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streams are tightly coupled with catchment characteristics. Drainage basins or catchments (i.e., the river valley in Hynes' context) may indeed be characterized as ecosystems composed of a mosaic of terrestrial "patches" (Pickett and White 1985) that are connected (drained) by a network of streams. Of course, the lotic environment itself is a smaller scale patchwork or mosaic of habitats in which materials and energy are transferred (connected) through dynamic, biodiverse food webs. In most catchments, on-channel lakes and floodplain aquifers dramatically increase the complexity of the ecosystem in contrast to the contemporary view of rivers as dynamic channels bounded by a riparian corridor (Sedell et al. 1989). In this paper we discuss the catchment in ecosystem terms (Lotspelch 1980, Naiman and Sedell 1981), stressing the ecological coupling that characterizes aquatic components of catchments, and discuss natural and human disturbances that influence biophysical connectivity. We describe how management actions can work at cross purposes when the interactions of natural and human disturbances are not considered from a catchment ecosystem viewpoint and we discuss the difficulties of assessing cumulative effects of human perturbations. We use the Flathead River (British Columbia, Montana) as an example of a large river ecosystem influenced or partially uncoupled by a myriad of anthropogenic effects and competing management bureaucracies and interests. Finally, we propose an alternative general approach to natural resource management, an approach that begins with revised college curricula for training resource managers as conservators of ecological connectivity in river ecosystems. Habitat Dimensions, Ecological Connectivity and Natural Disturbance within River Ecosystems In the USA, the term watershed is often misused in the context of river basin research and management. By proper definition, the watershed is the ridgeline or elevation contour that delimits drainage basins or catchments (McKechnie 1983). The catchment is bounded by the watershed and since water flows downstream from the watershed through the catchment, thereby integrating influences of natural and human disturbances within the catchment, we use the watershed as the natural ecosystem boundary. Obviously, in these terms an ecosystem may be very small, such as a first-order catchment (sensu Strahler 1957), or it may be very large, encompassing entire river systems (e.g., the 671,000 km2 catchment of the Columbia River, USA). Choice of 4