 We have seen that the data given for the exercises we have a side droll system, the climate is warm, maritime with the evapotranspiration activity, the peak evapotranspiration rate of 7 millimeters per day and the meteorological data we had noted down what is the meteorological data which is available for that area during that period, allowable deficit which we can have is at 2 millimeters, maximum application rate is also given then there was some constraints that the uniformity coefficient which is desirable, 35 percent and adequacy level of 90 percent is desirable. There is a constraint on the spacings, the main line spacing either you can choose 15 meters or 18 meters and the later spacing of 12 meters and then we had mentioned about some constraints on the operation, the operation has to be performed in such a way that the system to run a schedule of 9 out of 10 days during peak period which makes the time interval may be something of the order of magnitude of 10 days. This becomes a time interval which is available. You can also have a bigger time interval but it should be multiple of this limit, okay. If you want to have a few feel that the time interval is this of 10 days is not sufficient you might go in for 20 days time interval but it has to be multiple of this 10 days period which is the basic period of schedule. Then in terms of the number of hours available in a day for which you can do the perform the operation of the sprinkler system, it is 24, 20 hours out of the 24 hours for these many hours you can have the sprinkler system on and these 4 hours is kept for the moves or if you have a system where you might be removing the pipes and going to the next set that time is required then it was also desirable that the operating pressure should be as low as possible but then you have to see that they are within the permissible limits and use of single nozzle is put as another constraint. Now let us go through the procedure how we should go about the design if we have this basic data available. So the first thing which you will check is whether the irrigation interval is adequate or not. So if I say that maximum irrigation interval which will be required has to be dependent on what is the total allowable deficit, evapotranspiration rate of the crop which in this particular case this is 82 millimetres and this is 7 millimetres per day which you get as 11.7 days. So the maximum period which can be made available for performing your irrigation operation can be 11.7 days, this is more than 10 days operation schedule which you are which is the desirable limit which has been put. So from that angle this is this interval is okay because it is less than 11.7 days. As long as your actual period of irrigation is within this period is okay, you can you can manage that but if it was more than this 11.7 days then you have problem. In that case by the time you come back to the same area you might find that the deficit in the soil has gone to a level which is detrimental for the crop production. Next we look at what is the the evaporation and wind drift losses at this stage we can we can go in for the selection of a nozzle, we can select a nozzle and we can also select that under what pressure this nozzle will operate. So if you make a selection of the nozzle, select a nozzle diameter of 3.572 millimetres, we had seen the tables of these respective, this is just randomly selected and the pressure the operating pressure of this nozzle the minimum operating pressure as recommended by the manufacturer was 276 kilopascal. So if we take this as the initial pressure with respect to the nozzle which we have selected then we can check the other quantities with respect to this selected set. Now let us find out the evaporation and the wind drift losses to do that the expression which we have for the evaporation and wind drift losses you need in that expression the vapor pressure deficit which we had expressed as E plus 237.3. So this is the vapor pressure deficit which we have the expression and if we put these values we know we have the values of temperatures which is the mean temperature and the mean relative humidity which we have the data available on and putting those values you will get that the vapor pressure deficit comes to 0.76 kilopascal and knowing this vapor pressure deficit now you can find out the evaporation and wind drift loss the expression is given earlier to you this gives the value of L s as 4.5 percent this is only a substitution of value which you have the expressions for. Now the evaporation and wind drift loss is one loss the other loss which is prevalent in the system is the deep percolation loss, deep percolation loss is we had used this expression where E is the function of the uniformity coefficient and the adequacy level we had that we had looked at that table where we had said that the E can be evaluated with respect to what is the U c and what is the value of adequacy and you can read the value of E from that table for U c is equal to 85 percent and A is equal to 90 percent the value of E is 0.750 thereby the deep percolation loss is 0.25 knowing these two losses you can find out the overall efficiency of the combined application distribution pattern efficiency which is we say the efficiency combined efficiency 1 minus L d expressed in fraction this L d which we have found out earlier now this L d is 0.25 only but L s we have found out as 4.5 percent when we use as the combined in the combined efficiency expression we are still keeping it as L s but it is an expressed in fraction now so this will be 1 minus 0.25 into 1 minus 0.045 it is 4.5 percent and this is 0.716 there is a combined efficiency which you will get with the present system now this combined efficiency can be used to compute the gross depth of irrigation the gross depth of irrigation if we y g is net depth divided by the combined efficiency the net depth is we have 7 millimetres for 10 days so this is your the gross depth of application which is required net we have assumed that it is equivalent to what is the requirement which is the peak in the interviews. Now having reached here having found out the gross depth of irrigation we now want to look at the operation how we are going to operate the system so if we look at the initial let us develop an initial operation schedule as a first step let us find out the first approximation of net application rate to find out the net application rate let me say that this is y g this is the gross application taken care of for the losses which are the wind and evaporation and wind drift losses so that we need not when we are looking at how much will be coming onto the soil will be less by those losses if the gross application less by the evaporation and wind losses divided by where is the time this particular component this is 98 into 1 minus L s which is 93.6 millimetres now this time which is the set time how long you want to irrigate how long you want to operate the system is dependent on that whether you want to operate 20 hours which you have kept or you want to use a lesser time or can you operate within those 20 hours can you have 2 settings of the sprinkler is all that is going to decide how much will be the quantities of water needed and what will be the rate of all those things you will have to check let us assume that the T set for which one setting is to be operated is 10 hours we are keeping it as a multiple of that time available 20 hours is available with you for operation out of 24 hours so if we say that let us complete one setting in 10 hours if we do that then the dA will be 93.6 millimetres by 10 which is 0.936 centimetres per hour because this is 10 hours now this rate this is the rate of application of water onto the soil we can check with what is the permissible rate of application the permissible rate y maximum we have we have mentioned at the beginning as part of the data that y maximum is 0.76 the maximum rate which is applicable which you should find your rate to is 0.76 centimetres per hour that means if you have the setting time as 10 hours you want to dump the water in 10 hours then the rate of application will be much higher than what is desirable okay. So you have to choose that is not acceptable you will have to choose the T set as 20 hours which will provide depth of application or the rate of application on soil of 0.468 centimetres per hour which is much lesser than 0.76 centimetres per hour which is the maximum limit so this is acceptable. Now with respect to this selection of T set you can also find out the minimum gross application rate for those the warm maritime condition we had seen a table where we had given the what is the minimum gross application rates under different climatic conditions and for the warm maritime conditions if you look back you will find that the minimum gross application rate can vary between 0.4 to 0.5 centimetres per hour okay. Now you can make a check that in the present case the DG DG is 9.8 centimetres to complete this in 20 hours this works out to be 0.49 centimetres per hour which is just within the acceptable range. So from that angle also the gross the minimum gross application rate under the prevailing conditions is also satisfied. Now the next item which you want to look at is to find out what is the wetted diameter. Again if you remember we had shown a small table where you had looked at the various recommended spacings, the relationship between the lateral spacing whether it is the mean line spacing or the lateral spacing and the wetted diameter based on the wind speed range. In this case the wind speed range is taken as low wind speed range which is between 0 to 8 kilometres per hour and let us take SL to be 12 metre which is given and the mean line spacing you have the option either to go in for a 15 metre spacing or 18 metre spacing. We will check first with 18 metre spacing if we can afford to have 18 metre spacing then we will rather have 18 metre spacing because it will be more economical. So we will take this as the first choice, using that table based on SL you can find out what is the value of wetted diameter, SL and wetted diameter ratio is given in the table so you can find out from there wetted diameter which is SL by 0.6 because SL by DW was 0.6 which is the value corresponding to the low wind speed conditions. This gives a wetted diameter of 20 metres checking on the basis of the mean line spacing. The DW works out to be 0.65 so this is 18 metres by 0.65, 27.7 metres, now you have to, you have to check your parameters which you have selected, the nozzle size and the pressure which you have selected, can you afford to get a wetted diameter of 47.7 metres, that is what the check has to be made because you have made a selection about the nozzle size and the operating pressure, you can check whether this is no problem, this wetted diameter is smaller than this, so this will be the governing wetted diameter which has to be checked. You can also at this stage, you can also take advantage of the fact that you can use the offsets which we have studied, if you decide to use the offsets then you can accommodate the overlap by around 3 metres is what we had mentioned and your wetted diameter can be reduced appropriately, so by using the offsets at least 3 metres of adjustment can be made in the wetted diameter, so the wetted diameter using the offsets is approximately 25 metres which is required okay, after reducing from 27.7, 3 metres if you use a wetted diameter of around 25 metres and use the offsets along with that you will be quite safe. Based on this wetted diameter and the other selected spacing which we have just now decided that you will use SM of 18 metres, you can now find out the world required discharge Q, this is the expression which we have used for finding out the required discharge in litres per second, you know DG is 0.49 centimetres per hour, this is 12 metres, 18 metres by 360 and this gives discharge of 0.294 litres per second and now you can require in characteristics which you need to verify on the basis of what you have just computed that you require a nozzle which has a discharge of 0.294, it has a wetted diameter of approximately 25 metres, it runs on a pressure which is reasonably low pressure, it is a previous selected pressure and the neutral size combination which we had selected that will fail because of the DW because the wetted diameter is not the desired one which we want to have. So you will have to make a fresh look on the nozzle sizes and the printing pressures with respect to these requirements and you would want such selection is that if you have a nozzle diameter of 3.96 metres, the pressure selected is 310 kPa which is the minimum pressure under which it should be running, this diameter nozzle is recommended to be running, the corresponding wetted diameter for this is 26.2 metres and the discharge is 0.3 litres per second. So you have made a selection which is not having the exact values because it is not possible, you will have to make the selection from the nozzles which are manufactured nozzles which are in the available range and depending on those selection you are trying to be very close to the constraints which you have found out using those calculations. Instead of 0.294 you are having Q of 0.3 slightly higher is okay within permissible limits. DW also is slightly higher, slightly higher than 25 and this pressure is the one which is quite low with respect to the diameters under which it should be, the pressure under which it should be running and that is the lowest possible from the recommendations given by the manufacturer. So this, if this is the one which is selected now you will have to, you have one way is that you recompute all the other things which you have computed earlier but that recomputation is not needed. If your losses, the recomputation can be avoided if L s is, the difference in the L s is less than 10 percent between this setting and the or this selection and the previous selection of the difference in L s the losses, the evaporation and wind losses with respect to the present selection and the previous selection if it is less than 10 percent then you can avoid recomputing because it will be very close within the acceptable limits and you need not check all the computations again. But in any case you will like to know the actual, when you use this sprinkler nozzle now, what will be the actual setting, what will be the actual time for which the operation should be performed. So the actual set time operation schedule you will like to know. Now let us have a look at the gross application rate with respect to the selected nozzle. This will be 0.3 liters per second is the, that is the Q, the same expression you can use which is the expression between the spacings and the gross application rate and the small Q, small Q is given, the spacing is 12 meter into 18 meters into 360. So you get this as 0.5 centimeters per hour which is still within the permissible limits. The set time is 98 millimeters is the YG or the gross 5 millimeters per hour is the DG which we have just found out, so this is 0.5 centimeters per hour or 5 millimeters per hour and this gives you a requirement of 19.6 hours as a set time. So now you will have to run the system with respect to the selected nozzle for 19.6 hours for completing that irrigation. So that is what is just a glimpse of what the design is pertaining to in these and this particular method, what you look for when you go in for the design and there is only one type of, one example which has been picked up and shown to you to make the things clear. There are many other things which are, there is only half, half the story. We have not yet taken into consideration the network of these pipes. We are just looking, we are still at the individual nozzles level. We are looking at the averages, the average rates with respect to the nozzles or a specific nozzle assuming that whatsoever values are assigned to this one nozzle, there is only one of many in the total area. They will be applicable to the other nozzles also which is something which is not exactly true is that we will come to, we will come to that stage in may be by the next lecture. At this stage let us look at another associated aspect when we try to go beyond that one single nozzle, what happens or what are the other requirements. We will like to know what is the total discharge requirement and that total discharge requirement will be a function of how many nozzles are operating simultaneously or what is the extent of one setting. We have been talking of one setting right now. What is that one setting? That is one segment of the network which you are operating. So that setting is, there is lot of flexibility in that setting. It is entirely in the hand of the operator. How he confines his setting in terms of its dimensions, how many liters you want to use at one particular instance simultaneously. That will decide how much is the requirement in terms of the total discharge. The small q is only the discharge of a single nozzle. So what is the total discharge? That will in turn decide what type of pump will be required. How much will be the pump capacity which has to be selected. So let us talk of the system capacity. We are interested in knowing what is the flow rate required which I will call capital Q. This capital Q as I have just mentioned will be a function of how much area you are considering for one setting. What is the gross irrigation requirement? It will also depend on what is the operating schedule. Q is expressed as where Q we have just mentioned that this Q is continuous flow rate expressed in liters per second. Y g we have already seen earlier is the gross irrigation requirement expressed in millimetres. A is the total irrigated area which is in hectares. Nop is the number of days of operation or irrigation per irrigation interval in days. So for how many days the irrigation has to be done. Top is the number of hours of operation. Knowing this you can find out how much is the total Q requirement and that will be dependent on the setting. When we are talking of these quantities is for one single setting. For that setting the flexibility that is how you use the flexibility. You can divide your total area which might be much more into different settings and then you have to look at what is the total irrigation period available. Can you have those many settings done on those in that period? That is what is the overall beam of designing and this is the total irrigation period. Here there can be some difference because there is lot of subjectivity which can come here. That is how you want to operate your system. Though there are guidelines which if you use those guidelines strictly you will find that this subjectivity will be reduced given those guidelines. If the different individuals are using those guidelines and coming out with the design it might not vary very much. There can be some variation because of the fact that the way you are going to select various items from the available items. That is what we have seen just now. Now that is where we will go on to the next aspect of the design which is the distribution system and the layout because how you are going to layout your network is also going to have lot of impact on the overall design. The overall design how you are going to go about whether you are going to lay the main line in a particular direction or you are going to lay the lateral in that direction instead of the main line then we will decide what will be the sizes, what will be the lengths which will be selected and that can have lot of difference in the design. So let us first of all have a look at the lateral system design. You remember earlier we had used this expression to relate the discharge of a nozzle and the pressure. That is the way they are related to each other and we had also by then we had assumed we had made an assumption that the discharge does not vary from one individual sprinkler head to the next individual sprinkler head. That assumption is not true. That is the assumption which is not true at all. The discharge does vary when you are taking one lateral you might be having many sprinkler heads on that lateral. If this is once latest you might have a sprinkler head here and you have a series of those sprinkler heads. Since in this particular case if this is the upstream end of the lateral what is happening in this? As you go downstream your discharge is reducing. So it is a case of a spatially varied discharge. As you go downstream in this direction the discharge which is available here is less by the discharge which has already left this sprinkler. As you go to the next one it has to be less by the discharge of two sprinklers. So that is the reason that the discharge is not, it cannot be same on a lateral and when we design a lateral what will be the impact of that if the discharge is not going to be the same is going to have impact on the efficiencies, the distribution pattern because the discharge is a function of the pressure and the pressure is also going to reduce because of this variation you will find that if you keep on having a very long length of the lateral the variation between the discharge of the upstream, the uppermost sprinkler head or the sprinkler nozzle and the lowermost sprinkler nozzle will be will keep on increasing and that difference can become so much that your total distribution pattern can be entirely different in the two spots on the field. So when you design a lateral your aim is to reduce this difference and the thumb rule which is used in the lateral design is that the pressure difference, the pressure difference should be critical sprinkler heads. Now I am saying two critical sprinkler heads instead of saying the first and the last one because in normal conditions it will be the first and the last one which will be having the maximum and the minimum pressure but under some conditions it is possible that you have a critical nozzle which is not the last one it depends on how the how the laters are laid down. If the slopes are uniform then you might have the first and the last one as the most critical nozzles but if you have a situation where you have the in the middle the slopes are much different then the situation might arise when the critical might become the one which is somewhere in the middle and that location that we will see just now that what are the various conditions. But the design aspects have to be checked for the levels which are recommended levels if you are using either you can use the pressure variation or you can use the discharge variation. If you are using the discharge then the difference nozzle discharge single lateral should be less than plus minus 10 percent. There is a difference between the two points or if you are using the pressure variation it should be less than equal to 20 percent. So what you are what options you are having when you look at the design the design requires a balance between various items you have the you have the choice either to adjust the length of the lateral as if you find that the variation is becoming large you can reduce the length of the lateral. There is one option head loss due to friction is another source of loss that has to be taken care of when you are designing the lateral. You have to account for that you will also be required to account for the chain in elevation chain in elevation head features. Now it is possible that in some situations if you are going up slope increasing the difference between the the pressures on the contrary if you are moving down slope you are reducing the difference in pressure. So in such designs it is much more preferable to compensate some of the pressure variation by through the the down slopes if they are prevailing there in that those areas. So that is how you when you will come to the layout how you decide to use that natural topography for providing a suitable layout those are the things which you will take care of okay. We will stop here if you have any question I would like to answer those okay thank you.