Effective Conservation and Restoration of Desert Riverscapes Must Include Conservation of In-Stream Flows: What can we learn from a Case Study from the White River, Utah
Casey Pennock1*, William Macfarlane1, Phaedra Budy2,1, Justin Jimenez3, Jerrad Goodell4
1Department of Watershed Sciences, Utah State University, Logan, UT, USA; casey.pennock@usu.edu, wally.macfarlane@usu.edu
2U.S. Geological Survey, Utah Cooperative Fish and Wildlife Research Unit and Department of Watershed Sciences, Utah State University, Logan, UT, USA; phaedra.budy@usu.edu
3U.S. Bureau of Land Management, Utah State Office, Salt Lake City, UT, USA; jjimenez@blm.gov
4U.S. Bureau of Land Management, Vernal Field Office, Vernal, UT, USA; jgoodell@blm.gov
Water development has threatened the ecological integrity of riverine ecosystems directly and indirectly through habitat degradation. Riverscape conservation and restoration practioners must contend with compounding effects of increasing demand for water, persistent drought, non-native species establishment, and climate change which exacerbate effects of habitat degradation and loss in altered rivers such as the Colorado River basin, USA. To demonstrate the need to include conservation of in-stream flows in desert river restoration, herein, we present an adaptive conservation, restoration, and monitoring plan for the lower White River, UT, a tributary to the middle Green River, and discuss the importance of using flow conservation as a foundation for conservation and restoration actions. Previous conservation and restoration actions in the lower White River riverscape have primarily focused on removal of non-native Russian olive (Elaegnus angustifolia) in proximity to legacy stands of Fremont cottonwood (Populus fremontii), largely to reduce fire risk. In our plan, we focused on a coupled approach of conservation of the natural flow regime and restoration of riparian vegetation to prevent further vegetation encroachment on the active channel, and to encourage channel widening and meandering, and the contribution of large wood. As the focus of our proposed management actions, we identified the riparian and geomorphic features we hypothesize are contributing to in-stream habitat complexity. These features create linkages between the riparian area and the active channel (i.e., biological linkages) and geomorphic features within the active channel (e.g., side bars, point bars, etc., depositional areas), which we predict are prone to establishment of riparian vegetation. We identified biological linkages and bar features in four river reaches encompassing 95 km of the lower White River. We coupled these features with a comprehensive riparian vegetation classification to rank features for management actions. We then prioritized different conservation or restoration goals based on predicted annual flows. Traditionally, conservation and restoration actions in riverscapes have taken place at fine-scales and have largely focused on reducing densities of non-native species. Few efforts have considered flow conservation in prioritization schemes as well as annual flow characteristics; yet this approach allowed us to focus on ecologically and geomorphically-relevant features and scales at which to prioritize conservation and restoration. We contend that the natural flow regime is crucial to the long-term success of management efforts because of the critical role flow plays in the creation and maintenance of important habitat for both in-stream and riparian communities.