7746

• UCREFRP Catalog Number: 7746
• Author: Stanford, J. A. and J. V. Ward.
• Title: Management of Aquatic Resources in Large Catchments
• USFW Year: 1991.
• USFW - Doc Type: Recognizing Interactions Between Ecosystem Connectivity and Environmental Disturbance.
• Copyright Material: NO

because the attendant effects were so ecologically devastating (cf. Regier et al. 1989).
In most, if not all cases, precious little information about the connectivity of these large
rivers was recorded before major human disturbances took place. However, a number
of carefully researched case histories provide insightful syntheses of the interactive
nature of human and natural disturbances on the ecology of river systems (reviewed in
Davies and Walker 1986).
Rather than attempt to summarize the many important inferences of these and
many other studies chronicling human disturbance in catchments, we present below a
single case history of a large catchment that retains many pristine attributes but is
threatened by a variety of interactive effects. In this case the cumulative effects may not
be so profound that an ecosystem level understanding might be very productive in
fostering a new management ethic. The goal is to sustain the natural ecological
connectivity of the system. We use this example to set the stage for articulation of some
new approaches to that goal that may be useful elsewhere.
A Case History of Interactive Effects on Ecosystem Connectivity
Background
The Flathead River-Lake Ecosystem in northwest Montana provides a good
example of a tightly coupled system where natural and human disturbances are clearly
interactive. Understanding of this catchment is based on ecological studies by
scientists at the Flathead Lake Biological Station (a field station of the University of
Montana), where biophysical data have been routinely collected since 1896, and a
wide variety of management-oriented research has been conducted by Tribal, State
and Federal agencies (reviewed by Stanford in press). Salient points are summarized
here.
This 22,000 km2 catchment is dominated by runoff from the myriad of tributaries
that feed the 6th order Flathead River (mean annual discharge = 340 m3 sec-1), which
flows through 496 km2 Flathead Lake (Figure 3). Water quality in this river-lake system
is extremely good; solute concentrations and bioproduction are uniformly low
(oligotrophic), waters are usually highly transparent (secchi disk readings in Flathead
Lake routinely exceed 15 m autumn and winter) and native fisheries are healthy. Less
than 80,000 people reside in the entire catchment and no major industrial or
agricultural sources of pollution currently exist. The Flathead River dominates the
inflow of solutes and particulate materials that influence water quality, structure food
webs and drive bioproduction in the lake. For example, the river provides 65% of the
annual load of bioavailable phosphorus reaching the lake. Six of the 10 native fishes
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