Irrigation Engineering - Dec 17

Civil Engineering (Semester 7)

Total marks: 80
Total time: 3 Hours
INSTRUCTIONS
(1) Question No.1 is compulsory.
(2) Attempt any three questions from remaining five questions.
(3) Assume any suitable data where ever required.
(4) Figures to the right indicate full marks.

Q1) Attempt any four:

• a) Define irrigation. What is the necessity of irrigation?
• b) Explain the terms: aquifer, aquiclude and aquifuge.
• c) Describe various methods of computing average rainfall over a basin.
• d) Explain the term 'storage coefficient' and 'coefficient of transmissibility'.
• e) Explain Canal Lining.

(20 marks)

2(a) What are the factors affecting Run-off. What are various method of computing run-off? Explain any one method: (10 marks)

2(b) A canal takes off a reservoir to irrigate the areas given below. 40% of the water required for irrgation is assumed to be available directly from precipitation. Channel conveyance losses are 15%. Reservoir losses are 10%. What would be the capacity of reservoir needed?(The reservoir to be filled only once a year)

(10 marks)

3(a) Explain various types of Rain-gauge with neat sketches. (10 marks)

3(b) Find the ordinates of a storm hydrograph from a 3hr storm with rainfall of 2, 6.75 and 3.75 cm during subsequent 3 hr intervals. The ordinates of hydrograph are given in the following table:

Assume an initial loss of 5 mm, infiltration index of 2.5 mm/hr and base flow of 10 cumecs.

(10 marks)

4(a) Derive an equation for discharge from a well in an unconfined aquifier. (10 marks)

4(b) Explain various types of reserviors. What do you understand by multipurpose reservoir? (10 marks)

5(a) A rectangular masonry dam is 3mt at the base. Compute the maximum permissible height H (a) when no tension is permissible, and (b) when the factor of safety against sliding is 1.5. Given the following: i) $\mu$= 0.5, ii) density of masonry =24 times the of water, and iii) c=1. What will be corresponding values of H if uplift is neglected? (10 marks)

5(b) Discuss the causes of failure of earth dams. (10 marks)

Q6) Write short notes on following:

• a) Hydrologic Cycle and Types of Precipitation
• b) Silt extractor and silt ejector
• c) Cross Drainage Work
• d) Reservoir Planning. (20 marks)