer-Verlag New York, Inc. 1992