somendra sah Hydrology Report PDF.

Engineering Hydrology (EG 664 CE)

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)

Civil III/II-065 Batch 1


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 various relevant 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



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



OBJECTIVE OF FIELD TRIP The main objective behind the offering field trip on Engineering 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 cooperation 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 station To 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 in the 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 of discharge (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 hydrological cycle, streamflow is the only part which can be measured accurately. A 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. Floatation method was also done for velocity determination.

Methodology Area-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 must take 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 of the stream. 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, 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 at Roshi Khola

Fig.current meter Procedure: Suitable section of stream was first selected so that the reach is straight and is free from obstacles such as boulders, plants, etc. The width of the stream is divided into a number of segments, each segment 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 the single point observation method. Civil III/II-065 Batch


The total no. of revolutions in 30 seconds of time was noted from the digital counter. The process was repeated for other width increments.

Observations and Calculations

FOR AREA VELOCITY METHOD:Distance from left

Depth(Y)

1 2 3 4 5

0.46 0.56 0.45 0.36 0.1

Number Of Rev. Rev./10Sec(N. S.) 10 11 8 7 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. 2. 3. 4. 5. 6. 7. 8. 9. 10.

22 20 18 19 21 21 29 28 19 21

0.909 1 1.111 1.052 0.952 0.952 0.65 0.714 1.053 0.952

Civil III/II-065 Batch


11. 12.

18 26

1.11 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 Average Depth( e from width( y) left w) m. m.

Ns=Rev/s ec

1 2 3 4 5

1 1.1 0.8 0.70 0.2

1.5 1 1 1 1.75

0.46 0.56 0.45 0.36 0.1

Velocity V=0.51Ns+0. 03 m/sec 0.54 0.591 0.438 0.387 0.132

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 Civil III/II-065 Batch

Area (A) m2

Segmental discharge ΔQ(m3/se c) 0.345 0.186 0.56 0.33 0.45 0.197 0.36 0.139 0.087 0.011 5


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 and downstream 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 marked 30 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 presently operating in our country. 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 Symons’s 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 is expressed 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 ) Symons’s Gauge ( Non-recording Gauge) Symons’s 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.



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



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 that when 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 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 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 placed vertically. 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 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



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 long –terms 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.



BIBLOGRAPHY 1.Engineering Hydrology- K.Subramanya 2.A Course Manual on Engineering Hydrology -Er.Narayan Prasad Subedi


somendra sah Hydrology Report PDF.

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