CIVIC-PG Track A Building a coalition of scientists, Tribal representatives, and resource managers to test forest management effects on summer low flows in the Pacific Northwest

Summer streamflows are critically low in numerous Pacific Northwest watersheds and are projected to decline further as temperatures rise and snowpack diminishes. These flow conditions result in poor quality aquatic habitats that are detrimental to salmon and other fish. The Nooksack Tribe, along with other Tribes in the region, are looking closely at management options that could help to sustain the survival of salmon, which are critical for cultural, spiritual, environmental, and economic uses.

Forests are a key influence on the amount and timing of streamflow in a watershed, and forest management approaches such as thinning in lieu of clearcut harvest may drive increased streamflow during the dry summer season. A few previous studies support this concept based on observational data collection and numerical modeling, but there is limited confidence in these effects for western Washington due to a lack of regionally relevant observations and modeling.

This project will assemble a regional coalition of scientists, Tribal representatives, and resource managers to collect relevant data, implement modeling, and provide actionable results that can inform strategies, decisions, and policy.

In the Pacific Northwest region of the United States, threatened and endangered salmon species sustain continued losses due to low summer flows and elevated stream temperatures. These critical streams are fed by watersheds that have experienced over a century of clear-cut timber harvest rotations, which have resulted in a mosaic of young, regenerating forest stands.

Preliminary investigations of the effect of forest age and regeneration on summer low flows indicate that the legacy of even-age management may have contributed to declines in summer flows relative to mature old growth stands, but the issue is still understudied. For example, model representations of forest transpiration as a function of stand age is based on two studies located in the coastal range of Oregon, rather than in upland forest plantations of the western Cascades.

This project aims to build a community of Tribal representatives, scientists, and water managers to guide the development of a targeted, decision-relevant research plan. Stage 1 will include workshops, field reconnaissance, and instrumentation testing, and Stage 2 aims to collect sap flux, soil moisture, and snow data across forest types to support testing and implementation of two hydrological models.

Together, the field and modeling approaches will build actionable knowledge of the hydrologic linkages between the upper watershed, where forest management is occurring, and the stream channel, where salmon are spawning and rearing.

This project is in response to the Civic Innovation Challenge program’s Track A. Climate and Environmental Instability - Building Resilient Communities through Co-Design, Adaption, and Mitigation and is a collaboration between NSF, the Department of Homeland Security, and the Department of Energy.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.