CE2301

7/30/2019 CE2301

1/37

UNIT -1

INTRODUCTION

Importance of Irrigation

Definition Irrigation is the controlled application of water to croplands. Its

primary objective is to create an optimal soil moisture regime

for maximizing crop production and quality while at the same

time minimizing the environmental degradation inherent in

irrigation of agricultural lands

Estimates of magnitude world-wide: 544 million acres

(17% of land 1/3 of food production)Purpose

Raise a crop where nothing would grow otherwise (e.g., desert areas) Grow a more profitable crop (e.g., alfalfa vs. wheat) Increase the yield and/or quality of a given crop (e.g., fruit) Increase the aesthetic value of a landscape (e.g., turf, ornamentals) Providing insurance against short duration droughts Reducing the hazard of frost (increase the temperature of the plant) Reducing the temperature during hot spells Washing or diluting salts in the soil Softening tillage pans and clods

Delaying bud formation by evaporative cooling Promoting the function of some micro organisms

Reasons for yield/quality increase

Reduced water stress Better germination and stands Higher plant populations More efficient use of fertilizer Improved varieties

Other Benefits of Irrigation

Increase in Crop Yield Protection from femine

7/30/2019 CE2301

2/37

Cultivation of superior crops Elimination of mixed cropping: Economic development Hydro power generation Domestic and industrial water supply

Methods of Irrigation

Under gravity irrigation, water is distributed by means of open canals and

conducts with out pressure. Gravity irrigation methods are less expensive,

but requires more skill and experience to achieve rescannable efficiency.

This method also requires that the land to be irrigated should have a flatter

slope, other wise the cost of land leveling and preparation at times be come

very high. Gravity irrigation method. Includes furrow, boarder, basin, wild-

flooding and corrugation.

1. Furrow irrigation

In this method of surface irrigation, water is applied to the field by furrow

which are small canales having a continuous our nearly uniform slope in the

direction of irrigation. Water flowing in the furrow into the soil spreads

laterally to

irrigate the area between furrows.

The rate of lateral spread of water in the soil depends on soil type.i.e. For a

given time, water will infiltrate more vertically and less laterally in relatively

sandy soils than in clay soil.

Where the land grade is less than 1% in the direction of furrow, striate

graded furrows may be adapted. The grade can be as much as 2 to 3%

depending on the soil type and the rainfall intensity, which affects erosion.

When field sloped is too steep to align the furrows down the slope, control

furrows which run along curved routed may be used. Spacing of furrowsdepends on the crop type and the type of machinery used for cultivation and

planting.

Length of furrows depends largely on permeability of the soil, the available

labor and skill, and experiences of the irrigation.

7/30/2019 CE2301

3/37

Flow rates are related to the infiltration to the rate of the soil.

Longitudinal slope of furrow depends up on the soil type, especially its

errodiability and the velocity of flow.

slope may be related to discharge as follows.

2. Boarder - strip Irrigation

The farms are divided into number of strips of 5 to 20 meters wide and 100

to 400 meters long. Parallel earth bunds or levees are provided in order to

guide the advancing sheet of water.

Recommended safe limits of longitudinal slope also depends on the soil

texture:

Sandy loam to sandy soils 0.25 - 0.6%

Medium loam soils 0.2 - 0.4%

Clay to clay loam soils 0.05 - 0.2%

3. Basin irrigation

Large stream of water is applied to almost level and smaller unit of fields

which are surrounded by levees or bunds. The applied water is retained in

the basin until it filtrates.

7/30/2019 CE2301

4/37

Soil type, stream size and irrigation depth are the important factors

indeterming the basin area.

Method of irrigation Type of Crop suited

Border strip method Wheat, Leafy vegetables, Fodders

Furrow method Cotton, Sugarcane, Potatoes

Basin method Orchard trees

4. Wild flooding

Water is applied all over the field especially, before plowing for soil that

can't be plowed when dry.

Under closed conduit- there are two types of irrigation

1. Sprinkler2. Drip irrigation

1. Sprinkler irrigation:

It is mostly used for young growth, to humid the atmosphere, for soil

compaction( specially for sandy loam soils before planting, for land having

up and down slope and used to wash out plant leaves especially in dustyarea.

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

Advantages

7/30/2019 CE2301

5/37

Economical to labour & uniform distribution.2. Drip irrigation

This is used especially where there is shortage of water and salt problem.

The drip method of irrigation, also called trickle irrigation. The method isone 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.

Advantages

No loss. of water because all water drops at root zone. No water logging and rise of water table at result salinity

problems caused by this irrigation type is almost nil.

Uniform distribution of water. Good water management. Economical use of lobour.

CONSUMPTIVE USE OF WATER

The amount of irrigation water that is needed depends not only on the

amount of water already available from rain fail, but also on the total

amount of water needed by the various crops.

IRRIGATION WATER NEED = Crop water need available rain fall

The first thing you need to consider when planning your garden is what

growing zone you live in.

This is based on both the temperature range of your climate and the amountof precipitation. Take a close look at the area in which you are going to

plant your garden. If the ground tends to be very moist, choose plants that

can tolerate constantly wet soil, and even standing water.

If you live in an area that suffers from frequent droughts, however, select

plants that can tolerate going long periods without water, especially in light

7/30/2019 CE2301

6/37

of the frequent watering restrictions imposed on such areas.

If you are lucky enough to live in an area that has a balanced climate, you

have a wider range of choices for your plants.

Low Water Requirement Plants

Plants that require low levels of

water are often called drought

tolerant. Drought-tolerant plants

can thrive in hot, dry conditions

with very little water. They

include both perennials and

annuals. Most drought-tolerant

plants only have to be hand-

watered when they are plantedand while they are establishing

themselves. After that, they can be left to the natural cycle of the elements.

Popular drought tolerant trees include the red cedar. live oak, crape myrtle,

and the windmill and saw palmetto palm trees. All citrus trees are also

drought tolerant. Many homeowners in areas prone to drought, such as parts

of the southern United States, use shrubs and ground covering vines as part

of their landscaping. These include Texas sage, orange jasmine and Chinese

fountain grass. There are not many perennial drought-tolerant plants, but

amaryllis is one that is very popular, along with the African iris. Populardrought-olerant annuals include marigold, cosmos and the Dahlberg daisy.

Mid-Level Water Requirement Crops

Most plants land in this range when it comes to water requirements. These

plants do not need to be watered every day, but they need to be watered

when the soil has been dry for over a week or two. Sometimes these plants

are classified as plants lying in the "occasional water zone". These include

popular plants such as geraniums, most roses, wisteria, clematis and other

vine plants, sunflowers, spring flowering bulbs, and most floweringperennial shrubs. Note that flowering annuals planted in containers will need

watering at least once or twice a week, while annuals planted in the ground

will need watering less often.

High Water Requirement Plants

7/30/2019 CE2301

7/37

Some plants require large amounts of water. These plants typically grow in

marshy areas or bogs, or along the banks of rivers, streams and lakes. The

soil for these plants should always be kept moist. Standing water is not a

concern for these plants, so you don't have to worry about root rot.

Perennials are especially good for wet areas because they don't have to bereplanted year after year, which can be difficult in marshy areas. Popular

perennials for wet soil include iris plants, cannas, bee balms, ferns, and bog

salvia. Aquatic mint is a pleasant ground cover that likes wet soil. The red

osier dogwood does very well in wet conditions. Most annual flowering

plants also do well in constantly moist soil.

Water Requirement of Different Crops

Amount of water required by a crop in its whole production period is called

water requiremrnt. The amont of water taken by crops vary considerably.

What crops use more water and which ones less.......

Crop

Water

Requirement

(mm)

Rice 900-2500

Wheat 450-650

Sorghum 450-650

Maize 500-800

Sugarcane 1500-2500

Groundnut 500-700

Cotton 700-1300

Soybean 450-700

Tobacco 400-600

Tomato 600-800

Potato 500-700

Onion 350-550

Chillies 500

7/30/2019 CE2301

8/37

Sunflower 350-500

Castor 500

Bean 300-500

Cabbage 380-500

Pea 350-500

Banana 1200-2200

Citrus 900-1200

Pineapple 700-1000

Gingelly 350-400

Ragi 400-450

Grape 500-1200

Irrigation water requirement

This case study shows how to calculate the total water requirement for a

command area (irrigation blocks) under various crops, soil textures and

conveyance loss conditions. In order to evaluate the required irrigation gift

for the entire command area a simple water balance has to be set-up. Thetotal water demand for each irrigation block and the crops in each block are

calculated by summing the following components:

infiltration (percolation loss) through the soil (I)

seepage (conveyance loss) through the channel (S)

maximum evapotranspiration of the crop (ETm)

In this exercise, the irrigation water requirement is calculated for a 10-day

period during the harvest stage.

Evaluation of Percolation loss (I)

7/30/2019 CE2301

9/37

The command area is divided in irrigation blocks. First, these irrigation

blocks are crossedwith the soil texture map to determine the area of each

soil texture class in each block.

Percolation losses differ per soil texture class so a table with the following

percolation data is created:

TexturePercolation loss

(mm/day)

Clay 4

Loam 12

Sandy clay 14

Clay loam 7

The percolation table isjoinedwith the cross table to get the percolation foreach soil texture class in each block. The amount of water loss for each soil

texture class per block is calculated with a tabcalc statement. In order to get

the total percolation loss per block the results of the previous operation are

aggregated.

Evaluation of Conveyance loss (S)

Conveyance losses are calculated in about the same way as the percolation

losses. First, the map with the irrigation blocks is crossedwith the channel

distribution map. The conveyance loss per meter channel length differs per

channel type and is 0.2 m per day for clay channels and 0.01 m per day for

concrete channels. A new table indicating water loss per channel type is

created andjoinedto the cross table. The amount of water loss for each type

of channel per block is calculated with a simple tabcalc formula. Finally the

results are aggregatedto evaluate the total conveyance loss per irrigation

block.

Evaluation of maximum evapotranspiration (ETm)

Crop water requirements are normally expressed by the rate of

evapotranspiration (ET). The evaporative demand can be expressed as the

reference crop evapotranspiration (ETo) which predicts the effect of climate

on the level of crop evapotranspiration. In this case study the ETo is 8

mm/day. Empirically-determined crop coefficients (kc) can be used to relate

ETo to maximum crop evapotranspiration (ETm) when water supply fully

7/30/2019 CE2301

10/37

meets the water requirement of the crop. The value of kc varies with crop

and development stage. The kc values for each crop and development stage

are available in a table.

For a given climate, crop and crop development stage, the maximum

evapotranspiration (ETm) in mm/day of the period considered is:

ETm = kc * ETo

Maximum evapotranspiration refers to conditions when water is adequate for

unrestricted growth and development under optimum agronomic and

irrigation management. Maximum evapotranspiration is calculated in this

case study by crossing the irrigation block map with the map that shows the

different crop types in the command area,joining the cross table with the kc

table and by applying the maximum evapotranspiration formula with atabcalc statement.

Water balance calculation (S+I+ETm)

The required irrigation gift for the entire command area is equal to the sum

of water losses due to infiltration through the soil (I), seepage through the

channel (S) and maximum evapotranspiration (ETm) for each block. The

total amount of water requirement in harvest period for each block is

reclassifiedin irrigation classes using the following table:

Upper

boundary

Irrigation

class

4000 1

6000 2

8000 3

10000 4

12000 5

14000 6

Finally, you will create a script to automate the calculation procedure. With

the script, you can easily calculate the water requirements for other growing

stages.

7/30/2019 CE2301

11/37

Factors Influencing Crop Water Requirements for Irrigation

i. Influence of climate

A certain crop grown in a sunny and hot climate needs more water per day

than the same crop grown in a cloudy and cooler climate. There are,

however, apart from sunshine and temperature, other climatic factors which

influence the crop water need. These factors are humidity and wind speed.

When it is dry, the crop water needs are higher than when it is humid. In

windy climates, the crops will use more water than in calm climates.

The highest crop water needs are thus found in areas which are hot, dry,

windy and sunny. The lowest values are found when it is cool, humid and

cloudy with little or no wind.

From the above, it is clear that the crop grown in different climatic zones

will have different water needs. For example, a certain maize variety grown

in a cool climate will need less water per day than the same maize variety

grown in a hotter climate.

Effect of major Climatic Factors on Crop Water Needs

Climatic factor Crop water need

High Low

Sunshine sunny (no clouds) cloudy (no sun)

Temperature hot cool

Humidity low (dry) high (humid)

Wind speed windy little wind

Table - AVERAGE DAILY WATER NEED OF STANDARD GRASS

DURING IRRIGATION SEASON (mm)

Climatic zone Mean daily temperature

low (< 15C) medium (15-25C) high (> 25C)

7/30/2019 CE2301

12/37

Desert/arid 4-6 7-8 9-10

Semi-arid 4-5 6-7 8-9

For the various field crops it is possible to determine how much water they

need compared to the standard grass. A number of crops need less waterthan grass, a number of crops need more water than grass and other crops

need more or less the same amount of water as grass. Understanding of this

relationship is extremely important for the selection of crops to be grown in

a water harvesting scheme (see Chapter 6, Crop Husbandry).

Table - CROP WATER NEEDS IN PEAK PERIOD OF VARIOUS

CROPS COMPARED TO THE STANDARD GRASS CROP

-30% -10% Same as Standard Grass +10% +20%Citrus

Olives

Squash Crucifers

Groundnuts

Melons

Onions

Peppers

Grass

Clean cultivated nuts & fruit

trees

Barley

Beans

Maize

Cotton

Lentils

Millet

Safflower

Sorghum

Soybeans

Sunflower

Wheat

Nuts & fruit trees with

cover crop

ii. Influence of crop type on crop water needs

7/30/2019 CE2301

13/37

As different crops require different amount of water for maturity, duties are

also required. The duty would vary inversely as the water requirement of

crop.

The influence of the crop type on the crop water need is important in two

ways.

a. The crop type has an influence on the daily water needs of a fully grown

crop; i.e. the peak daily water needs of a fully developed maize crop will

need more water per day than a fully developed crop of onions.

b. The crop type has an influence on the duration of the total growing season

of the crop. There are short duration crops, e.g. peas, with a duration of the

total growing season of 90-100 days and longer duration crops, e.g. melons,

with a duration of the total growing season of 120-160 days. There are, ofcourse, also perennial crops that are in the field for many years, such as fruit

trees.

While, for example, the daily water need of melons may be less than the

daily water need of beans, the seasonal water need of melons will be higher

than that of beans because the duration of the total growing season of melons

is much longer.

Data on the duration of the total growing season of the various crops grown

in an area can best be obtained locally. These data may be obtained from, forexample, the seed supplier, the Extension Service, the Irrigation Department

or Ministry of Agriculture.

Table gives some indicative values or approximate values for the duration of

the total growing season for the various field crops. It should, however, be

noted that the values are only rough approximations and it is much better to

obtain the values locally.

There are three broad classes of irrigation systems:

Pressurized distribution

Gravity flow distribution

Drainage flow distribution.

7/30/2019 CE2301

14/37

1. Pressurized Distribution

The pressurized systems include sprinkler, trickle, and the array of similar

systems in which water is conveyed to and distributed over the farmland

through pressurized pipe networks. There are many individual system

configurations identified by unique features (centre-pivot sprinkler

systems).

2. Gravity Flow Irrigation System

Gravity flow systems convey and distribute water at the field level by a free

surface, overland flow regime. These surface irrigation methods are also

subdivided according to configuration and operational characteristics.

3. Control of drainage flow irrigation System

Irrigation by control of the drainage system, subirrigation, is not common

but is interesting conceptually. Relatively large volumes of applied irrigation

water percolate through the root zone and become a drainage or groundwater

flow. By controlling the flow at critical points, it is possible to raise the level

of the groundwater to within reach of the crop roots. These individualirrigation systems have a variety of advantages and particular applications.

Irrigation systems are often designedto maximize efficiencies and minimize

labour and capital requirements. The most effective management practices

are dependent on the type of irrigation system and its design. For example,

7/30/2019 CE2301

15/37

management can be influenced by the use of automation, the control of or

the capture and reuse of runoff, field soil and topographical variations and

the existence and location of flow measurement and water control structures.

Questions that are common to all irrigation systems are when to irrigate,

how much to apply, and can the efficiency be improved. A large number of

considerations must be taken into account in the selection of an irrigation

system. These will vary from location to location, crop to crop, year to year,

and farmer to farmer.

Compatibility of the irrigation systems:

The irrigation system for a field or a farm must be compatible with the other

existing farm operations, such as land preparation, cultivation, and harvest.

Level of Mechanization

Size of Fields

Cultivation

Pest Control

Topographic Limitations.

Restrictions on irrigation system selection due to topography include:

groundwater levels

the location and relative elevation of the water source,

field boundaries,

acreage in each field,

the location of roads

power and water lines and other obstructions,

the shape and slope of the field

7/30/2019 CE2301

16/37

UNIT-2&4

IRRIGATION METHOD

CANAL IRRIGATION

Cheap labour and availability of cement reduces the cost of canal

construction

Huge quantities of water from Monsoon rainfall & melting of snow can be

stored in reservoirs during summer season.

Irregular supply of water in the rivers is then regulated by construction of

dams & barrages. Canal system irrigates a vast area. Even the deserts have

been made productive.

TANK IRRIGATIONIndia, an irrigation tank or tank is an artificialreservoirof any size. (The word sagar

refers to a large lake, usually man-made).[1]

It can also have a natural or man-madespring included as part of a structure. Tanks are part of an ancient tradition of harvesting

and preserving the local rainfall and water from streams and rivers for later use,primarily for agriculture and drinking water, but also for sacred bathing and ritual. Often

a tank was constructed across a slope so to collect and store water by taking advantageof local mounds and depressions.

[2]Tank use is especially critical in parts ofSouth India

withoutperennialrainfall where water supply replenishment is dependent on a cycle ofdry seasons alternating with monsoon seasons.

Causes:

Abundance of silt eroded from the Karakoram, Hindu Kush and Himalayan

mountains.

Deforestation - ruthless cutting of trees for fuel and timber. Rivers form

narrow and deep valleys in the mountainous areas. Most of the eroded

material is washed down into the plains and piles up in reservoirs of the

dams.

Effects:

Blockage of canals because silt accumulates. Weakens the foundation of dams. Reduced capacity of reservoir and less flow of water affects the

generation of hydro-electric power. It also results in availability of

less water for irrigation purposes.
http://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Reservoirhttp://en.wikipedia.org/wiki/Reservoirhttp://en.wikipedia.org/wiki/Reservoirhttp://en.wikipedia.org/wiki/Irrigation_tank#cite_note-glossary-0#cite_note-glossary-0http://en.wikipedia.org/wiki/Irrigation_tank#cite_note-glossary-0#cite_note-glossary-0http://en.wikipedia.org/wiki/Irrigation_tank#cite_note-glossary-0#cite_note-glossary-0http://en.wikipedia.org/wiki/Irrigation_tank#cite_note-Tank_management-1#cite_note-Tank_management-1http://en.wikipedia.org/wiki/Irrigation_tank#cite_note-Tank_management-1#cite_note-Tank_management-1http://en.wikipedia.org/wiki/Irrigation_tank#cite_note-Tank_management-1#cite_note-Tank_management-1http://en.wikipedia.org/wiki/South_Indiahttp://en.wikipedia.org/wiki/South_Indiahttp://en.wikipedia.org/wiki/South_Indiahttp://en.wikipedia.org/wiki/Perennial_planthttp://en.wikipedia.org/wiki/Perennial_planthttp://en.wikipedia.org/wiki/Perennial_planthttp://en.wikipedia.org/wiki/Perennial_planthttp://en.wikipedia.org/wiki/South_Indiahttp://en.wikipedia.org/wiki/Irrigation_tank#cite_note-Tank_management-1#cite_note-Tank_management-1http://en.wikipedia.org/wiki/Irrigation_tank#cite_note-glossary-0#cite_note-glossary-0http://en.wikipedia.org/wiki/Reservoirhttp://en.wikipedia.org/wiki/India

7/30/2019 CE2301

17/37

Flow of floodwater is hampered which may cause heavy damage tothe dam because of mounds of silt which block the flow of water.

Large-scale afforestation especially on the foothills of Himalayas. Cemented embankment of canals. .

Installation of silt trap before the water flows to the dams. Structural measures such as operating the reservoir at lower level

during flood and allowing free flow during low flow season for

sluicing sediments from the reservoir.

Uses of CANAL Irrigation:

1. Soft soil and level land of the Indus Plain makes digging of canalseasier than in the rugged lands of Balochistan.

2. By canal irrigation millions of gallons of water are utilized that wouldflow into the Arabian Sea.

3. Cheap labour and availability of cement reduces the cost of canalconstruction

4. Canal system irrigates a vast area. Even the deserts have been madeproductive.

5. Irregular supply of water in the rivers is then regulated byconstruction of dams & barrages.

6. Huge quantities of water from Monsoon rainfall & melting of snowcan be stored in reservoirs during summer season.

7. Southward slope of the rivers makes construction of canals easier,because water flows southwards naturally.

Lining of Irrigation CanalsMost of the irrigation channels in Iraq are earthen channels. The

major advantage of an earth channel is its low initial cost, these suffer

from certain disadvantages, like the following:-

1- Maximum velocity limited to prevent erosion.

2- Seepage of water into the ground.

3- Possibility of vegetation growth in banks, leading to increased friction.4-Possibility of bank failure, due to erosion.

5-More maintenance requirement.Types of Canal LiningTypes of lining are generally classified according to the materials

used for their construction. Concrete, rock masonry, brick masonry,

bentonite-earth mixtures, natural clays of low permeability, and different

7/30/2019 CE2301

18/37

mixtures of rubble, plastic, and asphaltic materials are the commonly

used materials for canal lining. The suitability of the lining material is

decided by:

A- Economy.

B- Structural stability.

C- Resistance to erosion.

E- Durability.

F- Hydraulic efficiency.

[A] Concrete Lining[B] Precast concrete lining[C] Shotcrete Lining[D] Bricks, Tiles and Stone lining[E] Asphaltic Lining[F] Earth Linings1- Stabilized Earth LiningsSub-grade is stabilized using either clay for granular subgrade or by

adding chemicals that compact the soil.

2- Loose Earth Blankets

Fine grained soil is laid on the sub grade and evenly spread. However,

this type of lining is subject to erosion, and requires a flatter side slopes

of canal.

3- Compacted Earth Linings

The graded soil containing about 15 percent clay is spread over thesubgrade and compacted.

4- Buried Bentonite Membranes

Bentonite is a special type of clay soil, found naturally, which swell

considerably when wetted.

5- Soil-cement Linings:These linings are constructed using cement (15 to 20 per cent by

volume) and sandy soil (not containing more than about 35 per cent of silt

and clay particles). Cement and sandy soil can be mixed in place and

compacted at the optimum moisture content. This method of construction

is termed the dry-mixed soil-cement method.

3- Failure of Canal LiningThe main causes of failure of lining are the water pressure that

developed behind the lining material due to high water table, saturation

of the embankment by canal water, sudden lowering of water levels in the

7/30/2019 CE2301

19/37

channel, and saturation of the embankment sustained by continuous

rainfall. When the water level in canal was raised and lowered the banks

suffering from instability due to erosion and seepage through the banks

may be occurs. In order to minimize the seepage, a secondary berms were

constructed along the length of bank at various locations.Diversion head works: Weirs and Barrages, Layout of diversion head works andcomponents, failure of hydraulic structures on previous foundations, Blighs Creep

theory, Lanes weighted theory and Khoslas theory, concept of low net, u/s and d/scutoffs and protection measures, design of vertical drop weir.

Canal Structures: Types of falls and their location, design principles and Trapezoidalnotch fall, siphon well drop, straight glacis fall. Canal regulation works, alignment of off

taking canal. Distributary head regulators and cross regulation and their design. Canalescapes, types of metering flumes, types of canal modules and proportionality,

sensitivity, flexibility.

Cross Drainage Works: Definition, classification, design principles of aqueducts,siphon aqueducts, canal siphons, super passages and inlet and outlets, selection of crossdrainage works.

Bridges and Culverts: Discharge, Waterway and sour depth computations, Depth of

Bridge foundation, spans and vertical clearance, efflux computations, pipe culverts andbox culverts.

Water Power: Classification of Hydropower plants, definitions pf terms, load, head,power, efficiency, load factor, installed capacity, utilization factor, capacity factor, use of

mass curve and flow duration curve. Components of power plant-intakes, fore/bay,

penstocks, functions and types of sewage tanks, General arrangement of power house,sub-structure and super-structure.

.

Design of HydraulicStructures

Design of HydraulicStructuresCOURSE Contents

1. Introduction

7/30/2019 CE2301

20/37

2. Gravity Dams Site selection,

Forces,

Stability analysis.3. Diversion Works Weirs and

Barrages

4. Canals Design and Canal Falls.

5. Cross Drainage Works

6. Head Regulators and Crossregulators

IS CodesIS Code 6512: Criteria for Design of Solid Gravity

Dams

IS Code 1893: Criteria for Earthquake ResistantDesign of Structures

IS Code 7784-Cross-Drainage Works: Part 1 -

General

IS Code 7784- Cross-Drainage Works: Part 2 -

Aqueduct

IS Code 7784- Cross-Drainage Works: Part 2

Syphon AqueductIS Code 7784- Cross-Drainage Works: Part 2

Canal Syphon


Superpassage

7/30/2019 CE2301

21/37


Level Crossing

UNIT-3 DIVERSION AND IMPOUNDING STRUCTURES

Why study Hydraulic Structures?

INTRODUCTIONDevelopment of water resources of

a region

Requires

Conception

Planning

Design

Construction

Operation

of various facilities to utilise andcontrol water, and

to maintain water quality.

Utilize/Need water

7/30/2019 CE2301

22/37

Domestic & Industrial uses

Irrigation

Power generationNavigation

Other purposes

Water Resources Engineering

Utilisation of water

Control of waterWater quality management

Water is controlled and regulated

Flood control

Land drainage

Sewerage

Bridges

Not cause damage to property,

inconvenience to the

public, or loss of lifeWater-quality management

Required quality of water for

different uses

7/30/2019 CE2301

23/37

Preserve Ecological balance

Contamination of

Groundwater/Surface waterWater Resources development

projects are planned

to serve various purposes

Main Purposes

Domestic & Industrial uses,Irrigation

Power generation, Navigation,

Flood control

Secondary Purposes

Recreational, Fish and wild life,

Drainage control,

Watershed management, Sediment

control,

Salinity control, Pollutionabatement

Miscellaneous Purposes

7/30/2019 CE2301

24/37

Employment, Accelerate

development etc

Single-purpose andMulti-purposeWater Resources projects Two

Main Steps

First step How much water is

available?

Knowledge of HydrologyPrecipitation average

Abstraction Losses

Runoff, Yield of basin

Flood Peak runoff

Reservoir sizing Mass curve

Second step How to utilise and

control water?

Require various structure

Hydraulic StructuresTypes of Hydraulic Structures

Storage

Diversion

7/30/2019 CE2301

25/37

Transportation

Regulation

ControlMain source of water is

Precipitation

Precipitation is not uniform over

space and time

Monsoon, North East, Himalaya,W. Ghat

Store water at surplus location

during surplus

period Storage structures

Reservoirs

Dam and Reservoir coexist

Dam solid barrier across river

Reservoir artificial lake u/s of

damReservoirDam

Reservoir

7/30/2019 CE2301

26/37

Dam Spillway

RESERVOIRS RESERVOIRSTypes of Reservoirs Single-purposeand Multi-purpose

Storage (or conservation) reservoirs

Flood control reservoirs

Multipurpose reservoirDistribution reservoirs

Balancing reservoirs

Flood Control runoff exceeding

safe capacity of

river is stored in the reservoir.

Stored water is

released in controlled manner

Detention Reservoirs regulated byGATES

Adv: More flexibility of operation andbetter control of

7/30/2019 CE2301

27/37

outflow; Discharge from various

reservoirs can be adjusted

Disadv: More expensive; Possibility ofhuman error

Retarding Reservoirs UNGATES

Adv: Less expensive; Outflow is

automatic so possibility ofhuman error

Disadv: No flexibility of operation;Discharge from various

reservoirs may coincide heavy flood

Multipurpose ReservoirsServe two or more purposes. In India,

most of the reservoirs

are designed as multipurpose reservoirs

to store water for

irrigation and hydropower, and also toeffect flood control

Distribution Reservoirs

7/30/2019 CE2301

28/37

7/30/2019 CE2301

29/37

Serve two or more purposes. In India,

most of the reservoirs

are designed as multipurpose reservoirsto store water for

irrigation and hydropower, and also to

effect flood control

Distribution ReservoirsSmall storage reservoirs to tide over the

peak demand ofwater. The distribution reservoir is

helpful in permitting

the pumps to work at a uniform rate. It

stores water

during the period of lean demand andsupplies the same

during the period of high demand. As the

storage is

limited, it merely helps in distribution of

water as per

demand for a day or so and not forstoring it for a long

period. Distribution reservoirs are mainly

used for

7/30/2019 CE2301

30/37

municipal water supply but rarely used

for the supply of

water for irrigation.RESERVOIRS RESERVOIRSBalancing ReservoirsA balancing reservoir is a small reservoir

constructed d/s of

the main reservoir for holding waterreleased from the

main reservoir.

RESERVOIRS RESERVOIRSStorage Capacity of ReservoirsStorage capacity of a reservoir depends

upon the topography of

the site and the height of dam.

Engineering surveys

The storage capacity and the water

spread area at different

elevations can be determined from thecontour map.

In addition to finding out the capacity of

a reservoir, the

7/30/2019 CE2301

31/37

contour map of the reservoir can also be

used to determine

the land and property which would besubmerged when the

reservoir is filled upto various elevations.

To estimate the compensation to be paid

to the owners of the

submerged property and land. The time

schedule,according to which the areas should be

evacuated, as the

reservoir is gradually filled, can also be

drawn..

UNIT-5

IRRIGATION WATER MANAGEMENT

Both the elevation-area curve and the

elevation- storage curve on

the same paper. Abscissa - areas and

volumes - opposite

di ti

Area-Elevation Curve

from contour map An

7/30/2019 CE2301

32/37

elevation-area curve is

then drawn between

the surface area asabscissa and the

elevation as ordinate.

Elevation-Capacity

Curve: is determined

from elevation-area

curve using diffformulae.

Storage Capacity calculation

formulae

1. Trapezoidal formula2. Cone formula

3. Prismoidal formula

4. Storage Volume from cross-sectional

areas

Basic Terms and Definitions1. Full reservoir level (FRL): is the

highest water level to which

7/30/2019 CE2301

33/37

the water surface will rise during normal

operating

conditions. Also called the full tank level(FTL) or the

normal pool level (NPL).

2. Maximum water level (MWL): is the

maximum level to which

the water surface will rise when the

design flood passes overthe spillway. Also called the maximum

pool level (MPL) or

maximum flood level (MFL).

3. Minimum pool level: is the lowest level

up to which the water

is withdrawn from the reservoir under

ordinary conditions.

It corresponds to the elevation of the

lowest outlet (or

sluiceway) of the dam. However, in the

case of a reservoir forhydroelectric power; the minimum pool

level is fixed after

7/30/2019 CE2301

34/37

considering the minimum working head

required for the

efficient working of turbines.

Basic Terms and Definitions4. Useful storage: volume of water stored

between the full

reservoir level and the minimum pool

level. Also known as

the live storage.

5. Surcharge storage: is the volume of

water stored above the

full reservoir level upto the maximum

water level. Thesurcharge storage is an uncontrolled

storage which exists

only when the river is in flood and the

flood water is passing

over the spillway. This storage is available

only for the

absorption of flood and it cannot be used

for other purposes.

7/30/2019 CE2301

35/37

6. Dead storage: volume of water held

below the minimum pool

level. The dead storage is not useful, as itcannot be used for

any purpose under ordinary operating

conditions.

7. Bank storage: If the banks of the

reservoir are porous, some

water is temporarily stored by them whenthe reservoir is

full.

8. Valley storage: The volume of water

held by the natural river

channel in its valley upto the top of its

banks before the

construction of a reservoir is called the

valley storage. May

be important in flood control reservoirs.

9. Yield from a reservoir: Yield is the

volume of water whichcan be withdrawn from a reservoir in a

specified period of

7/30/2019 CE2301

36/37

time. The yield is determined from the

storage capacity of

the reservoir and the mass inflow curve.10 Safe yield (Firm yield): is the

maximum quantity of water

which can be supplied from a reservoir in

a specified period

of time during a critical dry year. Lowest

recorded naturalflow of the river for a number of years is

taken as the

critical dry period for determining the

safe yield

11. Secondary yield: is the quantity of

water which is available

during the period of high flow in the

rivers when the yield is

more than the safe yield. It is supplied on

as and when basisat the lower rates. The hydropower

developed from

7/30/2019 CE2301

37/37

secondary yield is sold to industries at

cheaper rates.

12. Average yield: is the arithmeticaverage of the firm yield

and the secondary yield over a long

period of time.

13. Design yield: is the yield adopted in

the design of a reservoir.

Fixed after considering the urgency of thewater needs and

the amount of risk involved. The design

yield should be such

that the demands of the consumers are

reasonably met with,

and at the same time, the storage required

is not unduly

large.

Documents

CE2301