VARDHAMAN COLLEGE OF ENGINEERING
(AUTONOMOUS)
B. Tech VI Semester Regular Examinations, May 2018
(Regulations: VCE-R15)
GROUND WATER HYDROLOGY
(Civil Engineering)
Date: 24 May, 2018 FN
Time: 3 hours
Max Marks: 75
Answer ONE question from each Unit
All Questions Carry Equal Marks
Unit I
1.

With the help of a neat sketch discuss the origin of groundwater. Differentiate between the zone of aeration and zone of saturation.
7M

Discuss briefly regarding the following and also explain their inter-relationship:
i. Porosity
ii. Specific yield
iii. Specific retention
8M
2.

Define aquifer. Explain briefly the various types of aquifers based on the geological formation.
7M

Define the following terms:
i. Hydraulic conductivity
ii. Transmissibility
iii. Storage coefficient
iv. Apparent velocity
8M
Unit II
3.

Derive the ground water movement governing equations.
8M

It was observed in a field test that 4 hours was required for a tracer to from one well to another well which was 25m apart, and the difference in their water surface elevation was 0.8m. Samples of the aquifer between the wells indicated a porosity of 15%. Determine the permeability of the aquifer and seepage velocity.
7M
4.

State Darcy's law and arrive at the equation with the help of a neat sketch.
7M

A 30cm diameter well completely penetrates a confined aquifer of permeability 30 m/day. The length of the strainer is 25m. Under steady state of pumping the drawdown data the well was found to be 4 m and the radius of influence was 400 m. calculate the discharge. For the same conditions, if the diameter of the well was 45 cm, determine the discharge.
8M
Unit III
5.

Illustrate any one of the recording type rain gauge with the help of a neat sketch.
5M

An infiltration test on a ring with 35cm diameter yielded the following data:
Time since start
in Minutes
0
2
5
10
20
30
60
90
150
210
Cumulative volume of water added in cm3
0
278
658
1173
1924
2500
3345
3875
4595
5315
i. Determine the infiltration capacity rates for the time intervals in the experiment
ii. What is the initial and ultimate infiltration capacity rate
iii. What is the average infiltration capacity for the first 10 minutes and first 30 minutes of the experiment
10M
Cont…2
2
6.

With the help of a neat diagram explain the various components of runoff.
5M

Thiessen polygon constructed for a network of 10 rain gauges in a river basin yielded Thiessen weights of 0.10, 0.16, 0.12, 0.11, 0.09, 0.08, 0.07, 0.11, 0.06 and 0.10. If the rainfall recorded for these gauges during a cyclonic storm are 132, 114, 162, 138, 207, 156, 135, 158, 168 and 150mm respectively. Determine the average depth of rainfall by Thiessen mean and Arithmetic mean methods. Also estimate volume of surface runoff at the basin outlet using both the methods if 35% of rainfall is lost as infiltration. Take the area of basin as 5800 km2 and express your answer in million cubic meters.
10M
Unit IV
7.

What is unit hydrograph? State assumptions and the limitations of unit hydrograph?
7M

Two storms each of 6 h duration and having rainfall excess values of 3.0 cm and 2.0 cm respectively occur successfully. The 2 cm ER rain follows the 3 cm rain. The 6 h unit hydrograph for the catchment is given below. Calculate the resulting DRH and plot the same.
Time
0
3
6
9
12
15
18
24
30
36
42
48
54
60
69
UH ordinate
0
25
50
85
125
160
185
160
110
60
36
25
16
8
0
8M
8.

With the help of a neat sketch explain the various methods available for the separation of base flow.
5M

Given the ordinates of a 4h unit hydrograph as below derive the ordinates of a 12h unit hydrograph for the same catchment using S-curve method. Also plot the 12 h UH.
Time
0
4
8
12
16
20
24
28
32
36
40
44
Ordinate of 4h UH
0
20
80
130
150
130
90
52
27
15
5
0
10M
Unit V
9.

Explain unsteady radial flow into confined aquifer equations and Jacob-Cooper method for determination of formation constants.
9M

During recuperation test conducted on an open well in a region, water level in then well was depressed by 3 m and it was observed to rise by 1.75m in 75minutes.
What is the specific yield of open wells in that region?
What could be the yield from a well of 5 m diameter under a depression head of 2.5
What should be the diameter of the well to give yield of 12 lit/s under a depression head of 2.0
6M
10.

Describe the recovery test to estimate the transmissibility of a confined aquifer.
5M

A pumping test was carried out on a new irrigation bore well penetrating fully into a confined aquifer at a rate of 22lit/s. the drawdown measured in an observation well located at 45.7 m from the pumping well during the test is as given below. Determine T and S of the aquifer, using Cooper-Jacob method.
Time t
0.5
1.8
2.7
5.4
9.0
12.0
18.0
30.0
54.0
Drawdown s
0.091
0.294
0.382
0.55
0.701
0.785
0.911
1.06
1.24