SPILLWAYS FOR RESERVOIRS AND CANALS. 9 



been built at Klamath Falls, Oreg. (fig. 1). The water spilled is 

 diverted to the Link Eiver after it has been used to generate power. 

 The fall from the canal to the river is 48 feet in a distance of about 

 170 feet. The canal would not permit of a rise greater than 1 foot 

 above flow line, because it was built along a steep side hill and it was 

 impractical to construct the banks of sufficient height to allow of any- 

 considerable rise. The conditions required a structure capable of 

 spilling the waste water resulting from the proper regulation of a 

 power plant above the structure without at the same time causing an 

 excessive rise in the canal flow line. The sudden closing down of the 

 entire plant presented an emergency in which the entire flow had to 

 be taken care of quickly without exceeding the limiting rise and fall 

 of flow line. An overflow spillway crest to satisfy such demands 

 with its safe coefficient of discharge was calculated to be about 200 

 feet long, and to utilize as small a horizontal distance as possible was 

 concentrated by indentations to a length of 61 feet as measured in a 

 straight line along the canal bank. 



The principal .reason for concentrating the over-all length of the 

 spillway was to provide a wasteway channel through which the 

 water would be conducted over the earthen slope to the river after 

 flowing over the crest. A section 3 by 8 feet with the slope of the 

 ground at the point was capable of taking care of the discharge after 

 it had been collected, but the concentration of crest length was to 

 reduce, as far as possible, the dimensions of the upper portion of the 

 collecting channel and therefore the cost. 1 The structure only re- 

 sulted in this saving, as the same length of spillway had to be pro- 

 vided with consequent cost of construction. It is another example 

 of the adaptability of the siphon spillway in cases where space and 

 close regulation are paramount. 



SPILLWAY CONTROL. 



It may be desirable normally to carry the water near the maximum 

 allowable level rather than sufficiently below that to provide for 

 emergency flow. This is provided for by placing the permanent 

 crest of the spillway sufficiently low to pass the maximum flow, 

 and placing on top of this temporary or movable parts which will 

 go out automatically or can be removed or adjusted in case of flood 

 so as not to interfere with floating debiis. The immediate removal 

 of these barriers is of particular importance, because having provided 

 an ample spillway it should be kept free of any obstruction and at 

 all times ready for any sudden demands made upon it, regardless of 

 other agencies which may be provided as additional facilities in 

 effecting discharge. Inadequate satisfaction of these conditions has 

 led to a great number of wrecked structures resulting in the loss of 



1 Description from an article in Engineering News, Sept. 9, 1900. 



