 Hello everyone, welcome to Rural Water Resource Management NPTEL course week four lecture five. So this will be the last lecture for week four and so we will do a short recap for some materials in groundwater. First let's look at the statistics for water resources here. We have gone through this in the initial classes where we looked at the annual water availability as in billion cubic meters. We have around 1800 or 1900 close to cubic meters of which usable is only 1100 or 1123 billion cubic meters of which surface water is 690 and groundwater has a very good share of 433. So what this clearly tells you is that of the usable water 433 billion cubic meter is supplied by groundwater. So given all the rainfall, the storage, the big dams still the groundwater usage is a very considerable amount in the annual groundwater use in India. It is also a very decentralized water wherein you don't need a channel, you don't need a dam to store and then do it but everyone who has access to wells and pumps can locally source the water. So because of these, because of the access and technology, the stress on this water has also increased. And it has been captured by different groundwater maps, especially the pre-mountain because that is the peak summer. So after all the rainfall, after all the recharge happens, you extract water and it is reflected in the pre-mountain season maps. If you look at 2014 and you could see that the pre-mountain levels are really concerning in central India where it goes to 5 to 10 meters, yellow color and pink color 10 to 20 meters, but most importantly Rajasthan, Punjab, Haryana, those regions have drastic groundwater levels depleted. The levels are ongoingly depleted and you know that what is the key livelihoods in those regions, it's mostly livelihoods are supported by agricultural activities. So agriculture has been a biggest consumer of groundwater and annually the water levels are decreasing in these regions. So it is not that okay depleted and then it comes back again annually but it's not. So there has to be some measures, some stringent rules on groundwater use and abuse and more progressive thinking on groundwater. Also a lot of people react later, very late. So by that time groundwater depletion has hit a level that it is almost irreversible. So it is more proactive measures are needed wherein visualizing the groundwater use, visualizing the groundwater demand, we need to understand and develop methodologies that can recharge faster or limit the use of groundwater. Let's look at a table of comparisons at a block level. And as I mentioned earlier, Central Ground Water Board characterizes the blocks as safe, semi critical, critical and overexploited based on the groundwater use. If they use 0 to 70 percent of the annual recharge, it is you can still use some water and 30 percent could be given to ecosystem services, base flow, stream flow generation, etc. 70 to 90 percent is semi critical and anywhere 90 to 100 percent, which means you're using the annual reprimicable water in the groundwater every year you're using it. So think about your bank account analogy again. If you have 1000 rupees coming in or 10,000 rupees coming in per month as a salary and by the end of the day, end of the month, if you have zero balance, then that is critical because if anything happens, you don't have water, you don't have money, but 70, 90 percent is semi critical, 0 to 70 percent is safe. Over 100 percent, which means you are using a past recharged water or someone else's water. So that means it is overexploited, that is the concern. So overexploited is the concern and critical is also a big concern because critical stages can easily jump into the overexploited. So think about a bank account, you have 10,000 coming in every month and at the last day of the month, if you say, no, I need more, I've exhausted my 10,000 rupees, I use a credit card or a loan and I take more, it adds up as a debt. So you are actually eating into your future water or you're taking some savings and then using your water. So overexploitation is bad. If you know the water levels, why would you go and use more water is the question. If you know, you're going to get 10,000, you should have your demands and also your needs within the 10,000 so that you are safe. Otherwise, it is overexploited and that is not sustainable. How long can you do that? At one point, you need to stop. Maybe you will say, okay, I won't spend that for some time. I will stop but water is not that. Every year you need water, every year the trees need water, every year the streams need base flow. So overexploitation and critical stages are very, very important and groundwater board and government agencies are working on arresting these groundwater, falling levels by putting in more infrastructures or mapping them for the government records and sensitizing people on not doing these kind of activities. The rules and regulations are not yet stringent because it is very hard to understand where the pumping is, who are pumping, etc. So 0 to 70% areas have groundwater potential for development. So you still can extract more and if you look across the years from 1995 to 2011, the percentage of districts in the past 20 years shows clearly that the safe level blocks and districts have come down from 92 to 71. So look at 1995, it was 92 districts were safe. 2011, 71, which means your safe districts are coming down whereas your overexploited and critical are increasing, especially your overexploited which was 3, it jumped to 14, 14 and 15. So within 10 years, you have a 14 districts overexploited, same in the critical stage also 1, 4, 4, 4. So what you see clearly is the safe and semi-critical have been converted as critical and overexploited. So this is why I'm trying to say that critical blocks, critical districts have to be managed with utmost care because they can any day become overexploited. Let's look at how it looks now compared to 2011 images. So in 2011 images, you saw a lot of green color here. Let's go back and show you quickly. So you saw a lot of green color which is 2 to 5 meters depth to the water level, which is still safe and 5 to 10, 10 to 20 are really bad, blues are okay. But when you come to 2019, which is the latest 2020 report image, you see clearly that okay, the borders of the green are still, but the central India is actually coming levels. It is the same legend. So the coloring is the same. So 2 to 5, which were here, all the green colors, all the green colors along this region, central India are now in the 10 to 20, not even 5 to 10. So you have jumped approximately 15 meters from your 2011 level. So within eight years or even nine to 10 years, your groundwater has fallen by 15 meters and that is not sustainable. Multiplied by the area, you would understand how much volume that is, which is very, very big compared to the water volume available. Let's see which other states, you saw the districts. Now let's see which other states that are using very high amounts of groundwater as personal development. And I said anything above 100 is bad, but we'll still put a ballpark around 90%, which is so 90 and above is not acceptable because it's very, very harmful to the groundwater aquifer. So you can come down to Delhi. Delhi's water is groundwater levels are above the recharge. So the use is above the recharge and the government is working on a lot of methods to bring back the water by recharge and other mechanisms, but the population is very high. So there's a lot of groundwater use. Coming to Haryana, which is an agricultural state, you could see the groundwater use is above your groundwater recharge because 100 is equal. Now the recharge is equal to groundwater use, but here is 133, so 33% above. And when you come down another 90 is Puducherry in a very small state, there's a lot of agricultural activities there and also urbanization. Punjab is purely driven by agriculture and you could see a lot of agricultural activities supported by groundwater. So groundwater has to be managed as much as in Rajasthan and other states. So all these states in 2011 have performed kind of on the critical or semi-critical levels and the handful which are on the over exploited, but in recent years the levels are not promising because everyone is now having easy access to groundwater. And so these are the characterizations of the blocks of semi-critical and over exploited are in the red colors. And you could see in 2011 most of it is in Haryana, Punjab, Rajasthan. Since there are some blocks, so within the district the image might not be that helpful. Part of the district is urban, part of the district might be a desert, part of the district might be a forest. So overall averaging of a district might not be that helpful, but a block image actually shows you where the water is being used more than the recharge. And now you could see more southern states have blocks that have high demand in groundwater, Bangalore, Chennai, all the big cities are there, Hyderabad, etc, etc. The reasons? Okay, leave the urban reasons. Let's look at the big, big states and big, bigger blocks. What is the reason? It is agriculture. So increase in groundwater utilization for irrigation has tremendously increased over the years. If you look at the agricultural statistics 24, you could see that the groundwater component in agriculture has increased from 30% to 60%, whereas the surface water has come 30%. So almost it is exchanging their responsibilities. So groundwater has been promoted as the key resource in those regions where surface water irrigation was happening. And that again, as I said, surface water is a more centralized approach where you have a dam and the dam releases water to farm lands, only to the farm lands where it has access to channels, whereas groundwater is, you just have to put in a pump and then suck all the water out. So coming back, so groundwater has overtaken surface water in some regions, but more importantly, the pattern is exchanging between themselves. So the role, the responsibilities have been taken up by groundwater and more and more areas are coming under groundwater irrigation. The other figure shows another story, tubers have increasing the care. So that actually is an indicator of groundwater being the source of irrigation. So if you look at the source of irrigation, channels which have surface water related have almost stagnated from 1950s to 2011. Tanks also as a surface water storage unit has also stopped or even come down in recent years, whereas wells have increased and most importantly, your tubers have just skyrocketed. Okay, it was zero, it was zero in the 1950s, 1960s, technology was expensive. There was not much development on groundwater pumps, but then slowly science and technologies have become prolonged effort in bringing up the groundwater pumps, electric pumps, diesel pumps, those kinds of things. And you could see skyrocketing increase in the number of tubers, even the easy access and easy installation of tubers has a big impact on the groundwater use for irrigation. So all this is not sustainable because initially one village would have two, three wells. I could imagine in my younger age when I was traveling in the villages, you could see only certain number of wells for irrigation, but now every small plot has its own well because there are some funds, there are some subsidies given and water is just being exhausted, but there is less and less groundwater recharge activities happening. So when and why, what is the reason for this tremendous increase? Because there is a lot of stress on farmers to produce more food, the population ever is ever increasing and the weight falls on the farmers' shoulders because they have to feed the crops. And also if they cannot allow the land to go fallow because of the technologies and they would just put in more and more crops, fertilizers, all these things have actually converted the land from a single crop rotation land into two or even three crop rotation lands. And with this rotation, there's more need of water and groundwater is being used because always you don't have rainfall for your career season. Because of this, compared to your 2011, you'll see more and more red blocks, overexploited, especially in the north northern regions. But I would say that the ground reality might be much, much important because if you go back to the issues and concerns I mentioned for groundwater monitoring, some of the wells are not representative or some of the wells are not pumping wells, it is monitoring wells. And if you come to your central part of India, this is where we tie up all their learnings from these two lectures on groundwater hydrology, what did we find in the central part of India? It's not a hard rock aquifers. And hard rock aquifers are not well connected because it has fractures and some of the wells would not be replying together. It won't tell the same story. So if you have one well which is pumped for farming, and right next to it, a well which is not being pumped, the water level will be always the same. So when you do a block estimation, you might be misguided. So there is a more, more need for augmenting groundwater data with other data to understand the reality of groundwater use. So if you look at the papers and all things that will be shown in the case study approach in the following lectures, you'll see remote sensing images and also land use, land cover, use data, all these combining to give a groundwater estimate, not just a groundwater level. Because at the end of the day, if you have a land full of crops in a non-rainfall season, how did the crop grow? You should have given groundwater, right? So that is where you link groundwater level with rainfall, with your land use and cover change to understand what is the reality on the groundwater. So with this, let's do a recap of week four. We did do a very focused discussion and learning on groundwater hydrology, where we focused on the overall hydrology, only the components which are necessary for groundwater hydrology. We looked at the most important components of precipitation infiltration and then how water moves down in the soil profile to different compartments in the aquifers, etc. We also looked at the very important material and material properties for groundwater hydrology, which is basically your sediment and soil materials, along with the porosity, the pore space where water can enter and store. So these components we looked at many illustrations and we understood that if there is a confining unit or an impervious layer in between the aquifers, then the aquifer is divided as an unconfined and confined aquifer. The unconfined aquifers have the top surface open to infiltration precipitation coming in, whereas the unconfined are having a confining unit both on the top and the bottom. So any system can have only one unconfined aquifer, but the confined aquifers can be multiple. And depending on the placement of your wells and the depth of the wells, the wells get different names. So if you put a well in your shallow aquifer, you will mostly be a dug well or you will have a well with a 30 meter depth. So it is annually charged. Shallow aquifers are annually charged or even within a couple of years, we looked at residence times, we looked at recharge times, et cetera, when we discussed about aquifers. When we have deeper aquifers, this is the bigger concern. Your deeper aquifers are going deep into the system right here and it is screened, so it doesn't take water from the shallow aquifers. It takes funding from the deep aquifers and you are using water which has been stored there or taken time around 100 years or even a millennia, a thousand years for the water to come there. So if you deplete it, you will have to wait another 100 years for the full aquifer recharge to happen, which is not possible in one's lifetime. So with utmost care and concern, aquifers should be used, especially the deep aquifers. If the shallow aquifers are depleted, then multiple opportunities are there to enhance the groundwater recharge, which we will be looking at in the coming weeks. But more importantly, we will be looking at how water structures, both natural and artificial, can aid in groundwater and surface water hydrology for total development. We also looked at zone of aeration versus zone of saturation, where a zone where it has the soils has pore spaces still without water or wide spaces without water are called zone of aeration because air is still present. Whereas zone of saturation is the zone where the void spaces are filled up with water. So all these things we looked at and we looked at the sloping nature of the land which helps in groundwater movement laterally. And we also discussed the stage where your groundwater recharge happens and it goes until your last impervious layer, which is your aquilute, aquitide or your bedrock. And after that water, even though gravity is acting on it, water does not move down but laterally. And once it goes laterally, there is a natural discharge. So discharge can happen in multiple ways. You can put a pump and take the water out. That is your artificial discharge, but naturally discharge is when groundwater goes and at one point comes out of your lithology or the earth's crust into the streams, rivers or springs. We also looked at perched water table, which is very less in number, and artisan wells, which are less in number and what are the reasons through which it happens. We looked at central groundwater data, how it's collected and other measurement devices. And the driving force here is the data is present, but to have more understanding and more management plans, there is a need for augmenting these observation data with remote sensing and other data like farmer crop data, yield data, etc. or even power use for groundwater pumps to estimate the amount of time the pump was running, which is also related to the amount of water it was pumping out from the aquifer. So all these data can be put together to better understand groundwater block characterizations, which is critical and semi-critical, etc. So with this, I'd like to conclude the groundwater hydrology lecture and look forward to meeting you in week five. Thank you.