 Hello everyone. Welcome to rural water resource management NPTEL course. This will be the last lecture for this week. We have been looking at the key hydrological parameters and of the hydrological parameters. We focused mostly on the parameters that are important for rural India and we broke it up in two parts. As I said week two was focusing on transpiration and runoff and discharge while the following week would be focusing on water storage structures, soil moisture and groundwater. Water storage structures not as dams and stuff, but where the water is being held. For example, you could see here some depressions where water is held. So in this past week we looked at how these three hydrological parameters namely precipitation, evapotranspiration and runoff contributed to the water budget or the water cycle equation. We also looked at define which is a key input to the system and which of these components is a loss to the system. So at fieldscape, how did we look at the hydrological components? In the precipitation part, we looked at how rainfall occurs and we have multiple methods for rainfall and one of them is your frontal and which is very, very important for understanding the small, small rainfall that occurs in India. So you have your rainfall through your orographic which is when a moist air or a cloud moves along the top of mountains and because it moves up, there is rainfall that occurs. So rainfall we also looked at what are the different methods to monitor. So that is this part of your hydrological cycle. Then we looked at once rainfall occurs, how is water being relocated to other compartments? Mostly the first part was your evapotranspiration. So rainfall occurs, some water is lost by interception from plants, whereas some water would go into the soil matrix where water would be taken up by the plants and transpired. So that is where transpiration goes in. Some of the water would still be on the ground as on the top surface and because of the sun, it evaporates. So please understand this is a different hydrological cycle figure I'm showing and as everything is there, the most important part is the driver which is a sun. So you have an evaporation from your lakes which is your stagnant water bodies, lakes and rivers and your oceans. Water vapor is cooled down and goes and forms clouds as part of condensation. Further condensation and pooling gets into rainfall and that is where this arrow is connecting. So you have your rainfall, part of the water goes into the soil, part of it goes as a runoff and then the runoff can be evaporated. So evaporation, evaporation, evaporation and then there's also water that mixes the sea evaporates into water vapor and then condenses as clouds goes back as rainfall. The water that goes into the soil is taken up by plants and that is being transpired. So you see the word transpiration here from living organisms. Some of the water on the surface here can also be evaporated because of the sun and that is being shown here as evaporation. So all of this give water vapor to the atmosphere and when the water vapor coalesce or join together and form clouds, further condenses and pools down to form rainfall. So that's how you get weight. The other component we saw is yes, we have evapotranspiration. What happens to the remaining waters? We had your precipitation which is coming down and of the parameters we saw only precipitation is the input to the system, all the input to the arrow coming down, whereas all the others is just relocation of water or a loss to the system. So you see water from here goes out. So that is a loss. So coming back, we looked at water coming into the ground as infiltration and part of it would come back into the groundwater and come out as base flow. So the water infiltrates, moves through the soil profile, hits the groundwater table or meets the groundwater table and then moves as groundwater flow. After some time, it would come out to the surface as base flow. Some of the rain would just hit the surface and go as a runoff and some of it as subsurface runoff. So the three components are also shown here. So this is a very focused hydrological cycle which depends on the three parameters that we discussed over the week. You could see that water doesn't move down because there is an impervious saviour layer. What is an impervious layer? A layer which prevents water from moving down. So it is impeding or impervious, so that is why water doesn't flow and goes in. We're not going to concentrate on water moving from ocean to land, which is not most cases in rural India. We are only focusing on how water management can occur. In the rainfall precipitation, we saw that rainfall is a type of precipitation. So when you discuss papers on rural water management, sometimes they will use the word precipitation because there is no snowfall for agriculture in small parts of India. Whereas the Ganges water, as I said, could be because of snow melt, but we don't focus it as snow water. We call it as discharge. So the key precipitation or the key type of precipitation that we use is rainfall. So most of the reports and government records will call it as rainfall. Why is it important? It is the driver for many activities, which means because it is the input to the system and in most cases, it is the only input to the system, accurate assessments are needed. And such assessments, such information on rainfall with aid in planning of rural water management, you would get better ideas on how to manage water if you know how much water is coming through rainfall. Can aid crop selection for Karif and Trape season? What do we mean here? So Karif is the monsoon crop and if you know, I get 1000 mm of rainfall, I would go below 1000 mm rainfall demand, water demand crop. Because at the end of the day, you don't want to take excess water from other resources for supporting your Karif. Rubby season is fine. Karif is your monsoon crop. So you want to have the crop mostly taking the monsoon rainfall. So normally people do not overshoot or put a crop above the rainfall level or the average rainfall level. Then you have the rubby season. The rubby season is the seasonal crop that is grown in the non-monsoon period. For that, rainfall still helps because if you know how much rainfall occurred and you know what are the storage losses in the system, the remaining rainfall goes into the groundwater. And that can be pulled up again for your rubby season. However, as I tell how important rainfall data is, it is costly to monitor and manage data. It's a big network you need. Very good job. But still there are some issues. And to overcome the issues, we looked at how the observation data can be merged or used along with the US French European satellites that are mapping the world, especially for temperature etc. So those data can be used along with your observation data. Once you assess rainfall, you can know the average rainfall for 10 years, 20 years, like the one they've done in the map I'm showing. What they're showing is, is the current year rainfall above or below the average rainfall? If it is above, we are happy. We color it blue. And the excess water can be used for future planning, storage, maybe excision of curry crop, another crop along with curry, etc. But if it is lower, that is your red spots you have, what it means is that you need to supply a subsidized water. You have to get other water resources for agriculture, dam, groundwater, etc. Or you will have to face crop loss because of water. So this is where your rainfall data can help. So after we looked at the input to the system, we looked into the evapotranspiration. It is one of the key and major laws of water from the system, even though plants do require water to transpire, and that transpiration is a function of the plant's growth, the water is lost from the system. Suppose the plant took the water up and then deposited back into the land, then it's fine. We won't call it as a loss of the system. Let the plant take the water and put it back into the ground. What it does is it takes the water and then converts it into vapor, pushes it into the atmosphere as transpiration. If a wind blows, then the water vapor can go somewhere else. So it is totally taken out of the system. So it is a loss to the system. So evapotranspiration is a loss. However, it is one parameter that the transpiration part, at least that we need to do in order to get the plant growth. It depends mostly on the land use and land cover. We call it LULC. It is a very common phrase that we use. So your evapotranspiration depends on your land use and is being used and land cover type. Land cover could be agriculture, forest, barren, etc. And land use is the land. For example, you're using a road on top of it or you're using management practice on top of it for agriculture. All these would impact your evapotranspiration. Needs to be assessed, managed based on the water availability. If you know evapotranspiration, you should go back and check how much water is available from the station. So that you can better manage crops. Let's see some examples. Assess rainfall and then plan on crops. Once you know the rainfall, you can actually evapotranspiration rates and then take the water volume needed for plant and choose those plans that are within your water budget. For that, we did go through in the evapotranspiration lecture. We did go through how to estimate a particular water demand for a crop using the KC method, crop coefficient method FA. So once you know that the rainfall is not enough for the particular crop, what can you do? You could change the crop type. For example, if I cannot grow sugarcane, can I grow cotton? Sugarcane is a very water-intensive crop. So I can tell a farmer, sorry, farmer, this year you didn't have 1500 mL. You only had 600 mL of rainfall. So you cannot afford to grow a high evapotranspiration ET plant. You have to go for an underworked plant and water-consuming plant. And that is where we can prescribe maybe turmeric, cotton, some other crop. So that is changing crop type. Suppose the farmer says, no, sir, I only want to grow sugarcane. Then we could say, okay, sir, instead of one acre, you do not have the volume for one acre, you could grow 50% of your acre, half an acre, 0.4 of an acre, for example. So that calculation can be done based on your rainfall availability and evapotranspiration. As I explained in the previous slide, there are some data issues that exist. And that is because not all plants are transpiring the same ring. Every method says, for example, for eggplant, the KC various it is an assumed value from a greenhouse or a value which is being used for a long time based on physical field experience. But your egg plant might not have as big lead or there could be differences between three, four egg plants in the same field. Right. So still, there are some data issues. That is what we're trying to say that ET estimations is hard. Even in the hard part, there is some data issues. There's need for better data. And for which there are a lot of these satellite based data for even the government websites would have a data driven model for ET estimates, which can help the farmers to tell how much water is being used for. Then we came about the surface runoff discharge. We looked at your surface runoff from the top overland flow. Sub surface runoff which goes right from which goes into the soil, moves laterally. And then you have a base flow, the water which further goes down vertically because of gravity meets the ground water and then moves laterally. And comes out from the surface as base flow. All the three components are very important and contribute to the discharge of the rate. It also depends on your land use land cover and your slope. How does land use land cover play a role? If you have a road, concrete path or a building that does not infiltrate water, then all the water will go down. What would happen to the base flow component? It is very much reduced. What would be the evapotranspiration? There's zero evapotranspiration because everywhere there is concrete. So all the water which falls on the road, part of it is used to wet the road, evaporation happens. Some water may go seep in very little water, but it doesn't stay there because it's not a soil. So all the water comes down as runoff. So this is a learning curve. Initially days, you will not see much floods in rural villages. There's very less amount of impervious layers. But in urban areas, you see a lot of floods because of high surface runoff. And this is because of the land use land cover which is being more urbanized. Less water infiltration, more runoff. So it needs to be managed. It is a very important resource that needs to be managed to minimize loss from the system. Because all the water that is going into the rivers and your streams are away from your watershed or your body of it is free field for example and it goes out of the system. So once it goes out of the system, it is a maximum loss. So it is very important to arrest the water, store the water, runoff water and use it for agriculture. One quick example would be rainwater harvesting. I didn't want to give all the methods for each of them because we do have lectures in the following weeks on very specific ways to conserve water. So this week let's just understand the different components. So we are in a better position to pick a method for rainwater harvesting. As we explained for the precipitation and evapotranspiration, data is also limited. Comparatively, you don't have remote sensing images for surface runoff. However, you can use models. So if rainfall, if I know the LULC type, the land use land cover and I know the evapotranspiration that occurs, I can estimate the runoff using a hydrological model. One model is this one model. So I want to assess that too. So all these models and different aspects are available for us to understand at a very, very high scale or a village field except for the rainwater. So once we know how much discharge is happening in the rivers, we can know how much is excess discharge. And once we know how much surface runoff is generated in a village, we can look at how we could minimize this loss from the system. Maybe create some storage structures that could stop the surface runoff, put the water back into the groundwater or as a surface storage and then use it in a later period of time. So all these are very important aspects that we need to cover when we discuss the hydrological parameters for rural India. So off the precipitation is always an input. It is not a loss. Evapotranspiration is always a loss. However, surface runoff and discharge can either be input to the system or loss. In most cases, it is a loss because when rainfall happens, water combines together and moves out of the system. So it is a loss. But that water which moves out of the system can be an input to the next field. So then it adds up with your precipitation in the next field and it is a positive or an addition to the watershed. So let's take a watershed. So this is a watershed initially, as I said, you can have a shape as a leaf or a fern type. So let's keep as this is the watershed and you have rainfall coming in and discharge happening and water does flow out. When it flows out, it can go to the next watershed. So that is what I mean when I say it could be an input not to your system but the next system. So when you have a field, you should look at what are the key inputs of water into the field. If it is rainfall, it is only one, which is easier. But if you have a channel that brings water, then it is a discharge that comes in as a positive. So on the left hand side, in our equations we had precipitation is equal to evapotranspiration minus runoff minus sex effects. But if you bring your runoff or discharge to the left hand side, then you have precipitation plus runoff would be a positive or input to the system. So these models also which are used like SWAT for understanding the surface runoff and discharge. Initially, you had to create all the databases and understand how to run the model, how to get the data and then validate the model. But nowadays, you do have data for India. The website that I've given SWAT, TAMU, Texas A&M University does have good data for India. So you can go and check the data sources and run these models to understand surface runoff. And most of it is derived by hydrological parameters. With this, I would like to conclude a week forward to meeting you all in week three, where we discuss more of the hydrological parameters, three more, not much, three more, so that we then close the watershed analysis, water scale, water cycle analysis, and then we get into details on how to conserve the water.