 Hello everyone, welcome to NPTEL course on groundwater hydrology and management week one lecture three. The previous lectures we looked at how and why groundwater is very important in the hydrological cycle. Then we focused on the different aspects in groundwater use between developing and underdeveloping nations, how groundwater is being used especially in underdeveloped and developing nations for agricultural activities. We then also looked into the disparity in water use which is leading to a disparity in water stress and we also looked at within India the water stress is leading to further depletion of groundwater. In today's lecture we will look more deeper into the hydrological cycle. We would also bring some concepts from the Central Ground Water Board in assessing the water stress. Let's understand the hydrogeological process for groundwater. What we see here is the hydrological cycle overall with a mass balance for a water balance which shows how much water is available as an example for a particular area and how the different water sources are contributing to the atmosphere and then coming back as rainfall. You could see that evaporation from the oceans is contributing 320,000 kilometer cube water to the total water which is 380. So a big portion of water does come from your oceans whereas evaporation also comes from your mountains and fresh water resources like lakes rivers etc and it comes back again as some amount of rainfall which we have here around 96 kilometer 1000 kilometer cube as rainfall along the slopes and on direct onto the ocean because ocean has a bigger space in area so on top of the ocean there's a good rainfall event also 284,000 kilometer cube right so if you add them it goes to 380,000 kilometer cube which is the total of the 96 some goes as runoff okay and some is converted into infiltration through your recharge activities into the ground. The water can come back into the oceans or small fresh water bodies or rivers, lakes etc and then eventually flow to the ocean. Lake water ponds etc may not flow back it can be evaporated but those which also go in the deep aquifers or deep groundwater parts eventually go to the oceans. So now what constitutes groundwater is it a different source of water? No it is coming from the same precipitation atmospheric process either it can be from snow converted into water so snow is kind of a solid face and then ice melting etc so once they melt it's called snow melt and that snow melt can come down from high elevations into rivers, water storage systems such as ponds, lakes and aquifers right and they can come down into the ground through infiltration. So infiltration is the process by infiltrating water into the soil it can move further as groundwater component. So what are the different sources atmospheric precipitation that infiltrates into the ground is the key source and of the atmospheric precipitation rainfall is the key source. There's multiple different ways in which precipitation can happen one is snow, hail, sleet, drizzle etc do you but we will focus on rainfall more because the rainfall process is easier to understand the flow into the rivers, lakes etc and you can also relate it directly to your infiltration. Surface water that becomes trapped in poor space of sediments during the deposition in lakes streams and especially the oceans is also a source for groundwater which means suppose you have a lake suddenly it can be trapped by some debris for example you have an erosion a lot of sand is going to be deposited on top of a lake what happens your water is pushed down or the water gets locked in the system. Once the water gets locked it cannot move anywhere either it constitutes or comes back to the other groundwater sources by further pressure or it stays there as a purged water table. So some surface water body can be stored. Water de-gas from cooling magmas which means your lava material is there when lava flows the molten material magma when it flows it can also de-gas and water is a byproduct so that water can be stored in your rocks and sediment as a groundwater source and then there are some metapharmic reactions that break down into hydroxide minerals. So the point here is we are not focusing on the deep deep water ground waters resources etc because that is not what we use and what we can manage the only management option is don't take that water we don't do factoring to take that water. So we will focus more on the water that is annually used for example groundwater for drinking water etc so that you could better manage the resource. So this course would be focusing on the hydrogeological process and the groundwater hydrology up to the confined or deep aquifers not very deep aquifers just to the deep aquifers which are being used and exploited for agriculture for industries and urban demand urban and also rural domestic demand. So that would be our focus for this course. Let's look in a pictorial diagram of what constitutes groundwater and in here you have the stars as snow and snow can convert into surface runoff which is easily explained using the rainfall so rainfall can hit the surface and convert into surface runoff. So water is hitting water hits it goes as surface runoff okay so water you see pooling floods all those are discharged or surface runoff due to rainfall. Okay let's start from the clouds you have precipitation precipitation can fall on the ground part of it or most of it can go as surface runoff it depends on the land use if we have urban centers houses etc most of the water goes off whereas if you have agricultural land or a forested land for a good part then water can infiltrate water infiltrates and goes into the root zone so you can see here water first infiltrates while runoff also you can infiltrate while on the river while and upon late water can infiltrate so it just needs extra time okay it's much much slower compared to the surface runoff process so when there is a slope an air so this is your land a slope water is falling as soon as water falls most of the water goes as runoff and very little water goes down as infiltration and that is because the infiltration rate is much slower than the precipitation rate and or the surface runoff discharge or the process that contribute to surface runoff. Moving on after infiltration some water goes in the infiltration can come from stream flow surface runoff precipitation and or stored water bodies like here so once it goes in it hits the root zone the first part is you have your soil the top surface water goes in the top part is organic matter and hummus etc which is okay but then when it goes in it goes as a root zone that is where the plants have their roots extended and it can easily take the water the ground water after the root zone you have a tree root zone okay there's a plant root zone there's a tree root zone both are not the same just a depth difference okay but you can combine both of them as a general root zone so the water can go into the root zone after the plant is taken it up after the relocation of water has been done subsurface in the lateral direction so this is vertical and this is horizontal or lateral so water moves vertically and then it can go spread out laterally also and then can continue to go down why is it going down it's because of gravity so gravity is the force which is responsible for the ground water hydrology component it drives the system otherwise water can just go up right from dissertation it comes on because of gravity it hits infiltrates because of gravity etc and once in the surface subsurface also inside the soil water will move down to the root zone because of gravity not just because of the plant's pulling capacity okay so once water moves to the root zone some soil would be taking up the water depends on the properties of the soil and some plants would be taking up the water at least plants would take it up and evaporate evapotranspiration happens whereas your soil just stores the water it's called soil moisture then we have the subsoils the subsoils is when you have a soil layer below the root zone where water can also enter so there are some part of the infiltrated water would go into the subsoils and that is where percolation happens percolation is further movement of water or relocation of water under the subsurface and then you have your bedrock and aquifer so bedrock would be your confining unit which is impervious most of the time but then you can have some water going through so it's a very slow process and then finally it can come to your aquifer after it bypasses your root zone and subsurface soils okay while you're in the root zone and subsoils after you have crossed it groundwater can also go laterally rather than vertical it can move laterally because of the bedrock or the impervious surface okay some water can go on the side and come out into oceans then evaporate go back to the rainfall and come back again so the cycle can go on what you see here is the remaining water after interflow after subsurface flow some water does enter the aquifers the aquifer is the storage part for groundwater where lot of porosity or space is available for the groundwater to be stored and groundwater to move please do not think it's like a river like the diagram here is showing it's just a soil material with a lot of holes soil or rock material it's a medium with a lot of holes where water can be stored and if the holes are connected water flows we will get through the each definition in the coming lectures so percolation is the important phase where the precipitation converts into groundwater resources because before that infiltration is the initial part but most of the water can be taken up by plants or soil it need not go down through right so that part will be very careful in understanding that only after percolation you have the concept of groundwater hydrology and some part of this water can go up due to capillary rise it's very very small but still we need to acknowledge it so capillary rise can happen because of the nature of the soil water can be pulled up and stored here even plants can pull up trees can pull up okay and again do not inter imagine this as a river flowing there are rivers that flow under the ground especially in caves but groundwater per se doesn't flow like a river but it is flowing through pores and it goes through a medium mesh of materials it's not an empty space like your river is there it's not an empty space where water can flow it is with materials and so it is very complex in nature and groundwater will eventually join the oceans or evaporate in your local water bodies so now you understand that compared to surface hydrology groundwater hydrology is much more complex you have here is all your surface hydrology components whereas your groundwater is more complex because of the complexities in the water reaching the aquifer and also how it flows through a porous medium it is not a river where you can put a dam and then store all the water right it is it can just bypass it because that's the way it was initially flowing so it is a porous medium medium with a lot of holes be it sediments or rocks soil etc and then through that water can move okay so again why is groundwater important let's look at one more analysis groundwater makes up a large pore portion of earth's hydrological budget water budget and it is widespread in the earth's because it's not just located like the oceans are located only in some areas not in the land groundwater is located everywhere okay even under the oceans you have groundwater aquifers and that is where it might be seeping and leaking into the ocean so 0.62% of total water budget compare this with FAO which was saying 0.69 and the other study which was calling it 0.5% of the total water budget is from groundwater okay so only 14.2% of earth's freshwater is accessible only 14.2 of earth's freshwater because most of it is in glaciers etc the 14.2 is because some groundwater cannot be accessed even though groundwater can be 20% it cannot be accessed so in the previous study we saw 2.5% here it's 2.8% and that 2.8% almost 90% or 80% goes into your glaciers and the 20% plus 1% is here so that 21% equates to only 0.62% and that 0.62% is also not fully used because you can somewhere groundwater is stuck okay so please understand that there is a hydrosphere which is the hydrological budget of all the water resources and no ocean component is this one okay so because you've taken the ocean out so you put this as 100% percent all these is to drive the factor that groundwater is high commodity compared to the freshwater available but the stress is making it very unsustainable and also on top of that why is the stress there because the freshwater availability on the planet is very less we've been thinking that everywhere there's water atmosphere there's water there's water in snow ice but it is such a small portion when you convert it to freshwater and even a smaller portion when you say accessible freshwater for example freshwater is inside our body but can we access it no we need to replenish it so when we drink we replenish it because we also have a sweat and our water comes out of your pores etc when we transpire so we also are like a small mini hydrological cycle we drink water and then we excrete water and also we transpire water what is it driven by so what is your all these budgets and hydrology driven by the first and foremost thing is your precipitation let's look at an iso-heater map from Professor Ragnar's book you could see that India has a unique and very different land use land cover pattern which enables different hydroclimatic zones so you can have the driest of the driest regions 25 centimeters and one of the top precipitation regions in the world around here Cherapunji etc and around the western blacks so think about 25 centimeters here whereas you get 250 centimeters on this side 500 centimeters on this side okay so that's 5000 millimeters of rainfall and here along this coast you get around 3000 millimeters of rainfall along the western north so that's why you have so much rain in Kerala and etc so almost double you get here however here on this side you don't even get 10 percent of it okay so five percent of that comes in and which is very very less compared to how much water so there is a big differences in water availability and this also drives the stress and because of that it also drives the need for a groundwater access the other thing which it drives is first you need rainfall to eventually recharge the other thing is you need a material to store the water and here the material is the hydrogeology wherein it is the geology the rock the sediment the materials where the water can store so the groundwater is not just a unique one process it is a combination of processes it has to start from your rainfall get into the soil the soil has to have conditions to promote groundwater storage and groundwater flow which you see from the maps here and then water should be able to be stored if water just flushes through it's not groundwater right it just moves through and goes somewhere else it has to be stored slowly it has to be released so if you look at here you have good groundwater yield areas here along the Ganges Indus Brahmaputra which is also regions with good decent rainfall it's also the Brahmaputra okay and then you come to Central India where you have a medium yield aquifers or yield groundwater storage units where they have consolidated some consolidated formations of rocks and those rocks cannot store much water and that is why you have a less yield yield is how much you can take out and this part is also if you remember the stress diagrams this part is also the regions where high water stress is being predicted high water stress is not predicted here because you have good rainfall and you have good potential of the aquifer to permit store and use the groundwater whereas here you have less rainfall first so you the farmers are forced to take groundwater and on top of it the geology doesn't support storage of big water storage units it's very small small water that you could store moving on it is a combination of your geology and hydrology and so you have the hydrogeological map and geology is a very very important process for groundwater movement and storage depending on this there's a lot of calculations done to understand how much groundwater we have how much is recharging etc and it is given in different units we'll be using the unit billion cubic meters per year by Central Ground Water Bowl and just giving an example you don't have to worry about how do you calculate all this these will be calculated in the following lectures the idea of this slide is to zooming in is to just show you a calculation let's take Madhya Pradesh for example it has annual replenishable groundwater resources which means count for groundwater and it gets replenished annually it's like your salary every month you get in money and you can use it throughout the month so for example you are getting money on the month end of 30 31st and then you use from 1 to 30 right so you repeat it and then it gets replenished in the month end so same way you you have estimates for annual groundwater use so these are the positives recharge is 28.22 BCM per year and then you have recharge from other sources 1.17 this could be your magmas surface water storage other things but recharge of rainfall is biggest okay then you have non monsoon recharge which is not from rainfall and recharge from other sources so industries rivers which are flowing can recharge etc total comes to 35.05 billion cubic meters per year and the natural discharge naturally water will go into your oceans I showed you in the hydrological diagram so that component is very small and if you subtract that from 35.05 you get 33.29 there are some decimals so you would see some adjustments so 33.29 now this is the natural draft natural extraction let's come to the human anthropogenic extraction so for irrigation that is the biggest use of water 17.48 out of 33 17.48 more than 50% okay is used for agriculture and then your domestic and industrial use still not as big but close okay very very close to your natural discharge which means your natural release of water then you have your total so if you subtract all these from 33.29 you get around 18.83 which is your net total draft okay so 17.48 135 gets you 18.83 which is your total draft you should add this with your discharge also or you can subtract this from 33.29 getting that you get a percentage of groundwater development these two are projected groundwater use for industry so this 1.35 can go up to 1.91 and groundwater available for future irrigation which is the remaining part is given here 13.90 either way what you see here is the stage of groundwater development so almost 60% of your groundwater in Madhya Pradesh is used every year so still it's on an okay number so they will call it semi-critical or safe why because you are getting 100 rupees and out of the 100 rupees only 60 you're using the remaining 40 you're saving like a bank account fixed etc the 40 won't stay because it is a leaky account what will go to some other place it moves into the oceans etc so under that circumstances 60% is still okay okay so the government doesn't put a cap on that value I'll come to the image here okay so you have critical over critical so it'll be around semi-critical to save which means not big management activities are needed at this stage okay so we looked at a particular state and I just took the top list so that we have the titles also moving on how much available water is there as per a basin size initially we saw a state state is more important because the administrative boundaries is where you can do management work you cannot do gadgets management across different states because some states may not be accepting the same project correct so what happens here is we are still showing the basin wise because basin is how the water comes through the hydrology through the climate weather and also your watershed approach so looking at that your Ganges basin is the biggest representational groundwater resource and also it uses very very low so that's why totally 33 percent of the groundwater is used so off the river basins the Madras and southern region basin which includes a small small rivers in the southern Chennai region is highest because it's also industrial and also urban use driven groundwater depletion the irrigation is also there so around 60 percent of the water is used so if you do a basin wise calculation all are safe which is wrong right you cannot do that because some blocks might be within your basin your basin size is pretty big and within the basin one or two blocks can be notorious and pump all the water out and that is where it will disrupt the system and you need to put some controls or management activities this is the annual application of groundwater resources as per the rainfall diagrams and and where water can replenish okay so unit recharge is up to 0.5 here and very very less in the light blue colors so you could see most of the Ganges in this basin Brahmaputra all in dark blues and along the deltas where the water river water discharges into the ocean you have a good dark blue color showing recharge anywhere from 0.5 to 0.25 after that it is pretty slow recharge rates so we need more activities and if you look at this image and this image you could see clearly wherever there's a slow recharge rate and less rainfall that is where people are actually consuming more and more groundwater Rajasthan, Haryana, Punjab etc etc Gujarat so and here you have in the southern region also Andhra, Karnataka, Tamil Nadu some parts of Kerala also so it is very important to understand these red color zones where immediate actions have to be taken to preserve groundwater red color means you are using more than your annual recharge so if 100 rupees is coming into your account you're using 120 rupees which means you're using a credit card or something so eventually you need to pay it off right and that is where it is marked in red and the government is telling that we need to kind of these images are telling we need to take stringent actions or management activities to change the color change it to a more critical or semi-critical stage so with this I would like to conclude the lecture we have gone through how water comes into the groundwater hydrological system and how groundwater data this recharge estimates can be used to understand the water budgets and then we ended up as hydrology and geology should be considered to understand the groundwater and demand and access etc I'll see you in the next class thank you