8/2/2019 somendra sah Hydrology Report PDF.
1/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
1
ACKNOWLEDGEMENT
We would like to acknowledge our obligation to Janakpur Engineering
College,Department of Civil Engineering for initating and faciliting one day
field tour of Engineering Hydrology. This Report is the outcome of field
visit in Engineering Hydrology carried by the Department of Civil
Engineering, IOE, Janakpur Engineering College,Tinkune Kathmandu. The
Purpose of this field visit was to make the each Student Independent to
carry out the work in real problem. We think, the purpose is fruitful and
which make us to produce the report of the fieldwork in time.
We are sincerely indebted to Department of Civil Engineering, Janakpur
Engineering College,. We would like to express our sincere gratitude to our
Field visit Coordinater Er.Ambikesh Kumar Jha, for his helpful suggestion
and instruction, during the fieldwork, without which it was very difficult to
do the work in the field and to produce the report, friendly behavior and
guiding any time during the whole work and also providing prompt
comments and rectification necessary before finalization of the report.We
cannot proceed further without thanking our Camp vice Coordinator Er.
Bir Bahadur Bohra, without whose valuable instruction we cannot finish
the work in such a worth manner.We are very thankful to our own College
that helped in lots of manner to make the field visit Successful.
At last, we would like to express our gratitude to everyone who
helped us and involved directly or indirectly for the execution of the
project.
Thank you
SUBMITTED BY:
1. Somendra Sah (065/BCE/44)
8/2/2019 somendra sah Hydrology Report PDF.
2/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
2
INTRODUCTION
Engineering Hydrology
Hydrology means the science of water on the earth. It deals with the
occurrence, circulation, and distribution of water of the earth and earth's
atmosphere.Hydrology is an interdisciplinary science for investigation,
draws support from allied sciences such as meteorology, geology, fluid
mechanics, physics, Chemistry and statistics.
In a general sense engineering hydrology deals with:-
Estimation of water resources.The study of processes such as precipitation,
runoff,evapotranspiration and their interaction
The study of problem such as floods and droughts and strategic to combat
them.
Hydrology is classified as:-
1. Scientific Hydrology: which is concerned with academic aspects.
2. Engineering Hydrology: This is concerned with its engineering
applications.
Sources of data
The main components of hydrological cycle are rainfall, evaporation,
Transpiration, Infiltration, Runoff and Ground water. Depending upon the
problems in hand, a hydrologist would require data relating to the variousrelevant data such as:
Weather records e.g.Temp, Humidity, wind velocity Precipitation data Stream flow records Evaporation and transpiration data Infiltration characteristics of area Ground water characteristics Physical and geological characteristics of area
8/2/2019 somendra sah Hydrology Report PDF.
3/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
3
General Knowledge of the measurement and reading of these data and the
instruments used for their measurement is of great importance in
Engineering Hydrology.
INTRODUCTION TO STUDY AREA:-
Rusi Khola is name of khola which is situated in Panauti.Panauti is 30 Km.
from Kathmandu.It lies in Kavre District &Bagmati Zone.
Other observation area is Cenral Weather Department which is situated in
Tribhuwan International Airport,Kathmandu.It lies Bagmati District &
Bagmati Zone.It is capital of Nepal.
Fig. Students at Roshi Khola
8/2/2019 somendra sah Hydrology Report PDF.
4/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
OBJECTIVE OF FIELD TRIP
The main objective behind the offering field trip onEngineering Hydrology is to consolidate and updates the theoretical
and practical knowledge of engineering in their actual field so that
one can build upone's confidence and experiences in the related
field.In addition to this ,it develops a kind of team sprit and co-
operation for the long-term works with the environment.
The main objective of field trip are summarized below:
To provide an access to flow of water in river.To enhace the study of meterological stationTo practise the weather record,stream flow measurement,
precipitation data
To measure discharge of river.To know about the discharge measurement of equipment.Know about the how to measure rainfall, snowfall,temperature
,wind velocity ,evaporation in one day.
To know how to get information about weather of our country& other country.
To know about the application of hydrological knowledge inthe field of civil engineering.
Stream Flow Measurement
A stream can be defined as a flow channel into which the surface
runoff from a specified basin drains. A stream flow is measured in unit ofdischarge (m3/s) occurring at a specified time and constitute historical
data. The measurement of discharge in a stream forms an important
branch of hydrometer.
Discharge Measurement
The measurement of discharge in stream forms an important branch
of Hydrometry, the science of water measurement. In the hydrologicalcycle, streamflow is the only part which can be measured accurately. A
8/2/2019 somendra sah Hydrology Report PDF.
5/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
stream is a flow channel into which surface runoff from a specified basin
drains.Firstly. We went to Roshi Khola Kavre Panauti for Stream
discharge measurement.
Discharge measurement was done by velocity area method. Floatationmethod was also done for velocity determination.
MethodologyArea-Velocity method:
This method of discharge measurement consists essentially of measuring
the area of cross-section of the river at a selected section called gauging site
and measuring the velocity of flow through the cross sectional area. This
method is the most practical method of measuring stream discharge.
In this method, the width of the stream is divided into a number of
increments. The following are some of the guidelines to select the number
of segments:
1. The segment width should not be greater than 1/15 to 1/20 of the
width of the river.
2. The discharge in each segment should be less than 10% of the total
discharge.
3. The difference in velocities in adjacent segments should not be
more than 20%
But most of the time all of these conditions cannot be fulfilled so we musttake steps according to the site condition.
For velocity measurement, for shallow sections, it is measured at 0.6 of the
distance from the water surface to streambed whereas for deep sections,
the average velocity is taken by measuring velocities at 0.2 and 0.8 of the
distance from the water surface to streambed.
The product of velocity, depth and width of the section gives sectional
discharge. The total sum of the sectional discharge is the total discharge ofthe stream.
8/2/2019 somendra sah Hydrology Report PDF.
6/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
Q= A x V
Where; Q = discharge (m3/sec)
A = sectional area ( m2
)
V = velocity (m/s)
To measure depth, for shallow streams, height-calibrated rod can be used
whereas for deep streams and for accurate depth measurements
electroacoustic instrument called echo-depth recorder is used. Velocity is
measured using current-meter so this method is also sometimes called
standard current meter method.
1. Current Meter:
The most commonly used instrument used in hygrometry to measure
velocity is a current meter. It consists essentially of a rotating element
which rotates due to the reaction of the stream current with an angular
velocity proportional to stream velocity.
There are two types of current meter
1. VERTICAL AXIS CURRENT METER
The vertical axis meter consists of a series of conical cups a vertical axis.
The cups rotate in a horizontal plane and a cam attached to the vertical
axial spindle records generated signals proportional to the revolutions of
the cup assembly. The disadvantage of such meters is that these are useless
in situations where there are appreciable vertical components of velocities.
The accuracy is higher in higher velocities than in smaller ones.
2. HORIZONTAL AXIS CURRENT METER
The horizontal axis meters consist of a propeller mounted at the end of
horizontal shaft and these rotate in vertical plane w.r.t. horizontal axis.
These meters are fairly rugged and are not affected by oblique flows of as
much as 15.The accuracy of the instrument is about 1% at the threshold
value and is about 0.25% at a velocity of 0.3m/s and above.
The current meter is so designed that its rotational speed varies linearly
with the stream velocity at the location of the instrument. A typical
relationship is given by,
8/2/2019 somendra sah Hydrology Report PDF.
7/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
V = aNs+ b
Where,
V = velocity of flow in m/s
Ns = no. of revolution per sec of the current meter
a and b are meter constants given by the manufacturer, or generally
determined by experiments. We used vertical axis current meter for
velocity measurements.
Current meter in the field atRoshi Khola
Fig.current meter
Procedure:
Suitable section of stream was first selected so that the reach isstraight and is free from obstacles such as boulders, plants, etc.
The width of the stream is divided into a number of segments, eachsegment usually containing no more than 10% of the total discharge.
For each incremental width, stream depth is measured.The current meter is placed at a depth where average velocity is
expected to occur (0.6 times the total depth from surface).This
procedure is known as thesingle point observation method.
8/2/2019 somendra sah Hydrology Report PDF.
8/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
The total no. of revolutions in 30 seconds of time wasnoted from the digital counter.
The process was repeated for other width increments.
Observations and Calculations
FOR AREA VELOCITY METHOD:-
Distance from
left
Depth(Y) Number Of
Rev.
Rev./10Sec(N.
S.)
1 0.46 10
2 0.56 11
3 0.45 8
4 0.36 7
5 0.1 2
Width of river=5.25m
FOR FLOAT METHOD:-
Width Of River=4.0m
Distance=20m
S.N. Time(t)sec Velocity(v)m/sec
1. 22 0.909
2. 20 1
3. 18 1.111
4. 19 1.052
5. 21 0.952
6. 21 0.952
7. 29 0.65
8. 28 0.714
9. 19 1.05310. 21 0.952
8/2/2019 somendra sah Hydrology Report PDF.
9/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
11. 18 1.11
12. 26 0.769
sum=11.224
CALCULATION & OUTCOME RESULT:-
FOR AREA & VELOCITY METHUD:-
1st Left
average width(w)=1.5m
Last Right
average width=1.75m
Other remaining
average width=1m
Distanc
e from
left
Average
width(
w) m.
Depth(
y)
m.
Ns=Rev/s
ec
Velocity
V=0.51Ns+0.
03
m/sec
Area
(A)
m2
Segmental
discharge
Q(m3/se
c)
1 1.5 0.46 1 0.54 0.345 0.186
2 1 0.56 1.1 0.591 0.56 0.33
3 1 0.45 0.8 0.438 0.45 0.197
4 1 0.36 0.70 0.387 0.36 0.139
5 1.75 0.1 0.2 0.132 0.0875
0.011
TOTAL DISCHARGE(Q)=0.863m3/sec
FOR FLOAT METHOD :
Total X-sectional of River=1.08 m2
Average velocity=11.224/12=0.935 m/sec
TOTAL DISCHARGE(Q)=1.009 m3/sec
8/2/2019 somendra sah Hydrology Report PDF.
10/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
2. Float Method
A floating object on the surface of the stream when timed can yield the
surface velocity by the relation.
Vs = S/t
Where, S =distance travelled in time t.
This obtained velocity Vs when multiplied by the cross sectional area A of
the stream along the mid point of the S distance gives the discharge Q using
the relation:
Q = Vs*A
This method of finding velocity and hence discharge finds applications in
special circumstances although is primitive method: ( I ) a small stream in
flood ( II ) a small stream with rapidly changing water surface and (III)
preliminary surveys and also for checking purposes.
There may be surface floats (simple float moving on the stream) or there
can also be the Rod Float, in which a cylindrical rod is weighed so that it
can float vertically.
Field Procedure:
After fixing the gauging site, a distance of 15 m. both upstream anddownstream was measured along the centre line of the river. Two
people stood at the two extreme points of the 30 m. length.
Then a surface float was allowed to flow through the above marked30 m. and the time taken to do so was measured using a stop watch.
The process was repeated as per required.
FIELD VISIT OF METEOROLOGICAL STATION AT AIRPORT
SINAMANGAL
The study of hydrology necessitates the collection of data on humidity,
temperature, precipitation, radiation, and evapotranspiration and wind
velocity. For the collection of these meteodata, number of meteostations is
fixed around the country. Around 400 meteorological stations are presentlyoperating in our country.
8/2/2019 somendra sah Hydrology Report PDF.
11/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
This meteorological station operates under Department of Hydrology and
Meteorology, Nepal. The various equipments and instruments we studied
at this station were:
1, Rain gauge
Symonss Gauge (Non-recording Type)Tipping Bucket (Recording Type)
2. Campbell Sunshine Recorder
3. Anemometer
4. Steven Box
5. Evaporimeter
Steven Box (Psychrometer) - Thermometers for measuring Min & Max
temp. And Relative Humidity.
1. Rain Gauge
The precipitation is measured by an instrument called rain gauge.Rain
gauge is also known as hyetometer,ombrometer or pluviometer.Rainfall isexpressed in terms of the depth to which rainfall water would stand on an
area if the rainfall was collected in it. The rainfall is collected and measured
in a rain gauge.
A rain gauge essentially consists of a cylindrical vessel assembly kept in the
open to collect rain. Rain Gauge is broadly classified as:
i. Non recording Rain gauge
ii. Recording Rain gauge
( I ) Symonss Gauge ( Non-recording Gauge)
Symonss Gauge consists of a circular collecting area of about 12 cm
diameter connected to a funnel. The funnel discharges the rainfall catch
into a receiving vessel. The funnel and receiving vessel are housed in a
container. Water contained in the receiving vessel is measured by suitably
graduated measuring glass with accuracy unto 0.1 mm.The non recording
rain gauge gives the amount of rainfall only.
8/2/2019 somendra sah Hydrology Report PDF.
12/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
They cannot provide the information regarding when exactly the rainfall
commenced.
(ii) Tipping Bucket rain Gauge (Recording Type)
Recording type rain gauges are those rain gauges,which can give
permanent automatic rainfall record without any bottle reading.Recording
gauge produce a continuous plot of rainfall against time and provide
valuable data intensity and duration of rainfall for hydrological analysis of
stroms. There is mechanical and electrical arrangement by which the total
amount of rain fallen gets recorded automatically on a graph paper. The
gauge thus produces a record of cumulative rain vs. time in the form of a
graph which is known as mass curve rainfall.
Rain water is first caught in a collector and is funnelled into a two
compartmental bucket of 0.25mm each. These buckets are so balanced that
when 0.25mm of rainfall collects in one bucket, it cannot withstand more
and tips round to bring the adjacent one in collecting position. The water
from tipping bucket can be collected. Further while tipping it actuates an
electrically driven pen to trace a record on clockwork driven chart. This
instrument can also digitize the output signal as seen to the automatic data
logger.
Fig.Rain gauge
8/2/2019 somendra sah Hydrology Report PDF.
13/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
2. Campbell Sunshine Recorder:
Campbell Sunshine recorder is used to measure the duration of bright
sunshine hours which mainly depends on the latitude of the place and
environment. The main principle of Campbell Sunshine recorder is thatwhen bright sun rays are converged using a lens into a paper it gets burnt.
The special paper used is known as Campbell Sunshine card.
Campbell Sunshine recorder consists of a special arrangement of
transparent spherical lens provided with hourly graduated paper
(Campbell Sunshine card). The sphere is faced directly towards the sun by
fixing the latitude of place. The card is concentrically mounted with the
sphere.
Continuous burnt line on paper represents continuous sunshine and as
paper is graduated for time in hours, the no. of hours can be determined.
The glass sphere is usually 10cm in diameter. The card is held below the
sphere in any one of the three grooves depending upon the seasons of the
year. There are different cards for different hemispheres of the earth as
well as different card for various seasons:
Fig: Campbell Sunshine Recorder Fig: Campbell Sunshine card
3. Anemometer
Anemometer is used for measuring the speed and direction of wind. The
speed of wind varies with temperatures; pressure and altitude. There are
two horizontal arms over which the instrument for measuring direction
8/2/2019 somendra sah Hydrology Report PDF.
14/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
and magnitude are mounted. Direction of wind is usually expressed in
terms of 16 compass points (N, NNE, NE, NEE, E, SEE,)
The anemometer used was a three cup anemometer with a vertical axis of
rotation.
Anemometer converts the rotational speed of the cups into linear speed.
The speed of wind is measured in km/day in the particular anemometer. It
was placed 2m above the ground surface.
Fig.Determinination ofDirection FigMeasurement of Magnitude of wind
Fig: Anemometer
4. Steven Box:
Steven Box consists of special arrangement of 4 thermometers with a view
to determine the maximum & minimum temperatures and Relative
Humidity.
Two small clips are placed inside the thermometers to measure the
maximum and minimum temperatures. When the temperature gets to the
minimum, the mercury remains at the same position even if temperatures
rises ( In case of minimum thermometers) whereas in case of maximum
thermometers its exactly the opposite. When the mercury rises to the
8/2/2019 somendra sah Hydrology Report PDF.
15/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
maximum temp, the mercury remains there and hence maximum and
minimum temperatures are recorded. When we visited, the maximum
temperature recorded was 180C.
For the measurement of relative Humidity, two thermometers were placedvertically. One of the thermometer's bulb was wrapped around a wet cloth
and the bulb of the other was kept dry. These two thermometers'
combination is also called psychrometer. Wet bulb loses water from the
cloth constantly due to evaporation due to which the temperature of this
thermometer is lower than dry bulb temperature. The rate of capillarity in
the cloth depends upon Relative Humidity.
Wet bulb Deficit or Wet Bulb depression is the difference in temperatures
of these two thermometers.
Fig: Steven Box
5. Evaporimeter
An Evaporimeter is used to measure the evaporation rate and hence
estimate the approximate rate of evaporation from a natural water body.
Evaporimeters are large water containing pans which are exposed to the
atmosphere. If rate of evaporation is to be determined using an
evaporimeter, other meteodata such as humidity, wind movement, air and
8/2/2019 somendra sah Hydrology Report PDF.
16/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
water temperatures and precipitation should be noted on a regular basis as
these parameters affect evaporation significantly.
Evaporation rate = (Evaporated volume) / Time taken to reduce the depth
Evaporimeters are generally placed at a height of 15cm above the ground
so as to allow free air circulation and on wooden blocks so that heat
transfer by conduction can be checked effectively.
Evaporation pans are not the exact models of reservoirs and posses some
drawbacks.
Fig: Evaporimeter
8/2/2019 somendra sah Hydrology Report PDF.
17/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
Conclusions and Discussions
Due to the importance given to field trip, the students were able to
updates their theoretical knowledge of engineering in their actual field.In
addition to this,it develops a kinds of team sprit and co-operation for longterms work with the environment. With this field visit, we had a chance to
be familiar with the different hydrological parameters measured in
meteostations and the instruments & equipments used to measure these
parameters.
The different hydrological parameters measured were wind velocity, R.H.
of air, Rainfall intensity, Sunshine duration, Air temperature, Evaporation,
etc.
During this visit, temperatures were the only parameters we could
measure as other parameters required ample time and due to instruments.
The automatic data logger which was supposed to record all the data was
out of order. But we had the general idea of all the instruments and their
uses in measuring of hydrological data.
Comments:
Here ,the velocity from two different method produced two different
discharges. This can be due to the fact that floatation method, although was
performed repeatedly, did not give accurate results in comparison to
velocity area method. The accuracy in determination of discharge by A-V
method depends upon the time and economy. If more accurate results are
required, small increments in depths are recorded. Also if a floating rod or
a specified object was used in floatation, it could give more accurate results.
In the field, we floated small papers, plastics, etc which may also be the
reason that the results given by two methods did match.
We believe that such educational tour will be a lot of help for us in
understanding the actual situation while undertaking any professional
tasks in the future and we hope that IOE will continue such field tours.
8/2/2019 somendra sah Hydrology Report PDF.
18/18
Engineering Hydrology (EG 664 CE)
Civil III/II-065 Batch
BIBLOGRAPHY
1.Engineering Hydrology- K.Subramanya
2.A Course Manual on Engineering Hydrology
-Er.Narayan Prasad Subedi