Limiting Factors



Columbia Plateau Province

Walla Walla Subbasin 376, 394, 396

BULL TROUT
Key Limiting Factor Impairment Habitat Affected Threat Type Threat Name Life Stage (s) Description
Food Competition -- Fisheries Management; Species Management Species Introduction; Interspecific Interaction Juveniles, adults Bull trout compete for food and space with nonnative rainbow trout and brown trout.
Habitat Quantity and Quality Access and Availability Freshwater-Instream Agricultural Practices; Dam or Hydropower Facility Management Migration Impediments Juveniles, adults Numerous dams and diversion structures have been constructed on the mainstem Walla Walla River and in tributaries.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Instream Agricultural Practices; Forest Management Riparian Degradation; Bank Destabilization Juveniles, adults Channel confinement and riparian function, along with lack of large woody debris, have the greatest impact on bull trout throughout the subbasin.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Riparian Agricultural Practices Riparian Degradation Juveniles, adults Channel confinement and riparian function, along with lack of large woody debris, have the greatest impact on bull trout throughout the subbasin.
Water Quality Temperature; Oxygen -- Agricultural Practices; Forest Management Riparian Degradation All Mill Creek, South Fork, and North Fork do not meet state criteria for temperature. Phosphates are elevated in the South Fork.
Water Quantity Decreased Water Quantity -- Dam or Hydropower Facility Management Water: Storage or Withdrawal All The North Fork does not meet state criteria for instream flow.
SPRING CHINOOK
Key Limiting Factor Impairment Habitat Affected Threat Type Threat Name Life Stage (s) Description
Habitat Quantity and Quality Access and Availability Freshwater-Instream Dam or Hydropower Facility Management Migration Impediments Adults The Siphon diversion and Hofer Dam partially block passage in the Touchet River. Numerous obstructions, including a U.S. Army Corps of Engineers project, and Yellowhawk and Bennington diversions impede passage in the Mill Creek watershed.
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.
Habitat Quantity and Quality Morphological Changes Freshwater-Floodplain Agricultural Practices; Urbanization Diking; Impervious Surfaces (Road Density); Riparian Degradation; Wetland Loss Juveniles Floodplains in the subbasin have been extensively altered by agriculture, livestock grazing, and transportation corridors.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Instream Agricultural Practices Diking; Filling; Wood/Structure Removal Juveniles Reduced habitat quantity in the lower mainstem impacts migrating adult Chinook and downstream migrants.
Instantaneous Mortality Anthropogenic Mortality -- Dam or Hydropower Facility Management Migration Impediments Juveniles Juveniles and adults must pass four mainstem dams during migration.
Water Quality Temperature -- Agricultural Practices Riparian Degradation All High summer temperatures cause losses to spawning and pre-spawning spring Chinook in the mainstem above the Touchet River.
Water Quantity Decreased Water Quantity -- Dam or Hydropower Facility Management; Agricultural Practices Water: Storage or Withdrawal All Reduced low flows cause losses to prespawn spring Chinook in Mill Creek.
SUMMER STEELHEAD
Key Limiting Factor Impairment Habitat Affected Threat Type Threat Name Life Stage (s) Description
Biological Viability Criteria Diversity -- Artificial Propogation Straying Adult spawners Out-of-basin stray steelhead spawning with indigenous populations pose serious genetic risks.
Habitat Quantity and Quality Access and Availability Freshwater-Instream Dam or Hydropower Facility Management Migration Impediments Adults The Siphon diversion and Hofer Dam partially block passage in the Touchet River. Numerous obstructions, including a U.S. Army Corps of Engineers project, and Yellowhawk and Bennington diversions impede passage in the Mill Creek watershed.
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.
Habitat Quantity and Quality Morphological Changes Freshwater-Floodplain Agricultural Practices; Urbanization Diking; Impervious Surfaces (Road Density); Riparian Degradation; Wetland Loss Juveniles Floodplains in the subbasin have been extensively altered by agriculture, livestock grazing, and transportation corridors.
Habitat Quantity and Quality Small-Scale Structural Complexity; Morphological Changes Freshwater-Instream Agricultural Practices Diking; Filling; Wood/Structure Removal Juveniles Reduced habitat quantity in the lower mainstem impacts migrating adult steelhead and larger downstream migrants. Lack of habitat diversity results in high losses of steelhead fry in the South Fork.
Instantaneous Mortality Anthropogenic Mortality -- Dam or Hydropower Facility Management Migration Impediments Juveniles Juveniles and adults must pass four mainstem dams during migration.
Sediment Conditions Increased Sediment Quantity Freshwater-Instream Agricultural Practices; Forest Management Sediment: Bank Destabilization; Sediment: Upland Disturbance All Sediment load impacts most life stages of steelhead in the mainstem from the mouth to Dry Creek, and in the lower Touchet River. Sediment also affects most life stages of steelhead in Pine Creek.
Water Quality Temperature -- Agricultural Practices Riparian Degradation All High summer temperatures cause losses to most life stages of steelhead in the Touchet River. High temperatures also impede fry colonization and juvenile rearing for steelhead in Mill Creek.
Water Quantity Increased Water Quantity -- Dam or Hydropower Facility Management; Agricultural Practices Water: Runoff Coefficient Alteration. Eggs, juveniles Increased peak flows impact steelhead fry in the South Fork.