Intensively Monitored Watersheds (IMW) Forum

An intensively monitored watershed (IMW) is an experiment in one or more catchments with a well-developed, long-term monitoring program to determine watershed-scale fish and habitat responses to restoration actions (e.g., Zimmerman et al. 2012).

The loss of Pacific salmon Oncorhynchus spp. and Steelhead O. mykiss is a significant ecological, economic, and societal issue facing the Pacific Northwest region of North America. Multiple factors including habitat loss, hatchery supplementation, hydropower, and overfishing have been identified as contributing to the decline or extirpation of these fish. The listing of many salmon and Steelhead populations under the Endangered Species Act (ESA) has resulted in approximately two decades of focused restoration efforts at the cost of several billion dollars (Bernhardt et al. 2005).

Restoration efforts are guided by the premise that increases in spawning and rearing habitat will improve juvenile life stage survival, ultimately increasing adult fish returns. However, linking habitat restoration to increased adult recruitment at the population level has been difficult (Roni et al. 2008). Further, effectiveness monitoring, the ability to monitor and detect a response from a restoration action, is not always funded or not funded at appropriate temporal and spatial scales to allow measurement of response. Therefore, monitoring and restoration practitioners often rely on incomplete or anecdotal evidence to infer responses in habitat and fish populations. Additional challenges to identifying successful population level responses (i.e., positive response to restoration) include experimental design, implementation, and analysis and monitoring issues (Roni et al. 2008; Bennett et al. 2016). In response to these challenges, IMWs have been implemented in many regions of the Pacific Northwest as long-term case studies to monitor, track, and report on the trajectory of habitat actions and fish population responses.