The Reaches Project : Ecological and Geomorphic Dtudies Supporting Normative Flows in the Yakima River Basin, Washington, Final Report 2002.
- University of Montana, Flathead Lake Biological Station, Poison, MT
The Yakima River system historically produced robust annual runs of chinook, sockeye, chum and coho salmon and steelhead. Many different stocks or life history types existed because the physiography of the basin is diverse, ranging from very dry and hot in the high desert of the lower basin to cold and wet in the Cascade Mountains of the headwaters (Snyder and Stanford 2001). Habitat diversity and life history diversity of salmonids are closely correlated in the Yakima Basin. Moreover, habitat diversity for salmonids and many other fishes maximizes in floodplain reaches of river systems (Ward and Stanford 1995, Independent Scientific Group 2000). The flood plains of Yakima River likely were extremely important for spawning and rearing of anadromous salmonids (Snyder and Stanford 2001). However, Yakima River flood plains are substantially degraded. Primary problems are: revetments that disconnect main and side channel habitats; dewatering associated with irrigation that changes base flow conditions and degrades the shallow-water food web; chemical and thermal pollution that prevents proper maturation of eggs and juveniles; and extensive gravel mining within the floodplain reaches that has severed groundwater-channel connectivity, increased thermal loading and increased opportunities for invasions of nonnative species. The Yakima River is too altered from its natural state to allow anything close to the historical abundance and diversity of anadromous fishes. Habitat loss, overharvest and dam and reservoir passage problems in the mainstem Columbia River downstream of the Yakima, coupled with ocean productivity variation, also are implicated in the loss of Yakima fisheries. Nonetheless, in an earlier analysis, Snyder and Stanford (2001) concluded that a significant amount of physical habitat remains in the five floodplain reaches of the mainstem river because habitat-structuring floods do still occur on the remaining expanses of floodplain environment. Assuming main stem and ocean bottlenecks are not overriding, restoration of floodplain connectivity by elevating base flows throughout the corridor, removing revetments and refilling gravel pits by natural riverine transport of gravel where possible could be successful in substantially enhancing Yakima salmon and steelhead runs. Hence, the overarching purpose of this research was to determine the ecology of major floodplain reaches of the Yakima River: Cle Elum, Kittitas, Naches, Union Gap and Wapato. Specifically, the study documented groundwater-channel connectivity and flow relations; use and quality of side channel and other floodplain habitats by salmonid fishes; and classification and analysis of floodplain habitat using remote sensing and documentation of geomorphic processes, required for a robust understanding of the feasibility of revetment removal and establishment of a normative flow regime for the mainstem river.
- Research Organization:
- Bonneville Power Administration, Portland, OR (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- 00005854
- OSTI ID:
- 828280
- Report Number(s):
- DOE/BP-00005854-1; TRN: US200427%%254
- Resource Relation:
- Other Information: PBD: 4 Oct 2002
- Country of Publication:
- United States
- Language:
- English
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