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Greater Yellowstone Ecosystem - Priority Ecosystem Science

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Understanding the Effects of Flow Regulation on the Snake River Ecosystem below Jackson Lake: Using Science in an Adaptive Management Framework

Snake River Dam, Jackson Lake, Grand Teton National Park.

Grand Teton National Park (GTNP) is an internationally recognized scenic area within an equally high profile ecosystem, the Greater Yellowstone Area (GYA). The Snake River hosts world class fishing and its riparian corridor supports abundant flora and fauna that depend on this system for all or part of their life cycle. The Snake River is also a working river, providing irrigation water stored in Jackson Lake for downstream agriculture, as well as recreational boating, rafting and fishing. Although located within a national park, the hydrology of the Snake River in GTNP is partly determined by releases from Jackson Lake Dam. The dam was first built in 1908, before GTNP was established and only became part of the National Park system when GTNP was expanded to include most of Jackson Hole. However, the Bureau of Reclamation (BOR) manages the dam and sets discharge schedules, primarily to meet agricultural needs, and to a lesser extent the needs of recreational river use. Management of instream flows from Jackson Lake dam has the potential to affect the riparian plant community, wildlife and fisheries and, as a consequence, is a major concern for federal and state managers within GTNP and surrounding lands. The potential for conflict among the various interests of stakeholder groups is high. In addition to GTNP and BOR, other federal agencies share an interest in management of the ecosystem (Bridger Teton National Forest, U.S. Fish and Wildlife Service, the Army Corp of Engineers [flood control]), and the state of Wyoming. The actions of the federal government are scrutinized by the public including private business interests, and groups such as the Greater Yellowstone Coalition and the Jackson Hole Conservation Alliance. Sound scientific data are required to assess the impacts of streamflow manipulation on the Snake River ecosystem in order to promote wise resource decisions. We need to understand the complexity and dynamics of the key components of the ecosystem in order to adaptively manage resources within the upper Snake River watershed below Jackson Lake.

Current Projects

  • Define the present geomorphic organization of the channel and its valley; describe the historical patterns of change in channel size, location, and planform; and describe the relation between those changes and changes in the flux of water and sediment associated with dam operations and climate-driven changes in watershed processes. (Pugesek, Schmidt)
  • Develop a budget for the bed material that comprises the Snake River. Changes in the delivery and export of bed material result in channel change, leading to the deposition of new islands in braided reaches and evacuation wherever sediment deficits occur. (Pugesek, Schmidt)
  • Define the riparian plant communities along the Snake River as they exist today. Inventory all vascular plant species in the river corridor and establish vegetation study plots. (Pugesek, Mellman-Brown)
  • Determine the physical and biological parameters that determine community type. (Pugesek, Mellman-Brown)
  • Determine distribution, relative abundance, and movement patterns of Snake River cutthroat trout Oncorhynchus clarki subsp. (Gresswell, Hommel)
  • Determine spawning areas currently being used by Snake River cutthroat trout. (Gresswell, Hommel)
  • Investigate the relationships among physical habitat, discharge, and distribution patterns of Snake River cutthroat trout in the study area. (Gresswell, Hommel)
  • Develop one- and two-dimensional flow and hydraulic models for prediction of channel stability/instability and evolution, modeling inundation regimes, as well as aquatic habitat. (Pugesek, Schmidt)
  • Develop riparian habitat change models based on changes predicted by hydrology models. (Pugesek)
  • Develop effects forecasts of trout distribution, survival and spawning as a consequence of flow regimes based on SEM causal models. (Gresswell, Pugesek)

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