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Set 325 Question Paper

Set 325

Course:Bachelor Of Science In Water And Environmental Engineering

Institution: Kenyatta University question papers

Exam Year:2010

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
OPEN, DISTANCE AND E-LEARNING EXAMINATION FOR THE DEGREE
OF BACHELOR OF SCIENCE
(WATER AND ENVIRONMENTAL ENGINEERING)

SET 325: GROUNDWATER HYDRAULICS

DATE: Friday 23rd July 2010 TIME:
8.00a.m – 10.00a.m

INSTRUCTIONS
Answer question 1 and any other two questions
1.
a)
Define the following terms as used in the study of groundwater.

i)
Groundwater recharge

ii)
Storativity

iii)
Specific yield

iv)
Perched aquifer

v)
Hydraulic gradient.

[5marks]

b)
With the help of a an appropriate sketch show that the coefficient of

permeability, k, is given by the relationship.
a L
H

1
K ?
303
.
2
log

10
A t
H2

List all the appropriate assumptions that Darcy made in the above

derivation.

[10marks]

c)
A sample in a falling head permeameter is 12 cm high and 10 cm in

diameter. It is desired that the head in the stand pipe drop from 20 to 8

cm in 5 minutes. Determine the size of stand pipe given that k is

0.001cm/se.

[5marks]

d)
Explain fully all the causes of groundwater contamination. [4marks]

e)
Discuss the importance of groundwater in Kenya.
[6marks]

Page 1 of 2

2.
a)
Define and explain seawater intrusion.

[5marks]

b)
The following drawdowns were observed in a pump test in Kahawa

Sukari. The drilling log indicated silty clay up to a depth of 25 m

underlined by a 30-m thickness of medium sand followed by fine sandy

and clayed sediment. The well screen was installed over the whole

thickness of the aquifer of medium sand. A discharge of 160 m3/h has

pumped for 20 hour drawdown became steady. Determine the aquifer

constants

Observation well at (m)
1.5

35.0
95.0

Drawdown (m)

1.90
0.60
0.15

Hint h2 = ho - 0.15; h1 = ho = 0.60

[6marks]

c)
Using a well labeled diagram show the extent of cone of influence.

[4marks]

d)
A sample of soil 15cm thick and 10 cm in diameter is tested in a falling

permeater under and initial head of 50 cm which falls down to half of it in

90 seconds. The stem is 2 cm in diameter. Find the coefficient of

permeability in mm/day.

[5marks]
3
a)
A 0.5 diameter well penetrates fully unconfined aquifer of 30-m depth.

Two observation wells located 30 and 80 m from the pumped well are

known to have drawdowns of 7 and 6.5m respectively. If the flow is

steady and k = 50m/day, what would be the discharge in m3/s.

[6marks]

b)
List the different methods of groundwater exploration.
[4marks]

c)
Describe fully the electrical resistivity method of groundwater

exploration.

[8marks]

d)
What is seepage?

[2marks]
4.
a)
Describe fully how existing open wells are revitalized.
[4marks]

b)
List and explain all the well completion operations.
[4marks]

c)
Which factors influence the methods of installing well screens.

[4marks]

d)
Discuss the challenges of groundwater development and management in

Kenya.

[8marks]
Page 2 of 2

Set 325 Question Paper

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