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Vulnerable Waters – Headwater Streams and Non-Floodplain Wetlands – are Essential to Watershed Resilience (2023 ICRW)
Citation:
Lane, C., I. Creed, H. Golden, S. Leibowitz, D. Mushet, M. Rains, Q. Wu, E. D'Amico, L. Alexander, G. Ali, N. Basu, M. Bennett, J. Christensen, M. Cohen, T. Covino, B. DeVries, R. Hill, K. Jencso, M. Lang, D. McLaughlin, D. Rosenberry, J. Rover, AND M. Vanderhoof. Vulnerable Waters – Headwater Streams and Non-Floodplain Wetlands – are Essential to Watershed Resilience (2023 ICRW). 2023 Interagency Conference on Research in the Watersheds (ICRW), Corvallis, OR, June 05 - 08, 2023.
Impact/Purpose:
Headwaters and non-floodplain wetlands affect hydrologic/biogeochemical storage and flux. Watershed resilience and state are adaptively maintained by these vulnerable waters. Vulnerable water modification presages hydrologic/biogeochemical regime shifts.
Description:
Watershed resilience is the ability of a watershed to maintain its characteristic system state while concurrently resisting, adapting to, and reorganizing after hydrological (e.g., drought, flooding) or biogeochemical (e.g., excessive nutrient) disturbances. Vulnerable waters include non-floodplain wetlands and headwater streams, abundant watershed components representing the most distal extent of the freshwater aquatic network. These systems are termed “vulnerable waters” due to their susceptibility to modification and destruction because of limited regulatory protections and the insufficiency of their mapped extent. Vulnerable waters are hydrologically dynamic and biogeochemically reactive aquatic systems, storing, processing, and releasing water and entrained (i.e., dissolved and particulate) materials along expanding and contracting aquatic networks. The hydrological and biogeochemical functions emerging from these processes affect the magnitude, frequency, timing, duration, storage, and rate of change of material and energy fluxes among watershed components and to downstream waters, thereby maintaining watershed states and imparting watershed resilience. We present here a conceptual framework for understanding how vulnerable waters confer watershed resilience. We demonstrate with examples from the literature how individual and cumulative vulnerable-water modifications (e.g., reduced extent, altered connectivity) affect watershed-scale hydrological and biogeochemical disturbance response and recovery, which decreases watershed resilience and can trigger transitions across thresholds to alternative watershed states (e.g., states conducive to increased flood frequency or nutrient concentrations). We subsequently describe how resilient watersheds require spatial heterogeneity and temporal variability in hydrological and biogeochemical interactions between terrestrial systems and down-gradient waters, which necessitates attention to the conservation and restoration of vulnerable waters and their downstream connectivity gradients. To conclude, we provide actionable principles for resilient watersheds and articulate research needs to further watershed resilience science and vulnerable-water management.
