ED – 701

*ED701* V Semester B.E. (Civil) Degree Examination, December 2014/January 2015 (Y 2K 11 Semester Scheme) CIVIL ENGINEERING CE 502 : Hydrology and Irrigation Engineering Time : 3 Hours

Max. Marks : 100

Instructions :1) Part – A is compulsory. 2) Answer any five of the remaining questions, selecting atleast one from Part – B and one from Part – C. 3) Assume any missing data suitably. PART – A 1. a) Define cyclone and Anti-cyclone. b) Explain how wind affects evaporation. c) Define Infiltration Index. d) Define unit hydrograph. e) Define Duty and Delta. f) Explain how quality of water affects duty of water. g) 10 cm depth of water per hectare produces 2.5 tonnes of crop. What is the transpiration ratio ? h) A ditch discharges 128 litres per second and drains 260 hectares. What is the drainage coefficient ? i) Define Field Irrigation efficiency. j) Define Evapotranspiration.

(10×2=20) PART – B

2. a) Explain with a neat sketch the Engineering representation of Hydrologic cycle.

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b) A storm commenced at 7.00 hours. The ordinates of the rainfall mass curve of this storm in mm as recorded by a recording rain gauge at 15 minute intervals are 0, 9.5, 17.0, 27.0, 40.5, 49.0, 63.0, 84.0, 95.0, 102.0, 110.0, 112.0 and 112.0. Compute the maximum rainfall intensities for durations of 15, 30, 45 and 60 minutes.

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P.T.O.

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3. a) Discuss the factors affecting evaporation.

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b) An infiltration test conducted on a double ring infiltrometer with an inner ring of diameter 30 cm yielded the following data : Time in minutes

0

5

10

30

60

120

180

240

300

360

Cumulative volume of water added in cm3

0

46

90

246

435

662

842

1000

1154

1300

Determine the infiltration capacity rates for the time intervals in the test. 4. a) Explain briefly the factors affecting runoff.

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b) The average annual rainfall of 5 rain gauges in a basin are 89, 54, 45, 41 and 55 cm. If the error in the estimation of basin mean rainfall should not exceed 10%, how many additional gauges should be installed in the basin ?

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PART – C 5. a) Describe the methods of separating the base flow from the total runoff. b) The following table gives the ordinates of a direct runoff hydrograph resulting from two successive 3 hour duration of rainfall excess values of 2 cm and 4 cm respectively. Derive a 3 h unit hydrograph for the catchment. Time (h)

0

3

6

9

Direct runoff (Cumecs)

0

120

480

12

15

18

21

24

27

30

660 460 260

160

100

50

20

0

6. a) Explain how a 2D hour unit hydrograph is derived from a D hour unit hydrograph.

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b) The ordinates of a 4 hour unit hydrograph are given below, derive the ordinates of a 2 hour unit hydrograph for the same catchment by S-curve method. Time (h)

0

4

8

12

16

20 24

4 h Utto (m3/s)

0

100

190

110

30

6

0

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7. a) Write a note on Irrigation efficiencies.

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b) 3.5 cumecs of water was diverted from a river into a canal, of this 3.0 cumec was delivered to the farm. The surface runoff from the irrigated area averages 0.30 cumec. The contribution to the groundwater is 0.20 cumec ; i) What is the water conveyance efficiency ? ii) What is the water application efficiency ?

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8. a) Write briefly on the following : i) Saturation capacity ii) Field capacity iii) Wilting point iv) Optimum water.

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b) Wheat is to be grown at a certain place, the useful climatological conditions are given below : Compute the evapotranspiration and consumptive irrigation requirement of wheat crop. Also calculate the field irrigation requirement if the water application efficiency is 75%. Use Blaney Criddle equation and a crop factor of 0.80.

Month

Average Monthly temperature in °C

Monthly percent of day time hours of the year

Useful rainfall in cm

January

17.5

7.40

2.35

February

18.0

7.35

2.05

March

18.5

7.30

1.75

April

19.5

7.20

1.52

9. a) What is Waterlogging ? What are its ill-effects ? b) What are the causes of Waterlogging ? ––––––––––––––

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