Tribhuvan
University
Khwopa College of Engineering
Libali-2, Bhaktapur
Field REPORT on
Hydrology Tour
Dolalghat 2072
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Submitted to: Submitted
by:
Khwopa College of
Engineering Ganesh Pandey 58
Department of
Civil Enginnering
Date: 2072-12-11
Acknowledgement
I would like this opportunity to express my gratitude to everyone
who supported me to prepare this report. I am thankful for their aspiring
guidance, invaluably constructive ideas and friendly advice during the tour
day. I am grateful to them for sharing their truthful and best ideas on number of
issues related to the topic of the report.
I express my warm thanks to my freinds of my section and group
"C" for their support and guidance at the field.
I would like to thank my Hydrology Teacher Er. Sunil Duwal for
guiding us with sufficient knowledge on and off the field. Also, to the civil
department head Mr. Rameshowr Shrestha who provided us with best facilities
required and conductive condition for the tour.
Abstract
Hydrology is an important subject to be
studied in Civil Engineering. Hydrology covers most of the natural phenomenon
on the nature occurring on day to day basis. So engineers and hydrologist study
about different phenomenon that occurs on the surrounding. This project includes
one of the aspects of hydrology i.e. calculation of discharge of the river on
the field. It is important to estimate the flood on the large rivers, so the
basic objectives are to find the discharge of a river and find the resulting
properties of the river.
With those objectives, we, the students of
Khowpa College of Engineering 070 batch made a visit to a Dolalghat on date
2072-11-13. We made a trip with some objectives and at the end we concluded
with some concrete ideas and knowledge of the methods to calculate discharge in
the field. The same ideas, data and information are explained in this report.
Table
of Content
- Introduction
- Theory
- Materials and methods
- Results
- Discussion
- Conclusion
- References
Table 1: Current meter method of discharge measurement
Table 2: Calculation of average velocity
Table 3: Calculation of Discharge at 0 m
Table 4: Calculation of discharge at 25 m
Table 5: Calculation of Discharge at 50 m
Table 6: Table of Calibration
Table 6: Average discharge calculation
Table 7: Discharge calculated from three methods
List of Pictures
Fig 1: Hydrology Cycle
Fig 2: Dolalghat Doban
Fig 3: Measuring velocity
by current meter
Fig 4: Measuring Cross
Section area of the stream
Fig 5: Preparing Salt
solution for salt dilution process
Fig 6: Taking reading of
conductivity after diluting salt in stream
Introduction
Hydrology is the study of water, tracking its
very movement between the atmosphere, water bodies and earth, how it is
distributed between these realms and various aspects pertaining to its quality.
You might be familiar with the water cycle, and a quantitative &
qualitative study of water at different stages of the cycle is what hydrology
deals with. Hydrologists study trends in rainfall, once rain falls, how much
runoff is generated on earth's surface, and how much of it percolates into the
ground, and how much of it replenishes the streams in the area. Hydrology is
more significant these days because we plan ahead of time to deal with extremes
(scarcity of water leading to droughts, and overflowing of water bodies leading
to floods). Another significant area of research is looking into impacts of
climate change in the hydrologic components in an area or watershed. It is
important to study hydrology at any given point of time, and constantly
hydrologists are working round the globe to provide accurate models,
predictions and impact assessments.
Fig 1: Hydrology cycle
Theory
River discharge is the
volume of water flowing through a river channel. This is the total volume of
water flowing through a channel at any given point and is measured in cubic meters
per second (cumecs). The discharge from a drainage basin depends on
precipitation, evapotranspiration and storage factors.
Drainage basin discharge =
precipitation – evapotranspiration +/- changes in storage.
Discharge of the river can be calculated by different methods:
1)
Current meter
method
The most common method used by the USGS for
measuring discharge is the mechanical current-meter method. In this method, the
stream channel cross section is divided into numerous vertical subsections
(diagram to the left). In each subsection, the area is obtained by measuring
the width and depth of the subsection, and the water velocity is determined
using a current meter (left-side picture below). The discharge in each
subsection is computed by multiplying the subsection area by the measured
velocity. The total discharge is then computed by summing the discharge of each
subsection.
2) Flow Velocity
Method
If a flow
meter is not available or a rough estimate is adequate, you can measure flow by
using a float. The float can be any buoyant object, such as an orange or a
partially filled plastic water bottle. It needs to be heavy enough so that
about an inch of it is below the water line. (Don’t use glass or any material
that may cause problems if you can’t retrieve the float after the measurement.)
3) Salt dilution
method
The Salt Dilution Gauging method is a technique used for
investigating the discharge of turbulent rivers. This method is an alternative
method to the most commonly used Velocity Area Method technique.The
accuracy of the velocity area method reduces in channels characterised by
turbulent flow. Glacial and mountain streams tend to be turbulent and
dilution gauging is therefore more suited.
Methodology
Hydrometric method was used in the field to estimate the
discharge of the stream.
Three methods that were used on the field were as
follows:
·
Current Meter methods
·
Float method
·
Dilution method
Current Meter method
Materials used
Materials used
a)
Current meter
b)
Tape
c)
Staff
Procedure
a)
At, first a good cross section without any
disturbance is chosen.
b)
Tape is laid from one side to another making
zero end at the edge of the stream.
c)
The depth of the stream measured with the help
of staff at different intervals (20cm) starting from 0 to the opposite edge of
the river.
d)
Current
meter was used to find the velocity at different intervals (3 positions) by
recoding the revolution made by it in a minute.
e)
The average of the velocity was calculated.
f)
The average width was found and multiplying with
the depth Area was calculated.
g)
Finally discharge was calculated with the
obtained Area and Velocity.
Float Method
Materials used
a)
Tapes
b)
Float (Water Bottle)
c)
Staff
Procedure
a)
The tape was laid longitudinally at the center
of the river ( about 50m upstream).
b)
Bottle was taken as a float.
c)
The bottle was made to float from the upstream
and the time to reach the downstream by 50m was recorded. It was performed 3
time and averaged.
d)
The area of the cross section was taken at 3
time by similar method as in Current meter method. (Start, 25m downstream and
end point).
e)
Velocity was calucalted by V=Distance/Time
f)
And discharge was calculated by the obtained
Area and Velocity.
Dilution Methods
Materials used
a)
500 ml measurement flask
b)
1ml pipette
c)
1 lit jug
d)
Salt solution of 3g salt per 1000 ml distilled
water
e)
A robust, field proof conductivity meter
Procedure
i)
Calibration Procedure
a) Prepare
a salt solution with 3 g salt per 1000 ml distilled water using the same salt
that will be injected into the watercourse.
b) Measure
out exactly 500 ml of stream water.
c) Put
the stream water into 1 liter clean jug.
d) Turn
on the conductivity meter and put the sensor into the jug.
e) Measure
the conductivity meter and note it.
f) Add
1 ml of the prepared salt solution and stir thoroughly.
g) As
soon as the value is constant and unchanging, measure the conductivity and note
it again on the back of the data input sheet.
h) Repeat
the procedure until the volume in the jig or beaker in 510 ml.
Measurement Procedure
a)
Dissolve the appropriate amount of salt in the
bucket.
b)
Inject the salt solution into the stream by
gently pouring the contents of the bucket into the steam line without splashing
and then rinsing out the bucket wit water taken from above the point of
injection and pouring this water downstream.
c)
As soon as the salt cloud is seen to reach the
measurement point, not down the time for injecting the salt, the measured value
from the conductivity meter on the data input sheet and repeat measurements
every five second.
d)
Continue taking measurements every five seconds
until the value returns to the base level conductivity.
Results
The following results were obtained by the following three
methods:
1) Current meter Method
distance from left bank (cm)
|
width (cm)
|
Depth (cm)
|
C/s area (A)
|
rev/sec
|
Velocity (V)=0.26125N+0.04
|
Discharge(Q)=V*A
|
0
|
0
|
0
|
0
|
0.7
|
0.22288
|
0
|
20
|
20
|
5
|
100
|
0.22288
|
0.00223
|
|
40
|
20
|
10
|
400
|
0.22288
|
0.00892
|
|
60
|
20
|
13
|
780
|
0.22288
|
0.01738
|
|
80
|
20
|
12
|
960
|
0.22288
|
0.0214
|
|
100
|
20
|
18
|
1800
|
0.22288
|
0.04012
|
|
120
|
20
|
16
|
1920
|
0.22288
|
0.04279
|
|
140
|
20
|
16
|
2240
|
0.22288
|
0.04992
|
|
160
|
20
|
17
|
2720
|
0.22288
|
0.06062
|
|
180
|
20
|
17.5
|
3150
|
0.22288
|
0.07021
|
|
200
|
20
|
14
|
2800
|
0.22288
|
0.06241
|
|
220
|
20
|
14.5
|
3190
|
0.22288
|
0.0711
|
|
240
|
20
|
8
|
1920
|
0.22288
|
0.04279
|
|
260
|
20
|
12
|
3120
|
0.22288
|
0.06954
|
|
280
|
20
|
11
|
3080
|
0.22288
|
0.06865
|
|
300
|
20
|
7
|
2100
|
0.22288
|
0.0468
|
|
320
|
10
|
2
|
640
|
0.22288
|
0.01426
|
|
330
|
0
|
0
|
0
|
0.22288
|
0
|
|
sum
|
0.68913
|
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Table 1: Current meter method of discharge
measurement
2)
Flow Velocity Method
DISTANCE
|
0m
|
25m
|
50m
|
|
TIME(sec)
|
0
|
29.53
|
46.47
|
|
0
|
31.54
|
37.46
|
||
AVERAGE TIME
|
0
|
30.535
|
41.965
|
|
VELOCITY(M/S)
|
0
|
0.8187326
|
0.59573
|
|
AVERAGE VELOCITY
|
0.707233571
|
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Table 2: Calculation of average velocity
AT 0m
|
||||
distance from left(m)
|
Width(m)
|
Height(cm)
|
Area(m2)
|
DISCHARGE(m^3/sec)
|
0
|
0
|
0
|
0
|
0.5275962
|
0.4
|
0.4
|
3
|
0.012
|
|
0.8
|
0.4
|
2.5
|
0.01
|
|
1.2
|
0.4
|
5
|
0.02
|
|
1.6
|
0.4
|
8
|
0.032
|
|
2
|
0.4
|
11
|
0.044
|
|
2.4
|
0.4
|
13
|
0.052
|
|
2.8
|
0.4
|
17
|
0.068
|
|
3.2
|
0.4
|
19
|
0.076
|
|
3.6
|
0.4
|
21
|
0.084
|
|
4
|
0.4
|
22
|
0.088
|
|
4.4
|
0.4
|
24
|
0.096
|
|
4.8
|
0.4
|
16
|
0.064
|
|
5.2
|
0.4
|
17
|
0.068
|
|
5.6
|
0.4
|
8
|
0.032
|
|
5.9
|
0.3
|
0
|
0
|
|
sum
|
0.746
|
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Table 3:
Calculation of Discharge at 0 m
AT 25 m
|
||||
Distance from left(m)
|
Width(m)
|
Height(cm)
|
Area(m2)
|
DISCHARGE(m^3/sec)
|
0
|
0
|
0
|
0
|
0.46818862
|
0.4
|
0.4
|
1
|
0.004
|
|
0.8
|
0.4
|
2
|
0.008
|
|
1.2
|
0.4
|
4
|
0.016
|
|
1.6
|
0.4
|
6
|
0.024
|
|
2
|
0.4
|
9
|
0.036
|
|
2.4
|
0.4
|
11
|
0.044
|
|
2.8
|
0.4
|
8
|
0.032
|
|
3.2
|
0.4
|
7
|
0.028
|
|
3.6
|
0.4
|
8
|
0.032
|
|
4
|
0.4
|
8
|
0.032
|
|
4.4
|
0.4
|
4
|
0.016
|
|
4.8
|
0.4
|
1
|
0.004
|
|
5.2
|
0.4
|
2
|
0.008
|
|
5.6
|
0.4
|
3
|
0.012
|
|
6
|
0.4
|
10
|
0.04
|
|
6.4
|
0.4
|
17
|
0.068
|
|
6.8
|
0.4
|
28
|
0.112
|
|
7
|
0.2
|
33
|
0.066
|
|
7.2
|
0.2
|
40
|
0.08
|
|
7.4
|
0.2
|
0
|
0
|
|
sum
|
0.662
|
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Table 4: Calculation of discharge at 25 m
AT 50 M
|
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distance from left(m)
|
Width(m)
|
Height(cm)
|
Area(m2)
|
DISCHARGE(m^3/sec)
|
0
|
0
|
0
|
0
|
0.52759624
|
0.4
|
0.4
|
3
|
0.012
|
|
0.8
|
0.4
|
2.5
|
0.01
|
|
1.2
|
0.4
|
5
|
0.02
|
|
1.6
|
0.4
|
8
|
0.032
|
|
2
|
0.4
|
11
|
0.044
|
|
2.4
|
0.4
|
13
|
0.052
|
|
2.8
|
0.4
|
17
|
0.068
|
|
3.2
|
0.4
|
19
|
0.076
|
|
3.6
|
0.4
|
21
|
0.084
|
|
4
|
0.4
|
22
|
0.088
|
|
4.4
|
0.4
|
24
|
0.096
|
|
4.8
|
0.4
|
16
|
0.064
|
|
5.2
|
0.4
|
17
|
0.068
|
|
5.6
|
0.4
|
8
|
0.032
|
|
5.9
|
0.3
|
0
|
0
|
|
SUM
|
0.746
|
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Table 5: Calculation of Discharge at 50 m
AT
|
DISCHARGE(m^3/sec)
|
AVERAGE DISCHARGE
|
0m
|
0.52759624
|
0.5077937
|
25m
|
0.46818862
|
|
50m
|
0.52759624
|
Table 6: Average discharge calculation
3)
Salt Dilution Method
Volume of water in jar (ml)
|
Measured Conductivity
(I S/cm)
|
Salt Concentration (mg/l)
|
500
|
31
|
0
|
501
|
32
|
6
|
502
|
33
|
12
|
503
|
34
|
18
|
504
|
36
|
24
|
505
|
37
|
30
|
506
|
38
|
36
|
507
|
39
|
42
|
508
|
41
|
48
|
509
|
42
|
54
|
510
|
43
|
60
|
Table 6: Table of Calibration
Method
|
Discharge(m3/s)
|
Remarks
|
Current meter
|
0.68913
|
|
Flow Velocity
|
0.5077937
|
|
Salt Dilution
|
Table 7: Discharge calculated of three methods
Discussion
In the field
we performed the discharge calculation by three different methods. Area
velocity method was the first one where area was measured by width and velocity
by the current meter. Similarly on flow velocity method a float(bottle) to find
the velocity. And on the salt dilution method conductivity was measured by conductivity
meter and discharge was measured accordingly.
Salt dilution
method is the best method for the discharge measurement. So assuming it to be
the correct there are minor deviation with other two methods. This might be due
to the carelessness in performing the project like recording time, reading width
and depth etc.
Conclusion
Hence, current meter method, flow velocity method and salt
dilution method were performed in the field successfully and the resulting
discharge was calculated correctly.
References
-Engineering Hydology by Er. KN
Duwal and Sanjeev Baral
- Lecture: Professor, Mark Serreze
-Google.com (photos
Photoes of the tour day
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