Abstract

Northwest streams represent important cultural values for communities and provide critical habitat for our region’s fish, wildlife, insects, avian species, and ecosystems. Most streams in the region currently run dry at some point in the year, and many more are likely to dry as the climate changes. Understanding which Northwest streams will be resilient to drier conditions, which will dry up and when -- in other words, understanding more about streamflow permanence -- can help communities make climate-smart decisions to protect streams and the fish, wildlife and people that depend on them, along with the cultural values they support.

This report summarizes the process and outcomes of the Northwest Climate Adaptation Science Center’s (CASC) Deep Dive on climate change and stream permanence in the Northwest. We convened natural resource managers and scientists from Northwest Tribes, universities, non-profit and private sectors, and federal, state and local governments to collaboratively review what is currently known about stream permanence and how it affects people and places in the region. We also identified research and capacity needs for understanding and responding to changes in stream permanence. As in previous years, the Deep Dive served as an opportunity for participants to share knowledge, network, and collaborate on an issue of shared interest and importance.

The Deep Dive was designed to facilitate coproduction of all aspects of the process, from problem identification to the specifics of the action agenda. As in 2020, the entire process was conducted virtually in accordance with public health guidelines regarding the novel coronavirus.

Key findings from the research synthesis:

• People value intermittent streams differently, and those values shape policy and management actions. Equitable and efficient management decisions are challenged by inequitable power dynamics, a scale mismatch between river systems and societal expectations, and the constraints of western water law.
• Changes in stream permanence are being observed across the Northwest and are projected to continue under a changing climate. Yet little is known about the implications of changing stream permanence for specific communities across the Northwest.
• Streams culturally, physically, and biologically connect landscapes. As stream drying increases, these connections will become more seasonal, change, or stop altogether.
• Declining snowpack is expected to be a primary driver of climate-driven changes in stream permanence. Other potential factors include higher water demand by forests/crops, declines in summer precipitation, and changes in the amount and timing of groundwater recharge. Changes in stream permanence threaten stream-dependent species and can influence ecosystem processes, with potential downstream and cascading effects. Ecological diversity can buffer stream-dependent plant and animal communities against negative effects of stream drying.
• Though various land and water stewardship actions could potentially mitigate climate-induced changes in stream permanence, little is known about which actions are most effective or how their effectiveness will vary across different landscapes.
• Incorporating different forms of knowledge, especially Traditional Knowledge, into science, education, training and management decisions can facilitate equitable, innovative outcomes related to decisions that affect stream permanence.

In addition to synthesizing the research, our report proposes both research and capacity needs that, if pursued, could improve our understanding of changing stream permanence and our capacity to manage these changes. As part of the workshop, participants voted on the needs. Below is a summary of the top-scoring needs:

Research Needs:

• Hydrologic and climate studies to better quantify climate impacts on stream permanence. Including surface water – groundwater connections.
• Studies linking land and water use activities (e.g., logging, irrigation), and disturbance (e.g., wildfire, bark beetles), with changing stream permanence.
• Evaluate the adaptive capacity of flora and fauna to intermittency of varying durations (weeks, months, years), and resilience of ecological functions.
• Evaluate effectiveness and potential scope of mitigation actions, including: land and riparian cover, water conservation, groundwater recharge. • More and better baseline data to support improved predictions of stream permanence.

Capacity Needs:

• Facilitate data collection through standardized practices and by expanding low-cost, robust, and automated monitoring systems for non-perennial streams.
• Facilitate knowledge sharing across the region (e.g., best practices, research).
• Improved collaboration between Tribes and non-Tribal entities; better incorporation of Traditional Ecological Knowledge, more widespread training on ethical collaboration and knowledge-sharing.
• Tools and strategies to support adaptation to changing stream permanence, tailored to address the needs of different contexts (e.g., regulatory vs voluntary mitigation, high desert vs montane ecosystems).

From this list, participants identified four key needs to discuss in further detail; breakout sessions for each of these needs were used to brainstorm specific actions that could address each need (Appendix D). 

We also identified eight pilot project ideas (Appendix E). Ranging from mapping tools to training resources to fact sheets, these are low-effort / low-cost actions that could be taken in the near term to advance our understanding and capacity to address changing stream permanence.