LOW-HEAD DEVELOPMENTS 73 



instances the entire water conductor from the diversion dam to 

 the wheels may be of enclosed pressure type. The quantity of 

 water is usually much smaller than in low-head plants. 



High-head developments are characteristic of the California 

 water powers where the high mountain storage of the winter 

 flood waters can be used during that part of the year when the 

 run-off is a minimum. 



A typical high-head installation is shown in Fig. 27. It con- 

 sists of a diversion dam with spillway for impounding the waters 

 of the river, thus forming a reservoir of considerable size. The 

 intake is located at right angles to the dam, thus lessening the 

 accumulation of ice, logs, trees and other floating debris in front 

 of the intake trash racks. 



The water conductor connecting the intake and the turbines 

 in the power-house consists of five sections; a reinforced concrete- 

 lined tunnel blasted through rock, a wood-stave pipe, a steel 

 pipe, a distributor and finally the steel penstocks. 



