Transcript
Hydrology and Irrigation Engineering
10CV55
Assignment Questions Unit 1: INTRODUCTION & PRECIPITATION 1. Define hydrology. With a neat sketch, explain the Horton's qualitative representation of the hydrologic cycle. 2. Discuss briefly the importance of hydrology and its practical applications in civil engineering. 3. Draw the Horton’s qualitative representation of hydrological cycle .Explain the cycle of all components /phases? 4. Draw a neat sketch showing the catchment Hydrological cycle. Write down the 'water budget' equation for any one of the zones. 5. Explain with neat sketch, Horton's Engineering representation of' Hydrologic cycle. 6. Hydrology is a highly inter - disciplinary disciplinary science. Justify. 7. What are the seasons of India? Discuss the movement pattern of wind during monsoon and retreating monsoon seasons in the country. 8. Describe the features - type, amount and distribution of rainfall, of the three seasons of rainfall in Karnataka. 9. List out the various practical applications of hydrology? 10. Define precipitation. Explain different forms o f precipitation? 11. What are the forms of precipitation? Explain any one o f them? 12. Describe various types and forms of precipitation. 13. Describe the methods of recording of rainfall 14. What are the advantages and d isadvantages of recording type of rainguage? 15. Describe the principle of working of a float type recording rainguage with a neat sketch. Discuss its advantages and disadvantages. 16. Differentiate between recording and non - recording type of raingauges. 17. Critically compare recording rainguage (self) with non recording type rainguage. 18. Describe the three methods of determining the average depth of rainfall over an area. Bring out the merits and demerits of each method. 19. An area is composed of a square of side 10 km and an equilateral triangles placed on the left side. The annual precipitation recorded at four corners and the centre of the square considered clock wise from the top left corner is 460mm, 650mm, 760mm, 800mm and Dept of Civil Engineering, SJBIT
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700mm respectively. The apex of the triangle has recorded 600mm of annual precipitation. Find the mean precipitation over the area by Thiessen polygon method and find the percentage difference with that of the arithmetic mean method. 20. Thiessen polygons constructed for a network of the raingauges in a river basin yielded. Thiessen weights of 0.10, 0.16, 0.12, 0.11, 0.09, 0.08, 0.07, 0.11, 0.06 and 0.10. If the rainfalls recorded at these gauges during a cyclonic storm are 132, 114, 162, 138, 207, 156, 135, 158, 108 and 150 mm respectively. Determine the average depth of rainfall by Thiessen mean and arithmetic mean method. 21. A catchment is in the shape of an equilateral triangle placed over a square. Rain gauges of the apex of the triangle and the next two successive corners of the square record 23, 18 and 16cm during a storm, determine the Theissen mean rainfall for the catch ment. 22. A storm produced rainfall of 65, 74, and 100mm at three stations P, Q, and R respectively. The normal annual rainfall at the stations X, P, Q and R are 660, 792, 786 and 1040 respectively. Estimate the missing storm rainfall at station X. 23. The normal annual precipitation of five rain gauge stations P, Q, R, S and T are 1200, 1020, 780, 1135 and 1350mm respectively. During a particular storm the precipitation recorded by stations P, Q, R and S are 135, 95, 70 and 100mm respectively. The instrument at 'T' is inoperative during that storm. Estimate the missing precipitation at station T. 24. During a month, a rain guage went out of order while the other four gauges in the basin reported rainfalls of 110, 90, 120 and 115mm. If the normal annual rainfall for these four gauges are 115, 95, 125 and 120mm respectively and the normal rainfall for the broken gauge is 98cm, estimate the monthly rainfall at t he broken gauge. 25. Explain how the double mass curve method is used to test consistency of rainfall record. 26. Explain the method of checking rainfall data for consistency and show how records can be adjusted for the current regime. 27. Estimate from depth – area curve , the average depth of precipitation that may be expected th
over an area of 2400 Sq.km due to the storm of 27 September 1978 which lasted for 24 hours. Assume the storm centre to be located at the centre of the area. The isohyetal as map for the storm gave the areas enclosed betwee n different isohyetes as follows.
Dept of Civil Engineering, SJBIT
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21
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20
19
18
17
16
15
enclosed 54
134
203
254
295
328
353
Area
5
0
5
5
0
14
13
12
388
391
0
5
(mm)
3
371
5
0
2
(km )
28. The annual rainfall data being reported from a station A for 22 years are available, since 1969. In order to check the consistency of the data, six neighboring stations have been chosen and the annual rainfall values of these stations have been averaged for all the years on record since 1969. These values are given below: Year
9 0 6 7 9 9 1 1
1 7 9 1
3 7 9 1
5 7 9 1
7 7 9 1
8 7 9 1
9 7 9 1
0 8 9 1
1 8 9 1
2 8 9 1
3 8 9 1
4 8 9 1
5 8 9 1
6 8 9 1
7 8 9 1
8 8 9 1
9 8 9 1
0 9 9 1
7 4 8 7 4 7 1 1 1
4 9 1
6 9 1
0 6 1 8 5 2 8 2 0 0 7 0 3 6 9 4 5 4 3 5 4 4 4 3 3 3 6 1 1 1 1 1 1 9 1 1 1 1 1 1 1
3 2 6 4 3 4 1 1 1
1 6 1
2 5 1
8 3 6 4 5 3 5 5 3 5 3 0 6 1 2 9 5 6 5 4 1 3 6 3 4 3 4 6 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Yearly Precipitation at station A in cm Station
average
yearly precipitation in cm `
i) Find out if any inconsistency in precipitation record of station A is indicated. And if yes, since when, a change in the precipitation regime is indicated? ii) Adjust the recorded data at station A and det ermine its mean annual precipitation. 29. What are the recommendations of Indian standard institution on rain gauge network establishment? Briefly explain optimum number of rain gauge stations in a catchment. 30. Explain the method of finding optimum number of rain gauges in a catchment. 31. A catchment has five rain gauge stations, which record 66, 74, 81, 69 and 90 cm of rainfall in a year. Determine the percentage error in the arithmetic mean for the area. If the error is to be 2% less than this, determine the additional number of stations required. If you use a formula, derive it. 32. During a storm, one of the ra in gauge stations 'X' failed to record the rainfall. Data in four surrounding stations during the same storm are recorded as 7.5, 10, 12 and 9mm. Coordinates of these four stations in km with station 'X' as the origin are (18, 4) , (-8, 16),
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(-13, -21) and (-16, 23) respectively. Determine the missing rainfall record at station 'X’. 33. A catchment has 8 rain gauges of which one is a self recording type and 7 are the standard type. For a 5% error in the estimation (E) of the mean rainfall, what should the required no. of additional rain gauges, if annual precipitation at the 8 stations are? Station
A
B
C
Rainfall (cm)
74
87 94
D
E
88 104
F
G
H
118
60
95
34. The average annual rainfalls in cm, at four existing raingauge stations in a basin are 105, 79, 70 and 66. If the average depth of rainfall over the basin is to be estimated within 10% error. Determine the additional number of gauges needed. 35. The annual rainfall at 7 rain gauge stations in a basin is 580, 940, 600, 450, 200, 880 and 680mm respectively. What is the percentage accuracy of the existing network in the estimation of the average depth of rainfall over the basin? How many additional gauges are required if it is desired to limit the error to only 10%. 36. A catchment has six rainguage stations. In a year, the annual rainfall recorded by the gauges are as follows: Station
A
B
C
Rainfall (cm)
82.6
102.9 180.3
D
E
F
110.3
98.8
136.7
For a 10% error in the estimation of the mean rainfall, calculate the optimum number of stations in the catchment. 37. Define rainfall hyetograph. How to construct the double mass curve? 38. Explain mass curve analysis, with a neat sketch. Define intensity, duration and frequency of rainfall. 39. Following are the rain gauge observations during a storm: Time since start of storm, mins.
5
10
15
Accumulated rainfall , cms
0.1
0.2 0.8
20
25
30
35
40
45
50
1.5
1.8
2.0
2.5
2.7
2.9
3.1
Construct i) Mass curve of precipitation ii) Hyetograph.
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40. The annual rainfall values at a P for a period of 20 years area as follows Year
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
Annual
120
84
68
92
102
92
95
88
76
84
101
rainfall (cm)
Determine i)
The value of annual rainfall at P with a recurrence interval of 15 years.
ii)
The probability of occurrence of an annual rainfall of magnitude 100cm at a station P
iii)
75% depenable annual rainfall at the station.
Unit 2: LOSSES FROM PRECIPITATION 1. Define evaporation. With a neat sketch, explain the measurement of evaporation using IS class A pan. 2. Discuss briefly the various abstractions from precipitation. 3. Briefly explain "Evaporation Process". 4. Describe briefly a) Reference crop evapotranspiration b) Actual evapotranspiration 5. Distinguish between a) Infiltration capacity and infiltration rate. b) Actual and potential evapotranspiration c) Field capacity and permanent wilting point d) Depression storage and interception. 6. Define i) evaporation ii) potential evapo transpiration iii) Actual evapotranspiration iv) Pan coefficient. 7. Describe the factors influencing evaporation rate from an open water surface. Define the terms potential evapotranspiration and actual evapotranspiration, giving their relationship with evaporation. 8. Explain how consumptive use can be estimated using the Blaney - Criddle method. 9. Describe the factor affecting evapotranspiration process. 10. State Dalton's law of evaporation and discuss the significance of each parameter in Dalton's equation. Dept of Civil Engineering, SJBIT
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11. What is the actual evaporation, if 9 litres of water is removed from an evaporation pan of diameter 1.22mm, to maintain the stipulated water level in the pan? A rainfall of 9mm has been recorded simultaneously. Pan coefficient is 0.9 for the evaporation pan considered. 12. Calculate the daily lake evaporation from the following data from a class A pan. Assume pan coefficient-0.75. Date
7/6/06
8/6/06 9/6/06
10/6/06
11/6/06
Rainfall (mm)
06
00
16
03
05
Water added (mm)
+08
+12
-05
+10
+09
13. Write a neat sketch showing the IS - Pan evaporatimeter. Describe how it is used to measure the evaporation rates. What are its drawbacks? 14. Explain any three methods for determination of lake evaporat ion. 15. Describe the importance of pan coefficient in the det ermination of lake evaporation. 16. Define pan coefficient with a neat sketch. Explain the IS1 standard evaporation pan. Explain i) Actual evapotranspiration
ii) Potential evapotranspiration
iii) Available
water. 17. What are the measures taken to reduce t he rate of evaporation? 18. The water spread area in a lake nearby in the beginning of Jan in a year was 2.8 sq. km and at the end of Dec it was measured as 2.55 sq km. Calculate the loss of water due to evaporation assuming pan coefficient of 0.7. 19. Determine the E.T. and irrigation requirement for wheat, if the water application efficiency is 65% and the (Cu) coefficient for the growing season is 0.8 from the following data:
Month
Mean monthly temp. °C Monthly % of sunshine hrs.
Effective rainfall cm
Nov
18.0
7.20
2.6
Dec
15.0
7.15
2.8
Jan
13.5
7.30
3.5
Feb
14.5
7.10
2.0
20. Following are the data of average monthly percentage sunshine hours (p), mean monthly Dept of Civil Engineering, SJBIT
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temperature (Tm) and vegetable's crop coefficient (k) for a place at 20 °N latitude. Month Jan
Feb
Mar April May June July Aug Sept Oct
Nov Dec
P
7.73 7.26 8.2
8.52
9.14 9.2
9.25 8.95 8.30 8.19 7.58 7.88
Tm
12
15
20
22
22
20
K
0.5
0.55 0.6
0.65
0.7
0.75 0.8
16
20
15
10
11
8
0.8
0.7
0.65 0.55 0.5
If a farmer grows vegetables from July to December, what is total evapotranspiration during that time period?
21. At site the value of evaporation in cm from Jan - Dec are 16.7, 14.3, 17.8, 25.0, 28.6, 21.4, 16.7, 16.7, 16.7. 21.4, 16.7, 16.7. Determine the evapotranspiration and irrigation requirement for wheat if the water efficiency is 65% and the consumptive use coefficient for the growing seasons following data. Month
Mean
Monthly Monthly
% Effective
Temperature (°C) Sunshine hours
Rainfall (cm)
Nov
18
7.2
2.6
Dec
15
7.15
2.8
Jan
13.5
7.3
3,5
Feb
14.5
7.1
2.0
22. Define infiltration. What are the factors that affect infiltration? 23. Explain the factors affecting infiltration capacity. 24. Explain the methods of estimating yield of a catchment. 25. Explain factors affecting Infiltration capacity. 26. What are infiltration indices? Distinguish between Φ - Index and W - Index. 27. Explain with a neat sketch, the method of determining infiltration. 28. Describe a double ring infiltrometer for measuring infiltration rate. What is the significance of the outer ring? 29. Define infiltration. Explain how the constant fc, fo and k in the Horton’s equation can be obtained from the Experimental data. 30. Total observed runoff volume during a 6 hr storm with a uniform intensity of 15mm/hr is 21.6xl06 cum. If the area of the basin is 300 sq.km, find the average infiltration rate for Dept of Civil Engineering, SJBIT
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the basin. 31. A 6 hour storm produced rainfall intensities of 7, 18, 25, 12, 10 and 3mm / hr in successive one - hour intervals over a basin of 800km2. The resulting runoff is observed to be 2640 hectare - mt. Determine the ø - index of the basin. An infiltration test on a ring with 35cm diameter yielded the following data. Time
from
the
starts
(mts) Cumulative vol. of water added (cm3).
0
2
5
10
20
30
60
90
150
0
178 658 1173 1924 2500 3345 3875 4595 5315
i) Determine the infiltration capacity rates for the time intervals. ii) What is the average infiltration capacity for the first 10 minutes and for the first 30 minutes? 32. The rates of rainfall for the successive 30 min period of a 3 hr storm are 1.6, 3.6, 5.0, 2.8, 2.2, 1.0 cm/hr. Corresponding surface runoff is estimated to be 3.6cm. Establish ø - index. Also determine W - index. 33. Define infiltration. The rate of infiltration from the beginning of a storm are given below Time (mm)
5
30 60
90
120
150
180
210
240
Rate of infiltration mm/hr
600
54 22
20
16
14
12
08
08
Fit an infiltration capacity curve of the exponential form. 34. A storm with 10.00 cm precipitation produced a direct runoff of 5.8 cm. Given the time distribution of the storm as below, estimate the ø - index of the storm. Time from start (hr) Incremental rainfall in each hour (cm)
1
2
3
4
5
6
7
8
0.4
0.9
1.5
2.3
1.8
1.6
1.0
0.5
35. The total observed run off volume during a 6 hour storm with a uniform intensity of 1.5 6
3
3
cm/hr is 21.6 x 10 m . If the area of the basin is 400 km , find the average infiltration rate for the basin. 36. Explain briefly: i) infiltration capacity ii) ø - index
iii) w - index. -4t
37. Infiltration equation for a basin is given by f = 5 + 21e , where f is in mm/h and t is in hours. Determine the values of initial infiltration capacity (f 0), final steady infiltration rate Dept of Civil Engineering, SJBIT
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(fc) and decay coefficient (k). For a storm of
intensity more than f 0, determine
infiltration depth and average infiltration rate for first 15 and 60 minutes. 38. What are phi - index and w - index? Explain determination of effective rainfall of a watershed by the phi - index method. 39. An infiltration test using a ring infiltrometer with 30cm diameter yielded the following data : Time from the start 0
2
5
10
20
30
60
90
150
210
278
658
1173 1924 2500 3345 3875 4595 5315
(minutes) Cumulative volume of 0 water added (cm3) i) Determine the infiltration capacity rates for the time intervals in the experiment. ii) What is the ultimate infiltration capacity rate fc? iii) What is the average infiltration capacity for the first 10 minutes and for the first 30 minutes of the experiment? 40. The infiltration rates measured during a test are listed below. Determine the para meters of the Horton's curve, by the graphical procedure. (10 Marks) Time (min) :
0.5
2.5
10
30
60
90
150
f(mm/h)
8
7.5
6.8
5.6
3.6
2.1
2.0
:
41. Rainfall during the successive 15 minutes of a storm are 6, 20, 24, 28, 12 and 9mm. Determine the Φ - index for the catchment, (Hint: consider Φ per 15 - minutes for calculations) if the runoff is 39mm. (10 Marks)
42. A 6 hr storm producing rainfall intensities of 7, 18, 25, 12, 10 and 3mm/h in successive one hour interval over a basin of 800 sq.km. The resulting runoff is observed to be 2640 ha -m. Determine the Φ - index for the basin.
43. The mass curve of a rainfall of duration 100 min is given below. If the catchment had an initial loss of 0.6cm and Φ -index of 0.6cm/hr . Calculate the total surface runoff from the catchment
Dept of Civil Engineering, SJBIT
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Hydrology and Irrigation Engineering Time
from 0
start
of
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20
40
60
80
100
0.5
1.2
2.6
3.3
3.5
rainfall (min) Cumulative
0
rainfall (cm)
44. In a 140-min storm the following rates of a rainfall were observed in successive 20-min intervals 6.0, 6.0,18.0 ,13.0, 2.0, 2.0 and 12.0 mm/h . Assuming the Φ – index value as 3.0mm/h and a initial loss of 0.8mm, determine the total rainfall, net runoff and W- index for the storm.
Unit 3:HYDROGPRAPH 1. Explain 'Unit hydrograph theory'. Derive the unit hydrograph from an isolated storm. 2. Define the term Runoff and list the various factors that affect the runo ff of a given area. 3. Define Runoff. With a neat sketch, explain the runoff process. 4. What is unit hydrograph? Discuss its use and limitations. 5. Critically explain any five factors affecting runoff. 6. Compare any three methods used for determining runoff. 7. Distinguish between i) direct run off and base flow, ii) overland flow and interflow. 8. Briefly explain 'schematic representation of runoff components. 9. What are the components of hydrograph? Explain how base flow is separated from a simple storage hydrograph. 10. With a neat sketch, explain the various components of a flood hydrograph. Also explain any one method of base flow separation. 11. Write a note on water budget equation. List the factors affecting runoff. 12. Define runoff. Annual rainfall and runoff in mm, over a cat chment area are given below : Year
1980 81
Rainfall 910
82
83
84
85
86
87
88
89
90
91
1110 605 1300 1470 990 1480 520 1195 900 660 750
(mm) Runoff
305
515
245
620
750
403 654
165 472
390
275 230
(mm) Develop a rainfall - runoff relation by the method of least squares. Find the correlation Dept of Civil Engineering, SJBIT
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coefficient. If the rainfall for a particular year is 125cm, what will be the runoff for that year? 13. The data in respect of a catchment are as follows : Intensity of rainfall = 1 cm/hr; Duration of rainfall = 4 hours Runoff coefficient = 0.5, 0.6, 0.7 and 0.8 for 1st hour, 2nd hour, 3rd hour and after 3rd hour respectively. Zone
I
II
III
Area
20 ha 30 ha
50 ha 40 ha
Time of concentration
1 hr
3hr
2hr
IV
4hr
Determine contribution to runoff from all the zones at the end of each hour starting 1st hour ending 8th hour after commencement o f rainfall.
14. Derive the unit hydrograph for a catchment of 200 km2 if the following discharges were Time (hrs) Discharge
17
18
09
10
11
12
13
14
15
16
19
20
21
22
23
24
25
26
3
(m /s) observed in the stream as a result of 6 – hour rainfall storm. The base can be assumed to have increased linearly.
15. The ordinates of a 4h unit hydrograph of a basin area 630 Km2 measured at 2 hour interval are given below. Obtain the ordinates of 6h unit hydrograph for the basin using S curve technique.
Time hrs
0 2
4
4h UH (cumec)
0 25 100
6
8
10
160 190 170
12
14 16
18
110
70 30 20
20
22
24
6
1.5 0
16. Derive the ordinates of a 3 – hour unit hydrograph, if the 6 - hour unit hydrograph for the basin has the following ordinates (m3/s) at 3 – hour intervals: 0, 20, 80, 130, 150, 130, 90, 52, 27, 15, 5, 0. Work only up to the peak. 17. Given below are the monthly rainfall P and the corresponding runoff R values covering a Dept of Civil Engineering, SJBIT
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period of 18 months for a catchment. Develop a correlation equation between R and P. Month
1
2
3
4
5
6
1
8
9
P
5
35
40
30
15
10
5
31
36
R
0.5
10
138 8.2
3.1
3.2
0.1
12
16
Month
10
11
12
13
14
15
16
17
18
P
30
10
8
2
22
30
25
8
6
R
8
2.3 1.6
0.0
6.5
9.4
7.6
1.5
0.5
18. Calculate Φ - index of a storm from the following data. Plot the rainfall histogram and mark the Φ - index on the plot. Catchment area = 430 sq. km ; Volume of direct runoff 3
after separation of base flow = 10.75mm . Runoff started at 3pm on 17/8/2007 Time of rainfall (hrs)
15 18
21
24
03
Depth of rainfall (mm)
12 15
09
22
02
19. A catchment is divided into five sub areas as g iven below : Subarea (km'*)
1.5 3
2
1
2.5
Runoff coefficient (c)
0.7 0.6
0.4
0.55
0.9
Calculate the 25 year flood using the rational method. Assume a concentration time of 35 min and use the function I = 75T0.22 , where I is in cm/hr and t is in min. (t + 12)
0.85
20. How do you determine the stage for zero discharge, if the stage and corresponding discharge data of a stream section are available? 21. Rainfall intensity of a Watershed of 5 sq.km area is given by 0.2
I= 100Tr (t + 16)
….mm/hr
0.8
where Tr = return period in years and t = time of concentration in minutes. The wat ershed has a slope of 0.005 with maximum travel length of 2000m, the land use pattern has 20% agricultural land (c = 0.3), 10% forest land
(c = 0.16) and rest is impervious.
Estimate 50 year peak flood for the area, c = coefficient of runoff. Dept of Civil Engineering, SJBIT
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Unit -4: ESTIMATION OF FLOOD & FLOOD ROUTING 1. What do you mean by the term flood? Mention any two factors affecting flood? 2. Mention any two empirical formulae for estimating flood? 3. What do you mean by flood control? Explain any two methods of flood control. 4. Distinguish between a) Hydraulic and hydrological method of flood routing b) Hydrologic storage routing and hydrologic channel routing c) Prism storage and wedge storage. 5. What are the basic equations used for flood routing a) Hydrologic method and hydraulic method. 6. Describe a numerical method of hydrologic reservoir routing.
Unit -5: INTRODUCTION TO IRRIGATION 1. Define the term irrigation. What are the reasons for adopting it? 2. Define irrigation. What is the necessity of irrigation? 3. Define Irrigation. What are the types of flow irrigation? Explain any two flow irrigation systems. 4. What are the benefits and ill effects of irrigation? 5. List the benefits of irrigation. 6. What are the benefits that can be accrued from irrigation projects? Explain in brief. 7. List the benefits and ill effects of irrigation. 8. Explain Flow irrigation with the help of neat sketches. 9. List the methods of irrigation and explain any three methods. 10. What are the primary objectives of an irrigation method? List the various methods of irrigation adopted for distribution of water in the field. 11. List out the various methods of application of irrigation water. (including subgroups)
12. What are the methods of applying water to crops? Explain any two surface irrigation methods. 13. What is Bandhara irrigation? What are its advantages and disadvantages? Explain Phad Dept of Civil Engineering, SJBIT
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system of irrigation. 14. With neat sketches, explain Bandhara irrigation. List its advantages and disadvantages. 15. Discuss Phad system of irrigation as applied to Bhandhara irrigation. 16. List the advantages of sprinkler irrigation, with its limitations. 17. What are the limitations of sprinkler irrigation system? 18. Explain drip irrigation. List its advantages and disadvantages. 19. Write short notes on supplemental irrigation. 20. Write a short note on infiltration galleries.
Unit – 6: SOIL-WATER-CROP RELATIONSHIP
1. Give brief classification of Indian soils. 2. What are the functions of irrigation soils? Explain briefly. 3. What are the physical properties of soil? 4. Explain frequency of irrigation and irrigation efficiency. 5. Define crop rotation. What are its advantages? List some crop rotations. 6. How do you estimate the frequency of irrigation on the basis of soil moisture basis? 7. After how many days will you supply water to soil (clay loam) in order to ensure efficient irrigation of the given crop if: i) Field capacity of soil is 27%
ii) Permanent wilting point is 14%.
iii) Density of soil is 1.5 g/cc
iv) Effective depth of root zone is 75cm
v) Daily consumptive use of water for the given crop is 11mm. 8. After how many days will you supply water to soil in order to ensure sufficient irrigation of the given crop, if the field capacity of the soil = 30%, permanent wilting point = 14%, density of soil = 0.0125 N/cm3, effective depth of root zone = 70 cm and daily consumptive use of water for the given
crop = 10.5 mm.
9. After how many days will you supply water to soil in order to ensure sufficient irrigation of given crop, if Field capacity of soil
= 28%
Optimum moisture content, when water is be supplied Dry density of soil Effective root zone depth Dept of Civil Engineering, SJBIT
= 16%
=13 kN/m3 = 0.7 m Page 14
Hydrology and Irrigation Engineering Daily consumptive use of water for given crop
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10. Calculate the depth of available soil moisture in the root zone of the clay loamy soil using the following data. Also find after how many days will you supply water to the soil in order to ensure efficient irrigation of the given crop if Field capacity = 27% Permanent wilting point = 13% Dry density of soil = 1.5 gm/cm Root zone depth = 1.25 m Daily consumptive use of water for the given crop = 20 mm. 11. After how many days will you supply water to soil (clay loam) in order to ensure efficient irrigation of the given crop if, Field capacity of soil = 27% Permanent wilting point = 14% 3
Density of soil =13 kN/m
Effective depth of root zone = 0.75 m Daily consumptive use of water for the given crop =1.1 cms 12. When will a soil be fertile? How can soil fertility be maintained? 13. Write a note on crop rotation?
Unit – 7 :WATER REQUIREMENT OF CROPS 1. What do you mean by Duty and Delta? How are they expressed? 2. Define duty, delta and base period. Obtain the relationship between them. 3. Define 'flow duty' and 'quantity duty'. Obtain the relationship between Duty, Delta and Base period. 4. Explain i) Gross command area ii) Culturable command area iii) Consumptive use 5. Define duty, delta and base per iod and establish the relationship between them. 6. What are the factors affecting duty? 7. Define various irrigation efficiencies used in irrigation system. 8. A water course commands an irrigation area of 800 ha. The intensity of irrigation for rice in this area is 50%. The transplantation of rice crop takes 15 days and the total depth of water required by the crop is 60 cm. Determine
i) Duty on the field during
transplantation ii) Duty at the head of distributory assuming losses of water to be 20% in Dept of Civil Engineering, SJBIT
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Hydrology and Irrigation Engineering
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the water courses. iii) Calculate the discharge required in the water course. 9. Culturable command area under a canal system is 50000 hectares. Base period, intensity of irrigation and duty of various crops are given in the table below. Determine the discharge for which the canal is to be designed. Base period Intensity
Crop
of Duty
(days)
Irrigation (%)
(hectares / cumec)
Kharif
110
30
900
Rabi
120
45
2000
Sugarcane 360
20
2500
10. The base period, duty at the field of difference crops, and area under each crop in the command area are given below. Find the required reservoir capacity to cater to the needs of the crops. Crops
Base period Duty @ field Area under the (days)
(Ha/cumec)
crop (Ha)
Wheat
120
1800
4800
Sugar cane
360
800
5600
Cotton
200
1400
2400
Rice
120
900
3200
11. A main canal taking off from a storage reservoir has to irrigate a land with the following crops, the details of which are given below. Crop
Crop
period Area to be irrigated Duty
(days)
(Hectares)
(Hect/cumec)
Sugar cane (Perinnial )
365
1250
850
Paddy (Kharif)
120
1500
850
Wheat (Rabi)
120
2500
1700
Assuming 25% losses in the canal system and giving an allowance of 20% for peak demand, calculate the capacity of the main canal. What is the total volume of water required for each crop? 12. Culturable command area of a reservoir is 50000 hectares. Find out the reservoir
Dept of Civil Engineering, SJBIT
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Hydrology and Irrigation Engineering
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capacity, if the canal losses are 5% and reservoir losses 8%. Base period, intensity of irrigation and duty of various crops are given in the following table:
Base period Duty
Intensity of irrigation
(days)
(hect/cumecs)
(%)
Wheat
120
2000
20
Rice
140
900
15
Cotton
180
1600
10
Sugarcane
360
2500
20
Crop
13. What shall be the reservoir capacity for the season, if it is serving 24000 ha of paddy, 6000 ha of ground nut, 6000 ha of maize and 12000 ha of cotton? The following depth (cm) of water is required during different months? Month
Paddy
Ground nut
Maize
Cotton
September (1-30) 7.9
—
—
—
October (1-31)
29.9
—
3.4
4.0
November (1-30) 20.7
6.3
15.1
8.0
December (1-31)
16.2
23.8
20.6
—
Assume 25% canal losses and 20% reservoir evaporation losses.
Unit – 8: CANALS 1. With a neat sketch, explain any one type in each of cross drainage work 2. Carrying canal water over the drainage ii) Carrying drainage over the canal. 3. What is a Canal? Explain the general considerations for alignment of Canals. 4. Explain various considerations for alignment of a canal. 5. With a neat sketch, explain the cross drainage works constructed for bypassing canal over drainage. 6. Design an irrigation channel in alluvial soil according to Laceys silt theory for the Dept of Civil Engineering, SJBIT
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following data: Full supply discharge=10 cumec, Lacey’s silt factor=0.9, Side slope of channel=½(H):1(V) 7. Design an irrigation channel to carry a discharge of 45 cumecs. Assume N = 0.0225 and m = 1. The channel has a bed slope of 0.16 meter per kilometer. Use Kennedy's theory. Assume a trial depth for D as 1.8m. 8. An irrigation engineer has designed an irrigation canal using Kennedy's theory, for the following details. He had concluded that full supply depth of 1.8 m is sufficient for the canal. Check whether his design can be adopted. Discharge
= 45 cumecs
Manning's Rugosity coefficient
= 0.0225
Bed slope of channel
=0.16 m/km
Critical velocity ratio
=1
9. Give the classification of canals. Explain salient features of each of them. 10. Write the steps involved in hydraulic design of an aqueduct . 11. Design an irrigation canal for the following data using Lacey's silt theory. Full supply discharge = 35 cumec, silt factor = f = 1 side slope = 1H : 2V. 12. What are the factors to be considered in alignment of an irrigation canal? What are the main functions of head regulator and cross regu lator? 13. A channel section has to be designed for the following data: Discharge Q = 30 cumecs,
Silt factor f - 1.00,
Side slope : 0.5 H : 1 V
Find also the longitudinal slope. 14. List the functions of head regulator and cross regulator work. 15. Design an irrigation channel in alluvial soil according to Lacey's silt theory for the following data: Fully supply discharge =15 m/sec; Lacey's silt factor = 1.0; Side slope of channel =2 H: 1V 16. "Lacey's conception of design of canal on an alluvial soil is superior to Kennedy’s concept". Justify the statement. 17. Explain the design principle of trapezoidal notch type of fall. 18. Design an irrigation channel to carry 50 cumecs of discharge. The channel is to be laid at a slope of 1 in 4000. Take CVR = 1.1 and Chezy's C - 49.726 in the equation V = C RS. Assume trial depth = 2.7 m. Whether the trial depth is suited for the discharge? Dept of Civil Engineering, SJBIT
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