 having looked at all the various possible methods which are being used in the present day context and some of those methods are cage old methods, we will start looking into each individual method and go into the depth even those old methods for example the border irrigation method is an old method but we will try to look at how we can make use of the present knowledge to refine those methods, to make those methods more efficient and based on better principles the design parameters have to be evaluated. So that is what we will go into, now I do not want to again repeat those things that what the border irrigation method is will directly start with the design aspects, how we will look at the design aspects which are the various design aspects which we will have to concentrate on and that will be quite in line, so if you think of the design aspects first look at what is the objective of your design, objective of design in this method or for practical purpose in all the methods which we will look into, the objective will remain same, so it is more important to first clarify what is the objective, with what objective we are trying to go into the design aspects and this I think if you remember we had discussed this in detail and we had said that if you take the help of the two curves the recession curve and the advance curve, this is the recession curve and the advance curve these curves are characteristic of the other parameters for example this will be depending on what type of soil you are having, what type of slope is the prevailing slope and along with that what is the stream size, all those things put together they will decide what is the advance curve. So in this if you look at this uhh total picture we had also mentioned that at each individual point if this is a upstream end and this is the downstream end of the field, this is the field along the field at each individual location we can know what is the the opportunity for the water to infiltrate into the soil and thereby get absorbed into the soil as a function of what is the difference between these two curves. So the first objective and the only objective which will satisfy all your other requirements will become that if we can find all those techniques or all those possible uhh settings if we can make so that we can get a balance, get a balance between these two curves in such a way that these two curves produce an opportunity time along the total length of the field which is comparable from one to the other opportunity time or in other words if these two curves are parallel to each other the more they are parallel to each other you will have the chances of the opportunity time being seen those chances will increase. So as you go further down if you will try to go further down you will find that the opportunity time is reducing and this opportunity time on what basis it reduces this is all a function of the other set of conditions which are prevailing in the area in the location which is your target location. So that is what are when you are looking at the design you have to first consider all those conditions which are important conditions from this point of view and then evaluate what will be the possible recession and the advance curve and then come out with the design parameters which are many for example to give you an idea that when you say design parameters there are some parameters which are in your control. So if you change those the whole concept or all these details will also change. Example if you change the stream size your advance and the recession curve is going to be different. If you change the that is immediately in your control you can afford to your maximum might be dependent on what the irrigation department or what is the maximum capacity available at that particular location but below that is under your control you can always reduce your stream size lower than what is available at that location. So there is one option then you can also think in terms of shaping your area to get a different grade. So if you change the slope of your field then again you will get a different set of curves that is something which you can take a decision at the time of when you form your land before the sowing is done when you are repairing the field for the sowing. So at that time you can decide do you want that grade or you want a different grade again that is in your control. Now when it comes to the soil type it might not be in your control but to a certain extent by doing some cultivation uhh practices you can slightly modify the behaviour of the soil by doing the tilling process. All those things all those different procedures can help the farmer to certain extent but not to a very large extent. If the basic type of the soil is some uhh if it is a silty soil it will remain silty soil or by adding the manure you might be slightly modifying the the characteristics of the soil the infiltration characteristics of soil or the moisture holding capacity of the soil. Those are only slight modifications. So there are some out of the total set of parameters for example in this case now the size of the field what is the length of the border which you will select in this particular specific case when you are looking at the border irrigation system. The length of the field will be again in your hand. As a farmer you can decide what is the maximum length of the field which you should be selecting. So out of the total set of parameters there are some parameters which are uhh easily manipulated. There are some parameters which are not as easily manipulated. So once you decide on what is the what is your uhh what is your preferences how you want to which parameters you want to restrict and which parameters you have the flexibility accordingly your design will be uhh you can use the design procedures and find out the set of dimensions with respect to the other selected conditions okay. That is the whole uhh gambit of the total uhh this uhh design procedure which we are going to look into. Now with that objective let us try to look at the various uhh uhh other quantities which we will be requiring when you are going for the design which are very important which you will have to consider. You cannot help you cannot proceed without those quantities with those those uhh items. The first of this though we have discussed all these things in some form or other we will try to just look over uhh uhh consider those things once again the soil intake characteristics. This we had discussed in detail when we are when we were discussing the infiltration process. So that time we had mentioned that the soil intake characteristics the area of irrigation water management we are basically interested more interested in the accumulative infiltration depth and we had also mentioned that this we can express in the form of this equation which we have discussed earlier. Now these cumulative intake equation is used because at at any time we want to know what is the value of infiltration which has taken place at a particular location with respect to the opportunity time. So this time is the opportunity time. There is the time for which the water availability was there on the top of the soil surface and the other A, B, C are the coefficients which can be evaluated for a particular soil which means that when you when you talk of the accumulative infiltration depth because basically the accumulative infiltration depth is nothing but indirectly is your demand that is what you want to store into the soil which is to be used by the crop ultimately. So when you look at uhh this equation this equation is dependent on what type of soil you are talking about and with that uhh uhh thing in mind is is quite difficult to evaluate these parameters every time every time you go in for a design you might not might find it difficult to have uhh these A, B, C evaluated for that specific soil. What the soil conservation service of US department of agriculture they came out with a set of a family of intake curves and this I had shown you at that time when we were discussing the infiltration process set of intake uhh curves what they are giving they give us the characteristics of soil intake with respect to the specific type of soil. So if you know your soil type you can find out what will be the various parameters of this equation this is available in the form of uhh coefficients is also available in the form of actual curves in the form of a plot or the set of curves which are plotted on and they can be used directly. These family of intake curves what do they mean what has been done we had discussed that every infiltration curve if we take the infiltration capacity curve that is the rate of infiltration versus time depending on the soil characteristics the infiltration capacity of the infiltration rate which is the the capacity rate that gets a specific value depending on the type of soil you are considering. Now this this this steady state infiltration capacity rate we had called it the basic infiltration. The basic infiltration basic infiltration rate is something which is unique for the soil for a specific soil you will get a steady state infiltration rate which will remain same which will remain similar irrespective of the conditions of the soil because that is that is something which is achieved after a long period under the conditions when this soil becomes quite saturated and that is what has been used to designate these these families. The family numbers have been given with respect to the basic infiltration rate. So once you know the the family with respect to the basic infiltration rate which is a unique characteristic then you can find out what is the relevant for that number this has been drawn the infiltrate the cumulative infiltration curves have been drawn for that basic infiltration rate numbers. The the family numbers of the the intake curves have been given numbers which are dependent on basic infiltration rate okay. Then another parameter which is quite important and you will be using quite often is the Manning coefficient of roughness designated as small n. Now whenever you are talking in terms of the flow characteristics it will be highly dependent on what is the roughness coefficient and the roughness coefficient varies a lot in the case of agricultural fields because of the fact that agriculture fields they go from the change of surface which is experienced on the fields is so much different and it varies from the time of preparation of the fields to the time when the ultimately the the crop is cultivated. So you will find that this one parameter and it needs a very very good evaluation you need to know this parameter quite quite closely you have to have reasonable values evaluated for this parameter because if this will go around all your computations which you are making during the process of your design they will also have a tendency to go around and it will give you some inferences which are not the true reflection of the actual conditions. To give you an idea you can see that the variation how much it varies let us take the case of smooth bare soil value of n can be 0.04. If you take small grain and you have drilled the rules parallel to the the strips value might be 0.1. If you change the the way you have done the sowing because in the case of it depends how you have sown the area so if the sowing is done in the perpendicular direction you have drilled the holes in the perpendicular direction of the border then you will have a value let me say dense either you have dense crops or you have small grain crops little rows across the strip the value can be as high as 0.25. See the variation that with just the way you have planted the crop that is also going to make lot of difference is going to create lot of resistance to the flow of water and that has to be taken into concentration. So the n value the Manning coefficient is a very important parameter and all your computations are dependent on this one parameter it can make lot of variations you have to be careful about this. Now let us come to the design equations how you proceed with the designs and the first of most important parameters which you might like to look into is the inflow rate what should be the inflow rate or what stream size you should select. One option is that you have a fixed stream size where you do not have any option available you might have to use that if that is the stream size as such the stream size is quite low you do not have any option available because you cannot go to a very low value of stream size. What we will do is that we will first look at we will have to look at the various design parameters from different angles. First we can look at the various equations which can be used then we will try to formulate some check conditions which can be used to check whether your design is appropriate or not. So considering the inflow rate let us try to consider a strip and try to find out what is the volume. If I assume a flow rate of small cube you know that what is the opportunity time which is required because when I start irrigation I am aware of how much is the net irrigation requirement. We have already discussed that the net irrigation requirement is because of the deficit which has been created in the root zone depth. So how much deficit has been created at the time when you are deciding to irrigate and that is a function of how much deficit can be tolerated by the crop. So once you have found that this is the deficit which can be tolerated by the crop you decide you have to go in for irrigation at that time how much is the amount of deficit that you either replenish the total deficit or you might decide to replenish deficit partly. So in that case your depth of irrigation requirement will be less than the total deficit which is available at that time okay but at the most it can be. So in any case whatever user is your decision I had given you the concept of deficit which is a function of the management decision. So that is what we are discussing. Let us not go into that let us try to assume that what is the deficit to be replenished you know so indirectly you know what is the opportunity time required to take care of the deficit. So if this T is known and you know you assume that Q is the sorry if you assume that Q is the stream size or the inflow rate and in the case of border irrigation the Q is taken in terms of a rate per unit width so this Q is available in terms of meter square per second. That is what is the volume which is needed to be admitted into the field and this will give you the total volume the discharge rate into the time the opportunity time for which the water has to be admitted. This is only one approximation we are not looking at the other things we will introduce the remaining concepts also the remaining requirements which are taking care of the other efficiencies that we have not yet considered. We are trying to look at what is the volume the minimum volume you can say which needs to be admitted if this depth what is always the depth it has to be taken care of. So this volume should be equal to this volume. Similarly on the requirement side if I want to know what is the volume of water required it can also be given in terms of this depth if I say that this depth is y n so this much depth over the total length of the field the length of the field is l this is the volume of water required per unit width of the border. I can use this this water balance or these two should match basically these two quantities should match so you can say that q into t should be equal to your y n into l this is the first design criteria this is the first design criteria which you can take which you can consider and you can find out now you have found a relationship between the two you can find out any quantity knowing the other set of quantities now here comes a decision what you know and what you want to find out. So let us assume that your interest is at this stage the inflow rate you want to know how much of the inflow rate. The inflow rate let me call it q u to make it per unit width this will be equal to y n into l by t now this t is a time is the application time or this is the opportunity time let us come back to this figure which we had used earlier which we had constructed we were discussing the total process of irrigation when we really apply the irrigation what are the various phases of irrigation and we had said that when we start the application this is the time to start and then keep on supplying the water at the upstream end at some time we stop the application that is the time when you finish the application. So t f was corresponding to the time when you have finished the application. Now if I if I see from the point of view at the upstream end of the border for how long I have supplied the water only from this end from t s to t f but for how long the water has been available at the upstream end the water has been available for some more time because the fact that the water when it was supplied the depth of water got accumulated over the surface so there was some retention of water there was some depth which got accumulated over the surface and that is a function of what are the characteristics what is the slope of the field and that depending on those characteristics there will be some depth of water which will be which will be established at the top of the surface and it will take some time to deplete from that particular location and that is what we had said was the depletion phase. So if we if we are interested in the total opportunity time the total opportunity time is different than the time for which you require to supply the water that is the point which we are trying to make. So there is some time which is if I say that I want to introduce that for how long I have to because this q u should be a function of the actual time for which you are supplying the water not the time of the time the opportunity time for which the water is standing there because we have seen that the water keeps standing there for some time over and above the time for which we have applied the water. So if I want to account for that then I should introduce that this is the if T n is the total time the total opportunity time I am reducing the lag time which is because of the depletion phase. This T l is will introduce those quantities l is the length let me use this l is the length of the border strip if we express that in meters y n is the net depth of application and normally this depth we express in millimeters and T n is the opportunity time this is expressed in minutes T l is the lag time again in minutes. So the lag time is the time for which the water will be available on the at the head end even after the water supply has been stopped. Now that is we have incorporated that here plus we can also incorporate the efficiency the application efficiency we had considered that while applying the water to achieve this you might need to apply some more water so it is a function of how much application efficiency we are achieving depending on the application efficiency you can use that application efficiency to find out how much is the intake rate which is desirable. So now this becomes a modified equation where you have here is the application efficiency in percentage. Now because of the units which we have used you will find that you will have to use some coefficient which has to be evaluated and that coefficient you can find out. Okay let us do that here. You have q u you want in if I say that q u should be in meter square per second okay y n is in millimeters so if I make this as meters l is in meters no problem then T n is time in minute so you want in second so you divide by 60 because the seconds are this is to be converted into seconds so it is basically minutes to seconds and what else you have in percentage instead of a fraction so you will have to multiply or divide this by 100 this will be multiplied by 100 okay that is the fraction which will be getting this fraction is 1 by 600 so you will get a fraction here into if you use these units this will be taken as 0 0 1 6 7 is it alright is it okay this equation now the q u equation is transformed into this equation which where you have taken care of the dimensions you have taken care of the efficiency you have taken care of the lag time and that can be that can be used. Let us look at the lag time the one way is that you observe the lag time but for every condition unless you go in for the evaluation procedures again that also we will try to deal with for every irrigation method there are 2 ways one is that you go into the field perform the irrigation and observe the data so that is the experimental method but that you cannot afford to do every time under every situation what is being done is that you are collecting the data through those evaluation procedures and then you are trying to establish the relationships and then you are on those relationships you are extending those relationships to find out how those relationships can be diversified to cover all the possible conditions practically is not possible to cover each individual condition and if there is a variation how those conditions will be changing conditions will be can be taken care of without going in for the actual practical procedures that is what we are trying to establish. But basically there are many times they have been checked they have been still there are some experimentation which is being done all over the world in various agricultural universities in various other agencies where they are trying to improve upon these these procedures and the set of relationships which are being given they are also being evaluated being updated and we are we are trying to is always easy whenever you are talking of a design procedure to have a set of procedures which are analytical which you can use comfortably with the help of your system or even manually you can afford to handle those. In the case of lag time two possible conditions have been separated out one is because the lag time or the recession the depletion phase will be a function of what type of slopes you are what are the prevailing slopes or it will be a dependent it will be a value which will be dependent on what is the normal depth how quickly you achieve the normal depth in that type of slope and which is a function of slope the slope is the predominant parameter in this particular case. So there are two conditions which have been classified first when you have the high gradient borders and the high gradient borders are the the value which has been taken is that anything steeper than 0.5 or 0.4 percent slope is termed as high gradient borders. So if you have slopes which are steeper than 0.4 then you will use this relationship and this QU we have already defined is the intake rate in meters, meters cube per second and is the merring coefficient S0 is the slope of the land surface. So the slope of the border strip in this particular case when the gradient is high you will find that in the this is basically this is derived from the Manning's equation in Manning's equation your S0 is not the land slope is the energy gradient line. So what you are approximating is that if the gradient is high you can take a slope the land slope can be approximated to the energy gradient slope whereas this would not be so if you have the gradients which are low gradients. So in that case if you have low gradient borders in which the slopes is slopes are less than 0.4 then your the relationship which is used for lag time is a similar relationship as you had other relationship but it is corrected for the slope of the the slope is not cannot be taken as the land slope anymore that slope has been corrected. So this is the final expression you see here that this is the additional this is only additional component which is nothing but it gives you the correction to S0 because in this particular case what is happening is that the normal flow is not reached that early it takes it might not be achieving the normal flow. So in that situation you will find that the energy gradient line and the the slope of the the field the wound match. So the the lag time can be I mean you can use the lag time equation depending on what type of conditions you are having what type of slope is the prevailing slope and that can be used for your design purpose. That means that your inflow time you can call it as T a inflow time for any particular location of the field you can evaluate knowing that how much is the total net time the net opportunity time and correcting that for the lag time. We will stop here because then we will next time in the next class we will we will try to cover the other aspects of the design parameters which can be considered or which are the possible options available and then we will also deal with the other quantities which are the check quantities because what happens in this particular case you have to ensure in the design parameters can be misleading at times. You might get a value of the intake discharge which is not suitable value from the practical concentrations and there is no provision in the design equations to give you a value there is no check which can evaluate that whether the value is the permissible value or it is some value which is not spreadable. Consider a value which is very low value and you will find that the basic impact of that if you will try to see on this it might give you a a advance curve which will become a very sharp it can it can be something like this can have a very steep slope because of the fact that the water has taken a lot of time to reach the downstream end. If you would have used a stream size which was reasonable size for the same slope you would have got a advance curve which is something entirely different because the shape of the advance curve is dependent on the soil characteristics as well as on the stream size as well as on the slope. So these three things put together will decide what is the advance curve. Let me give you an example what I am trying to bring home the point is that if you have one case where the stream size is very low you might get a advance curve which is this and let us assume that we we know the the slope for a particular set of conditions this advance curve if everything else remains same only that the Q u is changed by changing that Q u you can get another advance curve which is something like this. Now as far as the recession curve is concerned recession curve is not entirely dependent on the features what was the flow available or what was the size of the stream is a function of what has been established on the surface how much retention storage has been established and how it will deplete. So it might not change very much under the similar conditions when you have these two stream sizes the recession curve still might be something of this nature but if the recession curve remains similar and this changes drastically in one case you are getting the opportunity time which is highly different from this end to this end and the other case by just changing the stream size you are able to have opportunity time which is now almost parallel so that is what you will select that is what is your intention when you are going further when you are looking for the design parameters you are trying to find a combination which can give you this the set of these two curves so that your opportunity time is not varying very much from one section to the other section of the field and once you achieve that then you are indirectly achieving a uniform distribution okay. Any questions? Thank you.