256 



FARM DEVELOPMENT 



Section 



throus* 



X-Y 



ranged that all the water flowing in the stream passes 

 through the notch. The Cippoletti weir is a notch of a 

 given form, and formulae have been constructed to apply 

 to the depth of the water flowing out, by this means 

 reducing the record of outflow to cubic feet per second. 

 In Figure 151 is shown the weir in perspective; and in 

 Figure 152 the form of notch, with measurements, is 

 shown in detail. 



Since the level of the water at the point where it flows 

 out of the notch is somewhat depressed the measure- 

 ment of the height 

 of the water above 



9 



the knife edge, or 

 bottom of the notch, 

 is usually taken 

 some feet from the 

 notch. This may be 

 arranged for by hav- 

 ing a peg driven in 

 the ditch, the top of 

 which is level with 

 the knife edge, that 

 by means of a pocket ruler the depth of the water may 

 be measured ; or a graduated measure may be attached 

 to the side of the weir box, as on the left side of the box 

 in Figure 151. 



The construction of the weir box 8 feet long, 4 feet 

 wide and 3 feet deep, of I and 2-inch lumber, as shown 

 in Figure 151, will cost $5 to $9. The floor is extended 

 beyond the lower end to serve as a platform to prevent 

 the falling water from washing out the ditch, and where 

 needed the sides of the ditch may be further protected 

 by riprapping with rock. The weir is more accurate if 

 the notch is chamfered with the sharp edge up stream. 

 The weir box should be large and deep in proportion to 

 the opening of the notch, that the stream may flow out 



* from Above 



Figure 152. Details of weir board. 



