CE6703 Water Resources and Irrigation Engineering - Bharathidasan ...

BHARATHIDASAN ENGINEERING COLLEGE NATTRAMPALLI Dr.R.Madheswaran Water Resources and Irrigation Engineering Department of civil Engineering

CE6703 Water Resources and Irrigation Engineering TWO MARKS QUESTIONS 1. Define irrigation. (May/June 2012) 2. What is irrigation engineering? 3. What is the necessity of irrigation? (April/May10, Nov/Dec 06&12) 4. What are the benefits of irrigation? 5. What are the disadvantages of irrigation? 6. What is the purpose of irrigation? 7. What are the types of irrigation? 8. Define crop ratio. 9. What are kharif crops? 10. What are rabi crops? 11. What is meant by overlap allowance? 12. What is meant by consumptive use of water? 13. What are the factors affecting consumptive use of water? 14. Define duty. 15. Define delta. 16. Define base period. (Nov/Dec 09&11) 17. Define crop period. (Nov/Dec 09&11) 18. What is mean by crop rotation? (May/June 2011) 19. What are the factors affecting duty? (May/June 2012) 20. What are the methods for improving duty? 21. Define irrigation efficiency? 22. Write the types of irrigation efficiencies. (Nov/Dec 10) 23. What is meant by crop rotation and what is its advantage? (May/June 10)

Prepared By, Dr.R.Madheswaran Department of civil Engineering Bharathidasan Engineering College

SIXTEEN MARK QUESTIONS 1. Explain the necessity and scope of irrigation. 2. Discuss in detail the benefits and ill-effects of irrigation. (May/ June 12 & 09 & 10) 3. Define duty and explain in detail the various factors affecting duty. How can duty be improved? Explain. (May/ June 11 & 10, Nov/Dec 10&12) 4. A watercourse has culturable command area of 2600 hectares, out of which the intensities of irrigation for perennial sugarcane and rice crops are 20% and 40% respectively. The duty for these crops at the head of watercourse is 750 hectares/cumec and 1800 hectares/cumec respectively. Find the discharge required at the head of watercourse if the peak demand is 20% of the average requirement. 5. Explain irrigation efficiencies and its types. (May/ June 12 &11&10, Nov/Dec13&07&09) 6. How will you describe planning of irrigation projects? (May/June 2013)

UNIT-II TWO MARKS QUESTIONS 1. What are the different classifications of method of irrigation? 2. What do you mean by flow irrigation? 3. Define lift irrigation. 4. Differentiate between lift and flow irrigation. (Nov/Dec 11) 5. Define perennial irrigation 6. Define direct irrigation. 7. What do you mean by uncontrolled and controlled flooding? 8. What are the basic requirements for adaptation of any irrigation method? 9. What do you mean by free flooding? 10. Write about the advantages of furrow irrigation. 11. Under which favorable conditions the sub-surface irrigation is practiced? 12. Where sprinkler irrigation is more useful? 13. Write about the advantages of sprinkler irrigation. 14. Write about the limitations of sprinkler irrigation.


15. Write about the advantages of drip irrigation (May/June12) 16. Write about the disadvantages of drip irrigation 17. Write about the advantages of furrow irrigation. 18. Define Tank Irrigation (May/June12, Nov/Dec 06 & 10) 19. What are the different types of sprinkler systems? ( April/May10) SIXTEEN MARK QUESTIONS 1. Write a note on sub-surface irrigation, state clearly the conditions under which this method is suitable. What are the essential requirements for a successful sub-surface irrigation? 2. Describe the various methods of surface and subsurface irrigation. (May/ June 10) 3. Describe border strip method of irrigation. Derive the expression for the time required to cover a given area by this method, for a given rate of discharge and the rate of infiltration of water in the soil. 4. Explain in detail about sprinkler method of irrigation and how far it is suitable in Indian conditions. (May/June 2013) 5. Write a note on drip irrigation. Write about the advantages and disadvantages of drip irrigation system. (May/June 2013) 6. Define surface irrigation. Why it is widely practiced method of irrigation? What are the advantages and disadvantages of the method? 7. Describe briefly the various flooding methods of irrigation, (May/June 11) 8. Write a note on free flooding. 9. Describe check flooding and basin flooding. 10. Describe furrow method of irrigation. 11. Describe about tank irrigation. (May/ June 10) UNIT-III TWO MARK QUESTIONS 1. Define diversion headwork. 2. Write about the purposes of diversion headwork. 3. Define weir. 4. What are the component parts of diversion headwork? 5. Define dam.


6. What are the types of dam? 7. Define gravity dam. 8. What are the forces acting on a gravity dam? 9. What is meant by arch dam? 10. What are the forces acting on arch dam? 11. What are the various types of earth dam? 12. What are the types of failure that occur during construction of earth dam? 13. Define tank. 14. Define tank sluice. 15. How will you select a site for a tank sluice? 16. Define spillway. 17. Write about the advantages of earth dam? 18. Write about the disadvantages of earth dam? 19. Write about the functions of scouring sluices. 20. Under what conditions gravity dam can be adopted? SIXTEEN MARK QUESTIONS 1. Write in detail about the component parts of diversion works. 2. Write about the types of weirs on permeable foundation. 3. Write in detail about the tank surplus works. 4. What are the causes of failure of earth dams and its remedies? 5. Write about the factors affecting the selection of type of a dam. 6. Write about the favorable conditions, advantages, disadvantages, pressure distribution and elementary profile of a masonry dam. 7. Write about the criteria for safe design of earth dam. 8. Describe the forces acting on a gravity dam. 9. What are the types of dams and what are the comparative merits and demerits of various types of dams? UNIT-IV CANAL IRRIGATION

1. 2. 3.

TWO MARKS QUESTIONS Classify the rivers. What are the causes of meandering? What are the objectives of river training works?


Classify the river training works. 5. Define groyne. 6. Classify the groynes. 7. Give an equation for silt factor. 8. Give Kennedy’s critical velocity equation. 9. Define critical velocity. 10. What is meant by regime channel? 11. What is meant by contour canal? 12. What is a ridge canal? 13. Give the Lacey’s equation for wetted perimeter. 14. Give the Lacey’s equation for bed slope of a canal. 15. Write about the significance of Lacey’s theory. 16. When the channel is said to be in regime? 4.

SIXTEEN MARK QUESTIONS 1. How are canals classified? Describe them briefly 2. Explain the various considerations for alignment of a canal. 3. Why are canal falls necessary? Describe with sketch briefly the various types of canal falls. 4. What are the types of cross drainage works? Describe them briefly with sketches. 5. Define Lacey’s regime theory and its design procedure of channel. Also list the defects in Lacey’s theory. 6. Write the design procedure for Kennedy’s theory for the channel. 7. Design an irrigation channel to carry 40 cumec of discharge with B / D ratio as 2.5. The critical velocity ratio is 1.0. Assume suitable value of rugosity co-efficient and use Kennedy’s method. 8. Compare Kennedy and Lacey’s silt theories. 9. What is the necessity of river training works? Describe different types of river training works. 10. What is meant by guide banks? What are their functions and effects?


1. 2. 3. 4. 5. 6. 7. 8.

UNIT-V IRRIGATION WATER MANAGEMENT TWO MARKS QUESTIONS What is meant by Productivity? Define equity. Write about the conjunctive use of water. What is meant by short – term stability? Define long – term stability. Write about the main components of soil reclamation. Why a proper plan for operation & maintenance of irrigation system is necessary? What are the main objectives of canal lining?

9. What are the factors to be considered during the selection of particular type of lining? 10. How can the water losses be controlled? 11. What is meant by water logging? 12. State the effects of water logging? 13. Write the methods used for controlling water logging? 14. Define 0n-farm water management. 15. What do you meant by water user association (WUA)? 16. What are the problems of irrigation management without participatory management? SIXTEEN MARKS QUESTION 1. Discuss the inadequacies of present – day canal irrigation management in India. 2. Describe the common criteria for judging the performance of an irrigation system. 3. Describe the evaluation of performance of canal irrigation systems. 4. What are the methods adopted for improving canal irrigation management? Explain in detail. 5. Why should lining be provided in canals? What are the merits and demerits of canal lining?


6. Write the different types of canal lining. Explain them. 7. How can water be lost from a reservoir? How can the losses be controlled? 8. What kinds of participation are necessary for irrigation management activities? 9. What is meant by percolation pond? Draw a neat sketch of a percolation pond. 10. What is the need for WUA? 11. What is the need for optimization of water use? PART – A 1. What are the benefits of irrigation?

(10x2=20)

 Increase in yield and value of crops  Protection from famine by giving employment,  Cultivation of cash and commercial crops,  Addition to the wealth of the country  Generation of hydroelectric power. 2. What are the types of irrigation?

3. Define crop ratio.


It is the ratio of the area irrigated in Rabi season to the area irrigated in kharif season. 4. What is mean by crop rotation? When the same crop is grown again and again in the same filed the fertility of land gets reduced as the soil becomes deficient in plant floods favorable to that particular crop. 5. What do you mean by flow irrigation? Flow irrigation is the type of irrigation in which the supply of irrigation water available is at such a level that it is conveyed on to the land by the gravity flow. 6. What do you mean by uncontrolled and controlled flooding? In the controlled flooding, water is spread over the land, with proper methods to control the depth of application. In the uncontrolled flooding, water is spread of flooded on a rather smooth flat land, without much control or prior preparation. 7. Write about the advantages of furrow irrigation.  In the furrow irrigation, water contacts only 1/5 to ½ of the land surface, thereby reducing pudding and crusting of the soil. Evaporation losses are also reduced.  It is specially suitable for those crops (like maize) they are injured by contact with water.  Labour requirements in land preparation and irrigation are very much reduced.  There is no wastage of land in field ditches. 8. Define canal irrigation. An irrigation canal is a waterway, often man-made or enhanced, built for the purpose of carrying water from a source such as a lake, river, or stream, to soil used for farming or landscaping. 9. Define drip irrigation. Its also known as trickle irrigation or micro irrigation or localized irrigation, is an irrigation method that saves water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and


emitters. It is done through narrow tubes that deliver water directly to the base of the plant. 10. Define perennial irrigation. In this perennial irrigation system, the water required for irrigation is supplied in accordance with the crop requirements throughout the crop period. PART – B

(5x16=80)

11. a) i) what are the major problem occur in irrigation planning and developing. ii) Explain duty, delta, base period, overlap allowance. Define delta. It is the total depth of water required by a crop during the entire period the crop is in the field. Define duty. Duty represents the irrigating capacity of a unit of water. It is the relation between the area of a crop irrigated and the quantity of irrigation water required during the entire period of the growth of that crop. Define base period. Base period for a crop refers to the whole period of cultivation from the time when irrigation water is first issued for preparation of the ground for planting the crop, to its last watering before harvesting. What is meant by overlap allowance?


The crops of some season may overlap some period of the next crop season. When such

overlapping takes place the

crops of both the season require water simultaneously. or b) i).Explain advantages and disadvantages irrigation.  Increase in yield and value of crops

of

 Protection from famine by giving employment,  Cultivation of cash and commercial crops,  Addition to the wealth of the country  Generation of hydroelectric power. Disadvantage  Gives rise to disease like malaria  Excessive seepage causes water-logging and  The climate becomes cooler and makes the locality damp resulting illhealth

of the public. ii) Explain types of irrigation with detail manner.

12 a) i) Describe the crop seasons in India and explain various crop seasons.


kharif The kharif crops are rice,bajra,jawar,maize,cotton,tobacco, groundnut,etc. rabi Rabi crops are wheat,barley,gram,linseed,mustard,potatoes,etc

Or ii) Explain consumptive use of water and factors affecting consumptive use of water. Evapotranspiration or consumptive use of water by a crop is the depth of the water consumed by evaporation and transpiration during the crop growth including the water consumed by the accompanying weed growth. Factors affecting consumptive use of water.  Evaporation.  Mean monthly temperature.  Growing season of crop and cropping pattern.  Monthly precipitation in the area.  Soil and topography.  Wind velocity in the locality.

13 a) Explain about sprinkler irrigation and write advantage and disadvantage about sprinkler irrigation. Sprinkler irrigation is a method of applying irrigation water which is similar to natural rainfall. Water is distributed through a system of pipes usually by pumping. It is then sprayed into the air through sprinklers so that it breaks up into small water drops which fall to the ground. The pump supply


              

system, sprinklers and operating conditions must be designed to enable a uniform application of water.  The land cannot be prepared for surface methods.  Slopes are excessive  Topography is irregular.  Soil is erosive.  Soil is excessively permeable or impermeable. Advantages of sprinkler irrigation. Erosion can be controlled. Uniform application for water is possible. Irrigation is better controlled; light irrigation is possible for seedlings and plants, which are young. Land preparation is not required. Crop damage from frost can be reduced. Can be applied to areas of variable topography. Suitable for most crops, not all, and are adaptable to most irrigable soils. Flexibility is possible because sprinkler heads are available in a wide range of discharge capacities. Water measurement is easier than surface irrigation system. Less interference with cultivation and less land loss. Higher application efficiency. High and frequent application can be effectively accomplished. Easy mechanization and automation. Chemical and fertilizer applications are easily used with sprinkler systems. Water application efficiency under sprinkler irrigation is strongly affected by wind.

Disadvantages  Some crops are particularly sensitive and may suffer leaf scorch because of the salts deposited on the leaves as the intercepted irrigation water evaporates.  Some crops are especially sensitive to fungal diseases, leaf scorch, or fruit damage, and tall crops may obstruct hand-move or side-roll portable systems.


 Falling drops on bare soil, causing slaking and surface sealing (crusting) which can be severe when the sodium ion predominates in the water affecting the soil’s clay fraction.  High maintenance requirements, constant and meticulous maintenance of sprinkle irrigation systems is crucial if these systems are to justify their costs.  High operating pressures  The danger of system failure increases with technological complexity and requirements of expertise and quick availability of spare parts.  A malfunction of one of numerous parts can soon transform a working marvel of technology into a standing monument of inefficiency.  High initial cost.  High operating cost.  Wind drift.  A stable water supply is needed.  Saline water may cause problem.  Water must be free from sand, debris and large amount of salt.

Or b) i) Write about canal irrigation structures . An irrigation canal is a waterway, often man-made or enhanced, built for the purpose of carrying water from a source such as a lake, river, or stream, to soil used for farming or landscaping. ii) Types of canal irrigation. Based on lined  Lined canal  Unlined canal Based on excavation material  Alluvial canal  Non-alluvial canal


14

a)

Explain

the

types

of

surface

irrigation.

Or b) Describe about free flooding, check flooding, basin flooding and border flooding.


Basin flooding 15 a ) Explain lift irrigation , flow irrigation ,Direct irrigation and what do you meant by storage irrigation. Lift irrigation.


Lift irrigation is practiced when the water supply is at too low a level to run by gravity on to the land. In such a circumstances water is lifted up by mechanical means. Flow irrigation. Flow irrigation is the type of irrigation in which the supply of irrigation water available is at such a level that it is conveyed on to the land by the gravity flow. Direct irrigation In this system, water is directly diverted to the canal without attempting to store the water. For such a system, a low diversion weir or diversion barrage is constructed across the river. Storage irrigation In this system, a solid barrier, such as a dam or storage weir is constructed across the river and water is stored in the reservoir or lake so formed.

       

Or b) i) What are the basic requirements for adaption of any irrigation method . The method should be such that uniform water distribution with as small as 6 cm water depth applications can be made for light irrigations. At the same time, it should afford heavy uniform application of 15 to 20 cm water depth. It should allow the use of large concentrated water flows for reduction of conveyance losses, and labour cost. It should be suitable for use with economic conveyance structure. ii) Write advantages of furrow irrigation. In the furrow irrigation, water contacts only 1/5 to ½ of the land surface, thereby reducing pudding and crusting of the soil. Evaporation losses are also reduced. It is specially suitable for those crops (like maize) they are injured by contact with water. Labour requirements in land preparation and irrigation are very much reduced. There is no wastage of land in field ditches.


iii) Explain furrow irrigation. Furrow shape The shape of furrows is influenced by the soil type and the stream size. Soil type In sandy soils, water moves faster vertically than sideways (= lateral). Narrow, deep V-shaped furrows are desirable to reduce the soil area through which water percolates (Figure 28). However, sandy soils are less stable, and tend to collapse, which may reduce the irrigation efficiency. In clay soils, there is much more lateral movement of water and the infiltration rate is much less than for sandy soils. Thus a wide, shallow furrow is desirable to obtain a large wetted area (Figure 29) to encourage infiltration. Figure 28 A deep, narrow furrow on a sandy soil

Figure 29 A wide, shallow furrow on a clay soil


Stream size In general, the larger the stream size the larger the furrow must be to contain the flow. 3.2.3 Furrow spacing The spacing of furrows is influenced by the soil type and the cultivation practice. Soil type As a rule, for sandy soils the spacing should be between 30 and 60 cm, i.e. 30 cm for coarse sand and 60 cm for fine sand. On clay soils, the spacing between two adjacent furrows should be 75-150 cm. On clay soils, double-ridged furrows sometimes called beds - can also be used. Their advantage is that more plant rows are possible on each ridge, facilitating manual weeding. The ridge can be slightly rounded at the top to drain off water that would otherwise tend to pond on the ridge surface during heavy rainfall (Figure 30).

UNIT – II IRRIGATION METHODS Canal irrigation – Lift irrigation – Tank irrigation – Flooding methods – Merits and demerits – Sprinkler irrigation – Drip irrigation.


TWO MARKS QUESTIONS AND ANSWERS 1. What are the different classifications of method of irrigation?

2. What do you mean by flow irrigation? Flow irrigation is the type of irrigation in which the supply of irrigation water available is at such a level that it is conveyed on to the land by the gravity flow. 3. Define lift irrigation. Lift irrigation is practiced when the water supply is at too low a level to run by gravity on to the land. In such a circumstances water is lifted up by mechanical means. 4. Define perennial irrigation In this perennial irrigation system, the water required for irrigation is supplied in accordance with the crop requirements throughout the crop period.


5. Define direct irrigation. In this system, water is directly diverted to the canal without attempting to store the water. For such a system, a low diversion weir or diversion barrage is constructed across the river. 6. What do you meant by storage irrigation? In this system, a solid barrier, such as a dam or storage weir is constructed across the river and water is stored in the reservoir or lake so formed. 7. Define combined irrigation. In this system, the water is first stored in the reservoir formed at the upstream side of the dam, and this water is used for power generation. The discharge from the powerhouse is fed back in to the river, to the downstream side of the dam. Thus, sufficient quantity of flow is again available in the river. 8. What do you mean by uncontrolled and controlled flooding? In the controlled flooding, water is spread over the land, with proper methods to control the depth of application. In the uncontrolled flooding, water is spread of flooded on a rather smooth flat land, without much control or prior preparation.

   

9. What are the basic requirements for adaptation of any irrigation method? The method should be such that uniform water distribution with as small as 6 cm water depth applications can be made for light irrigations. At the same time, it should afford heavy uniform application of 15 to 20 cm water depth. It should allow the use of large concentrated water flows for reduction of conveyance losses, and labour cost. It should be suitable for use with economic conveyance structure. 10. What do you mean by free flooding? In free flooding method, the field is divided into a number of small sized plots which are practically level. Water is admitted to these plots at the higher end and the supply is cut off as soon as the lower part of the plot has received the sufficient depth of water.


   

11. Write about the advantages of furrow irrigation. In the furrow irrigation, water contacts only 1/5 to ½ of the land surface, thereby reducing pudding and crusting of the soil. Evaporation losses are also reduced. It is specially suitable for those crops (like maize) they are injured by contact with water. Labour requirements in land preparation and irrigation are very much reduced. There is no wastage of land in field ditches. 12.

Under which favorable conditions the sub-surface irrigation is practiced?  Impervious sub-soil at reasonable depth (2 to 3 m) or higher water table.  Permanent soil such as loam or sandy loam in the root zone of the soil.  Uniform topographic conditions.  Moderate slopes.  Good quality irrigation water. 13. Where sprinkler irrigation is more useful?  The land cannot be prepared for surface methods.  Slopes are excessive  Topography is irregular.  Soil is erosive.  Soil is excessively permeable or impermeable.         

14. Write about the advantages of sprinkler irrigation. Erosion can be controlled. Uniform application for water is possible. Irrigation is better controlled; light irrigation is possible for seedlings and plants, which are young. Land preparation is not required. Crop damage from frost can be reduced.

15. Write about the limitations of sprinkler irrigation. Wind may distort sprinkler pattern. A constant water supply is needed for commercial use of equipment. Water must be clean and free from sand. The power requirement is high.


16. Write about the advantages of drip irrigation  Less requirement of irrigation water.  Water supply at optimum level.  Water logging is avoided.  High yield.  Cultivation of cash crops. 17. Write about the disadvantages of drip irrigation  High initial cost.  Danger of blockade of nozzles.  Change in spacing of nozzles due to change in the crops may result in frequent replacement of trickle lines.  Shallow root depth of the crops, especially for fruit trees may result in instability of the crop or tree which may topple during high winds. SIXTEEN MARK QUESTIONS 1. Write a note on sub-surface irrigation, state clearly the conditions under which this method is suitable. What are the essential requirements for a successful sub-surface irrigation? 2. Describe border strip method of irrigation. Derive the expression for the time required to cover a given area by this method, for a given rate of discharge and the rate of infiltration of water in the soil. 3. Explain in detail about sprinkler method of irrigation and how far it is suitable in Indian conditions. 4. Write a note on drip irrigation. Write about the advantages and disadvantages of drip irrigation system. 5. Define surface irrigation. Why it is widely practiced method of irrigation? What are the advantages and disadvantages of the method? 6. Write a note on free flooding. 7. Describe check flooding and basin flooding. 8. Describe furrow method of irrigation.

UNIT-III


DIVERSION AND IMPOUNDING STRUCTURES Weirs – elementary profile of a weir – weirs on pervious foundations - Types of impounding structures - Tanks, Sluices and Weirs – Gravity dams – Earth dams – Arch dams – Spillways – Factors affecting location and type of dams – Forces on a dam – Hydraulic design of dams. TWO MARK QUESTIONS AND ANSWERS 1. Define diversion headwork. Any hydraulic structure, which supplies water to the off-taking canal, is called a headwork. A diversion headwork serves to divert the required supply in to the canal from the river. 2. Write about the purposes of diversion headwork.  It raises the water level in the river so that the commanded area can be increased.  It regulates the intake of water in to the canal.  It controls the silt entry in to the canal.  It reduces fluctuations in the level of supply in the river.  It stores water for tiding over small periods of short supplies. 3. Define weir. The weir is a solid obstruction put across the river to raise its water level and divert the water in to the canal. If a weir also stores water for tiding over small periods of short supplies, it is called a storage weir.


4. What are the component parts of diversion headwork?  Weir or barrage  Divide wall or divide groyne  Fish ladder  Head sluice or canal head regulator  Canal off-takes  Flood banks  River training works. 5. Define dam. A dam is a hydraulic structure constructed across a river to store the supply for a longer duration and release it through designed outlets. 6. What are the types of dam?  Solid gravity dam (masonry, concrete, steel and timber)  Arch dams  Buttress dams  Earth dams  Rockfill dams  Combination of rockfill and earth dams 7. Define gravity dam.


A gravity dam is a structure so proportioned that its own weight resists the forces exerted upon it. It requires little maintenance and it is most commonly used.

8. What are the forces acting on a gravity dam?  Water pressure  Weight of dam  Uplift pressure  Pressure due to earthquake  Ice pressure  Wave pressure  Silt pressure 9. What is meant by arch dam? An arch dam is a dam curved in plan and carries a major part of its water load horizontally to the abutments by arch action. The part of the water load depends primarily upon the amount of curvature. The balance of the water load is transferred to the foundation by cantilever action. 10. What are the forces acting on arch dam?  Water pressure  Weight of dam  Uplift pressure (negligibly small)  Pressure due to earthquake


 Ice pressure  Silt pressure 11. What are the various types of earth dam? Depending upon the method of construction, earth dam can be divided into,  Rolled fill dam  Hydraulic fill dam 12. What are the types of failure that occur during construction of earth dam?  Hydraulic failures : 40%  Seepage failure : 30%  Structural failure : 30% 13. Define tank. They are small storage meant for irrigating the local area. They may receive their supply from their own catchments. They may also have supply from a nearby river. 14. Define tank sluice. These are outlets that extend from the upstream face of a bund to the downstream face. They are provided to discharge the stored water either for irrigation or for any other purposes. 15. How will you select a site for a tank sluice? The site to be selected should be such that,


 The sluice commands the ayacut.  The sill level of the sluice is above the bed level of existing canal.  Good natural ground is available at the sill level.  It involves minimum cutting  It ensures the safety of the dam itself. 16. Define spillway. A spillway is the overflow portion of dam, over which surplus discharge flows from the reservoir to the downstream. A spillway is therefore called as surplussing work, designed to carry this flood water not required to be stored in the reservoir, safely to the river lower down. 17. Write about the advantages of earth dam? They can be designed and constructed to suit the soil available in the locality and the foundation conditions.  They can be constructed rapidly with relatively unskilled labour.  They are cheaper than other types.  They can be subsequently raised in height without much difficulty. 18. Write about the disadvantages of earth dam?  They are not suitable for greater heights.  They cannot be used as overflow dams.  They are not suitable for deep gorges.  They are not suitable in places of heavy rainfall.  They require heavy maintenance cost and constant supervision.


19. Write about the functions of scouring sluices.  To preserve a clear and defined river channel approaching the regulator.  To control the silt entry in to the canal.  To scour the silt deposited in the riverbed above the approach channel.  To help in passing low floods without dropping the shutters of main weir.  To provide additional waterway for floods, thus lowering the flood levels. 20. Under what conditions gravity dam can be adopted?  Good rock is available for foundation.  A narrow gorge exists to reduce cost and length of dam.  Construction materials are available closely in plenty.  A good site for the surplus weir exists. 21. Define sluiceway. Pipe or tunnel provided for the withdrawal of water from the dams is known as Sluiceway. SIXTEEN MARK QUESTIONS 1. Write in detail about the component parts of diversion works. 2. Write about the types of weirs on permeable foundation. 3. Write in detail about the tank surplus works.


4. What are the causes of failure of earth dams and its remedies? 5. Write about the factors affecting the selection of type of a dam. 6.

Write

about

the

favorable

conditions,

advantages,

disadvantages, pressure distribution and elementary profile of a masonry dam. 7. Write about the criteria for safe design of earth dam. 8. Describe the forces acting on a gravity dam. 9. What are the types of dams and what are the comparative merits and demerits of carious types of dams?

UNIT-IV CANAL IRRIGATION Alignment of canals – Classification of canals – Canal drops – Hydraulic design of drops – Cross drainage works – Hydraulic design of cross drainage works – Canal Head works – Canal regulators – River Training works.


TWO MARKS QUESTIONS AND ANSWERS 1. Classify the rivers. According to the topography of river basin it is classified as:  Upper reaches in the hilly region  Lower reaches in the alluvial plain Rivers in alluvial plain are further classified as:  Meandering type  Aggrading type  Degrading type 2. What are the causes of meandering? A primary cause of meandering is the excess of total charge during floods, when excess of turbulence is developed. It results from the local bank erosion and consequent over loading deposition by the rivers of the heavier sediments having along the bed. 3. What are the objectives of river training works?  High flood discharge may pass safely and quickly through the reach.  Sediment load including bed and suspended load may be transported efficiently.  To make the river course stable and reduce the bank erosion to minimum.  To provide a sufficient draft for navigation as well as good course for it.  To fix direction of flow through certain defined reach.


4. Classify the river training works.  High water training  Low water training  Mean water training 5. Define groyne. Groynes are structures constructed transverse to the river flow and extend from the bank in to the river up to a limit. 6. Classify the groynes. Classification according to material of construction.  Permeable groyne  Solid impermeable groyne. Classification according to its height below high water.  Submerged groyne.  Non-submerged groyne. Classification according to the function it serves.  Attracting groyne.  Deflecting groyne.  Repelling groyne.  Sedimentary groyne. 7. Give an equation for silt factor. f = 1.76

d

where, f = silt factor d = mean particle diameter. 8. Give Kennedy’s critical velocity equation.


Vo = 0.55 m D0.64 Where, Vo = critical velocity (m/s) m = critical velocity ratio (C.V.R) D = depth of water over bed portion of a channel in meters. 9. Define critical velocity. The critical velocity in a channel has the mean velocity, which will just keep the channel free from silting or scouring. 10. What is meant by regime channel? The channel will be in regime if it flows in coherent unlimited alluvium of the same character as that transported and the silt grade and silt charge are all constant. 11. What is meant by contour canal? A channel aligned nearly parallel to the contours of the country is called a contour canal. When the canal takes off from a river in a hilly area, it is not possible to align the canal on the watershed as the watershed on the top of the hill may be very high and the areas that need irrigation are concentrated in the valley. The canal is aligned roughly parallel to the contours of the country. 12. What is a ridge canal? A ridge canal or a watershed canal is aligned along a watershed and runs for most of its length on a watershed.


When the watershed takes a sharp loop, the canal should be aligned straight to save considerable idle length. 13. Give the Lacey’s equation for wetted perimeter. P = 4.75

Q

Where, P = Wetted perimeter. (m) Q = Discharge (m3 / s) 14. Give the Lacey’s equation for bed slope of a canal. S = f 5/3 / 3340 Q1/ 6 Where, S = Bed slope. f = Silt factor Q = Discharge (m3 / s) 15. Write about the significance of Lacey’s theory.  Lacey’s theory assumes that the velocity of flow depends on the hydraulic mean depth, not on the depth.  For a given discharge and given silt charge bed width, depth of flow and bed form is fixed.  For channel in final regime, velocity, hydraulic mean depth, wetted perimeter, discharge, bed slope and N are closely related to one another.  There is only section and only one longitudinal bed slope at which the channel will carry a particular discharge with particular silt grade.  The eddies generated from the sides are considered. 16. When the channel is said to be in regime? The channel is said to be in regime, when the following conditions are satisfied.  The channel is flowing in unlimited incoherent alluvium of the same character as that transported.


 Silt grade and silt charge is constant.  Discharge is constant. SIXTEEN MARK QUESTIONS 1. How are canals classified? Describe them briefly 2. Explain the various considerations for alignment of a canal. 3. Why are canal falls necessary? Describe with sketch briefly the various types of canal falls. 4. What are the types of cross drainage works? Describe them briefly with sketches. 5. Define Lacey’s regime theory and its design procedure of channel. Also list the defects in Lacey’s theory. 6. Write the design procedure for Kennedy’s theory for the channel. 7. Design an irrigation channel to carry 40 cumec of discharge with B / D ratio as 2.5. The critical velocity ratio is 1.0. Assume suitable value of rugosity co-efficient and use Kennedy’s method. 8. Compare Kennedy and Lacey’s silt theories. 9. What is the necessity of river training works? Describe different types of river training works.


10. What is meant by guide banks? What are their functions and effects? UNIT-V IRRIGATION WATER MANAGEMENT Need for optimisation of water use – Minimising irrigation water losses – On farm development works - Participatory irrigation management – Water users associations – Changing paradigms in water management – Performance evaluation. TWO MARKS QUESTIONS AND ANSWERS 1. What is meant by Productivity? Productivity is defined as the ratio of output and input. The output can be water delivered, area irrigated, yield, or income, and the input can be water in the root zone, at the farm gate at the outlet or at upstream points in the system including the point of diversion or storage. Improved water supply influences the adoption of high – yielding agricultural practices by farmers, which justify the productivity criterion of performance. 2. Define equity. Equity in canal irrigation systems implies equality, fairness, and even-handed dealing in matters of allocation and appropriation of irrigation water. There can be several ways to decide the equality of supplies to different farmers. Two of


them, practiced throughout the world, are the methods of prior appropriation and of proportionate equality. 3. Write about the conjunctive use of water. Conjunctive use means the water lifted from below the ground is used in conjunction with canal waters. It results in the coordinated, combined, and creative exploitation of ground water and surface water so as to minimize the dislocation caused by nature’s inconsistent rainfall pattern. Such coordinated use of surface and ground waters results in increased amount of available water, smaller surface distribution system, smaller drainage system, reduced canal linings, greater flood control, and smaller evaporation losses.

4. What is meant by short – term stability? The short – term or interseasonal stability refers to the variations in productivity and equity between irrigation seasons, and is a function of climate, water supply, storage and control, system management, and other factors such as pests, diseases, and availability of labour and other inputs. It can be measured by comparing performance between seasons. 5. Define long – term stability. The long – term stability is defined as “environmental stability” and “durability” and refers to the prevention or minimizing of adverse physical changes such as waterlogging,


leaching of nutrients form soils, salinity, erosion, silting, the ‘mining’ of ground water, and infestations with weeds. 6. Write about the main components of soil reclamation. The main components of soil reclamation works are as follows  Isolation of land areas according to their categorization and leveling and bunding of the affected land as per the category.  Provision of drainage (surface or subsurface or vertical) network to remove leaching water and to keep the water table to a safer level.  Breaking up of impervious subsoil layer in alkali soils by deep ploughing.  Adding suitable chemicals (such as gypsum, sulphur, etc.) depending upon the results of chemical tests of the affected soil. 7.

Why a proper plan for operation & maintenance of irrigation system is necessary?

 Achieve optimum use of canal water.  Provide detailed operation and maintenance guidelines during various anticipated scenarios of water availability, including equitable water distribution upto the tail-end of the system, and  Effect efficient coordination of staff, equipment, physical and financial resources and related disciplines, active involvement of farmers etc.  Achieve stipulated levels of project services including maintenance at minimum achievable cost. 8. What are the main objectives of canal lining? The following are the main objectives of canal lining:  To canal seepage.  To prevent water-logging.


 To increase the capacity of canal.  To increase the command area.  To protect the canal from the damage by flood.  To control the growth of weeds. 9. What are the factors to be considered during the selection of particular type of lining? The selection of particular type of lining depends on the following factors,

 Imperviousness.  Smoothness.  Durability.  Economy.  Site condition.  Life of project.  Availability of construction materials. 10. How can the water losses be controlled? The following are the measures that are generally taken to control the water losses from the reservoir. 1. Measure to Reduce Evaporation Loss a) The reservoir should be constructed of less surface area and more depth. b) Tall trees should be grown on the windward side of the reservoir which act as wind breakers and hence the rate of evaporation will be reduced. c) The reservoir basin should be surrounded by plantation or forest area so that cooler environment exists within the reservoir area.


d) Certain chemical like cetyl alcohol is spread over the reservoir surface. It forms a thin film on water surface reducing evaporation.

2. Measure to Reduce Absorption Loss a)

The weeds and plants at the periphery of the reservoir should be

removed b)

completely.

The weeds from the surface of the reservoir should be removed. 3. Measure to Reduce Percolation Loss

a) Geological investigations should be carried out to locate the zones of pervious formations, cracks and fissures in the bed and periphery of the reservoir basin. b) Suitable treatments should be adopted to stop the leakage of water through these zones. c) Soil stabilization methods should be adopted if the basin is composed of permeable bed soil. 11. What is meant by water logging? In agricultural land, when the soil pores within the root zone of the crops get saturated with the subsoil water, the air circulation within the soil pores gets totally stopped. This phenomenon is termed as water logging. The water logging makes the soil alkaline in character and the fertility of the land is totally destroyed and the yield of crop is reduced. 12. State the effects of water logging? The following are the effects of water logging:  Stabilization of soil


 Lack of aeration  Fall of soil temperature  Growth of weeds and aquatic plants  Diseases of crops  Difficulty in cultivation  Restriction of root growth

13. Write the methods used for controlling water logging? The following measures may be taken to control water logging:  Prevention of percolation from canals  Prevention of percolation from reservoirs  Control of intensity of irrigation  Economical use of water  Fixing of crop pattern  Providing drainage system  Improvement of natural drainage  Pumping of ground water  Construction of sump well 14. Define 0n-farm water management. It can be defined as manipulation of water within the borders of an individual farm, a farming plot or field.


Example: in canal irrigation system, OFWM starts at the farm gate and ends at the disposal point of the drainage water to a public watercourse, open drain or sink. 15. What do you meant by water user association (WUA)? It is a self-managing group of farmers working together to operate and maintain their irrigation and drainage network, to ensure fair and equitable water distribution, and to increase crop yield. 16. What are the problems of irrigation management without participatory management?  Inadequate water availability at the lowest.  Poor condition / maintenance of the system.  Lack of measuring devices and control structures.  Inadequate allocation fro operation and maintenance.  Lack of incentives fro saving water.  Poor drainage. SIXTEEN MARKS QUESTION 1. Discuss the inadequacies of present – day canal irrigation management in India. 2. Describe the common criteria for judging the performance of an irrigation system. 3. Describe the evaluation of performance of canal irrigation systems.


4. What are the methods adopted for improving canal irrigation management? Explain in detail. 5. Why should lining be provided in canals? What are the merits and demerits of canal lining? 6. Write the different types of canal lining. Explain them. 7. How can water be lost from a reservoir? How can the losses be controlled? 8. What kinds of participation are necessary for irrigation management activities? 9. What is meant by percolation pond? Draw a neat sketch of a percolation pond. 10. What is the need for WUA? 11. What is the need for optimization of water use?

CE 6703 WATER RESOURCES ENGINEERING UNIT I Water resources survey – Water resources of India and Tamilnadu – Description of water resources planning – Economics of water resources planning, physical and socio economic


data – National Water Policy – Collection of meteorological and hydrological data for water resources development. Engineering economy in water resources planning: All Water Resources projects have to be cost evaluated. This is an essential part of planning. Since, generally, such projects would be funded by the respective State Governments, in which the project would be coming up it would be helpful for the State planners to collect the desired amount of money, like by issuing bonds to the public, taking loans from a bank, etc. Since a project involves money, it is essential that the minimum amount is spent, under the given constraints of project construction. Hence, a few feasible alternatives for a project are usually worked out. For example, a project involving a storage dam has to be located on a map of the river valley at more than one possible location, if the terrain permits. In this instance, the dam would generally be located at the narrowest part of the river valley to reduce cost of dam construction, but also a couple of more alternatives would be selected since there would be other features of a dam whose cost would dictate the total cost of the project. For example, the foundation could be weak for the first alternative and consequently require costly found treatment, raising thereby the total project cost. At times, a economically lucrative project site may be causing submergence of a costly property, say an industry, whose relocation cost would offset the benefit of the alternative. On the other hand, the beneficial returns may also vary. For example, the volume of water stored behind a dam for one alternative of layout may not be the same as that behind another. Hence, what is required is to evaluate the so-called Benefit-Cost Ratio defined as below:


The annual cost and benefits are worked out as under. AnnualCost(C): The investment for a project is done in the initial years during construction and then on operation and maintenance during the project's lifetime. The initial cost may be met by certain sources like borrowing, etc. but has to be repaid over a certain number of years, usually with an interest, to the lender. This is called the Annual Recovery Cost, which, together with the yearly maintenance cost would give the total Annual Costs. It must be noted that there are many nontangible costs, which arise due to the effect of the project on the environment that has to be quantified properly and included in the annual costs. water resourcesdevelopment. Instructional Objectives On completion of this lesson, the student shall be able to know: 1. Principle of planning for water resource projects 2. Planning for prioritizing water resource projects 3. Concept of basin – wise project development 4. Demand of water within a basin 5. Structural construction for water projects 6. Concept of inter – basin water transfer project 7. Tasks for planning a water resources project

Introduction Utilisation of available water of a region for use of a community has perhaps been practiced from the dawn of civilization. In India, since civilization flourished early, evidences of water utilization has also been found from ancient times. For example at Dholavira in Gujarat water harvesting and drainage systems have come to light which might had been constructed somewhere between 300-1500 BC that is at the time of the Indus valley civilization. In fact, the Harappa and Mohenjodaro excavations have also shown scientific developments of water utilization and disposal systems. They even developed an efficient system of irrigation using several


large canals. It has also been discovered that the Harappan civilization made good use of groundwater by digging a large number of wells. Of other places around the world, the earliest dams to retain water in large quantities were constructed in Jawa (Jordan) at about 3000 BC and in WadiGarawi (Egypt) at about 2660 BC. The Roman engineers had built log water conveyance systems, many of which can still be seen today, Qanatsor underground canals that tap an alluvial fan on mountain slopes and carry it over large distances, were one of the most ingenious of ancient hydro-technical inventions, which originated in Armenia around 1000BC and were found in India since 300 BC. Although many such developments had taken place in the field of water resources in earlier days they were mostly for satisfying drinking water and irrigation requirements. Modern day projects require a scientific planning strategy due to: 1. Gradual decrease of per capita available water on this planet and especially in our country. 2. Water being used for many purposes and the demands vary in time and space. 3. Water availability in a region – like county or state or watershed is not equally distributed. 4. The supply of water may be from rain, surface water bodies and ground water. Water resources project planning  The goals of water resources project planning may be by the use of constructed facilities, or structural measures, or by management and legal techniques that do not require constructed facilities.  The latter are called non-structural measures and may include rules to limit or control water and land use which complement or substitute for constructed facilities.  A project may consist of one or more structural or nonstructural resources.  Water resources planning techniques are used to determine what measures should be employed to meet water needs and to take advantage of opportunities for


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water resources development, and also to preserve and enhance natural water resources and related land resources. The scientific and technological development has been conspicuously evident during the twentieth century in major fields of engineering. But since water resources have been practiced for many centuries, the development in this field may not have been as spectacular as, say, for computer sciences. However, with the rapid development of substantial computational power resulting reduced computation cost, the planning strategies have seen new directions in the last century which utilises the best of the computer resources. Further, economic considerations used to be the guiding constraint for planning a water resources project. But during the last couple of decades of the twentieth century there has been a growing awareness for environmental sustainability. And now, environmental constrains find a significant place in the water resources project (or for that matter any developmental project) planning besides the usual economic and social constraints.


Priorities for water resources planning Water resource projects are constructed to develop or manage the available water resources for different purposes. According to the National Water Policy (2002), the water allocation priorities for planning and operation of water resource systems should broadly be as follows: 1. Domestic consumption This includes water requirements primarily for drinking, cooking, bathing, washing of clothes and utensils and flushing of toilets. 2. Irrigation Water required for growing crops in a systematic and scientific manner in areas even with deficit rainfall. 3. Hydropower This is the generation of electricity by harnessing the power of flowing water. 4. Ecology / environment restoration Water required for maintaining the environmental health of a region. 5. Industries The industries require water for various purposes and that by thermal power stations is quite high. 6. Navigation Navigation possibility in rivers may be enhanced by increasing the flow, thereby increasing the depth of water required to allow larger vessels to pass. 7. Other uses Like entertainment of scenic natural view. This course on Water Resources Engineering broadly discusses the facilities to be constructed / augmented to meet the demand for the above uses. Many a times, one project may serve more than one purpose of the above mentioned uses.


Basin – wise water resource project development  The total land area that contributes water to a river is called a Watershed, also called differently as the Catchment, River basin, Drainage Basin, or simply a Basin.  A watershed may also be defined as a geographic area that drains to a common point, which makes it an attractive planning unit for technical efforts to conserve soil and maximize the utilization of surface and subsurface water for crop production.  Thus, it is generally considered that water resources development and management schemes should be planned for a hydrological unit such as a Drainage Basin as a whole or for a Sub-Basin, multi-sectorially, taking into account surface and ground water for sustainable use incorporating quantity and quality aspects as well as environmental considerations.  Let us look into the concept of watershed or basin-wise project development in some detail  The objective is to meet the demands of water within the Basin with the available water therein, which could be surface water, in the form of rivers, lakes, etc. or as groundwater  The source for all these water bodies is the rain occurring over the Watershed or perhaps the snowmelt of the glacier within it, and that varies both temporally and spatially.  Further due to the land surface variations the rain falling over land surface tries to follow the steepest gradient as overland flow and meets the rivers or drains into lakes and. ponds  The time for the overland flows to reach the rivers may be fast or slow depending on the obstructions and detentions it meet on the way.  Part of the water from either overland flow or from the rivers and lakes penetrates into the ground and recharge the ground water.


Ground water is thus available almost throughout the watershed, in the underground aquifers. The variation of the water table is also fairly even, with some rise during rainfall and a gradual fall at other times.  The water in the rivers is mostly available during the rains. When the rain stops, part of the ground water comes out to recharge the rivers and that results in the dry season flows in rivers. 

Surface and Ground Water Resources Instructional Objectives After completion of this lesson, the student shall know about 1. Hydrologic cycle and its components 2. Distribution of earth‟s water resources 3. Distribution of fresh water on earth 4. Rainfall distribution in India 5. Major river basins of India 6. Land and water resources of India; water development potential 7. Need for development of water resources Introduction Water in our planet is available in the atmosphere, the oceans, on land and within the soil and fractured rock of the earth‟s crust Water molecules from one location to another are driven by the solar energy. Moisture circulates from the earth into the atmosphere through evaporation and then back into the earth as precipitation. In going through this process, called the Hydrologic Cycle water is conserved – that is, it is neither created nor destroyed.It would perhaps be interesting to note that the knowledge of the hydrologic cycle was known at least by about 1000 BC by the people of the Indian Subcontinent. This is reflected by the fact that one verse of Chhandogya Upanishad (the Philosophical reflections of the Vedas)


points to the following: “The rivers… all discharge their waters into the sea. They lead from sea to sea, the clouds raise them to the sky as vapour and release them in the form of rain…” The earth‟s total water content in the hydrologic cycle is not equally distributedThe oceans are the largest reservoirs of water, but since it is saline it is not readily usable for requirements of human survival.Again, the fresh water distribution is highly uneven, with most of the water locked in frozen polar ice caps. The hydrologic cycle consists of four key components 1. Precipitation 2. Runoff 3. Storage 4. Evapotranspiration These are described in the next sections. Precipitation  Precipitation occurs when atmospheric moisture becomes too great to remain suspended in clouds.  It denotes all forms of water that reach the earth from the atmosphere, the usual forms being rainfall, snowfall, hail, frost and dew.  Once it reaches the earth‟s surface, precipitation can become surface water runoff, surface water storage, glacial ice, water for plants, groundwater, or may evaporate and return immediately to the atmosphere.  Ocean evaporation is the greatest source (about 90%) of precipitation.  Rainfall is the predominant form of precipitation and its distribution over the world and within a country. India has a typical monsoon climate.  At this time, the surface winds undergo a complete reversal from January to July, and cause two types of monsoon.  In winter dry and cold air from land in the northern latitudes flows southwest (northeast monsoon), while in summer warm and humid air originates over the ocean and flows in the opposite direction (southwest monsoon), accounting for some 70 to 95 percent of the annual rainfall.


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The average annual rainfall is estimated as 1170 mm over the country, but varies significantly from place to place. In the northwest desert of Rajasthan, the average annual rainfall is lower than 150 mm/year. In the broad belt extending from Madhya Pradesh up to Tamil Nadu, through Maharastra, parts of Andhra Pradesh and Karnataka, the average annual rainfall is generally lower than 500 mm/year. At the other extreme, more than 10000 mm of rainfall occurs in some portion of the Khasi Hills in the northeast of the country in a short period of four months. In other parts of the northeast (Assam, Arunachal Pradesh, Mizoram, etc.,) west coast and in sub-Himalayan West Bengal the average annual rainfall is about 2500 mm. Except in the northwest of India, inter annual variability of rainfall in relatively low. The main areas affected by severe droughts are Rajasthan, Gujarat (Kutch and Saurashtra).

The year can be divided into four seasons: • The winter or northeast monsoon season from January to February. • The hot season from March to May. • The summer or south west monsoon from June to September. • The post – monsoon season from October to December.  The monsoon winds advance over the country either from the Arabian Sea or from the Bay of Bengal.  In India, the south-west monsoon is the principal rainy season, which contributes over 75% of the annual rainfall received over a major portion of the country.  The normal dates of onset of monsoon rains provide a rough estimate of the duration of monsoon rains at any region.


Runoff      

Runoff is the water that flows across the land surface after a storm event. As rain falls over land, part of that gets infiltrated the surface as overland flow. As the flow bears down, it notches out rills and gullies which combine to form channels. These combine further to form streams and rivers. The geographical area which contributes to the flow of a river is called a river or a watershed. The following are the major river basins of our country, and thecorresponding figures, as obtained from the website of the Ministry of Water Resources, Government of India is mentioned alongside each. 1. Indus 2. Ganges 3. Brahmaputra 4. Krishna 5. Godavari 6. Mahanandi 7. Sabarmati 8. Tapi 9. Brahmani-Baitarani 10. Narmada 11. Pennar 12. Mahi

Storage Portion of the precipitation falling on land surface which does not flow out as runoff gets stored as either as surface water bodies like Lakes, Reservoirs and Wetlands or as sub-surface water body, usually called Ground water.  Ground water storage is the water infiltrating through the soil cover of a land surface and traveling further to reach the huge body of water underground. 


Asmentioned earlier, the amount of ground water storage is much greater than that of lakes and rivers.  However, it is not possible to extract the entire groundwater by practicable means. It is interesting to note that the groundwater also is in a state of continuous movement – flowing from regions of higher potential to lower.  The rate of movement, however, is exceptionally small compared to the surface water movement.  The following definitions may be useful: 

Lakes: Large, naturally occurring inland body of water Reservoirs: Artificial or natural inland body of water used to store water to meet various demands. Wet Lands: Natural or artificial areas of shallow water or saturated soils that contain or could support water–loving plants.

Evapotranspiration  Evapotranspiration is actually the combination of two terms – evaporation and transpiration.  The first of these, that is, evaporation is the process of liquid converting into vapour, through wind action and solar radiation and returning to the atmosphere.  Evaporation is the cause of loss of water from open bodies of water, such as lakes, rivers, the oceans and the land surface.  It is interesting to note that ocean evaporation provides approximately 90 percent of the earth‟s precipitation.  However, living near an ocean does not necessarily imply more rainfall as can be noted from the great difference in the amount of rain received between the east and west coasts of India


Transpiration is the process by which water molecules leaves the body of a living plant and escapes to the atmosphere.  The water is drawn up by the plant root system and part of that is lost through the tissues of plant leaf (through the stomata).  In areas of abundant rainfall, transpiration is fairly constant with variations occurring primarily in the length of each plants growing season.  However, transpiration in dry areas varies greatly with the root depth.  Evapotranspiration, therefore, includes all evaporation from water and land surfaces, as well as transpiration from plants. Water resources potential Surface water potential:  The average annual surface water flows in India has been estimated as 1869 cubic km.  This is the utilizable surface water potential in India.  But the amount of water that can be actually put to beneficial use is much less due to severe limitations posed by Physiography, topography, inter-state issues and the present state of technology to harness water resources economically.  The recent estimates made by the Central Water Commission, indicate that the water resources is utilizable through construction of structures is about 690 cubic km (about 36% of the total).  One reason for this vast difference is that not only does the whole rainfall occur in about four months a year but the spatial and temporal distribution of rainfall is too uneven due to which the annual average has very little significance for all practical purposes.  Monsoon rain is the main source of fresh water with 76% of the rainfall occurring between June and September under the influence of the southwest monsoon. 


The average annual precipitation in volumetric terms is 4000 cubic km.  The average annual surface flow out of this is 1869 cubic km, the rest being lost in infiltration and evaporation. Ground water potential:  The potential of dynamic or rechargeable ground water resources of our country has been estimated by the Central Ground Water Board to be about 432 cubic km.  Ground water recharge is principally governed by the intensity of rainfall as also the soil and aquifer conditions.  This is a dynamic resource and is replenished every year from natural precipitation, seepage from surface water bodies and conveyance systems return flow from irrigation water, etc.  The highlighted terms are defined or explained as under: Utilizable surface water potential: This is the amount of water that can be purpose fully used, without any wastage to the sea, if water storage and conveyance structures like dams, barrages, canals, etc. are suitably built at requisite sites. Central Water Commission:  Central Water Commission is an attached office of Ministry of Water Resources with Head Quarters at New Delhi. It is a premier technical organization in the country in the field of water resources since 1945.The commission is charged with the general responsibility of initiating, coordinating and furthering, in consultation with the State Governments concerned, schemes for control, conservation and utilization of water resources throughout the country, for purpose of flood control, irrigation, navigation, drinking water supply and water power development. 

Central Ground Water Board:


It is responsible for carrying out nation-wide surveys and assessment of groundwater resources and guiding the states appropriately in scientific and technical matters relating to groundwater.  The Central Ground Water Board has generated valuable scientific and technical data through regional hydro geological surveys, groundwater exploration, resource and water quality monitoring and research and development.  It assists the States in developing broad policy guidelines for development and management of groundwater resources including their conservation, augmentation and protection from pollution, regulation of extraction and conjunctive use of surface water and ground water resources.  The Central Ground Water Board organizes Mass Awareness Programmes to create awareness on various aspects of groundwater investigation, exploration, development and management. Ground water recharge:  Some of the water that precipitates, flows on ground surface or seeps through soil first, then flows laterally and some continues to percolate deeper into the soil.  This body of water will eventually reach a saturated zone and replenish or recharge groundwater supply.  In other words, the recuperation of groundwater is called the groundwater recharge which is done to increase the groundwater table elevation.  This can be done by many artificial techniques, say, by constructing a detention dam called a water spreading dam or a dike, to store the flood waters and allow for subsequent seepage of water into the soil, so as to increase the groundwater table.  It can also be done by the method of rainwater harvesting in small scale, even at individual houses.  The all India figure for groundwater recharge volume is 418.5 cubic km and the per capita annual volume of groundwater recharge is 412.9 cubic m per person. 


Development of water resources  Due to its multiple benefits and the problems created by its excesses, shortages and quality deterioration, water as a resource requires special attention.  Requirement of technological/engineering intervention for development of water resources to meet the varied requirements of man or the human demand for water, which are also unevenly distributed, is hence essential.  The development of water resources, though a necessity, is now pertinent to be made sustainable.  The concept of sustainable development implies that development meets the needs of the present life, without compromising on the ability of the future generation to meet their own needs.  This is all the more important for a resource like water.  Sustainable development would ensure minimum adverse impacts on the quality of air, water and terrestrial environment.  The long term impacts of global climatic change on various components of hydrologic cycle are also important.  India has sizeable resources of water and a large cultivable land but also a large and growing population to feed.  Erratic distribution of rainfall in time and space leads to conditions of floods and droughts which may sometimes occur in the same region in the same year. India has about 16% of the world population as compared to only 4% of the average annual runoff in the rivers  With the present population of more than 1000 million, the per capita water availability comes to about 1170 m3 per person per year.


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Here, the average does not reflect the large disparities from region to region in different parts of the country. Against this background, the problems relating to water resources development and management have been receiving critical attention of the Government of India.

The country has prepared and adopted a comprehensive National Water Policy in the year 1987, revised in 2002 with a view to have a systematic and scientific development of it water resources. Some of the salient features of the National Water Policy (2002) are as follows:  Since the distribution of water is spatially uneven, for water scarce areas, local technologies like rain water harvesting in the domestic or community level has to be implemented.  Technology for/Artificial recharge of water has also to be bettered.  Desalination methods may be considered for water supply to coastal towns. National Policy For Water Resources Development Instructional Objectives On completion of this lesson, the student shall be able to: 1. Appreciate the policy envisaged by the nation to develop water resources within the country 2. Conventional and non-conventional methods in planning water resources projects 3. Priorities in terms of allocation of water for various purposes 4. Planning strategies and alternatives that should be considered while developing a particular project 5. Management strategies for excess and deficit water imbalances 6. Guidelines for projects to supply water for drinking and irrigation 


Participatory approach to water management Importance of monitoring and maintaining water quality of surface and ground water sources. 9. Research and development which areas of water resources engineering need active 10. Agencies responsible for implementing water resources projects in our country 11. Constitutional provision guiding water resource development in the county 12. Agencies responsible for monitoring the water wealth of the country and plan scientific development based on the National Policy on water Introduction Water, though commonly occurring in nature, is invaluable! It supports all forms of life in conjunction with air. However, the demand of water for human use has been steadily increasing over the past few decades due to increase in population. In contrast, the total reserve of water cannot increase. Hence each nation, and especially those with rapidly increasing population like India, has to think ahead for future such that there is equitable water for all in the years to come. This is rather difficult to achieve as the water wealth varies widely within a country with vast geographical expanse, like India. Moreover, many rivers originate in India and flow through other nations (Pakistan and Bangladesh) andthe demands of water in those counties have to be honored before taking up a project on such a river. Similarly there are rivers which originate form other counties (Nepal, Bhutan and China) and flow through India. All these constraints have led to the formulation of the national water policy which was drafted in 1987 keeping in mind national perspective on water resource planning, development and management. The policy has been revised in 2002, keeping in mind latest objectives. It is important to know the essentials of the national policy as it has significant bearing on the technology or engineering that would be applied in developing and managing water resources projects. This section elucidates the broad guidelines laid own in the National Water Policy (2002) which should be kept in mind while planning any water resource project in our country. 7. 8.


Water Resources Planning Water resources development and management will have to be planned for a hydrological unit such as a drainage basin as a whole or a sub-basin. Apart from traditional methods, non-conventional methods for utilization of water should be considered, like • Inter-basin transfer • Artificial recharge of ground water • Desalination of brackish sea water • Roof-top rain water harvesting

Inter-basin transfer: Basically, it's the movement of surface water from one river basin into another. The actual transfer is the amount of water not returned to its source basin. The most typical situation occurs when a water system has an intake and wastewater discharge in different basins. But other situations also cause transfers. One is where a system's service area covers more than one basin. Any water used up or consumed in a portion of the service area outside of the source basin would be considered part of a transfer (e.g. watering your yard). Transfers can also occur between interconnected systems, where a system in one basin purchases water from a system in another basin. Artificial recharge of ground water: Artificial recharge provides ground water users an opportunity to increase the amount of water available during periods of high demand--typically summer months. Past interest in artificial recharge has focused on aquifers that have declined because of heavy use and from which existing users have been unable to obtain sufficient water to satisfy their needs. Desalination of brackish sea water:


Water seems to be a superabundant natural resource on the planet earth. However, only 0.3 per cent of the world's total amount of water can be used as clean drinking water. Man requires huge amounts of drinking water every day and extracts it from nature for innumerable purposes. As natural fresh water resources are limited, sea water plays an important part as a source for drinking water as well. In order to use this water, it has to be desalinated. Reverse osmosis and electro dialysis is the preferred methods for desalination of brackish sea water. Roof-top rain water harvesting: In urban areas, the roof top rain water can be conserved and used for recharge of ground water. This approach requires connecting the outlets pipe from roof top to divert the water to either existing well/tube wells/bore wells or specially designed wells/ structures. The Urban housing complexes or institutional buildings have large roof area and can be utilized for harvesting the roof top rain water to recharge aquifer in urban areas. One important concept useful in water resources planning is Conjunctive or combined use of both surface and ground water for a region has to be planned for sustainable development incorporating quantity and quality aspects as well as environmental considerations. Since there would be many factors influencing the decision of projects involving conjunctive use of surface and ground water, keeping in mind the underlying constraints, the entire system dynamics should be studied to as detail as practically possible. The uncertainties of rainfall, the primary source of water, and its variability in space and time has to be borne in mind while deciding upon the planning alternatives. It is also important to pursue watershed management through the following methodologies: Soil conservation This includes a variety of methods used to reduce soil erosion, to prevent depletion of soil nutrients and soil moisture, and to enrich the nutrient status of a soil.


Catchment area treatment Different methods like protection for degradation and treating the degraded areas of the catchment areas, forestation of catchment area. Construction of check-dams Check-dams are small barriers built across the direction of water flow on shallow rivers and streams for the purpose of water harvesting. The small dams retain excess water flow during monsoon rains in a small catchment area behind the structure. Pressure created in the catchment area helps force the impounded water into the ground. The major environmental benefit is the replenishment of nearby groundwater reserves and wells. The water entrapped by the dam, surface and subsurface, is primarily intended for use in irrigation during the monsoon and later during the dry season, but can also be used for livestock and domestic needs. Water allocation priorities While planning and operation of water resource systems, water allocation priorities should be broadly as follows: • Drinking water • Irrigation • Hydropower • Ecology • Industrial demand of water • Navigation

Drinking water: Adequate safe drinking water facilities should be provided to the entire population both in urban and in rural areas. Irrigation and multipurpose projects should invariably include a drinking water component, wherever there is no alternative source of drinking water. Drinking water needs of human beings and animals should be the first charge on any available water. Irrigation: Irrigation is the application of water to soil to assist in the production of crops. Irrigation water is supplied to supplement the


water available from rainfall and ground water. In many areas of the world, the amount and timing of the rainfall are not adequate to meet the moisture requirements of crops. The pressure for survival and the need for additional food supplies are causing the rapid expansion of irrigation throughout the world. Hydropower: Hydropower is a clean, renewable and reliable energy source that serves national environmental and energy policy objectives. Hydropower converts kinetic energy from falling water into electricity without consuming more water than is produced by nature. Ecology: The study of the factors that influence the distribution and abundance of species. Industrial demand of water: Industrial water consumption consists of a wide range of uses, including product-processing and small-scale equipment cooling, sanitation, and air conditioning. The presence of industries in or near the city has great impact on water demand. The quantity of water required depends on the type of the industry. For a city with moderate factories, a provision of 20 to 25 percent of per capita consumption may be made for this purpose. Navigation: Navigation is the type of transportation of men and goods from one place to another place by means of water. The development of inland water transport or navigation is of crucial importance from the point of energy conservation as well. Planning strategies for a particular project  Water resource development projects should be planned and developed (as far as possible) as multi-purpose projects .  The study of likely impact of a project during construction and later on human lives, settlements, socio-economic, environment, etc., has to be carried out before hand.  Planning of projects in the hilly areas should take into account the need to provide assured drinking water, possibilities of hydropower development and irrigation in such areas considering the physical features and


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constraints of the basin such as steep slopes, rapid runoff and possibility of soil erosion. As for ground water development there should be a periodical reassessment of the ground water potential on a scientific basis, taking into consideration the quality of the water available and economic viability of its extraction. Exploitation of ground water resources should be so regulated as not to exceed the recharging possibilities, as also to ensure social equity. This engineering aspect of ground water development has been dealt Planning at river basin level requires considering a complex large set of components and their interrelationship. Mathematical modelling has become a widely used tool to handle such complexities for which simulations and optimization techniques are employed. One of the public domain software programs available for carrying out such tasks is provided by the United States Geological Survey. • Ground Water • Surface Water • Geochemical • General Use • Statistics & Graphics

There are private companies who develop and sell software packages. Amongst these, the DHI of Denmark and Delft Hydraulics of Netherlands provide comprehensive packages for many water resources applications.


Guidelines for drinking and irrigation water projects The general guidelines for water usage in different sectors are given Drinking water Adequate safe drinking water facilities should be provided to the entire population both in urban and rural areas. Irrigation and multi -purpose projects should invariably include a drinking water component wherever there is no alternative source of drinking water. Primarily, the water stored in a reservoir has to be extracted using a suitable pumping unit and then conveyed to a water treatment plant where the physical and chemical impurities are removed to the extent of human tolerance. The purified water is then pumped again to the demand area, that is, the urban or rural habitation clusters. The source of water, however, could as well be from ground water or directly from the river. The aspect of water withdrawal for drinking and its subsequent purification and distribution to households is dealt with under the course Water and Waste Water Engineering. The following books may be useful to consult. Irrigation Irrigation planning either in an individual project or in a basin as whole should take into account the irrigability of land, cost of effective irrigation options possible from all available sources of water and appropriate irrigation techniques for optimizing water use efficiency. Irrigation intensity should be such as to extend the benefits of irrigation to as large as number of farm families as possible, keeping in view the need to maximize production. Water allocation in an irrigation system should be done with due regard to equity and social justice. Disparities in the availability of water between headreach and tail-end farms and (in respect of canal irrigation) between large and small farms should be obviated by adoption of a rotational water distribution system and supply of water on a volumetric basis subject to certain ceilings and rational water pricing. Concerned efforts should be made to ensure that the irrigation potential created is fully utilized. For this purpose, the command area development approach should be adopted in all irrigation projects.


Irrigation being the largest consumer of freshwater, the aim should be to get optimal productivity per unit of water. Scientific water management, farm practices and sprinkler and drip system of irrigation should be adopted wherever possible. Water allocation: Research on institutional arrangements for water allocation covers three major types of water allocation: public allocation, userbased allocation, and market allocation. This work includes attention to water rights and to the organizations involved in water allocation and management, as well as a comparative study of the consequences of water reallocation from irrigation to other sectors. A key aspect of this research is the identification of different stakeholders' interests, and the consequences of alternative institutions for the livelihoods of the poor. Rotational water distribution system: Water allocated to the forms one after the other in a repeated manner. Volumetric basis: Water allocated to each farm a specified volume based on the area of the farm, type of crop etc. Irrigation Potential: Irrigation is the process by which water is diverted from a river or pumped from a well and used for the purpose of agricultural production. Areas under irrigation thus include areas equipped for full and partial control irrigation, spate irrigation areas, equipped wetland and inland valley bottoms, irrespective of their size or management type. It does not consider techniques related to on-farm water conservation like water harvesting. The area which can potentially be irrigated depends on the physical resources 'soil' and 'water', combined with the irrigation water requirements as determined by the cropping patterns and climate. However, environmental and socioeconomic constraintsalso have to be taken into consideration in order to guarantee a sustainable use of the available physical resources. This means that in most cases the possibilities for irrigation development would be less than the physical irrigation potential. Command area development:


The command area development programme aims mainly at reducing the gap between the potential created for irrigation to achieve higher agriculture production thereof. This is to be achieved through the integrated development of irrigated tracks to ensure efficient soil land use and water management for ensuring planned increased productivity. Sprinkler irrigation: Sprinkler irrigation offers a means of irrigating areas which are so irregular that they prevent use of any surface irrigation methods. By using a low supply rate, deep percolation or surface runoff and erosion can be minimized. Offsetting these advantages is the relatively high cost of the sprinkling equipment and the permanent installations necessary to supply water to the sprinkler lines. Very low delivery rates may also result in fairly high evaporation from the spray and the wetted vegetation. It is impossible to get completely uniform distribution of water around a sprinkler head and spacing of the heads must be planned to overlap spray areas so that distribution is essentially uniform. Drip: The drip method of irrigation, also called trickle irrigation, originally developed in Israel, is becoming popular in areas having water scarcity and salt problems. The method is one of the most recent developments in irrigation. It involves slow and frequent application of water to the plant root zone and enables the application of water and fertilizer at optimum rates to the root system. It minimizes the loss of water by deep percolation below the root zone or by evaporation from the soil surface. Drip irrigation is not only economical in water use but also gives higher yields with poor quality water. Participatory approach to water resource management Management of water resources for diverse uses should incorporate a participatory approach; by involving not only the various government agencies but also the users and other stakeholders in various aspects of planning, design, development and management of the water resources schemes. Even private sector participation should be encouraged, wherever feasible. In fact, private participation has grown rapidly in many sectors in the recent years due to government encouragement. The concept of


“Build-OwnTransfer (BOT)” has been popularized and shown promising results. The same concept may be actively propagated in water resources sector too. For example, in water scarce regions, recycling of waste water or desalinization of brackish water, which aremore capital intensive (due to costly technological input), may be handed over to private entrepreneurs on BOT basis. Water quality The following points should be kept in mind regarding the quality of water:  Both surface water and ground water should be regularly monitored for quality.  Effluents should be treated to acceptable levels and standards before discharging them into natural steams.  Minimum flow should be ensured in the perennial streams for maintaining ecology and social considerations.  Since each of these aspects form an important segment of water resources engineering, this has been dealt separately in course under water and waste water engineering.  The technical aspects of water quality monitoring and remediation are dealt with in the course of Water and Waste – Water Engineering.  Knowledge of it is essential for the water resources engineer to know the issues involved since, even polluted water returns to global or national water content.  Monitoring of surface and ground water quality is routinely done by the Central and State Pollution Control Boards.  Normally the physical, chemical and biological parameters are checked which gives an indication towards the acceptability of the water for drinking or irrigation.  Unacceptable pollutants may require remediation, provided it is cost effective.  Else, a separate source may have to be investigated.


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Even industrial water also require a standard to be met, for example, in order to avoid scale formation within boilers in thermal power projects hard water sources are avoided. The requirement of effluent treatment lies with the users of water and they should ensure that the waste water discharged back to the natural streams should be within acceptable limits. It must be remembered that the same river may act as source of drinking water for the inhabitants located down the river. The following case study may provoke some soul searching in terms of the peoples‟ responsibility towards preserving the quality of water, in our country: Under the Ganga Action Plan (GAP) initiated by the government to clean the heavily polluted river, number of Sewage Treatment Plants (STPs) have been constructed all along the river Ganga. The government is also laying the main sewer lines within towns that discharge effluents into the river. It is up to the individual house holders to connect their residence sewer lines up to the trunksewer, at some places with government subsidy. However, public apathy in many places has resulted in only a fraction of the houses being connected to the trunk sewer line which has resulted in the STPs being run much below their capacity.

Lastly, it must be appreciated that a minimum flow in the rivers and streams, even during the low rainfall periods is essential to maintain the ecology of the river and its surrounding as well as the demands of the inhabitants located on the downstream.  It is a fact that excessive and indiscriminate withdrawal of water has been the cause of drying up of many hill streams, as for example, in the Mussourie area. 


It is essential that the decision makers on water usage should ensure that the present usage should not be at the cost of a future sacrifice. Hence, the policy should be towards a sustainable water resource development. Flood control and management  There should be a master plan for flood control and management for each flood prone basin.  Adequate flood-cushioning should be provided in water storage projects, wherever feasible, to facilitate better flood management.  While physical flood protection works like embankments and dykes will continue to be necessary, increased emphasis should be laid on non-structural measures such as flood forecasting and warning, flood plain zoning, and flood proofing for minimization of losses and to reduce the recurring expenditure on flood relief. Drought prone area development 

Drought-prone areas should be made less vulnerable to drought associated problems through soil conservation measures, water harvesting practices, minimization of evaporation losses, and development of ground water potential including recharging and transfer of surface water from surplus areas where feasible and appropriate.  Flood cushioning: The reservoirs created behind dams may be emptied to some extent, depending on the forecast of impending flood, so that as and when the flood arrives, some of the water gets stored in the reservoir, thus reducing the severity of the flood.  Embankments and dykes: Embankments & dykes also known as levees are earthen banks constructed parallel to the course of river to confine it to a fixed course and limited cross-sectional width. The heights of levees will be higher than the design flood level with sufficient free board. The confinement of the river to a fixed path frees large tracts of land from inundation and consequent damage. 


Flood forecast and warning: Forecasting of floods in advance enables a warning to be given to the people likely to be affected and further enables civil-defence measures to be organized. It thus forms a very important and relatively inexpensive nonstructural flood-control measure. However, it must be realized that a flood warning is meaningful if it is given sufficiently in advance. Also, erroneous warnings will cause the populace to loose faith in the system. Thus the dual requirements of reliability and advance notice are the essential ingredients of a flood-forecasting system.  Flood plain zoning: One of the best ways to prevent trouble is to avoid it and one of the best ways to avoid flood damage is to stay out of the flood plain of streams. One of the forms of the zoning is to control the type, construction and use of buildings within their limits by zoning ordinances. Similar ordinances might prescribe areas within which structures which would suffer from floods may not be built. An indirect form of zoning is the creation of parks along streams where frequent flooding makes other uses impracticable.  Flood proofing: In instances where only isolated units of high value are threatened by flooding, they may sometimes by individually flood proofed. An industrial plant comprising buildings, storage yards, roads, etc., may be protected by a ring levee or flood wall. Individual buildings sufficiently strong to resist the dynamic forces of the flood water are sometimes protected by building the lower stories (below the expected high-water mark) without windows and providing some means of watertight closure for the doors. Thus, even though the building may be surrounded by water, the property within it is protected from damage and many normal functions may be carried on.  Soil conservation measures: Soil conservation measures in the catchment when properly planned and 


effected lead to an all-round improvement in the catchment characteristics affecting abstractions. Increased infiltration, greater evapotranspiration and reduced soil erosion are some of its easily identifiable results. It is believed that while small and medium floods are reduced by soil  conservation measures, the magnitude of extreme floods are unlikely to be affected by these measures.

Water harvesting practices: Technically speaking, water harvesting means capturing the rain where it falls, or capturing the run-off in one‟s own village or town. Experts suggest various ways of harvesting water:  Capturing run-off from rooftops;  Capturing run-off from local catchments;  Capturing seasonal flood water from local streams; and  Conserving water through watershed management. Apart from increasing the availability of water, local water harvesting systems developed by local communities and households can reduce the pressure on the state to provide all the financial resources needed for water supply. Also, involving people will give them a sense of ownership and reduce the burden on government funds.  Minimization of evaporation losses: The rate of evaporation is dependent on the vapour pressures at the water surface and air above, air and water temperatures, wind speed, atmospheric pressure, quality of water, and size of the water body. Evaporation losses can be minimized by constructing deep reservoirs, growing tall trees on the windward side of the reservoir, plantation in the area adjoining the reservoir, removing weeds and water plants from the reservoir periphery and surface, releasing warm water and spraying chemicals or fatty acids over the water surface. 


Development of groundwater potential: A precise quantitative inventory regarding the ground-water reserves is not available. Organization such as the Geographical Survey of India, the Central Ground-Water Board and the State Tube-Wells and the GroundWater Boards are engaged in this task. It has been estimated by the Central Ground-Water Board that the total ground water reserves are on the order of 55,000,000 million cubic meters out of which 425,740 million cubic meters have been assessed as the annual recharge from rain and canal seepage. The Task Force on Ground-Water Reserves of the Planning Commission has also endorsed these estimates. All recharge to the ground-water is not available for withdrawal, since part of it is lost as sub-surface flow. After accounting from these losses, the gross available groundwater recharge is about 269,960 million cubic meters per annum. A part of this recharge (2,460 million cubic meters) is in the saline regions of the country and is unsuitable for use in agriculture owing to its poor quality. The net recharge available for ground-water development in India, therefore, is of the magnitude of about 267,500 million cubic meters per annum. The Working Group of the Planning Commission Task Force Ground-Water Reserves estimated that the usable ground-water potential would be only 75 to 80 per cent of the net ground-water recharge available and recommended a figure of 203,600 million cubic  meters per annum as the long-term potential for groundwater development in India.  Recharging: Artificial recharge provides ground water users an opportunity to increase the amount of water available during periods of high demand--typically summer months. Past interest in artificial recharge has focused on aquifers that have declined because of heavy use and from which existing users have been unable to obtain sufficient water to satisfy their needs. 


Transfer of surface water: Basically, it's the movement of surface water from one river basin into another. The actual transfer is the amount of water not returned to its source basin. The most typical situation occurs when a water system has an intake and wastewater discharge in different basins. But other situations also cause transfers. One is where a system's service area covers more than one basin. Any water used up or consumed in a portion of the service area outside of the source basin would be considered part of a transfer (e.g. watering your yard). Transfers can also occur between interconnected systems, where a system in one basin purchases water from a system in another basin. Implementation of water resources projects  Water being a state subject, the state governments has primary responsibility for use and control of this resource.  The administrative control and responsibility for development of water rests with the various state departments and corporations. 

Major and medium irrigation is handled by the irrigation / water resources departments.  Minor irrigation is looked after partly by water resources department, minor irrigation corporations and zillaparishads / panchayats and by other departments such as agriculture.  Urban water supply is generally the responsibility of public health departments and panchayatas take care of rural water supply. 


Government tube-wells are constructed and managed by the irrigation/water resources department or by the tubewell corporations set up for the purpose.  Hydropower is the responsibility of the state electricity boards.  Due to the shared responsibilities, as mentioned above, for the development of water resources projects there have been instances of conflicting interests amongst various state holders. 

Central agencies in water resources sector Some of the important offices working under the Ministry of Water Resources, Government of India which plays key role in assessing, planning and developing the water resources of the country are as follows: • Central Water Commission (CWC) • Central Ground Water Board (CGWB) • National Water Development Agency (NWDA) • Brahmaputra Board • Central Water and Power Research Station (CWPRS) • Central Soil and Materials Research Station (CSMRS) • National Institute of Hydrology (NIH) • Ganga Flood Control Commission (GFCC) • Water and Power Consultancy Services (India) ltd (WAPCOS) • National Projects Construction Corporation ltd (NPCC) . Precipitation And Evapotranspiration Instructional Objectives On completion of this lesson, the student shall learn: 1. The role of precipitation and evapotranspiration with the hydrologic cycle. 2. The factors that cause precipitation. 3. The means of measuring rainfall. 4. The way rain varies in time and space.


The methods to calculate average rainfall over an area. What are Depth – Area – Duration curves. What are the Intensity – Duration – Frequency curves. The causes of anomalous rainfall record and its connective measures. 9. What are Probable Maximum Precipitation (PMP) and Standard Project Storm (SPS). What are Actual and Potential 10. evapotranspiration. How can direct measurement of 11. evapotranspiration be made. 12. How can evapotranspiration be estimated based on climatological data. Introduction Precipitation is any form of solid or liquid water that falls from the atmosphere to the earth‟s surface. Rain, drizzle, hail and snow are examples of precipitation. In India, rain is the most common form of precipitation. Evapotranspiration is the process which returns water to the atmosphere and thus completes the hydrologic cycle. Evapotranspiration consists of two parts, Evaporation and Transpiration. Evaporation is the loss of water molecules from soil masses and water bodies. Transpiration is the loss of water from plants in the form of vapour. We proceed on to discuss precipitation, and its most important component in India context, the rainfall. Causes of precipitation For the formation of clouds and subsequent precipitation, it is for necessary that the moist air masses to cool in order to condense. This is generally accomplished by adiabatic cooling of moist air through a process of being lifted to higher altitudes. The precipitation types can be categorized as. 5. 6. 7. 8.

Frontal precipitation This is the precipitation that is caused by the expansion of air on ascent along or near a frontal surface.


Convective precipitation Precipitation caused by the upward movement of air which is warmer than its surroundings. This precipitation is generally showery nature with rapid changes of intensities. Orographic precipitation Precipitation caused by the air masses which strike the mountain barriers and rise up, causing condensation and precipitation. The greatest amount of precipitation will fall on the windward side of the barrier and little amount of precipitation will fall on leave ward side. For the Indian climate, the south-west monsoon is the principal rainy season when over 75% of the annual rainfall is received over a major portion of the country. Excepting the south-eastern part of the Indian peninsula and Jammu and Kashmir, for the rest of the country the south-west monsoon is the principal source of rain. From the point of view of water resources engineering, it is essential to quantify rainfall over space and time and extract necessary analytical information. Measurement of rainfall  One can measure the rain falling at a place by placing a measuring cylinder graduated in a length scale, commonly in mm.  In this way, we are not measuring the volume of water that is stored in the cylinder, but the „depth‟ of rainfall.  The cylinder can be of any diameter, and we would expect the same „depth‟ even for large diameter cylinders provided the rain that is falling is uniformly distributed in space. Now think of a cylinder with a diameter as large as a town, or a district or a catchment of a river.  Naturally, the rain falling on the entire area at any time would not be the same and what one would get would be an „average depth‟.  Hence, to record the spatial variation of rain falling over an area, it is better to record the rain at a point using a standard sized measuring cylinder.


In practice, rain is mostly measured with the standard nonrecording rain gauge the details of which are given in Bureau of Indian Standards code IS 4989: 2002.  The rainfall variation at a point with time is measured with a recording rain-gauge, the details of which may be found in IS 8389: 2003.  Modern technology has helped to develop Radars, which measures rainfall over an entire region. However, this method is rather costly compared to the  conventional recording and non-recording rain gauges which can be monitored easily with cheap labour. Variation of rainfall  Rainfall measurement is commonly used to estimate the amount of water falling over the land surface, part of which infiltrates into the soil and part of which flows down to a stream or river.  For a scientific study of the hydrologic cycle, a correlation is sought, between the amount of water falling within a catchment, the portion of which that adds to the ground water and the part that appears as streamflow.  Some of the water that has fallen would evaporate or be extracted from the ground by plants. 

CE 6703 WATER RESOURCES ENGINEERING UNIT III WATER RESOURCE NEEDS Consumptive and non-consumptive water use - Estimation of water requirements for irrigation, for drinking and navigation - Water characteristics and quality – Scope and


aims of master plan - Concept of basin as a unit for development - Water budget and development plan. Consumptive water use: 

Consumptive water use is water removed from available supplies without return to a water resource system (e.g., water used in manufacturing, agriculture, and food preparation that is not returned to a stream, river, or water treatment plant).

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Evaporation from the surface of the earth into clouds of water in the air which then falls to the ground as "rain" is excluded from this model.

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Crop consumptive water use is the amount of water transpired during plant growth plus what evaporates from the soil surface and foliage in the crop area.

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The portion of water consumed in crop production depends on many factors, especially the irrigation technology.

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Non-consumptive water use: Non consumptive water use includes water withdrawn for use that is not consumed, for example, water withdrawn for purposes such as hydropower generation. This also includes uses such as boating or fishing where the water is still available for other uses at the same site. The terms Consumptive Use and Non consumptive Use are traditionally associated with water rights and water use studies, but they are not completely definitive. No typical consumptive use is 100 percent efficient; there is always some return flow associated with such use either in the form of a return to surface flows or as a ground water recharge. Nor are typically non consumptive uses of water entirely non consumptive. There are evaporation losses, for instance, associated with maintaining a reservoir at a specified elevation to support fish, recreation, or hydropower, and there are conveyance losses associated with maintaining a minimum stream flow in a river, canal, or ditch


Irrigation Water Requirements Introduction  Irrigated agriculture is facing new challenges that require refined management and innovative design.  Formerly, emphasis centered on project design; however,current issues involve limited water supplies with several competing users, the threat of water quality degradation through excess irrigation, and narrow economic margins.  Meeting these challenges requires improved prediction of irrigation water requirements.  Irrigation water requirements can be defined as the quantity, or depth, of irrigation water in addition to precipitation required to produce the desired crop yield and quality and to maintain an acceptable salt balance in the root zone.  This quantity of water must be determined for such uses as irrigation scheduling for a specific field and seasonal water needs for planning, management, and development of irrigation projects.  The amount and timing of precipitation strongly influence irrigation water requirements. In arid areas, annual precipitation is generally less than 10 inches and irrigation is necessary to successfully grow farm crops.  In semiarid areas (those typically receiving between 15 to 20 inches of annual precipitation), crops can be grown without irrigation, but are subject to droughts that reduce crop yields and can result in crop failure in extreme drought conditions.  Subhumid areas, which receive from 20 to 30 inches of annual precipitation, are typically characterized by short, dry periods.  Depending on the available water storage capacity of soils and the crop rooting depth, irrigation may be needed for short periods during the growing season in these areas.  In humid areas, those receiving more than 30 inches of annual precipitation, the amount of precipitation normally exceeds evapotranspiration throughout most of the year.


 However, drought periods sometimes occur, which reduce yield and

impair quality, especiallyfor crops grown on shallow, sandy soils or that have a shallow root system.  Irrigation is not needed to produce a crop in most years, but may be needed to protect against an occasional crop failure and to maintain product quality. Irrigation requirements  The primary objective of irrigation is to provide plants with sufficient water to obtain optimum yields and a high quality harvested product.  The required timing and amount of applied water is determined by the prevailing climatic conditions, the crop and its stage of growth, soil properties (such as water holding capacity), and the extent of root development.  Water within the crop root zone is the source of water for crop evapotranspiration.  Thus, it is important to consider the field water balance to determine the irrigation water requirements.  Plant roots require moisture and oxygen to live.  Where either is out of balance, root functions are slowed and crop growth reduced.  All crops have critical growth periods when even small moisture stress can significantly impact crop yields and quality.  Critical water needs periods vary crop by crop.  Soil moisture during the critical water periods should be maintained at sufficient levels to ensure the plant does not stress from lack of water. The calculation of irrigation water requirements  Delineation of major irrigation cropping pattern zones.  These zones are considered homogeneous in terms of types of irrigated crops grown, crop calendar, cropping intensity and gross irrigation efficiency.  Represented on the map of Africa, they should be viewed as regions where some homogeneity can be found in terms of irrigated crops.  The cropping pattern proposed for the zone should be viewed as representative of an 'average' rather than a 'typical' irrigation scheme.


 Definition of the area of influence of the climate stations (in GIS) and quality check on the climate data.  Combination of the irrigation cropping pattern zones with the climate stations' zones (in GIS) to obtain basic mapping units.  Calculation of net and gross irrigation water requirements for different scenarios.  Comparison with existing data and final adjustment.

Delineation of irrigation cropping pattern zones  The criteria used for the delineation of the irrigation cropping pattern

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zones were, in order of decreasing importance: distribution of irrigated crops, average rainfall trends and patterns, topographic gradients, presence of large river valleys (Nile, Niger, Senegal), presence of extensive wetlands (the Sudd in Sudan), population pressure, technological differences and crop calendar above and below the equator (Zaire). The starting point was the type of irrigated crops currently grown in Africa. This resulted in 18 zones. From these zones, sub-zones showing a different cropping intensity or a different crop calendar were defied. This resulted in a total of 24 irrigation pattern zones which are considered to be homogeneous for: • crops currently grown; • crop calendar; • cropping intensity.

 Only the main crops currently grown, those occupying at least 85% of the

irrigated area, were considered.  Land occupation of the remaining 15 % by secondary crops was assigned to the main crops.  An 'average' typical monthly crop calendar was assigned to each zone, based on work done by FAO's global information and early warning system, and on information from the reference library of FAO's agrometeorology group, AQUASTAT and, for eastern Africa, from the IGADD crop production system zones inventory.


 For each crop the actual cropping intensity was derived from national

crop production and land use figures extracted from the FAO AGROSTAT [6] and AQUASTAT [21a] databases.  It ranges from 100 to 200%, according to the crop calendar.  The cropping intensity to be used in this study of irrigation potential ('potential' scenario) was generally estimated by increasing current values by 10 to 20%, but it was assumed that because of market limitations the current high intensity (in relative terms) of vegetables in certain parts of the continent would not be found in the potential scenario.  Therefore, intensities of cereal crops are higher in the potential scenario than in the actual situation.

Water characteristics and quality:  Physical characteristics  Chemical characteristics  Biological characteristics Physical characteristics

Turbidity  the clarity of water Transparency of natural water bodies is affected by human activity, decaying plant matter, algal blooms, suspended sediments, and plant nutrients  Turbidity provides an inexpensive estimate of total suspended solids  TSS concentration Turbidity has little meaning except in relatively clear waters but is useful in defining drinking-water quality in water treatment measures how deep a person can see into the water Total Solids (TS) - the total of all solids in a water sample Total Suspended Solids (TSS) - the amount of filterable solids in a water sample, filters are dried and weighed Total Dissolved Solids (TDS) - Non filterable solids that pass through a filter with a pore size of 2.0 micron, after filtration the liquid is dried and residue is weighed EPA Secondary Drinking Water Recommendation is for TDS of less than 500mg/L


Volatile Solids (VS) - Volatile solids are those solids lost on heating to 500 degrees C - rough approximation of the amount of organic matter present in the solid fraction of wastewater CHEMICAL CHARACTERISTICS Commonly measured chemical parameters are: – pH – Alkalinity – Hardness – Nitrates, Nitrites, & Ammonia – Phosphates – Dissolved Oxygen & Biochemical Oxygen Demand pH: The pH of water determines the solubility of many ions and biological availability of chemical constituents such as nutrients (phosphorus, nitrogen, and carbon) an heavy metals (lead, copper, cadmium) Hardness  Hard water is found in about 85% of USA.  Prevents lathering/sudsing - hotter water and extra rinse cycles may be required  Fabric appearance declines & life may be reduced  Minerals may clog pipes & cause excessive wear on moving parts Solutions: – Distill water to remove the calcium and magnesium – Soften the Water - Replaces calcium and magnesium ions with sodium or potassium ions Cation exchange Strong adsorption » » » Weak adsorption Al+3 > Ca+2 > Mg+2 > K + = NH4+ > Na + >H + Nitrogen  Nitrogen gas (N2) makes up 78.1% of the Earth’s atmosphere  An essential nutrient required by all plants and animals for formation of amino acids (the molecular units that make up protein) N must be


"fixed" (combined) in the form of ammonia (NH3) or nitrate (NO3) to be used for growth – N2 + 8H+ + bacteria = 2NH3 + H2 – NH3 + O2 + bacteria = NO2- + 3H+ + 2e– NO2- + H2O + bacteria = NO3- + 2H+ +2e Ammonia NH3 (extremely toxic) continually changes to ammonium NH4 + (relatively harmless) and vice versa, relative concentration depends on temperature & pH At higher temperatures and pH, more N is in the ammonia form Maximum Contaminant Level (MCL): nitrite-N : 1 mg/L nitrate-N : 10 mg/L nitrite + nitrate (as N) : 10 mg/L Sources: Fertilized areas; Sewage disposal; Feed lots; N cycle PHOSPHATES  Secondary Drinking Water Standard EPA recommendation– total phosphate should be