greater and the field must have a greater depth 

 if the fish are not literally to coast through the 

 field even after they are immobilized. An 

 electrical field for the diversion of salmon,- 

 therefore, should be of greater depth and less 

 intensity than for lamprey control. 



An idealized plan for installation of the 

 diversion weir is shown in figure 1 . This per- 

 spective drawing shows the hanging electrodes 

 upstream from the parallel ground line and 

 both forming an angle at the entrance to a fish 

 ladder. Concrete abutments have been used to 

 constrict the stream flow, to eliminate the 

 normal tapered stream bank and to ensure a 

 uniform, high velocity flow within the electrical 

 field. 



Figure 1 . --Perspective drawing of idealized 

 electrical weir installation with 

 concrete abutments to constrict 

 river flow. Fish ladder at left 

 leading to retaining area . 



The plan view of the installation and 

 actual detailed dimensions and materials used 

 are shown in figure 2. It is suggested that no 

 alterations be made either in materials speci- 

 fied, type of installation, or dimensions given, 



in weirs which do not exceed 200 feet in length. 

 Particular attention is directed to the method 

 for attaching the pipe electrodes to supporting 

 cables and to the anchoring and recessing of 

 the ground line. These are areas in which dif- 

 ficulties were encountered and for which 

 satisfactory solutions have been developed. 



Single-phase, 110-volt, alternating cur- 

 rent is used in this installation. The ground 

 line is connected to the grounded side of the 

 electrical circuit and the electrode cable to the 

 activated side. No pulsation other than the 

 normal 60 cycles is introduced. 



The electrode cable must be well above 

 the maximum high water level to allow for free 

 passage of floating debris at flood stages of the 

 river. The electrodes themselves should be of 

 sufficient length to protrude above the maximum 

 hig^ water level and to penetrate two -thirds of 

 the minimum low water depth. In the idealized 

 installation no feather -edged stream bank exists 

 due to the abutments which constrict the stream 

 flow. In some situations, specifically where 

 low stream banks preclude the constriction of 

 the flow by use of abutments, the electrodes must 

 extend into shallow water to establish a positive 

 barrier. Under such conditions a one -inch clear- 

 ance above the stream bottom is the minimum 

 practicable. Unless the stream bottom is of 

 uniform depth, which is highly improbable except 

 when a concrete apron is constructed, the pipe 

 electrodes must be cut to conform to the bottom 

 contour with allowance made for the desired 

 clearance. Numbering the electrodes will facil- 

 itate their installation each year . 



The principal differences between this 

 type of installation and the "type B" structure 

 recommended by Applegate, Smith, and Nielsen 

 (1952) are the substitution of flexible cable for 

 channel iron in the mounting of the electrodes 

 and the lengthening of the field from 8 to 15 feet. 

 The substitution of cable for channel iron allows 

 the electrodes to become free swinging in all 

 directions. Although the field is erratic close 

 to the electrodes it becomes stabilized within a 

 distance of four feet below the electrodes . Such 

 construction lightens the structure, simplifies 

 the installation, and lowers the cost . The length- 

 ening of the field is necessary because it reduces 

 the voltage within the field and increases the length 

 of the barrier . 



