Strategies for Restoring River Ecosystems: Sources of Variability and Uncertainty in Natural and Managed Systems

8. Watershed Assessment Techniques and the Success of Aquatic Restoration Activities

G. R. Pess, T. J. Beechie, J. E. Williams, D. R. Whitall, J. I. Lange, and J. R. Klochak

doi: https://doi.org/10.47886/9781888569469.ch8

Abstract.—A major challenge in planning and executing aquatic ecosystem restoration strategies is the need to make decisions without complete understanding of ecosystems or processes affecting their conditions. Information-gathering tools such as stream classification systems, riparian-growth and wood-recruitment models, watershed assessments, historical reconstruction, and decision-support models can help reduce uncertainty in defining a path for aquatic restoration activities. We demonstrate how these tools can be used to systematically gather information for achieving improved management decisions and restoration strategies. Two major sources of uncertainty are considered: inadequate knowledge of system behavior and natural variability. Uncertainty in assessing watershed and habitat conditions to be restored reflects the lack of prior knowledge of an ecosystem’s status and functions as well as problems of coupling scientific principles with management objectives. These shortcomings arise from difficulties in defining and understanding complex ecosystem interactions and from not recognizing human limits in controlling natural environments. Additional uncertainty is due to rivers having geographically diverse and unique arrays of environmental problems and societal situations. We suggest that watershed restoration plans and efforts that incorporate uncertainty will have a greater chance of long-term success.