Hello friends welcome to the NPTEL  course on Irrigation and Drainage. So,  

I am Damondhara Rao Mailapallli, I am an  assistant professor in Agricultural and Food  

Engineering Department IIT Kharagpur. So, in this course the highlights of the course  

includes; so, we going to have two modules.  So, one on irrigation, then the other one is on  

drainage. So, and then it is going to be 12 weeks  course and each week we are going to cover 5, 30  

minute 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 week  so that means, the 5th lecture in a week will  

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

problems. So, then it contains assignments to  give hands on you know training to the students  

and also the quizzes. So, update 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 have like  discussion online. So, then we going to have two  

technical assistants to support in this discussion  so, they are my Ph. D. students.  

So, what exactly the you know irrigation and  drainage? So, if you see in the agriculture  

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

the other case will be like a wet field  contains some water ponded on surface.  

So, in case of dry case; so, it doesn t means that  the water is not there, you know in the surface  

or definitely there is a water within the soil  profiles. So, that is called the groundwater. So,  

if the groundwater is nearer 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, 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 soil and available  

to the plant. Whereas, in other case. So, that  is in drainage case what happens the fields are  

ponded with water always. So, in order to grow  crops in that particular you now piece of land,  

you need to take out the water excess water from  the surface. So, how do you do that, you can  

either you can provide the channel, or they cut  the field on the surface or you can provide some  

you know the subsurface drainage pipes So, that the water will penetrate all the way  

though this and then ok so so, that is the major  difference between irrigation and drainage. So,  

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

you take out the excess water, which is ponded on  the surface by providing the by providing the tile  

drainage in the surface I mean underground. So, in the both cases so, our object is to to  

give suitable you know environment to the plants  to grow. So, that is the I mean the major goal in  

both irrigation and drainage. So, the learning  out come in this the course includes, the to  

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

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

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

water on the surface by gravity force, and 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 smaller  

pores 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 from you know the surface to the drains  in case of drainage. And to design surface and  

subsurface drainage systems so, once you  understand the governing equations and  

the principles. So, you will able to design  surface and subsurface drainage systems. And  

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

simulate irrigation drainages cases. So, we are going to discuss about those  

and to know about water lifting devices and  pumps. So, you have water undergrounds so,  

how to tap the water using the pumps. So,  that we are going to learn in this.  

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

be focusing on on I mean; So, this Irrigation  Theory and Practice by a A. M. Michael and,  

then Land drainage which is by Bhattacharya  and Michael. And there are other foreign  

editions you can go through. So, in order to  you know understand the principles.  

Yeah sustainable development so, if you  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 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 aquifers; So, and also incomplete  

or major and medium irrigation projects. So, the many projects are you know under  

construction, or even in the pending projects  so, because of you know 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 every budget so,  in the government budget you are providing lot  

of you know funds for irrigation, but the thing is  the amount of funds you are pouring in irrigation,  

it is not helping in increasing the gross  irrigated area. And then the quality of  

water in rivers and lakes are really degrading  day by day and increasing water conflicts.  

So, it is not only within India and across the  in the country, countries like our neighboring  

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

you have lot of water conflicts and within  India for example, Tamil Nadu and Karnataka,  

Maharashtra and Andhra so, there now  Telanganna. So, the conflicts are increasing so,  

because of this. So, the water management  is really challenging in India.  

Then though India has 16 percentage  of world s population, but has only  

four percentage of the total available  fresh water if you see this table.  

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

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

only 50 percent almost 50 percentage of that and  utilizable water resources could be 28 percentage  

of annual precipitation and, surface and ground  water is kind of you know like 70 percent.  

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

the annual precipitation about 4000 kilometer  cube, the average potential flow in rivers is  

almost 50 percent whereas, the estimated you  know utilizable water resources. So, that is  

about 28 percentage of annual precipitation  volume and, the utilizable is classified as  

surface and ground water resources. So, the surface water resources are  

around 60 percent and, whereas ground water  about 40 percent something like that and  

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

water availability which is declining but  with increasing population.  

But if you see this as per the international  norms per capita water availability, if it  

is less than I mean if it less than 1700 metre  cube per year per capita, the country is under  

water stressed. If it is less than 1000 metre  cube per year the country is water scarce. So,  

if you see this numbers we are going to hit  the water stressed condition and, in future  

the water scares 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 which is 43 percentages of 329  million hectares. So, this is what the net sown  

area; So, and then the gross irrigation area. So, that is 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, 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. Which is  

very low compare to the irrigated condition. So,  you can understand the irrigation potential here  

so and the importance of irrigation is. And the  food grain availability if you see around 523 gram  

per capita per day available these days. So, productivity of cereals in India, if you see  

this is rice is consuming you know almost double  the water required for other crops, around 120  

centimeter whereas, look at the yield. So, yields  of pretty much same but the water productivity  

definitely will be less in the case of rice  because, it consuming lot of water.  

So, the irrigation here what is exactly  the irrigation, irrigation is artificial  

application of water to the plant to the soil,  in order to grow the crop profitably 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 development has played a key role in first of all in strengthening economy  

because, the irrigation means what I mean  you know 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 grains produces it will more  

profits and the it strengthens economy and  then increasing employment opportunity. So,  

when the crop production is more, its definitely  drives the you know rural youth in to the into  

the agro business and definitely the  employment opportunity will increase.  

And the self-sufficiency in food production if you  see, the food production if you have lot of water  

and there will be lot of food production so, that  the sufficiency food will be attained.  

And the other benefits could be like raise of  a crop where, nothing would grow otherwise. So,  

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

and grow a more profitable crop suppose, if you  are comparing alfalfa which is fodder crop you  

put lot of water for fodder crop. So, instead of  that the water the same water can be use to grow  

a profitable crop like a wheat. And increase  the yield and a quality of given crop. So,  

definitely you are not making any water stress  condition and the quality of the crop will improve  

and also the produce will improve. So, increase  the aesthetic value of the landscape. So, you have  

lot of water, then you can use it for landscaping  and also the greenery other greenery purpose so,  

that the landscape will be green and, definitely  that improves the aesthetic value.  

So, and then 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 particles.  

And multiple cropping during an year so,  and you can grow like a 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  

crops under water stress condition definately  that will improve the crop condition and and no  

risk of crop failures; 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 irrigation so,  

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

water what happened the crop roots will be  under wet condition always and the water,  

which is on standing on the surface  will act has a barrier and it cannot  

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

And there by definitely the crop 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 leached into the groundwater  or transport into the surface waters.  

For example, you have sorry for example, you have  pesticides or fertilizers. So, yield reduction can  

be happen if you have a deficit irrigations. So,  not 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 so for example, here if you see the field  

so, the water is really ponding on the surface not  allowing any you know oxygen enter into the soil  

it is it is not a aerated condition. So, it is not  favorable to the plants and if you see this image,  

Indian image so, the ground water withdrawal as  percentage of recharge. So, the mostly the Punjab,  

Haryana, Delhi and Rajasthan, they withdraw ground  water more than the recharge. So, really it is  

alarming situation the groundwater table is really  depleting deeper deeper into the soil.  

So, the types of irrigation projects if  you see in India. So, they are classified  

into three major classes one is the major  irrigation projects. So, if the irrigation  

potential is greater than 10000 hectares and,  then cost of project is more than 5 cr 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 will  be like 25 to 50 lakhs. And the minor irrigation  

projects which will have a the irrigating  potential less than 2000 hectares and, the cost of  

project which will be less than 25 lakhs. So, the surface irrigation system if you see for  

example, if you have you know furrow 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 used for a gross irrigated area of  87 million hectares is 541 kilometer cube under  

surface irrigation systems. So, and the gross  water used if you see the wat the amount of  

water which is applying on top of the surface. So,  that is 1.45 meter in case of surface irrigation  

which is greater than the united states, I  mean where the united states they practice on  

the surface irrigation which is 0.9 meter. So, we are putting lot of water on top of the  

surface, compare to the United States, in case  of surface irrigation systems. So, the overall  

irrigation efficiency 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 by the plant, or by the farm.  

And if you see the I mean other river basins  like Krishna, Godavari, Cauvery and Mahanadi  

systems have very low efficiency of around 27  percent whereas, Indus ganga systems are doing  

better than 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 like drip irrigation  

sprinkler irrigation systems; So, drip irrigation  saves 25 to 60 percentage of water and increase  

yield up to 60 percentage. Whereas 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 have a target of about  10 percentage of you know gross irrigated area  

needs to be under brought under you know micro  irrigation or pesticide irrigates systems.  

So, the Maharashtra is being the largest, I  mean micro irrigation micro irrigation system  

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

If you see this irrigation efficiency surface  irrigation is about you know 30 to 40 percent,  

but why what is really causing the low  irrigation efficiency if you see. So,  

the most is the unlined canal systems with  excessive seepage so, cannal system we have  

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

lost through seepages or evaporation mostly. So, then lack of field channels the channels so,  

you have very you know properly designed  field channels required, for a delivering  

water efficiently to the fields. And then lack  of canal communication network, you don t have  

canal communication network and you don t know  when to you know release water for a particular,  

you know the area or command area. So, if you don t have proper communication  

definitely the scheduling will be you know faster  or slower, 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 increase  

the uniformity of uniformly distribution of the  water. And the price of water right know it is no,  

or you know 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 roads farmstead, the  lying between drainage boundaries which can  

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

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

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

you have some farmsteads ok. So, this is called  gross command area, but if you are only conc  

I mean accounting you 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 both so  

this is culturable command area and the other  area which is not culturable so, it is called  

unculturable command area. So, this sum of these  two will be the gross command area.  

So, as I said the culturable command area this  includes, 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 the intensity of irrigation so,  

this the ratio of irrigated to irrigable, or  irrigable area. You have some area available  

for irrigation, but based on your water  availability water resources so, you decided  

to irrigate part of that land and so, that ratio  the ratio of irrigated land to irrigable land  

will give the intensity of irrigation. And water tanks are really dug areas which  

can be useful to store the excess rain water. And outlets are kind of you know head regulator  

at the field level, to deliver water to  the fiel you know fields real fields. And  

water logged areas this is an agricultural  land it said to be water logged.  

When productivity of fertile 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 content  held in the soil after excess water has drained  

and plants can extract sufficient water  from the soil for its plant growth.  

So, if you see when there is a rainfall heavy  rainfall, there will be lot of water which is  

standing on the surface and, but if you go in  the next day morning the water will be receding  

slowly and you may not be seeing the water on the  on the surface. So, where the water has gone so  

the water has gone escape through you know over  land flow, or through deep percolation,so, the  

water but still the soil contains some water. So, the amount of water which is available during  

that time or after 1 or 2 days of heavy rainfall  is called the field capacity. So, and then the  

permanent wilting point the wilting coefficient  or permanent wilting point so the water content  

at which plants can no longer extract sufficient  water from the soil for its plant growth. So,  

here so, at this the water which is available  in the the soil particles soil which is not  

extracted by this plants. So, then the plant  show wilting nature ok. And this we will discuss  

more on these in the upcoming lectures. And the crop ratio the crop ratio generally so,  

we have two crops seasons here Kharif and Rabi  season. So, the crop ratio could be so, we are I  

mean tracking the whole year. So, 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 Rabi. 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 of I  mean water application, or the first watering to  

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

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

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

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

dead storage whereas, the stored reservoir  between the lowest supply level to the deep  

deepest river bed level, which is 10 percentage  of GS or a gross storage whereas, gross storage  

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

So, if you see this the gross storage which is  equal to you know live storage plus dead storage  

whereas, if you considering the 10 percent  10 percentage of GS. So, you have 0.1 GS so,  

which is equal to so GS which is equal to LS plus  0.1 GS, so if you take GS out then you got 0.9  

GS equal to LS and GS is equal to LS by 0.9. So,  this is the way we got this equation ok.  

So, so next is delta. So, what is the delta?  So 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 the total depth of water you are  providing to the crop during the base  

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

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

so, that will give 120 centimeter of depth of  water you provided during the base period. So,  

this is called delta. So, 120 centimeter,  or 1.2 m 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, or the  area you irrigated for unit volume of water. So,  

that is that is called 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 suppose if you have 3 cumec of  

irrigation of water, which is required for crop  sown over an area of fifteen hundred 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 discharge  would be required throughout the base period. So,  

don t forget this. So, we are targeting  the base period, whatever you are using so,  

this 3 cumec per. So, you are continuously  supplying during the base period.  

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

distributors. So, the this is because they  will lot of losses, if you consider. So,  

relationship between duty and delta if you see  so, the delta 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 second. So, hectares  is a 104 power 4 meter square and cubic meter,  

suppose this is cubic meter into second  ok. So, the 104 meter square for meter cube  

multiplied by you can convert that in days. So, that will be 8.64 into 10-4 less days. So,  

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

square meter square this is meters so, 8.64 into base period lets say 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 so this is D ok yeah.  So, these these are the units you can.  

So, example if you see here. Suppose if you have an if you have  

an irrigation canal, which has GCA which is gross  command area that is 80000 hectares out of which  

85 percent is culturable 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 is given for  

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

given so, how do you solve this basically? So,  in order to solve that sorry ok solution here;  

So, the culturable command area if you see = 80000  0.85 because 85 percentage of culturable area so  

you got culturable area 68000 hectares and then  area under Kharif season out of this culturable  

area only 30 percent is Kharif season. So, 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 Kharif season is so, area divided  

by cu I mean the cumec. So, area divided by cumec  you get 25.5 cumecs ok. And then Rabi season you  

get 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 do 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 in hectares divided by duty. So,  

that will be in hectares divided  by cumec right. So, then you get  

cumecs this is what you got fine. So, so how to decide which one really you  

want to go with like 25.5 cumecs or 24 cumec;  So, general thumb rule is you always go with  

higher you know the discharge. So, that it can  serve both Rabi and Kharif season.  

Whereas, example two the watercourse has a  culturable command area twenty 2600 hectares  

out of which the intensities of irrigation  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 is  750 hectares per cumec this is duty is given for  

both cases and, find the discharge required the  head watercourse, if the peak demand is 20 percent  

higher than the average water requirement. So, its similar to the previous example,  

if you see this ok the solution here if you  see area under sugarcane. So, let us say so,  

you have 2600 hectares, but 20 percent is you  know irrigable land sorry irrigated land. So,  

that is 550 hectares under sugarcane. And similarly under rice 40 percent So,  

that is 1040 hectares and water required for  sugarcane will be so, 500 hectares divided by duty  

you get 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 I mean what is the decision like  

I mean what water you need to provide.  So, since sugarcane is perennial crop so,  

you need to sum up these like sugarcane as well as  I mean rice crop the water required for sugarcane  

and rice can be combined and, you will have the  maximum water which is required that the total  

discharge during the year is 1.271 cumecs ok. Hence, the peak design discharged if you see this  

20 percent higher than. So, you can put like  20 percent 120 percent now. So, that is 1.2 so,  

that will be 1.52 ok. So, thank you for this  lecture this is the first lecture and we are going  

to cover more on the following lectures so; Thank  

you.