Contents preface (VII) introduction 1—37

Section A-A
Fig. 5.23 Parshall flume
There are 22 standard designs covering a wide range of discharge from 0.1 litre per second to 93 m³/s. The main dimensions of the Parshall flume are given in Table 5.3 and Fig. 5.23. The discharge characteristic of these flumes are given in Table 5.4.
5.12.3. Current Meter
The current meter is a widely used mechanical device for the measurement of flow velocity and, hence, the discharge in an open channel flow. It consists of a small wheel with cups at the periphery or propeller blades rotated by the force of the flowing water, and a tail or fins to keep the instrument aligned in the direction of flow. The cup-type current meter has a vertical axis, and is a more rugged instrument which can be handled by relatively unskilled technicians. The propeller-type current meter has been used for relatively higher velocities (up to 6 to 9 m/ s as against 3 to 5 m/s for the cup-type current meter). The small size of the propeller-type current meter is advantageous when the measurements have to be taken close to the wall. The propeller-type meter is less likely to be affected by floating weeds and debris.

CANAL IRRIGATION 205

	Z3613–––––––––––––––––––
	Y	13	25	38	76	76	76	76	76	76	76	76	76	76	76	229	229	229	229	229	229	229	229
	X	8	16	25	5	51	51	51	51	51	51	51	51	51	51	305	305	305	305	305	305	305	305
	R	–	––	406	406	508508	508	508	610	610	610	610	610	––––––––
	P	–	–	–	902	1080	1492	1676	1854	2222	2411	3080	3442	3810	4172	––––––––
	N	29	43	57	114	114	229	229	229	229	229	229	229	229	229	343	343	457	686	686	686	686	686
(9)	M	–	––	305	305	381381	381	381	457	457	457	457	457	––––––––
(mm)
	K	19	22	25	76	76	76	76	76	76	76	76	76	76	76	152152229305305	305	305	305
Table 5.3 Parshall flume dimensions
	H	203	257	309	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
	G	203	254	305	610	610	914	914	914	914	914	914	914	914	914	1829	2438	3048	3658	3962	4267	4877	6096
	L	76	114	152	305	305	610	610	610	610	610	610	610	610	610	914	914	1219	1829	1829	1829	1829	1829
	E	229	254	457	610	762	914	914	914	914	914	914	914	914	914	1219	1524	1829	2134	2134	2134	2134	2134
	D	167	214	259	397	575	845	1026	1206	1572	1937	2302	2667	3032	3397	4756	5607	7620	9144	10668	12313	15481	18529
	C	93	135	178	394	381	610	762	914	1219	1524	1829	2134	2438	2743	3658	4470	5588	7315	8941	10566	13818	17272
	B	356	406	457	610	864	1343	1419	1495	1645	1794	1943	2092	2242	2391	4267	4877	7620	7620	7620	7925	8230	8230
	a	242	276	311	414	587	914	965	1016	1118	1219	1321	1422	1524	1626	1829	2032	2337	2845	3353	3861	4877	5893
	A	363	414	467	621	879	1372	1448	1524	1676	1829	1981	2134	2286	2438	––––––––
	b (mm)	25.4	50.8	76.2	152.4	228.6	304.8	457.2	609.6	914.4	1219.2	1524.0	1828.8	2133.6	2438.4	3048	3658	4572	6096	7620	9144	12192	15240
	b	1 in	2 in	3 in	6 in	9 in	1 ftft6in	2 ft	3 ft	4 ft	5 ft	6 ft	7 ft	8 ft	10 ft	12 ft	15 ft	20 ft	25 ft	30 ft	40 ft	50 ft
								1

206			IRRIGATION AND WATER RESOURCES ENGINEERING