Integrating regional and local monitoring data and assessment tools to evaluate habitat conditions and inform river restoration..

Restoring degraded rivers requires initial assessment of the fluvial landscape to identify stressors and riverine features that can be enhanced. We associated local-scale river habitat data collected using standardized national monitoring tools with modeled regional water temperature and flow data on mid-sized northwest U.S. rivers (30-60 m wide). We grouped these rivers according to quartiles of their modeled mean August water temperature and examined their physical habitat structure and flow. We compared local conditions in the Priest River, a river targeted for restoration of native salmonid habitat in northern Idaho, with those in other rivers of the region to infer potential drivers controlling water temperature. We found that the warmest rivers exhibited uniformly simplified physical structure, suggesting that thermal and physical degradation together may comprise a syndrome. The Priest River sites had approximately twice as many deep residual pools and incision that averaged twice that in the coldest rivers. Percentage fines and natural cover in the Priest were also more typical of the higher-temperature river groups. We found low instream cover and low levels of large wood both across the region and within the Priest River. This approach can help define attainable goals for management and restoration.

Impact/Purpose

Recreationally and culturally important native trout species have recently declined in the Lower Priest River within the Kalispel Tribal lands of northern Idaho. Potential causes of the declines are changes in flow, temperature, and channel morphology relative to past conditions in the river. The Clean Water Act expresses the public interest in restoring the fishability of waters in the U.S. This research identifies factors limiting fishability in a cold-water river fishery that has had recreational importance and cultural importance to the Kalispell Tribe. Furthermore, it provides a template for restoring fish habitat supporting that fishery. The field and analytical methods used to evaluate channel morphology, fish cover, and habitat in this project were adapted from those of EPA’s National Aquatic Resource Surveys, demonstrating the relevance of those methods to the agency goal of assessing and restoring the fishability and biointegrity of waters in the U.S. In this study, the authors combined local habitat monitoring data combined with streamflow and broad-scale modeled water temperature data and compared habitat conditions and water temperature in the Priest River to other rivers throughout the Pacific Northwest region of the USA. They found that the warmest rivers had simplified channel structure, greater incision, excess fine sediments, reduced riparian cover, and diminished summer flows. The Priest river shared many of the characteristics of thermally degraded rivers. On the other hand, the Priest River had greater instream fish cover and smaller amounts of fine sediment – characteristics more typical of the coldest rivers. Their results suggest likely achievable target conditions for rehabilitating fish habitat and water temperature to inform and guide riverine restoration and management efforts in the Priest River and across the Pacific Northwest. The results will be directly applied by the Kalispell Tribe, Idaho Fish & Game, and USGS cooperators in planning fish habitat restoration on the Priest River. The river sampling design, methods, and general results serve as a template for cost-effective river fish habitat restoration in other rivers within the Pacific Northwest and some other regions.

Citation

Mejia, F., J. Connor, Phil Kaufmann, C. Torgersen, E. Berntsen, AND T. Andersen. Integrating regional and local monitoring data and assessment tools to evaluate habitat conditions and inform river restoration.. AFS Idaho Chapter Annual Meeting, Virtual, N/A, March 01 - 04, 2022.