IRRIGATION ENGINEERING

Hello friends ah welcome to the The Aimers course ah on irrigation and drainages.

So, I am Devraj, um I am an assistant professor in agricultural

and food engineering department. So, ah in this course the highlights of the course includes so, we going to ah have two

modules. So, one on irrigation, then the other one is on ah drainage.

So, ah and then it is going to be 12 weeks course and each week we are going to cover

5 ah 30 minute ah lectures. So, all together it will be like 60 lectures and also we going to have a tutorials on GATE

ICAR JRF problems at the end of each ah ah week so; that means, the 5th lecture in a

week ah will contain the tutorials. So, that will be will be talking about ah solving some GATE or ICAR JRF ah I mean problems.

So, then ah it it contains assignments ah to give hands on you know training to the

ah students and also the quizzers So, update the ah the course or other to update

the previous weeks, you know the syllabus of previous weeks course content.

And then a online discussion, if you have any questions or any enquires. So, we can ah have like ah discussion online.

So, then we going to have two technical assistants ah to ah support in this discussion so, they

are ah my phd students. ah So, what exactly the you know irrigation and

drainage. So, if you see in the ah agriculture fields.

So, the two cases you can really see in, the first case there is a dry fields and the other

case will be like a wet field contains some water pounded on surface. So, in case of ah dry case.

So, it does not means that the water is not there, in a ah in the surface or definitely

there is a water within the soil profiles. So, that is called the groundwater. So, if the groundwater is needed to the surface and the plants are grown in the fields.

So, you need not give irrigation to the plants because, plants can extract water from the

root zone, or from the water table ok. So, ah since the water table is you know deeper.

So, we need to give water artificially on the surface. So, that the water will penetrate into this ah soil and available to the plant whereas,

ah in other case. So, that is ah and in drainage case what happens the fields are pounded with water always.

So, in order to grow crops in that particular you now ah piece of land, you need to take

up the water excess water from the surface. So, how do you do that, you can either you can provide the channel, or or they cut the

field on the surface or you can provide some ah you know the subsurface drainage pipes

So, that the water will penetrate all the way though this and then ah.

so, so that is the major difference between irrigation and drainage.

So, the irrigation case you provide ah water artificial on this soil surface whereas, in

the drainage case you take out the excess water, which is pounded on the surface ah

by providing ah the detailed drainage in the surface I mean underground.

So, a in the both cases so, all object is to ah to give suitable you know environment

to the plants to grow. So, that is the major goal in both irrigation and drainage.

So, the landing out come in this ah course includes, ah the to understand irrigation

and drainage principles this is important to understand, or to design an irrigation

or drainage system. And to design ah gravity and pressurized irrigation systems.

So, if you are talking about irrigation so, will be surface irrigation where you provide

water on the surface ah by gravity force, you need not use any pump to pump the water,

where as in pressurized irrigation system for example, in case of micro irrigation or drip irrigation you need to pressurized the irrigation.

So, that water can penetrated to the the smaller forces ah which is in the dripper or you can

say this sprinklers ok, you need pressure for that. And to understand the groundwater hydraulics So, this is important to understand how water

flows ah from you know the surface to the drains in case of drainage.

And to design surface in subsurface drainage systems so, once you understand the governing equations and the principles.

So, you will able to design surface in subsurface drainage systems.

And to familiar with some irrigation drainage models so, there are models available to ah

simulate irrigation and the drainages ah cases. So, we are doing to discuss about those and to know about water lifting devices and pumps.

So, you have water undergrounds so, how to tab the water using ah and pumps. So, that we are going to in this.

And the reference books ah there are seven reference books available, but mostly we will

be focusing on ah on ah I mean. So, this irrigation theory and practice ah by A. Michael and, then land dryness which

is by ah Bhattacharya and Michael. And there are other foreign ah additions you can go through.

So, ah in order to you know understand the principles yeah.

This a sustainable development so, if you are coming into the introduction. So, are the efficient management of water is challenging in India because, the water

tables is getting declining day by day ah due to the over exploitation of water for

drinking and irrigation purposes. So, that really burden a farmer to tap water from the deeper, you know ah aquifers, so

and also ah incomplete or major and medium irrigation projects. So, the many projects are ah you know under construction, or even in the pending projects

so, because of in political or you know financial status. So, they are not able to you know finish in time.

So, and very slow increase in gross irrigated area so, in in in every budget so, in the

government budget you are providing lot of you know ah funds for irrigation, but the

the thing is the amount of funds you are pouring in irrigation, it is not helping in increasing the ah gross irrigated area.

And then ah the quality of water in rivers and lakes are degrading day by day and increasing

water conflicts. So, it is not only within India and across the ah in the country, countries like neighboring

countries for example, ah India and Pakistan, India and ah Nepal India and Bangladesh.

So, you have lot of water conflicts and with in India for example, ah Tamilnadu and Karnataka

Maharashtra and Andhra so, there ah now Telanganna. So, the conflicts are increasing so, because of this.

So, the water management is really challenging in India.

Then ah though India has 16 percentage of world's population, but as only four percentage of the total available fresh water if you see this table.

So, we have ah like the annual precipitation, we receive from ah rain fall including snow

fall. So, around four thousand kilometer cube, but ah the average annual potential flow in rivers.

So, this only 50 percent almost 50 percent is of that and utilizable water resource could

be 28 percentage deserve annual precipitation and, surface and ah ground water is kind of

you know ah like 70 percent.

You see the ah water availability or water resources in India so, we are receiving the

annual precipitation about 400 kilometer cube, ah the average potential flow ah in rivers

is almost a 50 percent ah whereas, the estimated you know utilizable water resources.

So, that is about 28 percentage deserves ah annual precipitation ah volume and, the utilizable

is classified as surface and ground water resources. So, the surface water resources are around 60 percent ah and, where as ground water about

40 percent something like that and

ok ok. So, the next is per capital water availability in India. So, this table shows ah per capital water availability which is declining ah but ah

with increasing population. But ah if you see this as per the international norms ah per capita water availability, if

it is less than ah I mean if it less than 17000 metric cube per year per capita, the

country is under water stressed. If it is less than ah 1000 metric cube per year the country is water scarce.

So, if you see this numbers we are going to heat ah the water stressed condition and,

in feature the water scares ah condition very soon.

And the irrigation potential of water so, the total geographical area of India is 329

million hectares and, the net sown area 141 million hectares is 43 percentages of 329

million hectares. So, this is ah what ah the net sown area. So, ah and then the gross irrigation area.

So, that is ah 87.23 million hectares and the net irrigated area 62.31 million hectares

so, the so the gross irrigated areas. So, net irrigated area the difference is [vocalized-noise so, in case of gross irrigated area.

So, you will be counting this crop which is grown in a repeatedly in a particular year.

So, and the productivity which is under irrigated condition 2.5 ton per hectares and whereas,

in rainfed condition 0.5 ton per hectares, so which is ah very low compare to the irrigated

condition. So, you can understand the irrigation potential here. So, ah and and and the importance of irrigation is.

And the food grain availability if you see around 523 gram per capita per day available

ah these days. So, productivity of cereals in India, if you see this is rice ah is consuming you know

almost double the water required ah for other crops, around 120 centimeter whereas, look

at the yield. So, yields are all of pretty much same ah the water productivity definitely will be

less in the case of rice because, it consuming lot of ah water. So, the irrigation here what is exactly the irrigation, irrigation is artificial application

of water to the plant ah to the soil, in order to ah grow the crop profitively ok.

So, and then irrigation water generally applied when there is no rainfall, or groundwater

sources. And the main concerns in irrigation is when to apply, how much to apply and how to apply.

So, these three things are very important when you decide, or when you schedule an irrigation

to a plant. So, the benefits of irrigation that includes. So, irrigation ah developments has played a key role ah in fist of all in strengthening

economy because, the irrigation means what ah I mean ah you are applying water for the

benefit of the crop; so indirectly you are I mean directly you are producing a crop so

that will influence the economy. So, if you have more gains produces having more profits and the it strengthen the economy

and then increasing employment opportunity. So, when the crop production is more, it is definitely drives the you know rural youth

in to the ah into the agro business and definitely the employment opportunity will increase.

And the self sufficiency in food production if you see, um the food production you have

lot of water and there will have food production so so, that the sufficiency food will be ah

attained And the other benefits ah could be like rise of a crop where, nothing would grow otherwise.

So, suppose if you have lot of water you can grow in deserts ok grow, grow crop in even

deserts deserts. So, and grow a more profitable crop suppose, ah if you are comparing alpha alpha which

is the fodder crop you put lot of water for fodder crop. So, instead of that the water the same water is use to grow a profitable crop like a wheat.

And increase the yield ah and a quality of given crop. So, the definitely you are not making any water stress condition and the quality of

the crop will improve improve and and also the produce will improve. So, ah increase the aesthetic value of the landscape.

So, you have lot of water, then you can use it for landscaping and and also the greenery

other greenery purpose so, that the landscape will be green and, definitely that improves

the aesthetic value. So, another other benefits will be the leaching of salts, if you have problems with salts

in soil and you have lot of water, then you can you know use water to leach out the salts

into the soil. And wind erosion can be controlled by applying you know water on tops.

So, that that will make the ground wet and wind cannot blow this soil particulars.

And multiple cropping during an year so, and you can grow like a not not single crop, you

can grow like a 3 crops or 2 crops in a year. And provides jobs already discussed and reduces risk of crop failures.

So, because you are not you know making ah crops under water stress condition defiantly

that will improve the crop condition and and no risk of crop failures.

ah Improves socioeconomic conditions. So, definitely that will help the rural population in income generation and increase this socioeconomic

condition. So, disadvantages of irrigation if you have you know lot of water and excess irrigations

so, it going to decrease the crop yield because, so like if if if you put lot of water what

happened ah the the the crop roots will be under wet condition always and and and the

water, which is on standing on the surface will act has a barrier and it cannot ah you

know help help out any oxygen which is on this surface go into the soil.

And there by ah definitely the crop ah yield is going to reduce because, the roots require

the oxygen. So, if you are not you know if you are making oxygen stress condition definitely the crop,

yield is going to decrease and the leaching transport of chemicals. So, the salt are in any other chemicals can be ah leached into the ah groundwater or transport

into the surface waters. For example, ah you have sorry for for example, you have ah pesticides or fertilizers.

So, yield reduction ah can be happen if you have a deficit irrigations. So, no only excess irrigation, even if you reduces irrigation so, that is called deficit

irrigation and yield definitely going to reduce. And then water logging and salinity could be a problem say for example, here if you

see the field ah so, the water is really pounding on the surface not allowing you know oxygen

enter into the soil it is it is not a irritated condition. So, it is not favorable to the plants and if you see this ah image, ah Indian image

so, the ground water with drool as percentage of recharge. So, the mostly the Punjab, Haryana, Delhi and Rajasthan, they withdraw ground water

more than the recharge. So, it really it is ah ah alarming situation the groundwater table is really defeating

ah deeper deeper into the ah soil. So, the types of irrigation projects if you see in India.

So, they are classified into three major classes one is the major ah irrigation projects.

So, if the irrigation potential is greater than 10000 hectares and, then ah cost of project

is more than 5 [FL] so, then you can say that the project is like a major irrigation project.

And the in the case of medium irrigation projects the irrigation potential is about 2000 to 10000 hectares.

So, that is irrigation potential and the cost of project ah will be like 258 to 50 lakhs.

ah And the minor irrigation projects which will have a the irrigating potential less

than 2000 hectares and, the cost of project which will be ah less than 25 lakhs.

So, the surface irrigation system if you see for example, ah if you have ah you know forever

irrigation, border irrigation, basin irrigation, all are called surface irrigation systems, if you see the status of surface irrigation systems in India.

So, the water is used for a gross irrigated area of 87 million hectares is 541 kilometer

cube ah under surface irrigation systems. So, and the gross water used if you see the water would the water which is applying on

ah top of the surface. So, that is 1.45 meter in case of surface irrigation which is greater than the united

states, ah I mean where where the united states practice ah on the surface irrigation which

is point nine meter. So, we are putting lot of water on top of the surface, ah compare to the united states,

in case of surface irrigation systems. So, the overall irrigation if you since in the country is 38 percent so; that means,

100 mm you are supplying to the field only 38 mm of water is being taken into the ah

by the plant, or by the form. And if you see ah the ah I mean other river basics like Krishna, Godavari, Cauvery and

Mahanadi systems have very low ah ah efficiency of around 27 percent whereas, Indus ganga

systems are doing better than the ah the Krishna, Godavari, Cauvery and the efficiency is improved

like 43 to 47 percent because, they have well structured water release systems called Warabandi

for example. So, the pressurized in case of pressurized irrigation systems ah like drip irrigation

sprinkler irrigation systems. So, drip irrigation saves 25 to 60 percentage of water and increase yield up to 60 percentage.

Have a sprinkler irrigation saves 25 to 33 percentage of water. So, the net irrigation under drip irrigation is 0.5 million hectares and the sprinkler

is 0.7 million hectares, though we we have a target of about 10 percentage of you know

gross irrigated area needs to be under ah ah brought under you know ah micro irrigation

or pesticide irrigates systems. So, the Maharashtra is being the largest, ah ah I mean ah micro irrigation micro irrigation

system practice state. ah ah So, this ok and then and then reasons for low irrigation efficiency.

So, if you see this irrigation efficiency surface irrigation ah is about you know 30 to 40 percent, but what is really causing the a low irrigation efficiency if you see.

So, the mostly the unlined canal systems with excessive seepage so, cannot system we have

is mostly unlined. . So, the water which is being delivered from the canal to field level, is been last through

seepages or vaporization mostly. So, then lack of field channels the channels so, you have ah very ah you know ah properly

designed field channels required, for a ah delivering water efficiency to the ah fields.

And then lack of canal communication network, you do not have canal communication network and you do not know when to you know release water for a particular, ah you know the area

or command area. So, if you do not know power communication definitely ah the the scheduling will be you

know faster or lower, or or one day early or one day you know delay can be happened.

So, that really causing the low irrigation efficiency. And the lack of field drainage this another important thing is so, the excess water you

are taking out, or the excess water which is accumulating on the surface needs to be

you know taken out from the fields for that the field drain drainage is requires. So, that is really lack.

And improper field leveling this is also very important in order to you know ah increase

the uniformity of in founded distribution of the water. And the price of water right know it is no, or in a very less.

So, this needs to be improved in this case. So, irrigation some of the irrigation terminology if you see the gross command area so, that

is a total area that includes ah roads farmstead, the line between drainage boundaries which

can be irrigated by a canal system. So, you have like a like a boundary ah suppose you so, you you have the water ah spread like

this is the ah drainage boundaries for example, these are the two drainage boundaries.

And you can have this area, you know is something roads, or you you have some trees so, everything.

So, you have some farmsteads ok. So, this is called gross command area, but if you are only I mean ah accounting you were

only accounting so, the farm lands. So, that is culturable command area. So, this what culturable command area so, the gross command area.

So, contains ah both so this is culturable command area and the other area which is not

culturable so, it is called unculturable command area. So, this ah some of these 2 ah will be 2 gross command ah area.

. So, has they said the culturable command area this includes, ah I mean gross command area, without unculturable command area such as

unfertile barren land, alkaline soil, local ponds, villages other area such as habitations

ok. So, then ah the intensity of irrigation so, this the ratio of irrigated to irrigable,

or irrigable area. You have some area available ah for irrigation, but based on your water availability water

resources so, you decided to irrigate part of that land and so, that ratio ratio of irrigated

land to irrigable land will give the intense of irrigation. And water tanks are really dug areas which can be useful to store the excess rain water.

And outlets or kind of you know ah head regulator of the field level, to deliver water to the

ah you know fields real fields. And water logged areas this is an agricultural land it said to be water logged.

When productivity of fertile ah or fertilities affected by high water table. So, in this case what happens water table rises up.

So, always you can see the water on the surface and, the field capacity it is the water contain

held in the soil after excess water ah as drained and plants can extract sufficient

water from the soil for it is plant growth. So, if you see ah ah when there is a rainfall heavy rainfall, ah there will be lot of water

which is standing on the surface and, but if you go next day morning the water will

be ah receding slowly and you you may not be seen water on the on the surface.

So, where the water as gone somewhat the water as gone escape through you know ah over land

flow, or through deflagration so, the water but still the soil contains some water. So, the amount of water which is available ah during the time ah or after 1 or 2 days

of heavy rainfall is called the field capacity. So, and then the permanent wilting point ah the wilting coefficient or permanent wilting

point So, the water contained at which plants can no longer extract sufficient water from the soil for it is plant growth.

So, here so, ah at this ah the water which is available in the in the soil particulars,

soil which is not extracted by this plants. So, when the plant show wilting nature ok.

And this we will discuss more on these the ah upcoming lectures. And the crop ratio the crop ratio generally so, we have two crops seasons here ah Kharif

and Rabi season. So, the crop ratio could be so, we are ah I mean tracking the whole year.

ah So, the the cultivable area under different crops during different seasons in a crop year

is called the crop ratio for example, you are cultivating rice in Kharif and Rabis.

So, the ratio of cultivable area during Rabi and Kharif will give the crop ratio.

And the crop period so, the number of days between sowing to the harvesting of crop is crop period.

And base period is a period ah of ah I mean water application, or the first watering to

the last watering or before harvesting. And the live storage dead storage ah and then ah ah gross storage.

So, these three terminology belong to the ah you know you have a ah reservoirs ok.

So, live storage is complete is water complete water stored in the reservoirs between full

ah reservoir level and at storage level. So, this water is really available ah for you know usage and the dead storage whereas,

the stored reservoir between the lowest supply level to the deep deepest river bed ah level,

which is 10 percentage reserve for ah GS or a gross storage whereas, gross storage is

the storage capacity between full water reservoir level and the deepest reservoir level.

. So, if you see this the gross ah storage which is equal to ah you know live storage plus dead storage whereas, he if you considering

the ah 10 percent ah 10 percentage of GS. So, you have 0.1 GS so, which is equal to so, GS which is equal to LS plus ah 0.1 GS,

if you take GS out where you had 0.9 GS equal to LS and GS is equal to LS by 0.9.

So, this is the way we we got this equation ok.

So, ah so, next is delta.

So, what is delta? Delta is a total depth of irrigation water required by a crop during the cropping period

here, we are talking about the base period ok. So, so, that is first water application to the last water application before harvesting

so, this is total depth of water you have providing to the crop during the base period.

So, suppose if a crop required about 12 irrigation ok of 10 centimeter depth.

So, ah then ah so, 12 irrigations 10 centimeter depth so, that gives you 12 multiplied by

10 centimeter so, that will give 120 centimeter of ah ah depth of water you provided during

the ah base period. So, this is called delta. So, 120 centimeter, or 1.2 is a delta ok.

So, and then suppose if the area under the crop is A hectare the total water require

would be 1.2 multiplied by area over the period of 120 days. So, this is the simple calculation receive.

And the other terminology is called duty, so, which is hectare per cumic cumec.

So, cubic meter per second so, the amount of the volume of water you are utilizing,

ah or the area you irrigated for unit volume of water. So, that is that is called ah duty.

So, it is the ratio between the irrigated crop area and the quantity of irrigation water

required during the base period. So, the definition is clear, suppose if you have ah suppose if you have three ah cumec

of irrigation of water, which is required for crop sown over an area of 5100 hectares.

So, the so, this is this is what this is the volume of water so, you are using right.

So, and then this is the area and the duty will be the area divided by the volume you

are using. So, that will be 1700 hectares cumec and 3 cumec ah discharge would be required throughout

the base period. So, do not forget this. So, we are targeting the base period, whatever you are ah using so, this 3 cumec per.

So, you are continuously supplying during the base period.

So the value of duty be different at the head of the watercourse, or at the head of the

distributors. So, that this is because they will lot of losses, if you constrain. So, relationship between duty and delta if you see so, the delta ah is equal to 8.64

B divided by D. So, how do you get that so, duty generally

duty is equal to hectare divided by cumec it is a cube cubic meter per ah second.

So, hectares is a 10 power 4 meter square ah and cubic meter, suppose this is cubic

meter into second ok. So, the 10 power 4 meter square for meter cube ah multiplied by you can convert that

in days. So, that will be ah 8.64 into 10 power minus four less days.

So, you get like you know ah this is ah 10 power 10 power gets cancels out and meter

square meter square this is ah meters so, 8.64 into base period lecture and this base

period and meters this is delta so, that is D. So, you finally, you get delta is equal

to 8.64 B by D. So, this is this is D ok yeah.

So, it is these these are the units you get.

So, example if you see here. Suppose if you have an if you have an irrigation canal, which has ah GCA which is gross ah

command area that is 80000 hectares out of which 85 percent is culturable ah area so;

that means, you have total area, but only 85 percent is culturable area the intensity of irrigation for Kharif season is 30 percent out of this culturable area, only 30 percent

for Rabi season a sorry Kharif season for Rabi season is 60 percent ok.

And find the discharge required at the head of the canal, if the duty duty is given for

the Kharif season and for Rabi season ok. So, this is the the problem.

So, since the GCA is given so, how do you solve this basically.

So, ah in order to solve that ah sorry ok solution here.

So, the culturable command area if you see 80000 ah multiplied by 0.85 because 85 percent

is the culturable area you got culturable area 68000 hectares and then area under Kharif

season out of this culturable area only 30 percent is Kharif season. So, ah multiplied by 0.3 you get 20400 hectares this is irrigated, This is during Kharif season

similarly for Rabi season you get 40800 hectares. So, water required at the head of the canal to irrigate during ah Kharif season is so,

area divided by I mean ah the cumec . so, area divided by cumec you get ah 25.5 cumecs

ok. And then ah ah Rabi season you get ah ah 40800 divided by 1700 cumec.

So, that will be 24 into cumec so, if you see this so this one so this number so, how

you get this. So, this is area ok divided by so, duty is given.

So, area divided by duty so, duty. So, that will give area and hectares divided by duty.

So, that will be in ah hectares divided by cumec right.

So, then you get cumecs this is what you got fine.

So, so how to decide which one you really want to go with like 25.5 cumecs or 24 cumec.

So, so general thumb rule is you always go with ah higher you know ah the the discharge.

So, that it can serve both Rabi and Kharif season. ah Whereas, example to the watercourse has a

culturable command area 2600 hectares out of which the intensities of irrigation ah

for perennial sugarcane and rice crops of 20 percent 40 percent respectively ok. So, here the intensity of irrigation is given.

So, intensity of irrigation so; that means so, you have a irrigable area, but only part

of that is irrigated for example, here 20 percent for a sugarcane and 40 percent for

rice crop respectively ok. The duty of these crops at the head of the watercourse 750 hectares per cumec this is

duty is given for both cases and, the discharge required the head watercourse, if the peak

demand is 20 percent higher than the average water requirement. So, it is similar to the previous example, ah if you see this ah ok the solution here

if you see area under sugarcane. So, let us say so, you have 2600 hectares, but 20 percent is ah you know ah irrigable

land ah sorry ah irrigated land. So, that is 550 hectares under sugarcane.

And similarly under rice ah 40 percent So, that is 10 50 hectares and water required

for sugarcane will be so, 500 hectares divided by duty you get ah you know 0.694 cumec.

And similarly for rice 0.577 cumec and so, if you see this since sugarcane is perennial

crop so; that means, you need to supply water throughout the year and rice requires you

know one season. So, here ah I mean what is the decision like ah ah I mean what water needed to provide.

So, since sugarcane is perennial crop so, you need to some of these like sugarcane ah

as well as ah I mean rice rice crop the water required for sugarcane and rice can be combined

and, you will have the maximum water which is required ah that the total discharge during

the year is 1.271 comecs ok.

Hence the peak design is charged if you see this ah 20 percent higher than. So, you can ah put like 20 percent 120 percent now.

So, here you have 1.2 so, that will be 1.52 ok.

So, thank you for this ah lecture this is the first lecture and we are doing to cover ah more on the the following lectures ah so.

Thank you.