of positive means of fish protection involving (1) a screen at 

 the Tracy Pumping Plant intake channel, and (2) an adequate method of 

 by-passing the screened fish to areas outside the influence of the 

 pump draft. 



Several plans for the protection of the fishery resources in the 

 Delta relative to the water-use projects have been considered by State 

 and Federal fishery agencies since construction of the Central Valley 

 Project was undertaken by the U.S. Bureau of Reclamation. Modifications 

 of this basic recommendation were mentioned briefly in the introduction. 

 The original plan of the U. 5. Bureau of Reclamation to transport Sacra- 

 mento River water through a closed channel to the Tracy Pumping Plant 

 was supported by fishery interests because it would have resulted in no 

 changes in existing flow conditions in the Sacramento-San Joaquin Delta. 

 Fish protection wo uld have been limited to the intake structure at the 

 point of diversion on Sacramento River, with very little required in 

 the way of protective devices along the closed channel. However, this 

 plan was abandoned in favor of the "State Plan", which proposed the trans- 

 fer of Sacramento River water to the Tracy Pumping Plant via existing 

 Delta channels. 



The original "State Plan", modified by the U. S. Bureau of Reclama- 

 tion, and called the Delta Cross-Channel, was thoroughly studied and 

 found to be the most economical and feasible means of delivering water 

 to the Tracy Pumping Plant. The Delta Cross-Channel will be a gravity 

 diversion with the point of diversion in the vicinity of Walnut Grove. 

 The natural diversion, Georgiana Slough, will also be used. As demands 

 increase, additional water will be obtained by constructing a diversion 

 near Isleton. The possibility of installing low-head pumps to supplement 

 flow has also been considered. Initial operation is scheduled for July 195l< 



This plan of operation imposes serious problems in the protection 

 and maintenance of the fishery resources dependent on the Delta. 



Time has not been available to carry through a screen-testing pro- 

 gram in relation to this project. However, a self-cleaning, traveling 

 water screen appears to be the most feasible because: it can operate 

 under the tidal conditions present; it can handle the great loads of 

 debris characteristic of Delta waters; and it offers a means of 

 collecting screened fish for transfer to a by-pass canal. 



* The screen structure should be located in the approach canal at a 

 point where the velocity of the current ranges between 1.5 and 2.5 feet 

 per second. Screens towed in the Delta through this range of velocity 

 demonstrated low mortality of screened fish. No trials were made with 

 velocities exceeding 2.5 feet per second. However, it is known that 

 excessive velocity does cause high mortality in the operation of station- 

 ary and rotary screens. 



Size of the screen mesh used in the traveling water screens for 

 ^ish protection is governed by the clearance between the stationary and 

 moving parts of the unit and by the sizes of fish to be screened. One 



ill 



