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 present an inland Northwest USA case study in which we integrated local scale river habitat data collected using national monitoring tools with modelled regional water temperature and flow data. We compare local conditions in the Priest River in northern Idaho with those in other rivers (30 to 60 m wide) of the region. We summarized the variation in several dimensions of physical habitat among rivers using principal components analysis (PCA), and evaluated statistical associations among habitat metrics, flow, and mean August water temperature for the region. Results revealed high variability in aquatic conditions, but generally low instream cover, and low levels of large woody debris (LWD) across the region and within the Priest River. Habitat metrics including depth and LWD in Priest River sites differed significantly from other rivers grouped according to the level of anthropogenic disturbance. Elevation, mean summer areal flow, and drainage area explained 74 percent of the variability in modelled water temperature across the region. These approaches can be used to inform management and restoration and to develop aquatic monitoring plans at local and regional scales.

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 and present land and water management.The researchers floated the lower 70 km of the river, using temperature probes and acoustic doppler current profiling (ADCP) to produce longitudinal profiles of thermal patterns, water velocity, and depth. They complemented these spatially continuous data with (1) in-situ thermographs placed every 2 km and at selected pools and tributary junctions, and (2) physical measurements of channel morphology, and instream and riparian cover using EPA National Aquatic Resource Survey methods. Results revealed high variability in aquatic conditions, but generally low instream cover, and low levels of large woody debris (LWD) across the region and within the Priest River. Habitat metrics including depth and LWD in Priest River sites differed significantly from other rivers grouped according to the level of anthropogenic disturbance. The results showed cooling of the river below the epilimnetic water release from the Priest Lake outlet dam and cold groundwater inputs along the river course, but solar radiation warmed it in wide, slow-moving stretches. Good conditions for the targeted fish were found where cold-water refuges coincided with adequate depth and cover. Large deep pools and cover for fish (e.g. overhanging vegetation, brush, large woody debris, and undercut banks) were limited in the river, and cold-water areas associated with tributary junctions were localized.These findings can be used to design restoration efforts focused on increasing instream cover, habitat complexity, and riparian shading can be focused on restoring and enhancing these riverine features at specific locations where cold water enters and is entrained in the river channel. The study demonstrates the importance of high-resolution, spatially extensive assessments of the ecohydraulic landscape to help prioritize the selection of sites for restoration. 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.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.

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. Elsevier Science Ltd, New York, NY, 131:108213, (2021). [DOI: 10.1016/j.ecolind.2021.108213]

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