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use projects. 



From 30 to 60 percent of historical anadromous salmonid spawning habitat in the Columbia 

 basin has been lost forever because of water-use projects. Remaining habitat has been degraded 

 by water and land use. About one-third of historical anadromous habitat has been lost in Oregon 

 and about 17 percent in Washington. Where upstream passage has been provided, effectiveness 

 of this passage is a problem. The best available estimate of upstream passage failure in about 

 10 percent per project (dam and reservoir) for the Columbia and Snake rivers. This includes 

 direct and indirect mortalities. Cumulative upstream mortality for adult salmon passing six dams 

 to return to the Imnaha River in Oregon, as an example, is about 60 percent. 



Downstream passage for juveniles is even more perilous. Cumulative mortalities at Columbia- 

 Snake River projects for Snake River basin salmonids can exceed 90 percent. Turbine mortalities 

 are about 11 percent per project and reservoir mortalities are about 1 percent per mile of 

 reservoir. 



A large percentage of summer runoff is diverted for agriculture irrigation throughout the Pacific 

 Northwest. Seasonal availability is insufficient to meet human use demands, and fish needs are 

 secondary to human use. Irrigation is the dominant consumptive use. Water flows in streams 

 are significantly reduced, which reduces salmonid stream habitats. At present, only 2 percent 

 of 56,000 diversions in Oregon that potentially affect fish are screened. Some 3,200 priority 

 unscreened diversions have been identified in the state. Although not as bad, the problem does 

 exist in Washington. It is difficult to assess juvenile salmonid diversion losses to agriculture and 

 other diverted uses, but probably billions of anadromous fish have been lost. In addition, flow 

 reductions increase summer temperatures in streams and increase the concentrations of 

 pollutants. Warmer temperature cause chronic stress in salmonids and promote pathogen 

 infections. Several authors concluded that water developments in the Columbia basin have altered 

 the physical-chemical environment so that conditions are now suboptimal for salmonids and more 

 optimal for disease pathogens and predators. 



Local flood protection measures have destroyed hundreds of acres of flood plain riverine habitats 

 and shallow estuary habitats. Historically, these were very productive nursery habitats. Ninety 

 percent of estuary losses were related to diking that was used to create and protect agricultural 

 lands. 



Water-use impacts in the Columbia basin have been severe, and these developments have 

 seriously reduced the number of native anadromous salmonids and limited their potential 

 recovery. The area above Bonneville Dam has the highest proportion of salmonid stocks with 

 decreasing spawning escapement trends. 



Land Use 



Land use-impacts are secondary to water use-impacts for native salmonids in the Columbia basin 

 but are the major source of impacts in coastal and Puget Sound basins. As the Pacific Northwest 



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