^_ \VA'I Gl III '.1-1 I RS 149 



accur.iti-U to \snrs us,-d 111 the li.-lil, tinier they are of the 

 same design and are M-I up in the field and u*ed under the 

 same condition* that exi*ted wh.-n they were rated. 



The ng precaution* hould be observed when using 



r- in tin- 



No water should be allowed in leak pa*t the ends of the 



it. In the ra*e of permanent %% 



unions are taken during confirm tion in guard against such 

 !. In the case of lem|M>rary weim particular attention 



niii-t I-- paid to tin- lift. ul. <.unn\ -. iit-niU used 



\Mih I.-MIJM.I.U \ u. ,i - i.. JM. \.-ut leaks. Sand bags and puddles 



ha\e also IM-.-H l|s,-d. 



The water should fall i -lie crest of the weir and 



tli* distance from (lie crest to the Ixittom of the h.inn. I in which 

 it i- m- it. .1 s||,,uld I.. ' than three times the head of 



water on tin- rn-M in onln not to suppress the contraction. 

 ill-- >ame reason, on a u< ir \\ith end "n tractions the distance 

 between the edges of the weir and the sides of the channel 

 should lx three times the depth ol the rest The depth of 

 st of a iiMLilU much less than the 



breadth <>f the rest. "I!..- .i.-pth -\i,.M 1..- not l*ss than 0.1 

 more than 4.5 feet, in order to keep within the range of 

 tests on ihe -i. in ir. 'Hie hrcadth of the crest onlinarily 



ranges I rt \sei-n <>.."> I.M.I .ni.l Jn feet 'I li- DUUdflKDH JO* i r .- 



that can be gaged convenient K on a weir 20 feet long is about 

 200 second feet. 



ll the water approaehes the crest of the weir with a veil* itv 

 exceeding 0.5 foot per second, a discharge formula involving 

 velocity of approach should be used. 



The a uioni.it i.- water stage register should be placed far 

 enough upstream from the crest of the weir to be beyond the 



-ur\e Likrn l.\ the u.tdT as it approaches- the wc-ir. 



A full discussion of the theor\ r ineasurementii will 



'iiii.l in tr\t I ..... ks MM Ihdraulics, many of whieh include 

 tables that facilitate computations ,,t discharge. In Water 

 Supply Paper No. 200, U. S. Geological Sur\e\, will lie found 

 a vahul is^iiin hy Mr. R. H Morton. M. \m. Soe. C L 



of man> 



