 Hello everyone. Welcome to Rural Water Resources Management NPTEL course. This is week 9, lecture 3. In this week, we are looking at engineered structures that can help in Rural Water Resource Management. We found that in the previous week, a lot of water is wasted, a lot of water is not captured, and management is lacking. So how can we increase these aspects? There is natural based waste and engineering based waste. In this week, we are looking at engineering based methods to improve Rural Water Resources. In the last lecture, we looked at dams and check dams. Now we will continue to see how different models exist with check dams. A series of check dams can also be built. In the previous lecture, I showed you how one check dam is there, water comes, gets stored and then the recharge happens. But there can be also cascading effect, which means you can have one after the one after the other very strategically placed to have a cascading effect. Let's see how that looks. This is a single check dam and the check dam can have a kind of a water area that it is storing. So it also looks like a tank. A tank should be all sides closed. But here you could imagine that water is coming and filling a tank and then it goes to another tank. Or one dam goes to another dam goes to another dam. So that is what is called a cascading dam. This involves many small dams along the same river or stream network and after one fills the other one fills. So hereby, you are not letting the water go escape out of the watershed, especially into the oceans and big rivers where the volume doesn't matter for the big river and ocean. But it does matter for the local public. Okay, so as I said, if water flows out, it is a loss to the watershed. And this is very important when the watershed is leaving the water into a bigger water body, especially large rivers and oceans. So it is okay to store the water as a cascading effect. When you have the cascading effect, many important parameters get recharged. Let's look at some. Slowing down surface runoff. So the major first goal is you slow down the surface runoff. The water that flows on the top after you have precipitation and infiltration, etc. The water which flows on top of the surface continues to flow along with other water runoff and then forms into rivers and streams. So this is being slowed down because of these check times. You are slowing down the water increase in water release to the streams. You are slowing down, thereby not letting the water escape the system, but slowly releasing the water into the streams. So for example, this is your stream. If runoff was coming very fast, it would escape the stream network and go. So in three months, all the flow is gone. However, if you stop it at periodic intervals, the water gets only slowly, slowly released in the stream, thereby increasing the longevity of the stream. Most importantly, it lets into recharge, base flow, groundwater, aquifer, recharge, etc. And those water would come back to the stream as river flow through base flow, which actually increases the flowing period of the stream. It increases groundwater recharge and sustains base flow. So this is what I mean as, once the water goes into the ground and then goes out as base flow, the stream gets more water. Let's have a quick diagram of how it works. So you have your stream and along the stream you have check dams. So if the check dams were not present, water would just flow out fast. Because you have the check dam, the water would go into the ground and then come back out into the ground and then come back out. This causes a delay in the water leaving the stream, thereby the going in is called recharge and then coming out to the stream is called base flow contribution. So by this process, water going into the ground and coming out, you are slowing the flow of the water in the stream, thereby increasing the period over which the stream flows. For example, if the stream was flowing like this, just four or five months, because it went into recharge and comes out of base flow, it will flow like this. So all throughout the year, you would see groundwater flow. Isn't this the way that initially all the water bodies were? Yes. Initially all the water bodies would be flowing. Every, the major water bodies, the reverse streams will be flowing throughout the year. You would have heard stories from your grandparents or even your parents that some of these water bodies, reverse streams were having water throughout the year. But now it is not happening. So there is a series of check dams can be built to increase the water in the stream. That is one method that a lot of studies have promoted, and especially one person has done a lot of these works in Rajasthan. And he was awarded the Stockholm water price, which is considered as the Nobel Prize for water, kind of that highly regarded price for creating this series of check dams to revive, revitalize the streams and rivers. So we work up a lot of people to get into these series of check dams, and many, many rivers and streams have been benefited. However, so here's where I'm going to stop with the engineered aspect for rural water management for surface water, because you can do only less amount of surface water interventions. It's not that easy to make multiple interventions. For example, you cannot cut a channel and then bring the water out to your house and stuff, which is not allowed in many, many aspects, right? You can put a pump and take it as lift irrigation. Even that is not allowed in a canal system. So think about all these regulations and that is where people have been not much abusing the reverse water bodies, etc. But where most of the abuse is happening is in the groundwater for rural systems. India is the chief groundwater extractor and there is a big need to conserve that resource. Let's see how you could do groundwater recharge activities in rural villages. So since it is not natural-based, it is called artificial recharge techniques. If it is nature-based, it is like forest and then you have more infiltrated soil, percolated soil where you have multiple nature-based solutions to increase the recharge. However, the speed is still low. So for that, there is a lot of artificial recharge techniques, which involves a lot of engineering aspects. Let us look at some of them in this class today. So first, artificial recharge techniques are divided into direct and indirect methods. In the direct method, you have surface spreading techniques where you increase the time of the water in connection with the land. So if water is flowing very fast on land, then there is the time of connection between the water, the connect, between the water and the stream is very less, the water in the land body. And that causes less infiltration time, less percolation time, thereby less groundwater. So how can you increase this connection between contact, between the water and the land, the contact time? You could increase that by flooding. You flood the area, let the water pond up. Similarly, a thickness of water is on the land and that time is given to the land to infiltrate the water and take it to the groundwater. Multiple methods are there. Others are basins or percolation tanks, stream augmentation, ditch and furrow system. We have seen this in the previous lecture also the ditch and furrow system, but here we will look at it how it is in the groundwater network. In the subsurface we have the recharge well, the recharge split shaft and the dug well. Where most of these are wells and those wells have to be built inside the ground, whereas the surface techniques are on top of the ground. Subsurface techniques are you have to dig and then put it in for the action to be taking place. The indirect is induced recharge, which is mostly by pumping water into it, which is not a very commonly used method. So we will focus on the direct method. There are a lot of schemes versus methods. So these are the techniques which I've shown here. Grounds cannot stand alone because the problem is complex, groundwater recharge is complex. So let's look at some schemes where they take multiple methods and then work on the net groundwater recharge. The first one is the Ganges water machine, which is thesis as I mentioned from a Indian student at MIT Stanford, where they worked on these topics for inducing groundwater recharge along the Ganges. It was a very old thesis, and now a lot of people are working on it. There's a book by Adam Tenney in 2015 on this Ganges water machine. Please see if you could look at it and what they talk about. I will give you some examples of what it is. What does Ganges water machine mean for groundwater? The Ganges has a lot of water as surface water, but in recent years along the Ganges, the rural areas, the groundwater has been depleting. So what the Ganges water machine concept thinks about is if you pump along the Ganges before the monsoon, along means along the riverbed where you can put a big pump and pull out the water. If you take the water out before the monsoon, which is the time when you need more water for irrigation and agriculture. So if you take the water before the monsoon, then what happens is when a big flood of water comes in the Ganges during the monsoon, then there is space for the water to recharge, which can be taken out later. So I'm going to draw how it should look like. So you have a land and what they're claiming to do is you pump before the monsoon, you take out the aquifer volume pump. So basically empty the aquifer and when water starts to flow in the monsoon, so when water flows, it goes inside and recharges. Thereby, the water level might come down in the Ganges, which means the floods might come down. Still all of this is a thesis, a theory. So there's a lot of experimental methods that needs to be done to prove it. But what I'm trying to tell you is by these methods, you can actually recharge as per the science and the book, which has explained. So you pump before the monsoon along the Ganges and then you have recharge of water in the riverbed. So basically the flood comes in the monsoon, it goes into the riverbed and recharges the soil. So even if you pull it out before the monsoon, the water, it doesn't affect the groundwater use because you are actually recharging it every year. So the riverbed, the riverbed as a groundwater storage. So initially the riverbed is always full of groundwater because no one is putting a pump and taking the water. No one is actually using the underground of the riverbed where there's good aquifer storage. Mostly only the river is used and there's banks of the river where the groundwater is there, they use it. So the riverbed sometimes is mostly less affected and that is where the study is saying use the riverbed to take water out and use during post monsoon season where you can recharge the groundwater in the monsoon and then post monsoon you can take it out and use it thereby emptying the space again. So it is a machine. So you are converting the Ganges riverbed into a machine where water comes, you recharge it and then the flood is reduced. But then after the flood season is gone, you take the water and use it for agriculture, keep the water aquifer empty. Another annual river water comes and goes in. So it keeps continuing like a cycle. However, so these are the benefits. Let's look at the practical problems. That is why I'm saying it still needs a lot of testing. The energy consumption is intensive. A lot of energy is needed to take water out of the riverbed and then where to use it, how to spread the water out is a concern. Please understand that the Ganges riverbed and Ganges area already has a lot of water resources. So why would someone put energy and pump and then use it for agriculture is a question. So all these still have to be debatable. A lot of big agencies are working on it. As example, Imi, who has a lot of funds from big banks to work and test this system because once they test it, they can actually use it for groundwater recharge and for the taming of floods, which is what this second team that we are going to look at or the scheme. In this scheme, you see underground taming of floods for irrigation, UTFI. So you are having the floodwater coming on the surface, which is washing away the rural areas and stuff, not much agricultural benefit. It is not stored in the aquifer, so there's a lot of loss of the floodwater. What this scheme does, if you look at it, this is the wet season or the monsoon season without UTFI scheme. In without the UTFI scheme, there is a rain, all the water comes as runoff. It goes into the rivers and streams and floods the cities and rural villages. In UTFI, what happens is there are these long shaft, groundwater recharge shaft where water is stored in these small, small recharge ponds and pushed into the groundwater through the recharge shaft thereby increasing your groundwater recharge. Now your flood volume is much, much attenuated in the streams and rivers before the city and also the rural villages. More importantly, your water can be used in the dry season, which is the next season. You could see that groundwater is being pumped and agricultural activities are happening. So this is with UTFI. So all UTFI does is it captures your monsoon rainfall. Remains the floods, pushes the floodwater into or before even the flood happens because you're capturing the water before the flood happens and pushing it into the groundwater storage through recharge shafts. And this water is available in the dry season for agricultural activities. During wet season, floods can develop due to less groundwater infiltration also because the soil is very wet and so the infiltration is very slow. However, if you have this long recharge shaft, I'll show you the figures of how a recharge shaft looks like. It's an engineered product where you could push water into the recharge shaft faster and thereby actually not in the shallow aquifer. It goes directly to the deep aquifer. So there's a lot of volume which has already been depleted by rural activities, especially agriculture. So what the scheme says is already the groundwater is depleted. Why don't you take the floodwater, push it inside and then use it for post-monsoon activities. Again, these are still being tested for recharge rates, water quality, quantity, and once they get tested and scientifically validated, then big schemes can be implemented in India. So this study has also been tested in India where there's a lot of engineering aspects, artificial engineered products to enhance the groundwater. Even groundwater is low, the water cannot infiltrate rapidly to lower floods because floods happen at a very fast speed whereas the infiltration is a much slower process. That is where UTFI smartly enables shafts to augment natural recharge rates. Augment means add on or fasten the natural recharge rate. Let's look at how it's done. So you have here the recharge shaft as I mentioned and you have a canal where the water is flowing, canal stream or river network. Water is being shunted into a renovated pond. Initially, all these areas does not have groundwater because the groundwater is very deep. Nothing is growing, the villages are not having water for agriculture. The pond has no water because of climate extreme and nothing is growing along the banks of the pond. So it's just wasted water resource and water body. Look at how deep the groundwater is. So now what they claim is if the canal water is there and this canal has nothing to do with the pond, there's no recharge happening. So now what UTFI scheme does is take the canal water, divert it into the pond, part of it, not all canal water is lost, only part of it. So there is first aid diversion of water and that water is put into these recharge shaft. You can see the recharge shaft and groundwater goes faster, much faster into the shaft and to the deep deep aquifer. So you could see that the deep aquifer is getting all the water, which then recharges the entire aquifer. So from here, it has gone up to here during the UTFI scheme. Ponds are dug and fit with deep shafts. So the ponds, getting the pond land is a concern, but if you already have a river and a pond nearby, then you can easily talk to the villagers and see how the scheme can work. That is how they have done a testing site in the Ganges. They have identified a farm pond, which has not had water. They have said, okay, let's take some canal water through permission and put it in the pond. If you just leave it in the pond, the recharge rate is slow. So to augment it, to increase that, these recharge shafts have been built engineered. So basically they are a column which goes into the deep aquifer and water is being pushed into these recharge shafts to go faster and then recharge. So you could see the faster recharge is happening compared to the recharge here from the pond. These can connect to the deep aquifers rapidly than through the soil matrix because if water has to go through the soil, it is very slow process. What they do is they put gravel and other layers of soil and rock in the recharge shaft, put the water on it so that the water moves slowly and all the impurities are kept on the top. Then water just goes faster into the pipe. So this pipe, there's no soil, so water can just go faster. Once it goes faster, it recharges the deep aquifer, thus increasing infiltration and percolation rate. To be honest, there is no percolation rate needed because infiltration just takes the water straight to the deep aquifers. You are bypassing the percolation path. This can reduce flood because you're quickly catching the flood water and putting it in thereby reducing the flood peak. And more importantly, you're also recharging the groundwater. And this is where two aspects have been satisfied because when floods come, your rural agriculture is gone. A lot of fields have been washed away. Too much water is also bad. So you're capturing the water, putting it into the groundwater and recharging. And after the flood, after the flood season, this water can be pumped through the deep aquifer pumps and used for agriculture. As I said, this has been tested widely and still the results are coming. And just recently, last year, we have papers. So look at the wet season without UTFI and wet season with UTFI. You don't have groundwater recharge here. There's a good groundwater recharge. And most importantly, the flood level has reduced. So look, plan view with UTFI is you have these recharge ponds and around the recharge ponds or inside the recharge ponds. You have the recharge shaft, which actually pushes water faster into the groundwater. And during the dry season, this groundwater is being tapped for agriculture. So it reduces the floods, protects the rural villages, assess livelihoods from flood damage, and groundwater recharge happens. Distributed upstream recharge of excess flood water to aquifers. Water is pushed into these because when the pond level rises, for example, now the pond doesn't have water, since water comes, the pond level rises and can go into the brown space you can see here, which has layers of materials that can remove the impurities or filter impurities and the cleaner water can go into the aquifer. This aquifer water can be used to boost irrigation during the dry flow season or the non-monsoon season, to increase access to groundwater and increase agricultural production and livelihood improvement. So this is a win-win for everyone. But this is only the schemes that I've been talking about. Now we will look at some of the methods. I will introduce the book. Please go through the book. It is a free open source book. I will discuss more about the methods in the next class. So the book is called Manage Aquifer Recharge, where groundwater recharge is slow. There needs to be methods to improve or increase the infiltration. And that has been widely used by managed aquifer recharge activities. It is called MAR, where you manage your aquifer through artificial means and your recharge happens. So engineer or natural activities that are done to increase groundwater recharge rate. The natural activities I would discuss in the next week. In this week, I will focus on the engineered aspects. The book by Gayle 2005 captures methods for rural India because there's a lot of examples from rural India, especially in semi-arid areas where rainfall is lesser than 750 millimeters. Or rainfall is only concentrated in a particular month, months, months and months. So what happens is you are capturing the rainfall. You are storing the water in particular methods to recharge locally in the aquifer. As I said, the book is free and open source. It looks like this. Please go ahead and download and read it for better understanding about managed aquifer recharge in semi-arid areas. Because if it's totally dry, there's no rainfall to capture and put in the aquifer. So there's already a loss. But in a semi-arid, you have some rainfall. Let's not waste the rainfall, capture it and put it in the groundwater is the concept. So I hope to see you in the next class with some models and interesting aspects and how to test this in the field. I will see you in the next class. Thank you.