 Hello everyone, welcome to NPTEL course on rural water resource management. This is week 9, lecture 4. In this week, we have been looking at options to manage rural water resources through engineering ways. More importantly, we looked upon dams and check dams for the surface water and for the ground water, we looked at managed aquifer recharge, especially artificial recharge through engineered aspects. We looked at some schemes in general, but today we will be looking at methods based from the MAR book that I have shared last time. I hope you could search the book and get it. Please use it for understanding about the managed aquifer recharge programs. As per the International Association of Hydrologists, which is also where the book is being published, we could see that not one specific structure is needed in a larger scale, but you can have multiple different methods to attain rural water management. If you look here, you have check dams on one location and if you look at the entire stream, you have multiple check dams along the stream, which is something I said about cascading check dams. So you have cascading check dams and one large small check dam, which is bigger than the smaller check dams and what it does is it stops the water, stores it. Now you could see that the volume is increasing. So from the watershed, the water is flowing towards the stream outlet or river outlet and you could see that wherever the check dam is placed, you have a volume of water which is being created and from there there will be lift irrigation and other schemes, but the surface water has definitely been improved. Then part of the water goes down as ground water recharge, which is also part of your management activity. Then we also have storage ponds along the river network. So there are two things. One is away from the watershed or the farthest part of the watershed boundary, what can you do and along the river, what can you do? So along the river, you could have storage ponds for bank infiltration where a pond is placed, water is sent and then the water recharge happens. Also the pond can serve as a surface water storage pond. We looked at this in the UTFI and then we also have aquifer storage and recovery in the deep aquifers and then recharge into the confined and unconfined aquifers. But we'll just look at mostly where you have other networks to capture rainfall, capture stream flow to store in the rural resources. So you can also see rainwater harvesting in the rural villages can be done. Leakage from pipes and sewers are taken where water leaks from pipes in the sewage system. Those can be recharged into the groundwater indirectly and also most importantly, you have a recharge basin or large dams inside your boundary of the river. Here since it's a rural setting, you only see small, small structures and we will get into the specifics of each structure in the coming slides. Let's look at some of the examples of the book. So this diagram is also taken from Gain which is the MIR book and you could see that all these systems have been used for increasing the groundwater recharge in the rural village and also the surface water storage. Now let's look at each one by itself, manage aquifer recharge. So even though it is for groundwater, there are some surface water storage also happening in these structures. So let's see how they happen. The first one is the farm ponds. What you see here is taken in the Maharashtra area where you could see that from the hill slopes. The picture is taken from top of the hill and on one side of the hill where there is good rainfall occurring. You could see that the farmers have been big ponds, farm ponds. So all the water which comes as runoff would go into these farm ponds and then recharge occurs. Also, the farm pond can store the water for a long time. So maybe a month or two after the monsoon which can be used for irrigation. So it captures runoff by storing the water in these ponds and you see that it's not only one. It's like a decentralized small small ponds but across the area so that all the farmers who have these small small acres of land can be satisfied with this surface water. The surface water also goes into the groundwater if the pond is not lined. In some areas you have plastic sheets under the pond. This prevents the water from infiltrating but it is mostly used as a surface storage like a swimming pool. In a swimming pool you don't see water going down. It is stored like a surface water body. So that is what it means. If you line it up, then it acts as a storage tank. High evaporation loss. There is a lot of evaporation happening. You can arrest the recharge by putting a plastic sheet under the bed but how do you arrest evapotranspiration? Evapotranspiration is losing of water to the atmosphere and it goes through mostly evaporation because it is the open surface evaporation. There could be some plants like water hyacinth and other things inside the water which can transpire but mostly it is evaporation. So even though there is good positives, there are a couple of negatives which you should take into account when discussing about farm ponds. Some people what they do, they put trees around the top trees around the farm ponds so that the top area would give a lot of shade, the canopy we call it. The branches would give shade to the ponds thereby reducing the evaporation. However, the trees can also take water because trees also need water to grow. So there is a give and take and depending on that these farm ponds are made. The next method the book describes is percolation ponds for deep aquifer recharge. So it is like a check dam. So a small barrier which is placed along the river or stream network or canal and the bottom of the layer, bottom of the check dam is layered with gravel and other materials which has higher infiltration rate. Thereby water would go faster down into the deep aquifers. So small barriers to promote groundwater recharge similar to farm ponds without lining and also it has materials to enhance the infiltration and percolation rate. Remember the farm pond can be acting as an infiltration pond which means water stores and then water is released also if it is not like water is recharged to the groundwater. But if it is put a plastic dark it is not allowing water to recharge. The next one we are going to see is the sand dam. Just look at how the sand dam has been constructed. You have a barrier which is this one along the slope of the hills or along the slope of the riverbed where you have water flowing. It could be a stream flow or it could be the runoff along where the runoff happens. What does this dam do the sand dam? It is filled with sand already. It is not sediments. It is sand which has high infiltration and percolation rates. So what happens is when this water comes in it actually flows into the sand because of the porous space and stays there. So it is a wet sand. It does not really release water to evaporation much on the surface here but underneath the surface the water is in still good amount. So the idea is you cover sand and silt along the dam so water is slowed down. So when water hits the dam it slows down because of the sand silt and then it stores in the porous space the sand and silt and then you can pump it out later. So you see here that they have put a pump and using it out during the lean season. So compared to the farm punks it has less evaporation. However the storage volume is also less because part of the volume is stored with sand particles. As I said the infiltration pond which you see on the top it is isolated ponds for shallow aquifers. It deals only with the shallow aquifer where on the bottom you do not do any change. You can just dig it up and then make sure that water is stored and it has space contact, contact with the ground and the ground slowly infiltrates the water to the aquifer. Since only infiltration we're talking about this is for shallow aquifers and also to increase soil moisture in the rural setting. Remember that soil also plays a big role in water resource management in rural areas because water gets stored in the soil the soil moisture goes up and that is what supports the plant life. You need the holistic picture not just dams not just groundwater also soil trees plants etc. So the infiltration ponds capture enough. It could be as simple as if this is your land okay a slope and then there's a land. You could put a pond along the slope where water can just accumulate like the picture I showed in the previous slide or it can be channelized into a small area and then you put the water in channel means you collect the water into small canals or channels and then you put the water inside the pond. Basically collecting the water and putting it and the third is as usual you have a river flowing and along the river you can put a pond and the water can be shuttled into the pond. So there are many many ways you could bring the water into the pond. What happens in the pond is that it captures the water and slowly the water goes down as the groundwater recharge. There's also water loss as evaporation on the top. Too many may reduce stream flow. So if you do put too much overdo it it may reduce the net flow because you're capturing water everywhere and what water can go into the stream. So you have to leave some water to go into the stream. If you capture everything then there is no water for the stream all the water is in storage. Injected recharge. This is similar to the UTFI we looked at in the previous day lecture 3 but here what happens the water is pushed inside using a pump. How a pump can pull water? Similar way you can make the pump to push water inside an aquifer but brutal force and that force can push water from streams and or flood plains or even a pond. It can take the water from a pond and push it into the aquifer. So it is called an injection well which connects the pump into the aquifer and directly the water goes into the aquifer. There's no slowing down no delay for percolation or infiltration because you are already making sure the water is clean. You take the water with the pump and push it inside. It can reduce floods but energy intensive. In some countries you would see where it is very very flood prone. However, if the country is rich and has enough money they would keep on pulling the water from the ground and shunting it or putting it somewhere else through pipe networks. So the idea is if you have energy you could still take the flood water reduce it by sending the flood water somewhere else or putting it into the ground. You don't have groundwater floods. You can have groundwater creating a flood. For example, if the groundwater is too much all the soil is full of water then infiltration doesn't happen. Then all the precipitation converts into runoff which can lead to a flood. But aquifer would resist. After one point if you keep pushing it cannot take water it will just resist. You cannot push water through a rock. So it will resist. At that point is also to be taken into note when you do injected lead charge. And the last but not the least in this slide is the rainwater harvesting. Remember that rainwater harvesting has been made mandatory in many urban cities in India. Example in Chennai if you want to build a new house or an apartment complex etc. The rainwater harvesting plan has to be identified along with the plan of the house. All of it has to be approved together. You don't say that no no I'll build the house and then I'll put the rainwater harvesting. That is not accepted. Why? Because the rainwater harvesting is to be included in the design. Otherwise you will just make some storage unit which is not a rainwater harvesting but just channelizing the water into one location. So what is rainwater harvesting? What does the name harvesting mean? Harvest means collect like you harvest crops you collect it put it into sack bags and then you send it to the market. Similarly here you collect the water from the rooftops and other land locations in the rural village and put it into storage tanks or groundwater. The storage tanks which I've seen in some of the villages are like the plastic ones called like the syntax ones like a drinking water can pick big ones and the water stores there for a long time and then they take it out, clean it and use it. At least for bathing, washing you can use. Normally rainwater is good but while you're collecting in the rainwater harvesting method some impurities can come. There are some places where rainwater is caught and put inside a subsurface tank where it recharges. So this figure from the book beautifully captures both the scenarios. On the left you see that rainwater is coming, water is being harvested, collected here into a storage tank. Now the house has the storage tank which can be used for simple works like flushing. Flushing also needs water so maybe that is used for flushing. On the other hand on the other side of the roof you see water hitting and going into the collection chamber. Here the collection chamber is inside the ground and that is where water is being put and after some time water recharge happens you can see the groundwater table increasing thereby collecting the water and putting it into the groundwater aquifer. Rainwater harvesting is most popular in urban India but things have to move to rural also these technologies because a lot of benefits have happened for the urban centers because of rainwater harvesting. And slowly the rural villages also are getting toilets and other facilities which requires more water. It can be practiced in rural regions, the roof to aquifer so you can connect the roof water to the aquifer. Only one concern is the housing may not be the same as an urban setting whereas a lot of concrete is used and also pipes are there to easily connect whereas in a rural system it might be different. The roof might be attached, the roof might not be good to collect rainwater or pipes to be put. Roof to storage tanks is also available as I show here which can be used for different aspects. I have known in villages some villages they would collect rainwater in big drums and use it for cooking. They'll just keep it in the open and the water is very clean in villages because the atmospheric pollution is less so the water would be clean. So they'll take it directly and then boil it and use it for cooking. Whereas in urban centers we don't do that but mostly it can be used to recharge the groundwater and the groundwater can later be used for cooking, drinking and all the other aspects. Most importantly you should look at both surface and rural groundwater resources because both are important. In these examples other than the injected well the examples that I've shown today you could see that you collect the water first in a surface storage. So A you are increasing the surface rural water resources then you are also pushing the water into the groundwater through infiltration, percolation or induced recharge which is also helping the groundwater network. So it's one water which comes from precipitation. You collect it in two different chambers. One is your surface storage and then the next one is the groundwater storage but both have to be improved. While these have been very successful in urban settings there are limitations and need for future directions. Let's see what are the limitations. First, exact impact of not quantified or qualitative all these are terms that you could use without numbers. You can say that groundwater recharged well. The groundwater is good quality but there's no number. So that is where qualitative stands but you would need to justify it with numbers. You should say the groundwater quantity increased by 10% from 5 liters to 10 liters or you could say that the groundwater quality is good because the nitrates are low below the WHO standards those kind of things. pH is more basic around 6.5 to 7. Something you should tell why these are better. One size fits all approach. The first point I think we should still debate that why is it hard to quantify because there's no data. I gave you this in lecture 6 or 7 where you looked at the issues in water management and data issue is a big issue because it's expensive and other reasons are there. Now you're talking about a decentralized approach where there is no agency to monitor the data, to post the data or to give the data to the public. There's no budget. In that case, it is very hard to quantify. So that is the first reason and not much interest to quantify the impact. They just want to do it. There is a one size fits all approach which happens. I can mention that there is a project done by Mr Rajendra Singh who built a lot of series of check dams and revived rivers. Now does that work in every location on India? No. There are some technicalities and suitabilities of the model which cannot be replicated easily that other ways. It cannot be easily used for other reasons. So that we need to be very careful about. So there's no one size fits all. Each size is for a particular person or particular member of the family. Same way, one size does not of one type of check dam cannot be suited for all applications. That is what is happening in most of these states where they say, oh, it worked in Tamil Nadu. It should work in Odisha. Bring the model and put it down and the model will fail. The model as I said, the method as more and more. So that is where we need more scientific validation data and then show if the one size can fit all or not. Since all the failures have been reported, we can definitely say that one size fits all does not work. It is more quantity, quality or both. So all these mayors, are they talking about quality or quantity or both? Please have this understanding of any water project that you look at. Is it only talking about quantity? Is it talking about quality or both quantity and quality? What is the return of investment? As I mentioned, the check dam is not as big as a large dam. However, a check dam is still expensive, somewhere 4 to 5 lakhs. You start and it can go to 15-20 lakhs depending on the length, depending on the height and where you're putting it. Is it easily accessible to materials or not? The return of investment is how much you put the budget and how long you're going to need to take the profit to earn the budget. For example, I say 5 lakhs for a check dam. I give it in 2020. If I get 5 lakhs worth of profit in 2022, then I'm getting the return of the investment in 2 years plus or minus your interest. But most importantly, the return of investment should come back. So how do I show the return of investment as profit? Because the 5 lakhs has been spent in building the check dam. Now I have to show that because of the check dam, there has been an increase in groundwater and because of groundwater increase, I have more sugar cane and that sugar cane profit is more than 5 lakhs. So this is how the return of investment is calculated. Blockage encroachment of channels everywhere. Unfortunately, there is a lot of blockage of waterways and so that where these programs would fail. For example, you can have a village farm pond. You can have a groundwater recharge pit. But if water is not flowing through it, then how do you get it? Initially, there was water and water was flowing into it. But now the channels are being encroached. Encroach means they would take the land and put a house or a car shed, for example. They fill the canal and put something, a building on top. Because the canal land is the government land. They'll just take it up. Some public people, I'm saying. Or they block it, throw rubbish, garbage and then those don't help the recharge estimates. So what can be done? Same as earlier I discussed in the capacity building and other things. Maintenance frameworks have to be worked upon. We have to discuss frameworks of maintenance. The cost and ownership has to be brought into account on May 1 when the project is on. We'll bring the ownership later. Let the stakeholders debate and if they want it, they have to take part in it. And capacity is more important also. You need to train everyone regarding the use of new science and technologies for water resource management and never overdo it. As I said, if it is okay in one location, it may not be okay in all locations. With this, I would conclude today's lecture. I just will show you this paper to be discussed in the next section, where we have multiple different methods and to study the return of investment and how these things work. I will start with this from the next class. Thank you.