CE1403 Hydrology

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2008 Regulation Question with

Answer

CE1403

Hydrology

CE1403 Hydrology TWO – MARK & QUESTIONS

SIXTEEN – MARK QUESTIONS

Regulation- [2008]

CE1403 Hydrology http://vigneshxbs.blogspot.com

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CE1403 Hydrology

TWO – MARK QUESTIONS

UNIT I PRECIPITATION

1. Explain the term precipitation

The term precipitation denotes all forms of water which are commonly about 0.5mm or more

in size that reach the earth from the atmosphere.

2. What are the common forms of precipitation?

The common forms are drizzle, rain, snow, glaze, sleet and hail.

3. What is a front?

A front is the interface between two distinct air masses.

4. What is a cyclone?

A cyclone is a low pressure region in which the winds move in an anticlockwise region in the

northern hemisphere.

5. What are the types of rain gauging stations?

They are non recording stations and recording stations.

6. Name the commonly used recording rain gauges

Tipping bucket type

Weighing bucket type

Natural syphon type

Telemetering rain gauges

Radar measurement

7. What is point rainfall?

Point rainfall refers to the rainfall data of a station.

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8. Explain mass curve of rainfall.

The mass curve of rainfall is a plot of the cumulative depth of rainfall against the time

interval.

9. What are the methods of determining the average depth of precipitation of an area?

Arithmetical mean method

Thiessen polygon method

Isohyetal method

10. Define hyetograph.

A hyetograph is the graph showing variations of rainfall intensity against the time.

11. Define Probable Maximum Precipitation (PMP).

It is defined as the greatest or extreme rainfall for a given duration that is physically possible

over a station or a basin.

12. Give an equation for determining PMP.

PMP = P+K£m Where P- mean annual maximum rainfall series, £m ¡Vstandard deviation of

the series and K= a frequency factor which depends upon the statistical distribution the series

, number of years of record and the return period.

13. What are the drawbacks of non recording rain gauging stations?

Non-recording rain gauges give the amount of rainfall only. They cannot provide the

information regarding when exactly the rain commenced, what the intensity of rainfall is,

how the intensity of rainfall varies with the duration of storm and when the rain ended.

14. What are the advantages of recording rain gauges?

Recording rain gauges record the beginning and end of the rain, measure the intensity of

rainfall and gives a continuous record of rainfall with time.

15. What are the factors affecting the colloidal stability of clouds?

The factors affecting the colloidal stability of clouds are

a) electrical charge



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b) size of droplets

c) temperature

d) relative motion of cloud elements and

e) the coexistence of ice crystals and water droplets.

16. Define dew point?

Dew point is the critical temperature at which air becomes saturated when cooling.

17. What are the types of precipitation?

The types of precipitation are a) cyclonic precipitation b) convective precipitation and c)

Orographic precipitation

18. What is intensity duration graph?

If the observed maximum rainfall intensities at a place for various duration are plotted against

the respective durations, the graph is known as intensity-duration graph.

19. Define an anti-cyclone

It is a high pressure region in which the winds move in clock wise direction in the northern

hemisphere.

20. Explain depth-area relation.

For a rainfall of a given duration, the average depth decreases with the area in an exponential

manner as:

P=Po exp (-KAn)

Where p= average depth in area of A, km2

Po=highest amount of rainfall in cm

K and n are constants

21. Define the term recurrence interval

Recurrence interval is defined as the number of years or period after which an event occurs or

repeats .i.e. a period after which a rainfall of given intensity occurs or a flood peak occurs.



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UNIT II ABSTRACTION FROM PRECIPITATION

1. What are the factors affecting infiltration rate of soil?

Characteristics of the soil

Surface entry

Fluid characteristics

2. What is meant by evaporation?

It is the process by which water changes into the gaseous state and escapes into the

atmosphere.

3. What are the factors affecting evaporation?

The factors affecting are vapour pressure, temperature, wind, atmospheric pressure, water

pressure and areal extent of water bodies.

4. Give Meyer¡¦s formula for the estimation of evaporation.

EL=Km (ew-ea) (1+U9/16)

EL- lake evaporation in mm\day; ew-saturated vapour pressure at the water surface in mm of

Hg; U9-Monthly mean wind velocity in km\hr at about 9m above ground ;

Km- coefficient with a value of 0.36 for large deep waters and 0.5 for small shallow waters;

ea- actual vapour pressure of overlying air at a specified height in mm of Hg.

5. What are the analytical methods for determining of lake evaporation?

Water- budget method

Energy- balance method

Mass-transfer method

6. What is meant by infiltration capacity?

The maximum rate at which a given soil can absorb water at a given time is defined as the

infiltration capacity.

7. How can we get information about the infiltration characteristics f soil?

We can get information by using infiltrometers. Two kinds of them are Flooding type

infiltrometer and rainfall simulator.



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8. What is . index?

The . index is an average rainfall intensity above which the rainfall volume equals the runoff

volume.

9. Explain W index.

This is a refined version of . index. It includes depression storage and interception from total

losses. It is the average infiltrating rate during the time rainfall intensity exceeds the capacity

rate.

10. Define pan coefficient.

Pan coefficient is the ratio of reservoir evaporation to pan evaporation.

11. What are the methods of reducing reservoir evaporation?

Reducing the exposed water spread area

Using mechanical covers like roofs, floating rafts, floating light weight concrete blocks

Suppression of evaporation by surface films (chemicals).

12. What is an infiltrating capacity curve?

The infiltrating rates are plotted against their time intervals as a bar diagram. By joining the

mid points of the bars we get the approximate infiltration capacity curve.

UNIT III HYDROGRAPHS

1. What is direct runoff?

That part of the runoff which enters the stream immediately after precipitation.

2. What are the parts of total runoff or direct runoff?

o Surface runoff

o Interflow

o Channel precipitation

3. Explain base flow.

The flow that reaches a stream essentially as groundwater flow is called base flow.



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4. What is a perennial stream?

A perennial stream is one which always carries some flow. There is considerably some

amount of groundwater flow throughout the year.

5. Explain an intermittent stream.

A stream which doesn¡¦t flow throughout the year is called an intermittent stream. During wet

season there is contribution of the base flow to the stream. During dry season the water table

becomes lower than that of the stream bed and the stream dries up.

6. What is an ephimeral stream?

A stream which becomes dry soon after the end of the precipitation. There will not be any

base flow contribution.

7. Define a hydrograph.

It is a plot of the rate of discharge in a stream plotted against time chronologically.

8. What are the uses of a hydrograph?

In calculating the surface water potential in a stream.

In reservoir studies

Drought studies

9. What is meant by precipitation excess?

That part of precipitation which contributes directly to the surface runoff.

10. What is effective rainfall?

That part of rainfall which contributes to the direct runoff.

11. Define a flow mass curve.

It is the plot of the cumulative discharge volume against time plotted in chronological order.



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12. What are the parts or elements of a flood hydrograph?

The rising limb

The crest segment

The falling limb or the depletion curve or recession limb

13. Explain a direct runoff hydrograph (DRG)

The surface runoff obtained after the base flow separation is known as DRH.

14. What is effective rainfall hydrograph (ERH)?

For purposes of correlating DRH with rainfall which produced the flow, the hydrograph of

rainfall are pruned by deducting the losses. The resulting hydrograph is known as ERH

15. Define a unit hydrograph.

A unit hydrograph is defined as the hydrograph of direct runoff resulting from one unit

depth(1 cm) of rainfall excess occurring uniformly over the basin and at a uniform rate for a

specified duration(D hours).

16. What are the basic assumptions of unit hydrograph theory?

The time invariance

The linear response

17. Explain an S curve or S hydrograph.

It is a hydrograph produced by a continuous effective rainfall at a constant rate for an infinite

period. It is a curve obtained by summation of an infinite series of D-h unit hydrographs

spaced D-h apart.

18. What is synthetic unit hydrograph?

The unit hydrographs derived from the relation based on empirical equations of regional

validity which relate the salient hydrograph characteristics to the basin characteristics are

known as synthetic unit hydrographs. This is done in areas which are remote with very scanty

data on rainfall and the resulting flood hydrograph.

19. What is an instantaneous unit hydrograph (IUH)?

The limiting case of a unit hydrograph of zero duration is known as IUH. IUH is a fictitious,



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conceptual unit hydrograph which represents the surface runoff from the catchment due to an

instantaneous precipitation of the excess rainfall volume of 1cm.

20. Define basin lag (Time lag).

Basin lag is defined as the time from the centre of rainfall to the hydrograph peak.

21. The recession curve is sometimes called the depletion curve. Why?

The water which is stored in channel, passes the measuring point is shown by this portion of

hydrograph. This portion of the hydrograph is independent of the rainfall characteristics and

is dependent on the physical feature of the basin and drainage channel.

22. What are the uses and applications of unit hydrograph?

The unit hydrograph are used in many hydrological problems such as

In the development of flood hydrograph corresponding to design storms which are required to

the design of hydraulic structures.

In watershed simulation models

In the studies of flood forecasting and flood warning systems

In extending the flood flow records based on rainfall records.

23. State the assumptions made in the unit hydrograph theory.

The basic assumptions are

The effective rainfall is uniformly distributed within its duration.

The effective rainfall is uniformly distributed through the whole area of the basin.

The base period of the direct runoff hydrographs produced by effective rainfall of the same

duration (though the intensities may be different) are also same.

The ordinates of the direct runoff hydrographs of a common base period are directly

proportional to the total volume of direct runoff represented by the respective hydrographs.

For a given drainage basin the hydrograph of runoff due to a given period of rainfall reflects

the unchanging characteristics of the basin.



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UNIT IV FLOODS AND FLOOD ROUTING

1. What is meant by flood routing?

It is a procedure by which the variation of discharge with time at a point on a stream channel

can be determined by consideration of similar data for a point upstream.

2. What are the types of flood routing?

Reservoir routing

Channel routing

3. What is reservoir routing?

In reservoir routing the effect of a flood wave entering a reservoir is studied to predict the

variations of reservoir

elevation and outflow discharge with time.

4. What is channel routing?

It is a method which uses mathematical relations to calculate outflow from a stream channel

once inflow, lateral contributions and channel characteristics are known

5. What are the uses of reservoir routing?

The uses are:

In the design of the capacity of spillway and other reservoir outlet structures and

In the location and sizing of the capacity of reservoirs to meet specific requirements.

6. Explain a flood.

A flood is an unusually high stage in a river normally the level at which the river overflows

its banks and inundates the adjoining area.

7. List the uses of flood routing.

Establishing the height of flood peak at a downstream location in short term flood

forecasting.

Estimating the protection that would result from construction of a reservoir.

Determining the required levee height for flood protection.

Determining the adequacy of spillway



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Predicting the behaviour of a river after a change in a channel condition.

In the derivation of synthetic unit hydrographs.

8. In the Muskingum storage equation what do the parameter k and x represent?

K is a constant of proportionality evidently possessing dimensions of time. x is a weighing

factor having the range 0<-x<-0.5

9. What is the basis of hydrologic routing method?

The basis is continuity equation.

10. What is the differential equation of storage in flood routing?

The equation is I-Q=ds/dt. Where I andQ are the inflow and out flow from a reservoir and s is

the storage in the reservoir.

11. What are the forms of storage in a channel reach?

They are prism storage and wedge storage.

12. Define attenuation and lag time

In reservoir routing, if peak inflow hydro graph and peak out flow hydrographs are drawn, it

is seen that the peak of the out flow hydrograph is smaller than the inflow hydrograph. The

peak of the outflow hydrograph occurs after the peak of the inflow hydrograph and the time

base of the outflow hydrograph is longer than the time base of the inflow. The reduction in

the peak outflow is called attenuation. The time difference between peak of inflow and

outflow is called lag time or lag.

13. What is the importance of flood peak studies?

They are important in design of bridges, culvert, water ways and spillways for dams and

estimation of scour at a hydraulic structure

14. What is gumbel¡¦s distribution?

It is one of the most widely used probability- distribution functions for extreme values in

hydrologic and meteorological studies for prediction of flood peaks, maximum rainfall etc,.



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15. What is the general equation of hydrologic frequency analysis?

The equation is XT=X+k£m.

Where

XT=the value of the variate x of a random hydrologic series with a return period

T, X= mean of the variate,

£m=S.D of the variate,

K=frequency factor which depends upon the return period T and

the assumed frequency distribution.

16. Explain the use of flood frequency analysis.

The flood frequency analysis is a direct means of estimating the desired flood based on the

available flood flow data of the catchment. The result of the frequency analysis depends upon

the length of the data.

17. What is design flood?

Flood adopted for the design of a structure.

18. Explain spillway design flood.

Design flood used for specific purpose of designing the spillway of a storage structure. This

term is used to denote the maximum discharge that can be passed in a hydraulic structure

without any damage or serious threat to the stability of a structure.

19. Define standard project flood (SPF)

The flood that would result from a severe combination of meteorological and hydrological

factor that is reasonably applicable to the region. Extremely rare factors are excluded.

20. What is probable maximum flood (PMF)?

The extreme flood that is physically possible in a region as a result of severe most

combinations including rare combinations of meteorological and hydrological factors.



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UNIT V GROUND WATER HYDROLOGY

1. What is an aquifer?

A geological bed or formation which can hold and transmit water and from which

considerable amount of water can

be extracted is called an aquifer. Ex: Sand, Sandstone.

2. What is an aquitard?

A saturated bed or formation, which will yield inappreciable quantities of water to wells but

appreciable leakage of water can take place to an aquifer below it. Ex: Sandy clay.

3. What is an aquiclude?

A saturated bed or formation which is impermeable to the flow of water. It can contain water

but through it movement does not occur. Ex: Clay

4. What is an aquifuge?

A geological formation which is neither porous nor permeable. Ex: a hard rock without

fractures

5. What is an unconfined aquifer?

An aquifer underlain by an impermeable bed and the upper part of which is generally the

unsaturated zone. The water table is under atmospheric pressure.

6. What is a confined aquifer?

An aquifer which is underlain and overlain by impermeable layers or aquicludes is called a

confined aquifer. The water in confined aquifer will be under pressure.

7. What is water table?

The upper surface of the zone of saturation is called water table.

8. What is meant by cone of depression?

When a well is pumped, there will be a decline in the water level and gradually it assumes the

shape of an inverted cone, which is called a cone of depression centred on the pumping well.



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9. Give Dupit’s assumptions for steady flow of groundwater

a) The curvature of the free surface is very small so that the stream lines can be assumed to

be horizontal at all sections.

b) The hydraulic gradient line is equal to the free surface slope and does not vary with depth.

10. What is steady state flow?

During pumping of a well, a stage occurs when there is no change in water level with time.

This condition is known as steady state flow.

11. What is tansmissivity?

The rate of flow of water through a unit cross sectional area under unit hydraulic gradient for

entire saturated thickness of the aquifer is known as transmissivity.

12. What is meant by specific capacity of a well?

The ratio of discharge to drawdown at the well (Q/Sw) is known as specific capacity of a

well.

13. What is an effluent stream?

Streams which receive groundwater flow are called effluent streams.

14. What is an influent stream?

A stream which contributes to the groundwater is known as influent stream.

15. State Darcy¡¦s law

It states that the flow rate through a porous media is directly proportional to the head loss and

inversely proportional to the length of the flow path.

16. What is meant by radius of influence of a well?

During pumping of a well, there will not be any drawdown at a place away from the well.

The distance from a pumped well to the edge of the cone of depression is known as radius of

influence (R).



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17. What is pumping test?

In a pumping test, a well is pumped at a constant rate for a considerable period of time. The

water level in the pumping as well as in one or more observation wells are noted during the

period. Observation wells are located at varying distances from the pumping well. Before the

test begins, water levels in the wells are measured to provide

static water levels. As the aquifer is pumped, the drawdowns are determined (the difference

between the static water level and the pumping water level) as a function of time. We can

determine the aquifer parameters (T, K and

S) based on the data collected from a pumping test.

18. Explain a recuperation test.

In a recuperation test, first the water level is depressed to some level below the normal water

level by pumping for a particular period of time. Then the pumping is stopped. The water

level in the well gradually raises i.e. the well starts recuperating. The rise in water level is

measured at frequent intervals. The drawdown below the original static water level during the

recovery period are known as residual draw down. The transmittivity of the aquifer can be

determined from the recovery (recuperation) test data.

19. What is safe yield?

The safe yield of groundwater basin may be defined as the amount of water which can be

drawn from it without producing any undesirable effects. Any withdrawal in excess of safe

yield is called overdraft.



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SIXTEEN – MARK QUESTIONS

UNIT – I

1 (i) Explain with the help of a neat sketch about the hydrological cycle with its

various components. (10)

(ii) The average annual rainfall of 5 rain gauges in a basin 890, 540, 450, 410 and

550 mm respectively. How many additional gauges are required if it is desire to

limit the error to only 10%. (6)

2. (i) How is precipitation measured? Discuss the three methods which convert the

point precipitation to areal precipitation and comment on the best method. (8)

(ii) Describe the working principle of a non-recording type rain gauge with neat

sketch, mentioning its advantages and disadvantages. (8)

3. (i) The annual average rainfall of four stations A,B,C and D in an area are 105,

122, 95 and 102 cm respectively. In a particular year station ‘C’ did not

function and the rainfall values of stations A,B and D are 90, 97 and 82 cm.

Compute the missing data. (12)

(ii) Compare the merits and demerits of arithmetic mean and thiessen polygon

methods of finding out average rainfall in an area. (4)

4. From the following information of a non-uniform rainfall over a catchment with

variable infiltration capacity, calculate the surface runoff ordinate from the

catchment. (16)



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% of Catchment

area

-index

(cm/hr)

Rainfall in

Ist hour (cm)

Rainfall in

2nd hour (cm)

Rainfall in

3rd hour (cm)

50 0.5 0.8 2.5 1.0

30 0.75 1.0 2.1 0.7

20 1.0 1.5 2.3 0.8

5. Describe the purpose of the different types of Instruments that are commonly installed

in an Hydrometeorological Station. (16)

6. How precipitation is measured and lists the errors that occur in the measurement of

precipitation? (16)

7. (i) Enumerate the various forms of precipitation and state, in brief, the characteristics

of any five of them. (8)

(ii) Enumerate the factors affecting infiltration capacity. Briefly explain how any

three of them affect the infiltration capacity. (8)

8. (i) Write short notes on ‘air mass’ and fronts’. (6)

(ii) List the four conditions necessary for the production of rainfall and explain them

briefly. (10)

UNIT – II

1. (i) State the Horton’s equation for infiltration capacity curve and sketch with

salient components of the curve. (8)

(ii) Explain briefly about the -index and W-index. (8)



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2. (i) Explain with neat sketch, the various methods of estimation of Evaporation. (8)

(ii) Differentiate the reservoir evaporation from the agricultural field evaporation. (8)

3. (i) An evaporation pan 1.2 m dia. was used to find out the evaporation loss from

reservoir. The pan was initially filled up with water to a depth of 8 cm. During the

period of observation, a rainfall of 4 cm was recorded. At the end of the period of

the observation, the depth of water in the pan was found to be 8.5 cm. If the pan

coefficient is 0.7, determine the evaporation from the reservoir? Assume the water

spread area of reservoir is 200 km2. (10)

(ii) Write short notes on Frequency Analysis of rainfall data. (6)

4. Derive the ordinates of 12 hr. Unit Hydrograph with the help of given 4 hr. Unit

Hydrograph and draw the Unit Hydrograph. (16)

Time: 0 4 8 12 16 20 24 28 32 36 40 44

U.H.O 0 20 75 125 150 125 90 50 25 15 5 0

5. Describe how the infiltration rate can be measured using a Double Ring

Infiltrometer. (16)

6. Describe the step by step procedure involved in the analysis for developing Intensity-

Frequency- Duration relationship. (16)

7. Enumerate the methods for computing the average depth of rainfall over a basin. (16)

Indicate which method must be used for the following conditions.



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(i) Basin is quite rugged and hilly.

(ii) Basin is not rugged rather plain.

(iii) If the gauging stations are few compared to the size of the basin.

(iv) If the network of rainfall stations within the storm area is sufficiently dense.

UNIT –III

1. What do you understand by unit hydrograph? How is it derived? Explain its use in

construction of flood hydrograph resulting from two or more periods of rainfall. (16)

2. A runoff data at a stream gauge station for a flood are given below in the table;

Drainage area is 42 km2. If the duration of rainfall is 3 hours, derive a 3 hours unit

hydrograph for the basin. (16)

Time (hrs.) 0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45

Total Runoff 50 47 75 120 225 290 270 145 110 90 80 70 60 55 51 50

(m3/s)

Base flow 50 47 46 45 45 45 46 48 50 53 54 57 60 55 51 50

(m3/s)

3. (i) A Catchment has six rain gauge stations as given below. The annual rainfalls

recorded by rain gauges are as follows. For a 10 % error in the estimation of

mean rainfall, calculate the optimum number of station in the catchment. (10)

Stations: A B C D E F

Rainfall (cm): 80.6 104 180 110 99 137



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(ii) Discuss briefly about the various methods of Evaporation Measurement. (6)

4. A 30 cm well fully penetrates an unconfined aquifer of 25 m depth when a

discharge of 2100 lpm was being pumped. The observation wells at radial distances

of 30 m and 90 m indicates draw down of 5 m and 4 m respectively. Estimate (i)

the coefficient of permeability, (ii) transmissibility (T) and (iii) draw down at the

pumping well. (16)

5. Describe the purpose for the concentration of a S-Curve Hydrograph? (16)

6. (a) (i) For the determination of ordinate of a UH, the base flow has to be separated

from the ordinates of total runoff hydrograph. Explain the well known method

of base flow separation. (8)

(ii) The following are the ordinates of a 3 – hour UH. Define the ordinates of 6-

hour UH and plot the same. (8)

Time (hour) 0 3 6 9 12 15 18 21 34

3-hr Uh

Ordinates (cumec) 0.0 1.5 4.5 8.6 12.0 9.4 4.6 2.3 0.8

7. (i) Define UH. Enumerate the steps adopted to derive a UH from an observed single

peaked flood hydrograph. (8)

(ii) A drainage basin has an are of 3800 km2. Determine (1) lag period, (2) peak

discharge, and (3) base period, of a 9 – hour unit hydrograph from the following

date:

Length of the longest water course, i.e. of the mainstream from the gauging station



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(outlet or measuring point ) to its upstream boundary limit of the basin, L = 320 km.

Length along the mainstream from the gauging station (outlet) to a point on the

steam opposite the areal center of gravity (centroid) of the basin, Lca = 200 km

Coefficient reflecting the size, shapes and slope of the basin, Ct = 0.9.

Empirical constant, Cp = 4.0.

UNIT –IV

1. (i) What are the methods of estimating design flood? What are their limitations? (6)

(ii) Describe the method of estimating a T- year flood using Gumbels limitations? (10)

2. (i) Derive the Muskingum routing equation and the expression for the routing

coefficients Co, C1, and C2. (10)

(ii) What are flood control measures? Mention some of the flood control measures to

mitigate the effect of floods. (6)

3. The rating curve of a current meter used for measuring velocity in a small river is

given as V = 0.51 N + 0.03 m/s, where N is the revolution / sec. Calculate the

discharge of the river from the following data. Velocity is measured at the mid of the

sections. (16)



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Distance (m): 0 1 2 3 4 5 6 7

Depth (m): 0 1.1 2.0 2.5 2.0 1.7 1.0 0

Revolutions at 0.6 D: 0 39 58 112 90 45 30 0

Duration of observation (sec.) 0 100 100 150 150 100 100 0

4. (a) (i) Define the following :

(1) SPF

(2) MPF

(3) Design Flood. (3 x 2 = 6)

(ii) Enumerate the methods for determining maximum flood discharge (peak

flood) in a river. (3)

(iii) Determine the design flood discharge (allowing an increase of one-third)

for a bridge site with the following data:

Catchment area = 2 x 105 hectares

Duration of the storm = 8 hours

Storm precipitation = 3 cm

Time of concentration = 2 hours.

Gauged discharge for a past flood with average maximum daily rainfall of

18 cm was 3400 cumec. (7)

5. (i) Explain reservoir routing and channel routing. (8)



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(ii) Explain Muskingum method of flood routing. (8)

6. How is the Gumble’s method used to determine the annual peak discharge? (16)

7. Explain the purpose and procedure for Reservoir Routing. (16)

UNIT –V

1. A stream flows in the approximate centre of a flat alluvial valley bounded by

impermeable shale. The valley average 2000 m in width and contains an alluvial

aquifer in hydraulic connection with the stream. The hydraulic conductivity of the

aquifer is 0.054 cm/s. During irrigation season recharge can be assumed to be steady

and uniform over the valley. Observation, wells indicate that during irrigation the

water table at a distance of 150 m from the stream is 3.5 m above the impermeable

shale and 1.5 m above the stream level. Make any suitable assumptions if necessary

and calculate the discharge from the aquifer to the stream and find the maximum

water table level. (16)

2. (i) Explain with neat sketches various types of aquifers. (12)

(ii) State Dupuit-Forcheimer assumptions and its uses in groundwater hydrology? (4)

3. (i) At certain point in an unconfined aquifer of 3 km2 area, the water table was at an

elevation of 102 m. Due to natural recharge in a wet season, its level raise to



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103.2 m. A volume of 1.5 MCM of water was then pumped out of the aquifer

carrying the water table to reach a level of 101.2 m. Estimate (1) specific yield

and (2) the volume of recharge during wet season. (12)

(ii) Distinguish between Confined and Unconfined aquifers. (4)

4. A 30 cm well fully penetrates an unconfined aquifer of 25 m depth when a discharge

of 2100 lpm was being pumped. The observation wells at radial distances of 30 m

and 90 m indicates draw down of 5 m and 4m respectively. Estimate (i) the

coefficient of permeability, (ii) transmissibility (T) and (iii) draw down at the

pumping well. (16)

5. Draw an neat sketch of a confined Aquifer with a well and the Drawdown Curve to

indicate the Radius of Influence (R) and drawdown (s). Define and also state

examples for an Aquifuge, Aquitard and Aquiclude. (16)

6. (i) State Dupuit – Forchheimer assumptions. (3)

(ii) A well with a radius of 0.5 m, completely penetrates an unconfined aquifer of

thickness 50 m and K = 30 m/day. The well is pumped so that the water well

remains at 40 m above the bottom. Assuming that pumping has essentially no

effect on water table at r = 500 m. What is the steady-state discharge? (12)

7. (a) (i) Differentiate between the following, in one or two sentences :

(1) Confined and unconfined aquifers.

(2) Specific yield and specific retention.



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(3) Field capacity and moisture equivalent. (3 x 2 = 6)

(ii) State Darcy’s law. What is its validity? (3)

(iii) A 200 mm well penetrates 30 m below static water level (GWT). After a long

period of pumping at a rate of 1800 lpm, the drawdowns in the observation wells

12 m and 36 m from the pumped well are 1.2 m and 0.5 m, respectively.

Determine (1) the transmisibiliy of the aquifer (2) the draw down in the pumped

well assuming R = 300 m. (7)

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CE1403 Hydrology