The estimated 1946 requirement of 128,000 acre-feet of water 

 for this plan (Table 22) Ib the amount needed for 15,000 salmon which 

 are believed to have passed Lewiston in 1946* The 1946 estimate was 

 established from observations of concentration on spawning beds during 

 that year compared with observed oonoentrations in 1944 and 1945 when 

 actual counts were made. 



Because of the unreliability in flow of tributary streams immediately 

 below Lewiston, required stream flows should be measured at Lewiston dam. 

 As shown in Table 2 3, there is very little water entering the river be- 

 tween Lewiston and Lowden during the salmon nesting season (October- 

 December). This early fall inflow is supplied almost entirely by 

 periodic rains, and in dry years it would be negligible in its effect 

 on salmon spawning conditions. It is, therefore, necessary to request 

 a quantity of resex-voir water for fishery management equal to the amounts 

 required by the plans discussed herein, to be certain of producing proper 

 spawning conditions each year. 



The studies that preceded the formulation of these management plans 

 were made during a period when no mining silt was introduced into the 

 river in the major areas involved. These plans, if they are to be 

 sticoessful, can be placed in operation only under similar conditions. 

 If a heavy load of mining silt were allowed to enter these crowded 

 spawning areas, the fishery might be seriously threatened. Regulated 

 flows are far below those normally encountered following salmon spawn- 

 ing under natural conditions; thus silt could settle out rapidly, impact 

 the gravel, and suffocate eggs and yotuig fish* Therefore, stringent 

 measures must be taken so that no mining silt will be introduced into 

 the river during the salmon and steelhead spawning ajad hatching periods 

 (October 1 through July 15). 



IJaprovement of tributary streams 



Four streams tributary to the Trinity River below the Lewiston 

 dam site might be developed for salmon and steelhead spawning. These 

 are Rush Creek, Browns Creek, the South Fork of the Trinity River, and 

 Hay Fork, a tributary to South Fork. Rush Creek and Browns Creek are 

 available for salmon spawning only after rains increase their flows, 

 and the South Fork has spring and fall migrations of salmon each year. 

 No salmon spawn in upper Hay Fork. 



Eaoh of these streams has been studies to determine the extent 

 to which it might be developed for salmon spawning. Information obtained 

 is not complete, but enough data have been gathered to show relative 

 possibilities. It has not been possible to make spawning bed surveys 

 of these streams during optimum flow conditions. Surveys have been con- 

 ducted, however, to determine the general stream types, and nest covuits 



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