This experiment was conducted to determine the cone of depression for a single well system at different pumping discharges. The apparatus used included a bench-mounted setup capable of demonstrating groundwater flow principles. Water was pumped from the setup at discharges of 72.363 ml/sec and 101.779 ml/sec. The cone of depression was measured to be 133mm and 70mm respectively by recording the water elevations in piezometers located at increasing distances from the pumping well. The shape and size of the cone of depression depends on factors like the pumping rate, aquifer properties, storage, and thickness.

1. CONE OF DEPRESSION
IN SINGLE WELL SYSTEM
SUBMITTED BY
ABHINAV DHAYAL
Manish kumar noniwal
SHASHI ranjan
Month- OCTOBER
Year - 2015-16

2. To determine the cone of depression for
an single well system

3. APPARATUS
REQUIRED
This bench-mounting apparatus is capable of
demonstrating, on a small scale, the hydrological principles
of ground water flow and the applications of these to certain
engineering constructions
Bench mounting apparatus

4. • Almost all deep excavations are now associated with the removal of
subsoil water for laying foundations of structures or underground
construction. Most of the structures have deep foundations involving
a substantial dewatering job. The overall land area around the world
remaining constant, the development arrow has begun to point
vertically upwards. Horizontal expansion has given way to
vertical expansion. As a result, the importance of using dewatering
equipment has increased manifold.
• In many projects, dewatering of foundations plays the key role in
deciding the overall completion period. Till the time the dewatering
equipment is successfully installed and foundations come up,
uncertainty prevails over the commissioning date of a project.
completion schedule suffers a setback. Thus, it is very important to
assess the quantum of dewatering work involved; choose the right
dewatering equipment; and keep standby arrangements in place.
INTRODUCTION

5. A confined aquifer

6. a. Cone of depression b. cone of impression

7. Confined aquifer
•(a) Radial flow to a well

8. PURPOSE
This experimental work is done to determine the effect of
pumping efficiency of the well, if the water is pumped at
different discharges. The pumping of water will affect the
water level at different locations. So, to understand this
effect on the water table depression following experiment is
useful.

9. 1. Turn on the water supply to the setup and allow water to flow till the soil is
saturated.
2. Adjust the control valves until equal readings obtained for piezometer 1 to 3
and 10 to19; Points 4 to 9 is neglected as they are in transverse direction.
3. Open the outlet valve that is present at the bottom of the setup.
4. Calculate discharge ‘Q’ using the measuring cylinder or by the discharge
measuring arrangement in the setup.
5. Measure the average discharge by calculating three different discharge
readings.
6. Record the piezometer readings once the condition gets stabilized.
7. Same procedure can be extended for different Discharge values.
PROCEDURE

10. 10 150 145
11 200 145
12 250 145
13 300 146
14 350 144
15 400 139
16 450 133
17 500 135
18 550 142
19 600 149
Piezometer Number Distance (mm) Water Elevation(mm)
1 0 151
2 50 146
3 100 145
q (ml) t (sec) Q (ml/sec)
825 11.55 71.428
800 11.06 72.332
800 10.91 73.327
Avg Q 72.363
OBSERVATIONS
Sample 1
Calculation of discharge
Observation

11. 152
150
(mm)
148
146
Elevation
144
142
140
Water
138
136
134
132
0 200 400 600
Peizo
meter
Positio
n (mm)
GRAPH

12. q (ml) t (sec) Q (ml/sec)
900 9.05 99.447
880 8.50 103.529
910 8.89 102.362
Avg Q 101.779
Piezometer Number Distance (mm) Water Elevation (mm)
1 0 90
2 50 89
3 100 88
10 150 87
11 200 86
12 250 85
13 300 82
14 350 80
15 400 75
16 450 70
17 500 72
18 550 78
19 600 85
Sample 2
Calculation of discharge
Observation

13. WaterElevation(mm)
Water Elevation
90
85
80
75
70
0 200 400 600
Peizometer Position (mm)
GRAPH

14. CALCULATIONS
• The cone of depression in sample 1 is 133mm
• The cone of depression in sample 2 is 70mm

15. Viva questions
Q1 What is cone of depression?
Ans
A cone of depression occurs in an aquifer when groundwater is pumped from a well.
Q2 What is it’s practical significance?
Ans
In an unconfined aquifer (water table), this is an actual depression of the water levels. In confined
aquifers (artesian), the cone of depression is a reduction in the pressure head surrounding the pumped
well.
Q3 On what factors shape of cone of depression depends ?
Ans
it depnds on following factors
1.pumping rate in the well
2. the type of aquifer material
3. The amount of water in storage
4. the thickness of the aquifer