SPILLWAYS FOR RESERVOIRS AND CANALS. 



15 



of the spillways of the United States Eeclamation Service at Boise, 

 Idaho, and on numerous other spillway crests in this country and in 

 Europe. 



On the Grand River, near Grand Junction, Colo., the spillway of 

 the United States Eeclamation Service is provided with seven such 

 rollers, six of which are 70 feet long and 10.5 feet high, and one 60 

 feet long and 15.33 feet high. They are set on the crest of a concrete 

 spillway of the ogee type, 24 feet high and 537 feet long as measured 

 between abutments, the spillway being designed to care for a dis- 

 charge of 50,000 second-feet. 



*-|4..0-> 



Fig. 4. — Holter dam of the Montana Power Co. Cross section of spillway of development 

 near Helena, Mont. Shows baffles at toe of dam td neutralize the energy developed by 

 the water pouring over the crest. 



All these devices, as stated, are for spillway control and add 

 nothing to its capacity or to its value as an automatic structure other 

 than to lower the crest in times of flood and permit of raising the 

 water level in normal times. 



SIPHON SPILLWAYS. 



As long ago as 1870 siphon spillways were used in Europe, but 

 their operation required an ejector to cause them to function prop- 

 erly. Later designs making them as nearly automatic as construc- 

 tion conditions permitted were perfected and installed at about the 

 same time by Heyn in Prussia, and Gregotti in Italy. 1 



Engineering News, Apr. 20, 1911. 



