Province Summary

Snake Lower Subbasin Summary

The Snake River flows across a major physiographic region of the Pacific Northwest known as the Snake River Plateau and along the southern portion of the Columbia Plateau. The Snake River Plateau extends from southwestern Oregon across southern Idaho and includes parts of Nevada and Utah. The Columbia Plateau extends south from the upper curve of the Columbia River to the Blue Mountains, west to the Cascades, and east above the Snake River, just east of the Washington-Idaho state line. These two regions are composed mainly of lava flows covered with soil. In areas where the Snake River has cut canyons, the dark basalt rock is a primary surface feature. Many of the soils of the Snake River Plateau are light and highly erodible, with low rainfall limiting the ability of vegetative cover to reestablish once removed. This results in heavy sediment loads in the river, especially during the spring runoff season.

The four dams on the Lower Snake River impound more than 96% (137 miles) of the Snake River in Washington from Asotin, Washington, to the confluence with the Columbia River at Pasco, Washington. Also impounded is the lower 3.7 miles of the Clearwater River in upper Lower Granite Reservoir. The remaining 6.0 miles of the Snake River below Ice Harbor Dam forms the uppermost reach of McNary Reservoir (Lake Wallula) on the Columbia River. The entire reach lies within a canyon cut through the Columbia plateau.

Source: Lower Snake Subbasin Plan

Status and Trends of Focal Species in Snake Lower Subbasin
Species ESU MPG Population Biological Objective (s) Biological Status Federal Status Data / Charts
Summer Steelhead Snake River  Multiple  Multiple upriver populations  Subbasin Plan Objective :
No numeric objective for adult escapement described in the subbasin plan:
Almota Creek - 62 returning adults expected if habitat objectives are attained
Deadman Creek - 80 returning adults expected if habitat objectives are attained
Recovery Plan Criteria :
Not applicable
Adult Counts (Dam)
2017: Ice Harbor Dam - 13,073 adults (wild)60
Lower Monumental Dam - 13,762 adults (wild)60
Little Goose Dam - 11,919 adults (wild)60
Threatened Status & Trends
View abundance data for Snake Lower Subbasin
Hatcheries located in Snake Lower Subbasin
**Hatchery data will be updated in 2016**

Hatchery / Acclimation Pond Hatchery Info Releases / Returns Program Reviews(APRE / HSRG / HGMP / USFWS) Map
Oxbow-Idaho Hatchery View   View View
Hatchery Releases and Returns to Snake Lower Subbasin363
**Hatchery data will be updated in 2016**

Some releases into subbasins may be from hatcheries located in other provinces and subbasins. Hatchery releases of anadromous fish, within the geographic range of an ESU/DPS, are listed accordingly.
Hatchery / Acclimation Pond Species ESU/DPS Released in 2009 Returns to Collection Facility in 2009 Data as of
Niagara Springs Hatchery Summer Steelhead Snake River Basin Steelhead DPS 526,743 8 / 30 / 2010
Rapid River Fish Hatchery Spring Chinook Snake River Spring/Summer Chinook ESU 375,750 8 / 30 / 2010
Recovery Status for ESA-Listed Salmon and Steelhead in the Snake Lower Subbasin

    No recovery status for Snake Lower subbasin.
Limiting Factors in the Snake Lower Subbasin

Key Limiting Factor Impairment Habitat Affected Threat Type Threat Name Life Stage(s) Description
Habitat Quantity and Quality Access and Availability; Morphological Changes Estuary Agricultural Practices; Urbanization Diking; Filling; Riparian Degradation; Wetland Loss Smolts Historical complex habitats have been modified through channelization, diking, development and other practices.
Instantaneous Mortality Anthropogenic Mortality -- Dam or Hydropower Facility Management Migration Impediments Juveniles Juveniles and adults must pass four to eight dams during migration.
Toxic Contaminants Water; Biota -- Pollution and Contamination Pollution: Biological Wastes, Fertilizer, & Pharmaceuticals All Contaminant inputs from upstream land-use activities are often trapped in the reservoirs behind the dams.
Water Quality Temperature -- Water Management Water: Temperature and Gas alteration All High temperatures during upstream migration of salmonids limit productivity.
Water Quantity Altered Flow Timing -- Dam or Hydropower Facility Management Water: Storage or Withdrawal, Channelization, Management Juveniles, adults Frequent water level fluctuations have a deleterious and sometimes fatal effect on juvenile salmoinds. Fluctuations in flows can delay adult salmonid migrations. Modification of the historic hydrograph due to dam operations can result in peak flows that do not coincide with optimal spawning temperatures and can result in year-class failures.