Bengal Engineering and Science University 2007 B.E Civil Engineering Water Resource Engineering-I - Question Paper
ques. paper is with the attachment.
B.E. (Civil) 6 Semester Final Examination, 2007
Sub: Water Resources Engineering - I (CE-605)
Time: Three hours
Full Marks: 70
(Figures in the margin indicate full marks)
First Half
Answer Q.5 and any two from the rest
a) The annual rainfalls at 7 raingauge stations in a basin are 58, 94, 60, 45, 20, 88 and 68 cm respectively. What is the percentage accuracy of the existing network in the estimation of the average depth of rainfall over the basin? How many additional gauges are required if the error to be limited to only 10%?
b) During a daily routine observation, 10 litres of water was added to bring the water surface in the evaporation pan to the stipulated level and the nearby raingauge measured 4mm of rainfall. What was the evaporation recorded for
the day if the diameter of the pan is 120cm?
(10+5)
a) A catchment area is approximated as a semicircle of diameter 40 km with an equilateral triangle of side 40 km below its diameter. Five rain gauges A (-10,10), B(10,10), C(10,-10), D(-
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10,-10), and E(0,0) are located within ths basin as shown in Figure. If the rainfall recorded by these gauges are 90, 95, 82, 100 and 75 mm respectively, determine i) the average depth of rainfall using Thiessen polygon method and ii) volume of surface runoff at the basin outlet if 40% of the rainfall is lost in evaporation and infiltration.
b) Find the missing data for rain gauge D using normal ratio method. (10+5)
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b) With neat sketch, derive the expression for EL. using energy budget method. What is pan coefficient and why it is used? (5+10)
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4. a) Discuss the relationship between rainfall intensity, infiltration rate and infiltration capacity.
b) The Horton's infiltration equation for a basin is given by fct = 5+ 25e'21, where fa is in mm/h and t is in hours. What are the fco, fct and K values? If a storm of uniform intensity 35mm/h occurs over this basin for 75 minutes, determine the average rate of infiltration and total depth of infiltration during this period.
c) The runoff from a catchment due to a 8h storm was found to be 5.8cm. Given
the mass curve of rainfall as below, estimate the <|>-index. (3+5+7)
Time from start (h) 01234 567 8 Acc. rainfall (mm) 0 4 13 28 51 69 85 95 100
5. Write a program to derive hyetograph from a given rainfall mass curve. (5)
Second Half
Answer Question No. 10 and any two from the rest.
6. a) A 200 g/l solution of common salt was discharged into a stream at a constant rate of 25 I/s. The background concentration of the salt in the stream water was found to be 10 ppm. At a downstream section where the solution has been completely mixed, the salt concentration was found to reach an equilibrium value of 45 ppm. Estimate the discharge in the stream. (Before solving the problem, derive the expressions first.)
b) Following data were obtained from a stream gauging operation. A current meter (calibration equation V = 0.32NS + 0.032 m/s) was used to measure the velocity a 0.6 depth. Calculate the discharge in the stream using Area-Velocity method. (6+9)
Distance from 0 2 4 6 9 12 15 18 20 22 23~ left bank (m)
Depth (m) 0 0.5 1.1 1.9 2.3 1.8 1.7 1.6 1.1 0.8 0
No. of rev. - 60 83 131 139 121 114 109 92 85
Time (s)_- 180 120 120 120 120 120 120 120 120 -
7. a) Following water surface elevations of a small stream were observed at a section A and at another station B, 10km downstream of A. Using slope-area method, estimate the discharge in the stream. Assume Manning's n =0.020, and eddy loss coefficient Ke=0.3 and calculate up to 3rd iterations.
Section Water surface Area of cross- Hydraulic Radius
elevation (m) section (m2) (m)
A 105.4 74.5 2.75
B 104.0 95.8 3.2
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b) Three points on a rating curve of a stream gauging station have the following co-ordinates: (100m3/s, 121.67m), (200 m3/s, 122.23m), and (400 m3/s, 123.04m). Compute the rating curve parameters. Also calculate the discharge for a depth of 124.5m. (10+5)
8. a) The ordinates of 6-h UH is given as follows:
Time(h) 0 3 6 9 12 18 24 30 36 42 48 54 60 66 Discharge 0 150 250 450 600 800 700 600 450 320 200 100 50 0 (m3/s)_
A storm had three successive 6-h intervals of rainfall excess magnitude of 3, 5 and 4 cm respectively. Determine the resulting flood hydrograph.
b) Derive a 2-h UH from the 4h UH given below. (5+10)
Time (h) 0 2 4 6 8 10 12 14 16 18 20 zT
4-hUH (m3/s) 0 25 100 160 190 170 110 70 30 20 6 0
9. a) From the following observed values of annual rainfall and annual runoff (yield) of a basin, find the correlation between rainfall and runoff assuming linear relationship. Check whether the assumption of linear relationship is correct or not. If not, then what type of relationship will you assume?
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Year |
1989 |
1990 |
1991 |
1992 |
1993 |
1994 |
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Annual Rainfall (cm) |
90.5 |
111 |
38.7 |
128.5 |
145.5 |
998 |
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Runoff (cm) |
30.1 |
50.0 |
5.3 |
61.5 |
74.8 |
39.9 |
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Year |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
|
Annual Rainfall (cm) |
50.9 |
120.2 |
90.3 |
65.2 |
75.9 |
82.5 |
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Runoff (cm) |
6.5 |
46.1 |
36.2 |
24.6 |
20.0 |
19.5 |
b) Describe the runoff characteristics of ephemeral stream. (12+3)
10. Write a program to determine the discharge in a stream using area-velocity method. (5)
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Attachment: |
| Earning: Approval pending. |
