Water Resource Engineering

Frequently Asked Questions

Section-A

1.      Name the major water resources (or rivers) in India.

Ans. The major water resource in India are as listed below; Narmada, Tapathi, Mahanadi, Godavari, Krishna, Cauvery, Pennar, Ganges and its tributaries, Indus and its tributaries, River Brahmaputra.

2.      Name the major water resource projects in Karnataka.

Ans. The major water resource projects in Karnataka are as follows;

·         Tungabhadrs project – Hospet

·         Upper Krishna project – Alamatti

·         Krishna Raja Sagar project – Mysore

·         Harangi project – Kodagu

·         Navilterth project – Savadatti

·         Linganamakki project – Jog

·         Vani Vilasa Sagar – Hiriyur

·         Basava sagar project - Narayanpura

·         Nugu reservoir – H.D Kote, Mysore, etc.

3.      What is a multipurpose project? Name the major multipurpose irrigation project in India. (Nov 2010 5m)

Ans. The projects which are planned and constructed to perform various purposes together are called as multipurpose projects. The reservoir not only serves one but various purposes such as protection of downstream areas from floods and serves as water supply unit for irrigation and industrial purposes. Some of the important multipurpose projects in India are as follows;

·         Bhakra Nangal Project – Himachal Pradesh

·         Tihari water Project – Uttarakhand

·         Nagarjuna Sagar Project – Andra Pradesh

·         Sardar Sarovar Project – Gujrat

·         Krishna Raja Sagar- Mysore

·         Tungabhadra Prpject – Hospet

·         Mahi Project

·         Gandak Project

·         Kosi Project

4.      Define irrigation. Briefly explain the necessity of irrigation. (May 2006 5m)

-          What is irrigation? What are its necessities?

Ans. Irrigation may be defined as the process of supplying water to the land by artificial means for the purpose of cultivation. The water supplied to the land naturally by rain is usually not sufficient for the proper growth of the crop, therefore, the objective of irrigation is to supplement the natural supply of water to land to obtain the optimum yield from the crop grown on the land. Generally, the following factors lead to the necessity of irrigation.

·         Low rainfall or non-uniform rainfall.

·         Additional requirement of water to the commercial crops.

·         To have a controlled and planned water supply.

5.      What are the advantages and disadvantages of irrigation? (May 2005 5m, Dec 2005 5m, May 2006 5m, May 2009 8m, Nov 2011 5m)

-          List the advantages and disadvantages of irrigation.

-          What are the benefits of irrigation? (May 2008)

Ans. Advantages-The following are the advantages of irrigation;

·         Protection from famine.

·         Improvement in yield and value of crop.

·         Generation of hydroelectric power.

·         Inland irrigation.

·         The irrigation canals can be used for domestic and industrial water supply.

·         Improvement in transportation due to road facility on canal banks.

·         Increase in ground water storage.

·         Improves canal plantation.

·         Increase in food production.

·         Fish industry can be developed along the banks of reservoir.

·         Increases the economy of the country.

·         Overall development of the country.

   Disadvantages-The following are the disadvantages of irrigation;

·         Irrigation results in colder and damper climate, causing outbreak of diseases like malaria.

·         Water logging is a major concern due to over irrigation, resulting in reduced crop yields.

·         Cost of irrigation is some times more than the revenue generated.

·         Presence of canals affect the drainage conditions of the area.

·         The irrigation water gets mixed with nitrates in the soil and seeps into the ground water to some extent, and pollute the ground water.

·         Deep canals may prove dangerous for people who do not know swimming.

·         Irrigation projects requires huge capitals, and also skilled labors are required for the construction.

6.      Write a note on world water resource.

Ans. Water is the most important natural resource and is vital for all living beings on the earth. Oceans cover about 71% of the total land surface and has 97% of water. 2% of water is present in frozen form as ice caps. Deep underground resource cover about 0.31%. Thus 99.31% of water is of no use to man. The remaining 0.69% of water represents the fresh water resource. Among fresh water, rivers and lakes holds 3% and the atmosphere holds 3%. Remaining percentage is distributed in other fresh water resources.

7.      Write a short note on India’s water resource.

Ans. The main source of water for India is rainfall over the most of the parts and snowfall in the north region. The rainfall varies from place to place every year. The average annual rainfall is about 119.4 cm. The total annual water resources are approximately equal to 4000km³. The total annual surface water flow is 1800km³, from which 150km³ is stored in various reservoirs, tanks etc. 1650km³ water is retained on soil and it goes to the atmosphere as evaporation and transpiration. 

8.      Explain with a neat sketch Hydrology cycle. (Vishwanath pg. 7 and sharp series pg. 6)

9.      Explain with a neat sketch working of float type automatic rain gauge. (Sharp series pg. 9)

10.  Explain with a neat sketch working of symon’s type rain gauge. (Sharp series pg. 6)

11.  Explain the factors affecting run-off from catchment. (Sharp series pg. 11)

12.  Explain the methods of finding out the average rain fall of a catchment. (sharp series pg. 12)

13.  Explain the types of precipitation. (sharp series pg. 17 & Vishwanath pg.8)

Ans. Conventional, Orographic, Cyclonic, Frontal, Non-frontal precipitation. (Refer text book)

14.  Define the following (For answers, Check out in blog - Irrigation water requirements)

a)      Crop period

b)      Base period

c)      Duty

d)     Delta

e)      Gross Commanded Area (GCA)

f)       Cultivable command Area (CCA)

g)      Intensity of irrigation

h)      Outlet factor

i)        Kor-period

15.  Explain the crop seasons – Rabi and Kharif. (For answers, Check out in blog - Irrigation water requirements)

16.  What are the factors affecting the Duty of water?

Ans. The following are the factors affecting the Duty of water:

1)      Type of crops.

2)      Climate condition of the area.

3)      System of irrigation.

4)      Method of irrigation.

5)      Method of cultivation.

6)      Quality of irrigation water.

7)      Type of soil and sub soil of the irrigated field.

8)      Time of irrigation and frequency of cultivation.

9)      Type of soil and subsoil of the area through which canal passes.

10)  Canal conditions.

11)  Skill of the cultivator.

12)  Method of assessment of irrigation water.

13)  Topography of land.

14)  Base period of crops.

17.  Explain sprinkler irrigation and mention its advantages and disadvantages. (Sharp series pg. 35)

18.  What is meant by drip irrigation? State the advantages of drip irrigation. (Sharp series pg.40)

19.  Differentiate between open well and tube well (Sharp series pg. 44)

Section-B

20.  Which are the factors considered in the selection of site for a reservoir? (May 2015 5m)

-          Discuss the factors influencing site selection for a reservoir. (Nov 2011 8m)

-          Explain the surveys to be conducted at a proposed reservoir site. (Nov 2013 5m) (Sharp series pg. 45)

21.  Write a short note on reservoir sedimentation. (Dec 2014 5m) (Sharp series pg. 78)

22.  Explain earthern dam with a neat sketch. (May 2011 5m)

-          Draw a cross-section of an earthen dam and mention its components. (Dec 2014 5m) (sharp series pg. 65)

23.  What are the causes for failures of earthen dam? Discuss in detail. (May 2015 5m)

-          Discuss the causes of failure of earthern dam. (Nov 2011 7m) (sharp series pg. 70)

24.  Define gravity dam. Explain the forces acting on a gravity dam. (May 2011 6m)

-          Name any five forces which acts on a gravity dam. (May 2015 5m)

-          Briefly explain the forces acting on a gravity dam. (Nov 2011 8m)

-          What do you understand by gravity dam? What are the forces that act on a gravity dam? (May 2014 5m) (sharp series pg. 47)

25.  What is a spillway? Enumerate various types of spillways. (May 2014 5m) (sharp series pg. 58)

26.  Write a short note on maintenance of tanks. (Dec 2014 5m)

-          Write a short note on restoration of tanks. (May 2011 5m)   (sharp series pg. 79)

27.  What is canal alignment? State the methods of canal alignment. (sharp series pg. 80)

28.  What is canal lining? What are its advantages? (sharp series pg. 83 & 84)

29.  What is canal drop? List the types canal drop. (sharp series pg. 87)

30.  What is canal? List the different types of canals. (sharp series pg. 91)

31.  What are characteristics of good lining? (Sharp series pg. 93)

32.  Discuss the maintenance aspects of canals. (sharp series pg. 94)

Section-C

33.  What is cloud seeding? Explain the technique of cloud seeding. (Sharp series pg. 135 and 136)

34.   Explain rain water harvesting. Mention its purpose, methods, and advantages also. (sharp series pg. 133 and 134)

35.   Write short note on ground water management. (sharp series pg. 137)

36.   Explain water shed management. (sharp series pg. 134)

37.   Explain flood management. (sharp series pg. 135)

38.  Write a note on ground water pollution. (sharp series pg. 130)

39.  Discuss the methods of ground water recharge. (sharp series pg. 129)

40.  Explain confined and unconfined aquifer. (sharp series pg. 126 and 127)

41.  Explain the following: Aquifer, Aquiclude, Aquitard, Aquifuge. Porosity, Ground water yield, permeability, specific yield, specific retention, transmissibility. (sharp series pg. 124, 125, and 126)

Mugshot for Third Internal Test-WRE

1.      Define Hydrology. Explain the use of hydrology in irrigation engineering.

2.      Explain the Hydrology cycle with its neat sketch.

3.      Explain the types of precipitation.

4.      Explain with a neat sketch Non-recording type rain gauge (Simon’s rain gauge).

5.      Explain with a neat sketch working of float type automatic rain gauge.

6.      Explain the factors affecting runoff.

7.      A catchment area has eight isohyets of value 7, 8, 9, 10, 11, 12, 13, 14 cm. Areas enclosed between successive isohyets are respectively 20, 70, 121, 79, 50, 44, 26 square kilometres. Determine the average value of precipitation in the area.

8.      There are 5 rain gauge stations A, B, C, D, E and areas in charge of each rain gauge and precipitations recorded by gauge stations are given as follows. Determine the average precipitation by Thiessen polygon method:

Gauge Station	A	B	C	D	E
Area (km2)	68	72	56	44	50
Rainfall (mm)	25	29	18	22	15

9.      The isohyets for annual rainfall over a catchment basin were drawn. The areas of strips between the isohyets are indicated below. Find the average depth of annual rainfall or precipitation over the basin.

Isohyets (cm)	Area (Sq. km)	Isohyets (cm)	Area (Sq. km)
75-85	580	105-115	1000
85-95	2960	115-135	610
95-105	2850	135-155	160

Mugshot for Second Internal Test-WRE

1.      What is reservoir? State the functions of reservoir.

2.      Discuss the factors influencing site selection for a reservoir.

3.      What is a dam? Give the classification of dam. 

4.      What are the causes for failures of earthen dam? Discuss in detail.

5.      Define gravity dam. Explain the forces acting on a gravity dam.

6.      Discuss the causes for the failure of gravity dam and remedial measures to prevent the failure.

7.      What is canal lining? What are its advantages?

8.      What is canal alignment? State the methods of canal alignment.

9.      Mention and explain the methods of canal lining.

10.  Explain with sketch, the layout of canal system.

11.  What is rain water harvesting? Explain the methods of rain water harvesting with neat sketch.

12.  What are the advantages and disadvantages of rain water roof catchment?

13.  Write a note on flood water management. And methods of flood water management.

14.  Write a note on water quality management. And mention the effective measures for water quality management.

Mugshot for First Internal Test-WRE

1.      What are the objectives of water resource development?

2.      What is irrigation? What are its necessities?

3.      What are the method of improving the Duty of water?

4.      Explain the crop seasons – Rabi and Kharif.

5.      Explain the sprinkler irrigation method and mention its advantages and disadvantages.

6.      Explain drip irrigation and mention its disadvantages.

7.      List the methods of irrigation.

8.      Explain with a neat sketch of strainer type tube well.

9.      What is a well? Mention its types.

10. Define the following

a)      Crop period

b)      Base period

c)      Duty

d)     Delta

e)      Gross Commanded Area (GCA)

f)       Cultivable command Area (CCA)

g)      Intensity of irrigation

h)      Outlet factor

i)        Kor-period

11.  Find out the capacity of reservoir if its cultivable area is 60,000 hectares, from the following data:

Type of crop	Sugarcane	Wheat	Rice
B in days	330	120	120
D in hect/cumec	2,200	1,800	800
Intensity of irrigation %	15	20	10

Assume canal losses as 6% and Reservoir losses as 10%.

12.  The duty of canal water for a tobacco crop was assumed to be 2200 hectares/cumec. First watering was done on 30^th of Nov. whereas last watering was done on 29^th March. Calculate delta for the crop. (Nov 2011 6m)

Irrigation Water Requirements of Crops

1.      What are the quality of irrigation water? (Nov 2011 5m)

-          Explain the quality of irrigation water required.

-          What are the quality of irrigation water? And list the impurities of irrigation.

Ans. The quality of suitable irrigation water is very much influenced by the constituents of the soil which is to be irrigated. The water containing impurities can be injurious to the growth of the plant is not satisfactory for irrigation, therefore, the quality of irrigation water depends primarily on silt content and salt constituents of the soil.

The impurities which make the water unfit for irrigation are classified as follows;

·         Sediment concentration in water.

·         Soluble salts in water.

·         Proportion of Sodium ions.

·         Concentration of potentially toxic elements in water.

·         Bicarbonate Concentration.

·         Bacterial contamination.

2.      Explain the effects of impurities of irrigation.

Ans. Following are the effects of impurities of irrigation.

a)      Sediment concentration in water:

·         Fine Sediment increases the soil fertility.

·         Sediment from eroded areas decrease the soil fertility and permeability.

·         Sedimentation in water causes silt formation in irrigation canals, therefore, increasing the maintenance cost.

b)      Soluble salts in water:

·         Salts of calcium, sodium, potassium and magnesium, when present in excessive quantity causes damage to the growth of the plant.

·         These can cause reduction in osmotic activities of plants.

·         Prevent adequate aeration.

c)      Proportion of Sodium ions:

·         Soil containing sodium ions more than 5%, the soil becomes less permeable.

·         Soil grains breaks down, thus soil becomes clayey

d)     Concentration of potentially toxic elements in water:

·         The elements like boron, selenium, etc., are toxic to plants.

·         Traces of boron are very essential for the growth of the plant, but it should not increase above 0.3ppm it may prove to be toxic to certain plants.

e)      Bicarbonate Concentration:

·         High concentration of bicarbonate ions may result in precipitation of calcium and magnesium.

·         Increasing the amount of sodium ions may be hazardous for growth of plant.

f)       Bacterial contamination:

·         It causes serious damage when crops irrigated with highly contaminated water are directly consumed without being cooked.

·         Cash crops like cotton, nursery stock, etc. which are processed after harvesting, can use the waste water without any trouble.

3.      Define the following

a)      Crop period

b)      Base period

c)      Duty

d)     Delta

e)      Gross Commanded Area (GCA)

f)       Cultivable command Area (CCA)

g)      Intensity of irrigation

h)      Outlet factor

i)        Kor-period

Ans. Following are the definitions of the terms given in the question.

a)      Crop period: It is defined as the total time that elapses between the sowing of the crop and its harvesting. Thus crop period represents the total time during which the crop remains in the field.

b)      Base period: It is defined as the total time between the first watering done for the preparation of land for sowing of a crop and the last watering done before its harvesting.

Note: Generally crop and base period are represented by B, which expressed in terms of days.

c)      Duty: Duty of the water is the relation between the area of the land irrigated and the quantity of water required to be supplied for growing a crop. The Duty of water is represented by D. It is generally expressed in hectares per cumec for the case of direct flow irrigation from canals, it is called as flow duty water. This may be also expressed in terms of the total area of land in hectares per million cubic metre of water stored in tank or reservoir, this case is called as quantity duty of water.

[Alternative definition - It is usually defined as the area of land in hectares which can be irrigated for growing any crop if one cumec (one cubic metre per second) of water is supplied continuously to the land for entire base period of the crop]

Following are the importance of duty:

·         It helps us in designing an efficient irrigation canal system.

·         An area to be irrigated can be easily calculated.

·         It helps in calculating the discharge for designing the channel.

·         It helps in checking the efficiency of working of the canal system.

d)     Delta: It is defined as the total depth of water over the irrigated land required by a crop grown on it during the base period of the crop. It is usually denoted by ‘Δ’. The delta may also be defined as total water required by a crop for its growth in hectare-metre per hectare.

e)      Gross Commanded Area (GCA): The total area, including the roads, villages, etc., which can be irrigated economically from irrigation projects such as a dam, a head work, etc., is called Gross Commanded Area (GCA).

f)       Cultivable command Area (CCA): The Gross Commanded Area (GCA) minus the uncultivable area (such as roads, villages, ponds, etc.) is called Cultivable command Area (CCA).

i.e., CCA = GCA – Uncultivable area.

g)      Intensity of irrigation: The percentage of cultivable command area (CCA) to be irrigated annually is called Intensity of irrigation.

Intensity of irrigation (%) = (Area to be irrigated/CCA) x 100

h)      Outlet factor: Duty based on the actual supply on the field through the outlet excluding all the losses in the canal system is called as outlet factor or outlet discharge factor. It is actually the duty at the head of the water course. Generally, it is the end point of the irrigation department.

i)        Kor-period: The limited period during which any crop requires more quantity of water for its growth is called Kor-period. The first watering given to a crop when it is few centimetres high is referred as Kor-watering. It must be applied within a limited period.

4.      What are the factors affecting the Duty of water?

Ans. The following are the factors affecting the Duty of water:

1)      Type of crops.

2)      Climate condition of the area.

3)      System of irrigation.

4)      Method of irrigation.

5)      Method of cultivation.

6)      Quality of irrigation water.

7)      Type of soil and sub soil of the irrigated field.

8)      Time of irrigation and frequency of cultivation.

9)      Type of soil and subsoil of the area through which canal passes.

10)  Canal conditions.

11)  Skill of the cultivator.

12)  Method of assessment of irrigation water.

13)  Topography of land.

14)  Base period of crops:

Note: For description of factors affecting duty, refer ‘Water Resource Engineering’ by P.M. Dhotrad, pg 48-49

5.      What are the method of improving the Duty of water?

Ans. The following are the method of improving the Duty of water,

1)      The land should be properly ploughed to a required depth and levelled before sowing the crop.

2)      The land should be cultivated frequently, which reduces the loss of moisture from the soil.

3)      Suitable methods of irrigation should be used.

4)      The canal should be lined. This will reduces the transmission losses.

5)      The canal should be close to the land to be irrigated.

6)      Volumetric assessment of irrigation water should be made.

7)      Good quality of water should be used for irrigation. The canal should not be allowed to get polluted.

8)      The alignment of the canal either in sandy soil or in fissured rock should be avoided.

9)      The cultivators must be trained to use irrigation water effectively and efficiently.

10)  Instead of large canals, smaller sized parallel canals with lower full supply level should be made.

11)  The canals should be properly maintained to reduce loss of water.

12)  Proper distribution of the land among the cultivators for effective use of water.

13)  Increasing the water holding capacity of the soil through suitable measures.

14)  The canal administration staff should be well trained to maintained the same.

15)  The cultivators must be encouraged to adopt modern methods of cultivation.

6.      Explain the crop seasons – Rabi and Kharif.

Ans. There are two main crop season in India, namely Rabi season and Kharif season.

·         Rabi season: In India, the winter season is called as Rabi season, normally starting from 1^st October and ends on 31^st March. The crops are sown in October and harvested in February, these crops are called as ‘winter crops’. Following are some of the crops grown in Rabi season;

a)      Wheat

b)      Barley

c)      Gram

d)     Linseed

e)      Mustard

f)       Potatoes, etc.

·         Kharif season: In India, the summer season is called as Kharif season, normally starting from 1^st April and ends on 30^st September. The crops are sown in April, May or June are harvested in September or early October, these crops are called as ‘summer crops’. Following are some of the crops grown in Kharif season;

a)      Rice

b)      Bajra

c)      Maize

d)     Cotton

e)      Tobacco

f)       Groundnut, etc.

Note –

§  The type of bifurcation of seasons are mostly applicable to North India, but in South India, there is no clear cut winter, spring, summer and autumn seasons as they are in North India.

§  These dates are not rigid dead line. The time may vary up to three months on either side.

§  Sugarcane, which is a cash crop, extends over both seasons.

7.      

Problems:

Relation between duty and delta:

Let there be a crop of base period B days.

Let one cumec (m³) of water be applied to this crop on the field for B days.

Now the volume of water applied to this crop during B days,

V = (60*60*24*B) m³

V = 86,400 m³

By definition of duty (D), one m³ supplied for B days matures D hectares of land.

This quantity of water (V) matures D hectares (10⁴) of land.

Therefore,

Total depth of water applied on this land =  unit in meters.

i.e Δ = (8.64*B)/D m

     Δ = (864*B)/D cm

Where, Δ is in meters or cm, B is in days and D is duty in hectares/cumec.

8.      A crop requires 90 cm of water for base period of 120 days. Find the duty of water. (May 2015 5m)

Sol. Given:

                  B = 120 days

                  Δ = 90 cm

      We know that,

Δ =  864B / D

90 = 864*120/D

            Therefore,

                        D = 1152 hectares/cumec Ans.

9.      The duty of canal water for a tobacco crop was assumed to be 2200 hectares/cumec. First watering was done on 30^th of Nov. whereas last watering was done on 29^th March. Calculate delta for the crop. (Nov 2011 6m)

Sol. Given:

                  Duty of the crop ‘D’ = 2,200 hectares/cumec

                  Base period of the crop ‘B’ = 120 days, i.e. Nov 30^th to March 29^th

        We know that,

Δ =  864B / D

Δ =  864*120 / 2200

Δ = 47.12 cm Ans.

10.  An irrigation canal has GCA of 80,000 hectare the CCA is 85% of GCA and the intensity of irrigation for kharif and rabi crops or seasons are 30% and 60% respectively. If the duties of water at the canal are 800 hectares/cumec and 1700 hectare/cumec for kharif and rabi crops respectively. Determine the head discharge of the canal. (May 2011 9m)

Sol. Given:

Gross commanded area (GCA) = 80,000 hectares

Cultivable commanded area (CCA) = 85% of GCA

i.e. CCA = 0.85 * 80,000 = 68,000 hectares

              We know that,

                        Area to be irrigated in kharif crop at 30% intensity = 0.3 * 68,000

                                                                                                          = 20,400 hectares

            Therefore,

                        The canal discharge = 20,400/800   = 25.5 cumec Ans.

                       

                        Area to be irrigated for rabi crop at 60% intensity = 0.6 * 68,000

        = 40,800 hectare

            Therefore,

                        The canal discharge = 40,800/1700 = 24 cumec Ans.

11.  Find out the capacity of reservoir if its cultivable area is 60,000 hectares, from the following data:

Type of crop	Sugarcane	Wheat	Rice
B in days	330	120	120
D in hect/cumec	2,200	1,800	800
Intensity of irrigation %	15	20	10

Assume canal losses as 6% and Reservoir losses as 10%.

Sol. Step 1: Delta Δ

                  Sugarcane

Δ =  8.64B / D

Δ =  8.64*330/ 2200 = 1.296 m

Wheat

Δ =  8.64B / D

Δ = 8.64*120 / 1800  = 0.576 m

Rice

Δ =  8.64B / D

Δ =  8.64*120 / 800 = 1.296 m

             

              Step 2: Area

                        Note: Area under sugarcane =  = 9,000 hect.

                                                            Or

                        Area under sugarcane = 0.15 * 60,000 = 9,000 hect.

                        Area under wheat = 0.20 * 60,000 = 12,000 hect.

                        Area under rice = 0.10 * 60,000 = 6,000 hect.

     

              Step 3: Quantity of water

                        Sugarcane: 9,000 * 1.296 = 11,664 hect. / meter

                        Wheat: 12,000 * 0.576 = 6,912 hect. / meter                         

Rice: 6,000 * 1.296 = 7,576 hect. / meter

Total quantity of water required = 11,664 + 6,912 + 7,576

    = 26152 hect. / meter

              Step 4: Losses

                        Canal losses = 6%

                        Reservoir losses = 10%

                        Therefore,

                        Total losses = 16%

                                            = 0.16 * 26152

                                            = 4184.32 hect.-meter.

              Step 5: Capacity of the reservoir = 26152 + 4184.32 = 31336.32 hect.-meter

  Say 31340 hect.-meter Ans.

Reference:

·         Irrigation and Hydraulics Structures, by S.K. Garg. Khanna Publisher, New Delhi, India.

·         Irrigation and Water Power Engineering, by B.C. Punmia, Pande, B.B. Lal. Lakshmi Publications,       New Delhi, India.