irrigation engg lec 01

7/21/2019 Irrigation Engg Lec 01

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Course Instructor

Engr. Afzal Ahmed

MSc Water Resource & Irrigation Engineering

UET Taxila

Sc Ci!il Engineering

UET Taxila

Irrigation Engineering CE"#$#%'$(


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Course ContentsWater Resources)

*lanning and de!elo+ment of ,ater resources +ro-ects. omestic/

Industrial/ Agricultural and other ,ater usages/ Water resources in*a0istan.

Irrigation:

e1nition and t2+es of irrigation. Merits and demerits of irrigation/Indus asin Irrigation S2stem (IBIS).

Canal Irrigation:

Elementar2 conce+t a3out canal head ,or0s/ selection of their site

and la2out/ ,eirs and 3arrages/ !arious com+onents and functions.

Measures ado+ted to control silt entr2 into canals/ silt e-ectors and

excluders. esign of ,eirs on +ermea3le foundations/ sheet +ilesand cut o4 ,alls. esign of irrigation channels/ 5enned26s and

7ace26s Theories. Rational methods for design of irrigationchannels. Com+arison of !arious methods. Com+uter Aided designof irrigation channels.


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Barrages and Headworks:

Canal head regulators/ falls/ 8umes/ canal outlets.

Cross drainage ,or0s) t2+es and functions. Canallining) ad!antages and t2+es. Maintenance ofirrigation canals.Monitoring of 8o,s"telemetr2 s2stem.

Irrigated Agriculture:

Soil",ater"+lant relationshi+. Water re9uirements ofcro+s/ dut2 of irrigation ,ater. elta of cro+s/consum+ti!e use/ estimation of consum+ti!e use/

methods used for assessment of irrigation ,ater.Irrigation methods and +ractices. Irrigationscheduling. Management of irrigation s2stems/+artici+ator2 irrigation management.


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Water logging and salinity:

Causes and e4ects of ,ater logging/reclamation of ,ater logged soils. rainsand tu3e ,ells. Causes and e4ects ofsalinit2 and al0alinit2 of lands in *a0istan.Reclamation methods. rainage net,or0 inirrigated areas.

Drainage:

e1nition/ 7and reclamation/ Surfacerainage/ Su3surface rainage/ Estimationof discharge ca+acit2 of Cross"drainage

structures/ is+osal of drainage e:uents.


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Text oo0

7insla2/ R.5. and ;ose+h/ .ill.

Reference oo0s?. 7insla2/ R.5. and ;ose+h/ .ill.

@. Siddi9ui/ I9tidar >./ Irrigation and

rainage Engineering/ xford Uni!ersit2*ress

. I93al Ahmed/ Irrigation Engineering and>2draulic Structures


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Water Resources

Cha+ter Bo $?


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IntroductionUtilisation of available water of a region for use of

a community has perhaps been practiced from the

dawn of civilization. In fact, the Harappa and

Mohenjodaro excavations have also shown

scientific developments of water utilization and

disposal systems. hey even developed an efficient

system of irrigation using several large canals. It

has also been discovered that the Harappancivilization made good use of groundwater by

digging a large number of wells.


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!f other places around the world, the earliest dams

to retain water in large "uantities were constructed

in #awa $#ordan% at about &''' () and in *adi

+arawi $gypt% at about -' (). he /oman

engineers had built log water conveyance systems,

many of which can still be seen today, 0anats or

underground canals that tap an alluvial fan on

mountain slopes and carry it over large distances,were one of the most ingenious of ancient hydro1

technical inventions, which originated in 2rmenia

around 3'''() and were found in India since &''

().


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7og ,ater con!e2ances2stem


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2lthough many such developments had ta4en

place in the field of water resources in earlier days

they were mostly for satisfying drin4ing water and

irrigation re"uirements. Modern day projects

re"uire a scientific planning strategy due to5

3. +radual decrease of per capita available water on

this planet and especially in our country.

-. *ater being used for many purposes and thedemands vary in time and space.


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*ater availability in a region 6 li4e county or state

or watershed is not e"ually distributed.

he supply of water may be from rain, surfacewater bodies and ground water.


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*ater resources project planning

he goals of water resources project planning maybe by the use of constructed facilities, or structural

measures, or by management and legal techni"ues

that do not re"uire constructed facilities. he latter

are called non1structural measures and may include

rules to limit or control water and land use which

complement or substitute for constructed facilities.

2 project may consist of one or more structural ornon1structural resources.


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*ater resources planning techni"ues are used to

determine what measures should be employed to

meet water needs and to ta4e advantage of

opportunities for water resources development, and

also to preserve and enhance natural waterresources and related land resources.

he scientific and technological development has

been evident during the twentieth century in major

fields of engineering. (ut since water resourceshave been practiced for many centuries, the

development in this field may not have been as

spectacular as, say, for computer sciences.


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However, with the rapid development of

substantial computational power resulting reducedcomputation cost, the planning strategies have seen

new directions in the last century which utilises the

best of the computer resources. 7urther, economic

considerations used to be the guiding constraint forplanning a water resources project. (ut during the

last couple of decades of the twentieth century

there has been a growing awareness for

environmental sustainability. 2nd 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.


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8riorities for water resources planning

*ater resource projects are constructed to develop ormanage the available water resources for different

purposes. he water allocation priorities for planning and

operation of water resource systems should broadly be as

follows5 3. 9omestic consumption includes water

re"uirements primarily for drin4ing, coo4ing,

bathing, washing of clothes and utensils and

flushing of toilets.

-. Irrigation *ater re"uired for growing crops in a

systematic and scientific manner in areas even with

deficit rainfall.


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&. Hydropowerhis is the generation of electricity by harnessing the power

of flowing water.

:. cology ; environment restoration

*ater re"uired for maintaining the environmental health of aregion.


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(asin 6 wise water resource project

development

he total land area that contributes water to a river iscalled a *atershed, also called differently as the

)atchment, /iver basin, 9rainage (asin, or simply a

(asin. he image of a basin is shown in 7igure 3.


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2 watershed may also be defined as a geographic area thatdrains to a common point, which ma4es it an attractive

planning unit for technical efforts to conserve soil and

maximize the utilization of surface and subsurface water

for crop production. hus, it is generally considered thatwater resources development and management schemes

should be planned for a hydrological unit such as a

9rainage (asin as a whole or for a >ub1(asin, multi1

sectorially, ta4ing into account surface and ground waterfor sustainable use incorporating "uantity and "uality

aspects as well as environmental considerations.


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ools for water resources planning and

management

he policy ma4ers responsible for ma4ingcomprehensive decisions of water resources planning

for particular units of land, preferably a basin, are

faced with various parameters, some of which are

discussed in the following sections.

3. >upply of water5

a. Water available in the unit

i. /ain falling within the region. his may be utilized

directly before it reaches the ground, for example, the

roof 6 top rain water harvesting schemes in water

scarce areas.


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ii. >urface water bodies. hese static $la4es and ponds% and flowing$streams and rivers%, water bodies may be utilized for satisfying the

demand of the unit, for example by constructing dams across rivers.

iii. +round water reservoirs. he water stored in soil and pores of

fractured bed roc4 may be extracted to meet the demand, for

example wells or tube 6 wells.

b. Water transferred in and out of the unit

If the planning is for a watershed or basin, then generally the water

available within the basin is to be used unless there is inter basin water

transfer. If however, the unit is a political entity, li4e a nation or a state,

then definitely there shall be inflow or outflow of water especially that of

flowing surface water. /iparian rights have to be honored and extraction

of more water by the upland unit may result in severe tension.


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c. Regeneration of water within the unit(rac4ish water may be converted with appropriate technology to

supply sweet water for drin4ing and has been tried in many extreme

water scarce areas. *aste water of households may be recycled, again

with appropriate technology, to supply water suitable for purposes

li4e irrigation.

-. 9emand of water5

a. Domestic water requirement for urban population

his is usually done through an organized municipal water

distribution networ4. his water is generally re"uired fordrin4ing, coo4ing, bathing and sanitary purposes etc, for the

urban areas.


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b. Domestic and livestock water requirement forrural population

his may be done through individual effort of the users by tapping

a local available source or through co1operative efforts

c. Irrigation water requirement of cropped elds

Irrigation may be done through individual effort of the farmers or

through group cooperation between farmers, li4e 7armers?

)ooperatives. he demands have to be estimated based on the

cropping pattern, which may vary over the land unit due to

various factors li4e@ farmer?s choice, soil type, climate, etc.2ctually, the term AIrrigation *ater 9emandB denotes the total

"uantity and the way in which a crop re"uires water, from the time

it is sown to the time it is harvested.


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c. Industrial water needshis depends on the type of industry, its magnitude and the

"uantity of water re"uired per unit of production.


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Canals/unnelshese are conveyance structures for transporting water over long

distances for irrigation or hydropower.

hese structural options are used to utilise surface water to its maximum

possible extent. !ther structures for utilising ground water include

rainwater detentions tan4s, wells and tube wells.

2nother option that is important for any water resource project is

*atershed Management practices. hrough these measures, the water

falling within the catchment area is not allowed to move "uic4ly to drain

into the rivers and streams. his helps the rain water to saturate the soil

and increase the ground water reserve. Moreover, these measures reducethe amount of erosion ta4ing place on the hill slopes and thus helps in

increasing the effective lives of reservoirs which otherwise would have

been silted up "uic4ly due to the deposition of the eroded materials.


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Management tools for water resource

planning

he following management strategies are important for water resourcesplanning5

C*ater related allocation;re1allocation agreements between planning

units sharing common water resource.

C >ubsidies on water use

C 8lanning of releases from reservoirs over time

C 8lanning of withdrawal of ground water with time.

C 8lanning of cropping patterns of agricultural fields to optimize the

water availability from rain and irrigation $using surface and;or

ground water sources% as a function of timeC )reating public awareness to reduce wastage of water, especially

filtered drin4ing water and to inculcate the habit of recycling waste

water for purposes li4e gardening.


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as4s for planning a water resources project

he important tas4s for preparing a planning report of a waterresources project would include the following5

C 2nalysis of basic data li4e maps, remote sensing images,

geological data, hydrologic data, and re"uirement of water use

data, etc.C >election of alternative sites based on economic aspects

generally, but 4eeping in mind environmental degradation

aspects.

C >tudies for dam, reservoir, diversion structure, conveyance

structure, etc.

C >tudies for local protective wor4s 6 levees, riverban4

revetment, etc.


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C 7ormulation of optimal combination of structural and

non1structural components $for projects with flood

control component%.

C conomic and financial analyses, ta4ing into account

environmental degradation, if any, as a cost.

C nvironmental and sociological impact assessment.


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Punjab

he public irrigation infrastructure in the 8unjab consists of 3& barrages

- siphons across major rivers

3- lin4 canals and -& major canal systems over an

aggregate length of &:,ystem. It serves an area of D.


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Sindh

3: publicly owned irrigation systems, which receivewater from three barrages across the /iver Indus.

hese systems, with an aggregate length of 3D,''' 4m

of canals, serve an area of about indh, which serve a total area of over &.< million

hectares and have an aggregate length of about :,D''

4m.


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5*5

< publicly owned irrigation systems in the Indus (asin, whichserve

a total area of '.&: million hectares. hese systems receive

water from two headwor4s across /iver >wat and *arsa4

9am. In addition, there are six other canal systems, whichserve a total of '.3& million hectares of land.

2lso has over -'' canals called Gcivil canalsG, which are

community or privately owned. hese irrigate an aggregate

area of '.D& million hectares.

here are four surface drainage systems in 8 comprising of

:


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Balochistan

(alochistan has two canal systems, which receivewater from the Indus (asin >ystem through +uddu

(arrage and >u44ur (arrage, located in >indh. hese

canal systems serve a total area of '.&& million

hectares. !ne of these, the 8at7eeder )anal >ystem, has been improved recently. In

addition, there are :&3 independent publicly owned

small irrigation schemes, which serve '.3: million

hectares. here are a few privately owned smallirrigation schemes too.

= d t f


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=round,ater usage forirrigation

2n estimated :3. M27 of groundwater is pumpedannually in 8a4istan.

2ccording to a study, more than F' of the extracted

groundwater is used for

irrigation purposes. +roundwater reservoirs are

recharged from the rivers as

well as the seepage losses from the canals,

watercourses, farm channels and the fields.

irrigation engg lec 01

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