What is notable about the 212 revolutions at 12 m?

It is much higher than neighbours and was used as given

What velocity results at 12 m?

N = 212/120 = 1.767 rps, v = 0.597 m/s

What is the discharge with 212 and with 121?

13.17 m^3/s with 212; 11.82 m^3/s if 121

2081 Bhadra · 8 marks

Discharge from current meter at 0.6d, stream gauging data

Short answer

Using the mid-section method with velocity v = 0.32N + 0.032 at 0.6d, discharge is computed as the sum of v × depth × segment width for each vertical. Total Q ≈ 13.17 m³/s.

The data pertaining to a stream gauging operation at a gauging site are given below. The rating equation of the current meter is $v = (0.32N + 0.032)$ m/s where N is revolution per second. Calculate the discharge in the stream.

Distance from right bank (m)	Depth (m)	Revolution of CM at 0.6d	Time (s)
0	0	0	0
2	0.5	80	180
4	1.1	83	120
6	1.95	131	120
9	2.25	139	120
12	1.85	212	120
15	1.75	114	120
18	1.65	109	120
20	1.5	92	120
22	1.25	85	120
23	0.75	70	150
24	0	0	0

The mid-section method is used with $v = 0.32N + 0.032$ , where $N$ = revolutions / time (rps), at 0.6 d.

q_i = v_i\,d_i\,\frac{b_{i+1}-b_{i-1}}{2}

Distance (m)	Depth d (m)	N = rev/time (rps)	v (m/s)	Width w (m)	Area $w\,d$ (m $^2$ )	$q = v\,w\,d$ (m $^3$ /s)
2	0.5	80/180 = 0.444	0.174	2	1.000	0.174
4	1.1	83/120 = 0.692	0.253	2	2.200	0.557
6	1.95	131/120 = 1.092	0.381	2.5	4.875	1.859
9	2.25	139/120 = 1.158	0.403	3	6.750	2.718
12	1.85	212/120 = 1.767	0.597	3	5.550	3.315
15	1.75	114/120 = 0.950	0.336	3	5.250	1.764
18	1.65	109/120 = 0.908	0.323	2.5	4.125	1.331
20	1.5	92/120 = 0.767	0.277	2	3.000	0.832
22	1.25	85/120 = 0.708	0.259	1.5	1.875	0.485
23	0.75	70/150 = 0.467	0.181	1	0.750	0.136
Total					35.375	13.172

Total area $= 35.38$ m $^2$ ; mean velocity $= 0.372$ m/s.

Answer: Discharge $Q \approx 13.17\ \text{m}^3/\text{s}$ .

Note: the reading of 212 revolutions at 12 m is much higher than its neighbours (139 and 114). It has been used as given. If it is a misprint for 121, the discharge would be 11.82 m $^3$ /s.

✓ Answer checked by Claude Sonnet 5.5

Current meter discharge, rating equation · Engineering Hydrology, chapter 4
Discharge from current meter at 0.6 depth · Engineering Hydrology, chapter 4
Discharge from multi-point current meter data · Engineering Hydrology, chapter 4
Stream flow from current meter data · Engineering Hydrology, chapter 4 · asked 2×
Mid-section method discharge from current meter data · Engineering Hydrology, chapter 4
Discharge of Jhiku khola from stream gauging data · Engineering Hydrology, chapter 4
Stream discharge from current meter revolutions (v = 0.55N + 0.04) · Hydro Power, chapter 2 · asked 2×
Stream discharge from current meter revolutions (V = 0.51N + 0.03) · Hydro Power, chapter 2 · asked 2×
Stream gauging with calibration equation · Hydro Power, chapter 2
Gauging site selection and current meter use · Hydro Power, chapter 2

All Engineering Hydrology chapter 4 questions →

Discharge from current meter at 0.6d, stream gauging data

Related questions