146 W. & L. E. GUR.LEY, TROY, NEW YORK 



Water Supply Paper 345 E, U. S. Geological Survey. In tins 

 method the estimates of daily discharge are based <m Loth tin- 

 gage height and the surface slope between two stations a suffi- 

 cient <li>ianr<- apart, the hydraulic radius at sections between 

 ihrm being constant. The registers should be local<<! far 

 -nough apart to show any appreciable change in slope, ami it i- 

 absolutely necessary that they be set to the same datum. Auto- 

 matic recording water stage registers should be used. See Figs. 

 77, 78 and 79, page 145. 



IUI5IGATION CANALS 



In all open channels in which a control section may be 

 established at which the relation of gage height and discharge 

 is constant, the current meter may be used with success, tin- 

 gage heights being recorded by automatic registers. Such 

 methods are applicable to main irrigation canals and in. MM 

 laterals of irrigation systems. The introduction of checks into 

 the subsidiary distributing channels in the course of tin ir 

 ordinary operation causes backwater along their entire length, 

 the slope being very small, and this makes it impossible to use 

 current meter stations which depend on continuous control 1W 

 their successful operation. 



HYDRAULIC POWER STATIONS 



The problem of making efficient use of the water a vail a Mr 

 for use in water wheels is constantly before operators of 

 hydraulic power stations. The results of many tests show that 

 operators heretofore have often failed to check up with -ullicient 

 care the hydraulic efficiency of their wheels to be sure that they 

 are getting all of the energy possible out of their installation. 

 Frequently, obstructions of various kinds have reduced the flow 

 into the water wheels to such an extent that they are operating 

 at an efficiency far below the manufacturers rating. 



It is now customary at well operated power stations to keep 

 careful records by means of which a loss of efficiency in the 

 operation of the plant is quickly detected and localized. 

 Operating efficiency requires that records be kept of the height 

 of water in the forebay, the height in the tailrace, and the height 

 of water flowing over the spillway of the dam. It is possible 

 to keep such records continuously by means of Gurley automatic 

 water stage registers. 



