 Welcome to this lecture number 19, so in this lecture we will continue with what we started in the previous lecture that is lecture number 18 which is the concept and methods of artificial groundwater recharge and after completing this we will move on to recharge mounds and induced recharge. So first we will continue with this concept of artificial groundwater recharge and here so basically this artificial groundwater recharge is necessary to supplement this is the concept of artificial groundwater recharge. So here it is to supplement the natural groundwater recharge in many cases many situations may prove to be inadequate to different degrees. So it is just like say for example the natural lighting which is I am just giving an analogy the natural lighting is always from dawn to dusk but the human activity has developed or extended to such a level so that even once the sun has set that means the dusk has the set in so still the human beings the human society and we want to do more work and we want to engage ourselves in more activities so in such cases so we need to go for artificial lighting so this is on a temporal basis and especially also so even in the broad daylight so some areas so they may have insufficient lighting so in that case we may have to take the help of artificial lighting so similarly so there is always this inadequate in different degrees both spatially and temporally that means both space wise as well as time wise so this natural groundwater recharge may prove to be inadequate so this it may be slightly inadequate or it may be significantly inadequate or it may be totally inadequate so it all depends upon the actual situation and so therefore here so this groundwater recharge and obviously so this commonsense says that so in areas where there is water logging that means excessive this natural groundwater recharge so then there is no question of this necessity of this artificial groundwater recharge so with this concept and then so there are many formulae to estimate the natural groundwater recharge and so and of course once they we estimate the natural groundwater recharge so we may find that the amount of volume of water which has gone into the that is the subsurface spaces which may be aquifers or it may be even wells or it may be any other subsurface storage spaces so in that case we have to adopt this artificial groundwater recharge and thereby so we improve our water security so this so this it improves that is water security stroke availability in general and groundwater security stroke availability in particular and so the now let us briefly discuss about the this purposes of this artificial groundwater recharge so let me abbreviate this as A G W R so purpose of artificial groundwater recharge so the following are the main purposes of artificial groundwater recharge the first one is to maintain or augment this is the most important this one natural groundwater as a resource and this resource it is economical resource as well as overall resource because there are certain parameters which cannot be quantified economically so like say such as the intangible benefits so once this artificial groundwater recharge is adopted or is employed so then it will also result in other intangible benefits like improvement in flora fauna and other things so which all of which may not be able may not be quantified so second purpose is to coordinate the operation of surface strokes subsurface reservoirs so this is the second purpose of artificial groundwater recharge and then thirdly the third purpose of artificial groundwater recharge is to that is to overcome adverse conditions adverse conditions like progressive lowering of groundwater level unfavorable or unfavorable or undesirable salt or salinity balance in water so which includes salt water intrusion also not salinity intrusion also or say brackish water intrusion so this is the third purpose and the next one is to provide additional subsurface storage for local or imported surface water so once we have this once we employ this artificial groundwater recharge so then it provides an additional storage additional reservoir subsurface reservoir which can be used for so which can be used either locally or which can be transported over short or medium or long distance so to meet the appropriate water use so next is this is to reduce or stop completely stop subsidence of land significantly see here so once this artificial groundwater recharge is adopted so it will improve the soil balance that is I am sorry the moisture content in the soil and thereby so it will improve the strength of the soil so it will be less susceptible for erosion so therefore and not only this one and also what happens is it will be less susceptible for subsidence and like the foundation and also it is the foundation that is settlement of foundation so unequal settlement or it can be even totally that is almost it is total settlement in all the areas so such which results in land subsidence so that can be reduced or stopped completely so that is one and then so the next purpose is to provide locally subsurface distribution system so this is subsurface water distribution subsurface water means basically groundwater distribution system through established or newly constructed wells so here so we will ensure that so there is an adequate supply of subsurface water and the additional adequate supply of a subsurface water which can be harnessed through either this already established wells or existing wells or newly constructed wells and then so this is the six purpose and then next is to provide treatment stroke storage for reclaimed wastewater for subsequent partial or total reuse it is said that the solution to pollution is a dilution so therefore so this wastewater when it is reclaimed so there the artificially recharge groundwater what it does is it will ensure that the that is the reclaimed wastewater is further diluted and so thereby the concentration of the pollutants in the wastewater is further minimized and many times it may be within the permissible limits or it may be even almost be much below the permissible limits so in such cases it can be used either for partial reuse or total reuse so here in this case I can give an example of this new water so basically in Singapore wherein so some fraction may be 5% or say 10% of the water which is being supplied is added with such treated reclaimed wastewater so and then so that is this one and then lastly the to conserve or extract energy in the form of hot or cold water so here we know that the there is always an optimum depth below ground where the temperature variation is minimum and we can use this utilize this fact to our advantage and then so we can create a reservoir through this artificial groundwater which as you can create a reservoir so which may be of great help especially in winters and which is also known as passive air conditioning technology and so or in summer when it is too hot so that time so it may provide it may be able to provide water which is significantly colder than the extreme summer temperature so all this can be so that can be one we can utilize the that is the ground as a reservoir or insulator wherein so this temperature can be one temperature variation can be reduced so these are the purposes and so and based on these purposes the concept of artificial groundwater recharge is hinged upon so now we will go to the methods of artificial groundwater recharge methods of A G W R so that is artificial groundwater recharge so there are various methods for this artificial groundwater recharge so let us list these methods and then briefly discuss one by one the first one is the basin method so this is followed by stream channel method and then the third method is this ditch and furrow method then there is flooding method the fifth one is the irrigation method and the next one I am writing here that is the pit method then lastly this is here let me write here only the recharge well method so these are the seven methods of which are generally used for artificial groundwater recharge so now we will briefly discuss these methods and and these methods are the names of these methods the titles of these methods of artificial groundwater recharge are self-explanatory now first let us go to this basin method basin method of artificial groundwater recharge I am extensively using the abbreviation A G W R which is artificial groundwater recharge here this case say basically what is done is see whenever there is excess supply of surface water so this surface water is stored in a basin which is in the vicinity of the stream or a water body and in this case say for example say suppose this is there is a stream say suppose there is a stream and let us consider the for let us say the flow is from right to left in the stream and here what this basin method does is so an additional basin is created and so this is the stream or river and then this is the diversion structure so it could be a small veer or a barrage and here so this is so this is the intake structure and here this is sediment retention basin or which is simply known as sedimentation basin and followed by so this is so these are let us denote this as B and here so that is like this so this is these are A so here this A represents a recharge basin and this B represents that is inter basin control structure control or regulating structure so this is the a typical plan or say top view of a multiple basin artificial groundwater recharge so it will be like this so basically so here what happens is so the this is it is in the same direction so initially there is an diversion structure which will create which will augment the head and then so the water is diverted through the intake structure and then from the intake structure it passes through the sediment retention or sedimentation basin and then so there is the intubation control structure so here by closing this bottom one that is the below one we can ensure that so these top three recharge basins can be recharged and similarly if we close the top one so this one we can ensure that so there is recharge only in these bottom three recharge basins so like that so this is the basin method so in which the area which is in and around the water body such as a stream wherein it is feasible topographically so it can be employed and so here this will induce so because of this large area of the basin so the flow velocity of water is significantly reduced and then so therefore it will result in this it will induce artificial groundwater recharge by significantly through infiltration so initially the top aquifer that is the unconfined aquifer is getting recharged and then again this subsequently it also results in the recharge of lower confined aquifers of course and if you want to further increase its size one so then obviously we have to use appropriate techniques so that it can be done so this is the basin method which is the first method of artificial groundwater recharges so now let us go on to the second method which is the stream channel method and of course in this case the so here let me so the second is the stream channel method of AGWR so here so what is done is suppose so this is the top view of a stream in this case a check dam may be constructed along the so this could be so this is a stream and then this is a so this is a rock and wire check dam so this is basically here you can so that is it is a dry rubble masonry so here what happens is this dry rubble masonry which is which forms what is known as a check dam so is constructed across the length of a stream or river and what it does is so initially it will the all the finer sediment particles which otherwise would have flown along with the stream water so these are trapped so their velocity is significantly reduced and then so these finer sediment particles so they basically get deposited in the that is the intermolecular spaces or say it is in the interstaces of the this dry rubble masonry and then so what happens is so this is initially it will start as a soil conservation measure and then it also conserves water and then eventually it will conserve vegetation also so which are the three important parameters to be conserved in integrated watershed management so therefore so the stream channel method in this what happens is so this is the suppose this is the here let me show this is the this is the original extent of stream channel and then the improved extent so because of this construction of this dry rubble masonry and all so what happens is so the this will be there will be an additional storage of water so this is the here so this is the improved extent of stream channel storage after this artificial ground water recharge and here so this is the original extent of stream channel so this is original extent of stream channel storage okay so this is the second method of artificial ground water recharge which is the stream channel method and now let us go to the third method that is the ditch and furrow method so this is the third is the ditch and furrow method of AGWR so in this what is done is so this is the ditches and furrows are created so that say this is the suppose if this is the original land profile so this is the so here this so here certain furrows so these are the furrows and then so this is maybe some this ditches also okay so these are the ditches this this as well as this and then so these are the furrows so they are all basically this are done as one or they may also have so these are the furrows so the new so this is the this is the modified land profile so by creating this ditches and furrows so we are going to increase the water retaining capacity or water withholding capacity and which will eventually result in artificial ground water recharge so this is the third method and so the fourth one is the flooding method so here it is self explanatory so in this case is simply water is allowed to flood so the precipitation water allowed to flood along the surface at the desired location or locations such that there is no mosquito so that means it is also known as a vector problem to menace problem okay so by doing this so that is we may adopt various methods so that flooding is there but at the same time so there is no growth of mosquitoes and undesirable organisms and so therefore so this is once this is the water is allowed to flood so then it automatically it will recharge that will flow by gravity in the vertically downward direction and then thereby this artificial ground water recharge is achieved so next is that is the irrigation method so here also it is self explanatory so in this case so what is done is that is so this is a crop sir excessively irrigated so that they can overcome this crop sir so that they can overcome the water shortage problem in the near future and also better utilize the existing excess availability of precipitation water or say rain water or precipitation water so this is the irrigation method and of course so once the excess water is allowed so then so this we may reduce the irrigation frequency this frequency and then we may even go for this deficit irrigation so that even if there is slight delay in the monsoon or this one so the plants are self sufficient to overcome that situation because of the that is the already achieved this one that is what I should say the because the already achieved water availability so this is the fifth one and then lastly so there is a pit method so this this pit method is also so that is the sixth one is the pit method of AGWR so this is self explanatory so this pits of appropriate sizes stroke shape dug at suitable locations where in excess water can get stored and bring about and say eventually bring about artificial ground water so this is the pit method so these are the six methods of artificial ground water recharge and of course these are not exclusive so we may adopt any new method which may be this artificial ground water recharge so to give one simple example so I can mention here so that is so this the terminology of rain water harvesting is very popular these days and of course so this rain water harvesting is essentially it is also one form of artificial ground water recharge and in this case I am I would like to bring it to the notice of this one of the fact that a village lady that is in an interior coastal the rather in coastal Karnataka near the town of Mangalore so she uses her old saris and so this she spreads these old saris around this one and then so the coastal area which is having a relatively large amount of humidity so the this water the the humid water it gets this one and then eventually so there will be condensation of this humid water and then so she gets may be some amount of may be few liters depending upon the size of the saris and all that as well as thickness of as well as the material so she gets this one so like that so the this she bring about and that is harvest or the locally available excess moisture and so with this they will complete as one and now we will go to what are known as the recharge mounds so these recharge mounds are essentially the mounds or humps which are created by artificial ground water recharge so these are here I can write down so these are the mounds the humps or mounds so these are the humps or mounds created by this artificial ground water recharge carried out on a sustained basis and here let me draw the a typical this one the cross section as well as in this case say for example say suppose this is the so this is the ground surface and here suppose this is the square recharge basin and here this is here this is a regular shaped so which in most of the cases may be recharge basin square and here what happens is so that is say suppose so this is the here you can say the average length of this one is a the regular shaped recharge basin so let me just differentiate so here what happens is so this is the the initial water table so this is the original water table or piezometric surface let me write this as and then because of the storage of this water in this recharge basin so here what happens is so it will form a mound here okay so this is the so this is the water table during or during stroke after artificial ground water recharge so therefore this is the the recharge mound is created here because of this the recharge in a regular shaped basin then so this is a so this is a typical recharge mound then we will go for this is the induced recharge in this case anyway I think we will stop here and we will continue with the induced recharge in the next lecture and okay so thank you