 Welcome to this lecture number 18. In fact, it starts with a spillover of lecture number 17 in which few topics could not be completed and so that is they are well protection, well rehabilitation and well testing for yield. And after dealing these topics, so this lecture will move on to the new module that is an artificial ground water recharge and so specifically in this lecture, it starts with the concept and methods. And so now, let us start with the topic on well protection and here, so this protection, so essentially, so it is a process or a mechanism wherein we protect the well water quality. So basically, well here we can more precisely, we may also write well ground water quality because after all the wells they do yield ground water only. And so this from either existing sources of pollution or potential sources of pollution, so which may exist either at or above the ground level or below the ground level, so that means which may exist either above the ground or below the ground. So basically, so this well protection is a preventive as well as curative process or curative phenomena and for the existing pollutant pollution sources, it is a preventive, it is a curative phenomena and for potential pollution sources, it is a preventive phenomenon. And there are different types of well protection, so depending upon the purpose as well as the type of well for which it is as well as the type of season also. So here, we can classify, so this well protection into three major categories. The first one is what is known as a sanitary well protection, as a name itself says, so there is always say in the water supply schemes, so there is, they are always in, even though it is unavoidable, so the undesirable by-product of wastewater as well as the wastewater system. So they will be in and around the vicinity of this water supply system, so therefore especially near the wells, so there is a need for protecting the wells from existing pollutants which will be generally found in the wastewater system which may be say sewer or which may be any a manhole or which may be any other facility or carrying wastewater, that may be a domestic wastewater or an industrial wastewater or a combination of both. So this, so there is a need to protect well from the, protect the well water quality that is the ground water quality and that is precisely known as sanitary well protection. And then coming on to the next is one, so here this is the spring well protection and this is basically a preventive phenomena wherein a spring which generally releases say possibly the best quality of ground water and so it needs to be protected from potential sources of pollution. So and here so basically it is a preventive process or preventive mechanism. And then thirdly there is also what is known as frost protection, so this frost protection is employed in severe winter conditions in cold regions. So here what happens is, see in case of winter especially around December, January, so most of the northern hemisphere as well as say that is June and July in significant parts of the southern hemisphere, so they are subjected to severe cold and this problem is getting aggravated because of the impact of climate change. And so here what happens is, so this many wells they do get affected by this frost. So basically the wells may fully the ground water which is stored in the wells, it may fully freeze and so it may be difficult to that is harness or extract this ground water to this pipeline system which starts from the ground water these wells. So therefore there is a need for protecting the wells from getting affected by frost which may stop or which may break the continuity of water supply scheme in a cold region especially during winter seasons. So now coming to this sanitary well protection, so let me discuss here the one typical schematic diagram of a sanitary well protection wherein a well is protected from an existing source of pollutant. Here so this one, so the schematic diagram for a sanitary well protection system and here the, so in this case system say for existing pollutants at surface level of course so this is reasonably simpler but if the pollutants are existing at the subsurface level then it makes it much more complicated. So in this case so here let us, so this is the ground level of course here it is generally wells they may not have this kind of upward mount but may be for protection so it may be so and so this is the ground level and here this is the, so the piezometric surface or the water table WT so that is piezometric surface here. So next we will, in this case so there is the well which may have say a kind of a casing and then so there may be, so this casing will extend even below the, this one also and so here we may have a foot wall and so this is further we may have a, so this is the lower most portion is the screen and then so this is the screen cap just at the bottom of this one and so this is, so this is the foot wall so this is the screen, so here so again let me show this with a casing is, let me show this casing with of course may be even in the, so let us say this well is drawing its water from unconfined aquifer as well as confined aquifer and here in this case say this is the confining layer which is the bottom confining layer for the unconfined aquifer and the top confining layer for the confined aquifer. And so this is a, and here this is the unconfined aquifer so this is a, so here we can say this is a slotted casing and here so this continues again so this is a casing, here this is a regular casing and then so this is the foot wall screen and then so here there is, so now so this is there is what is called a grout seal, so this is a cobbled drain, so here this is also cobbled drain and then this is the grout seal with cement concrete grouting and followed by and so here let us say this is the, here let us say so this is the outlet, so this is the outlet and above this so there is a pumping unit, so this is P, so this P represents pump unit and this case so this is the grout seal and so this the dimension of the grout seal may typically vary say and here it could be, so the formation could be clay and so this is and here this is a confined aquifer. So like this so here what is the grout seal which is, which almost extends up to the normal water table level as well as the cobbled drain which is seen at around this one, the grout seal, so this which is a cement concrete grout seal, so this is, so this will prevent as well as the modification in the ground slope so that the water, the polluted water does not get seeped or infiltrated into the well and then thereby that is causing the deterioration of the ground water quality, so here so this is, so here let me also write this is the modified land profile or say ground profile and then so this grout seal as well as cobbled drain, so this will, they will eventually succeed in preventing the water from this one. Now let us go to the second schematic diagram for spring well protection, in this case it is let us say schematic diagram, so in this case so let me, so draw this is the top view and then so here let me draw the front view, so in the top view so essentially we have, so there is an overflow pipe, so this is overflow, so you may want to denote this one, next there is to storage, so there is also another pipe which takes to storage, so this is to storage, so there is a third pipe which will take the water which is basically clean out drain, so this is and in the front view so obviously the clean out drain has to be at the bottom, the storage has to be in the middle and overflow has to be at the top, so this is obviously common sense and so here in the top view and in this case another thing that is a screened drain and in this case there is, so here this is the screened drain and so these are wall and box next is, so here there is a pipe which runs a perforated casing pipe, so essentially this is a perforated pipe and then there is also a surface water diversion ditch, so this is the surface water diversion drain or say ditch and then, so here there is a barbed wire fencing or any other suitable fencing, so this is the fence. So this is in the top view and now let me show the same thing in the front view, so here so that is, so this is the, so here we have the MWL maximum water level and so this is, so here there is a screen drain and this one, so there is a, so this wall and box, so this is a clean out, so this is a clean out drain here which is in the, this one at the top view and this is in the front view and this clean out drain, so this will take you and here you have that screened, so this is the clean out drain and then followed by the storage, so for the storage, so there will be a pipe, so this is a two storage, so here this is the wall and of course here also there is another screen drain is required and then, so there is just above the maximum water level, so there is a this overflow wall, overflow pipe, so this is overflow just above the maximum water level and here in this case the perforated pipe, so it runs like this and then, so here this is the perforated pipe and in the elevation, so this will be, so this is the perforated pipe in the front view and here we have, so this is the drain, so this is the ground level, so in this case let us say, so this is our ground level, so this is the wall to be operated, obviously both walls have to be above the ground and here, so this is the, so it goes like this and so here there is a break line and so in this case there is a surface ditch or drain and then followed by a fence here, so this is a typical spring well protection system, so here in this case, so any potential this one, so the pollutants are removed through the surface water drain and then, so this through the perforated pipe, so only clean water is allowed to enter the spring and then, so that is, so this is the front view of a typical schematic diagram for spring well protection. So next this frost, that is frost drainage, I am sorry frost well protection, so this is the very common especially in the winter season in cold areas and so here obviously, so there will be a mechanism to ensure that the water temperature does not fall below the freezing point and thereby the water supply is ensured even on the coldest of the winter day and of course, whatever precautions we take, so that is nature always shows that it is the real boss many times and then, so the cold winter storms, so you know how difficult it is especially in cold regions, so that is, so this completes the well protection and now we will go to this well rehabilitation and so in this well rehabilitation, so basically it is the process of ensuring maximum recovery of the well ground water production capacity lost due to various reasons by employing mechanical, stroke chemical and other means. Basically what happens is in well rehabilitation, so with time generally there is a very significant where is a strong possibility that the well production capacity or the yield or the specific capacity, so it goes on decreasing. So in this well rehabilitation, what is done is appropriate mechanical procedures or appropriate chemicals or even other means are used, so that the loss, the most commonly observed loss in the well production, well ground water production capacity is minimized, so thereby, so most of the well, the lost production ground water production capacity of well is restored, so that is well rehabilitation and of course, so many times, so this is even before we ensure that the production capacity of a well is restored, we need to ensure that the pump which is extracting the water from the well is properly functioning, so before identifying the reasons for loss of well production capacity, we need to make sure that the pump used for extracting ground water from the well is functioning satisfactorily, so this is a very important point. So once we ensure that the pump is functioning properly, so only then we can attribute any loss in the well capacity to various, that is subsurface phenomena which might be taking place below the ground level which as a result of which the well, the ground water production capacity of the well has received a significant beating, so this is a well rehabilitation and so here say some of the most commonly, that is commonly used well rehabilitation methods for different aquifers, here say this is a method, so let us briefly, so this is by, so this is courtesy Erikson and so this is, it was proposed by Erikson in 1961, so here this is the first column represents method and then say this is unconsolidated aquifers, then consolidated sandstone and then lastly consolidated limestone. So these are three different formations and for each of them, so how the method, the first method is that here you can also say this is serial number, the first is it is known as muriatic acid and this and chlorine Cl2, so this in case of unconsolidated aquifer it removes FeS, then CO3 deposits, that is carbonate deposits and whereas the same muriatic acid followed by chlorine, so this is for a consolidated sandstone not usually effective and similarly for a consolidated limestone, so this is sometimes effective best results when obtained by that is pressure acidizing, so this is one and then followed by the second method is polyphosphate followed by chlorine dynamite, followed by chlorine dynamite and this one in case of unconsolidated aquifer, it is a removes fine silt, clay or say colloids clay and this one that is disseminated shale etc. Whereas the same thing again here in case of consolidated sandstone, so this polyphosphate as well as chlorine dynamite that is also not usually effective and here also this is in this case also this is not usually effective. So like that so there are other this one that is methods are all there, that is other four more methods are there, so the remaining well rehabilitation methods using that is one compressed air, two that is dry ice that is obviously solidified carbon dioxide and then third is a surging chlorine and followed by lastly the caustic soda that is NaOH, so these are also used. So this will complete this well rehabilitation of course for want of time we are not able to give much of this one and next we will go to that is the well testing for yield, so in this case so this is a very important aspect of well and here so what is done is the yield is tested by using appropriate methodology using the appropriate materials and so therefore here so this pumping generally done by using a pumping equipment and in this case so a typical so this pumping equipment so which may be say for shallow wells and say for deep wells for shallow wells the pumping equipment will be different so it may use say a centrifugal pump whereas for deep well we have to use submersible excuse me submersible pump that to multi stage submersible pump say for example here that is centrifugal pump may be used in this case that is multi stage may be used and so here let me show a typical that is a method for well yield testing for a shallow well so here what is done is say suppose this is the let me start on a new this one this case a typical so this is the ground level and here we have the well and here we have the pipe through which so this is a storage reservoir so this is here you can say this is the water supply this one so this is a storage reservoir and then this is the pump this is the ground surface and then the static water table so here water table and after this pumping so they so there will be a formation of cone of depression and this is this one and below this so there is a screen and here so the typically so this is the pump axis and from the pump axis so this is the storage water level and here let me indicate the water level in the one and so here what happens is this is like this so this is the elevation so in this in this graph so this vertical axis represent elevation then so this is the frictional loss and here so in this one if you plot the of course here so this is the discharge and then this is the draw down and in this case this discharge versus draw down so this curve will be having a something like so this kind of a plot and this one is the static head or suction head so you take this one so this is the of course so this is a typical shallow well yield testing setup obviously so here this is the so this completes and obviously as we go for deeper tubal so then we have to go for say submersible pumps that could be multi-stage submersible pumps and so on so therefore it complicates things as well whereas that is why to avoid this complication so a simple this is a typical shallow well yield testing equipment is shown in the schematic diagram so this will complete the chapter on that is that is the well hydraulics and I am sorry the module the third module on well hydraulics and so I also take this opportunity to start this the new module that is artificial ground water recharge which is so this is module 6 and so the advanced well hydraulics is the third module which we discussed till now so the modules 4, 5 as well as 7 and 8 will be dealt by my colleague Professor Anirbhandhar and I will be in this lecture as well as in the subsequent two lectures I will be discussing briefly this artificial ground water recharge and here let us come to this concept whenever there is inadequate natural ground water recharge artificial ground water recharge needs to be employed to create water security and here so coming to this so this is the basically the concept and coming to the other one and in the next class we will discuss with the methods of ones and there are various methods like in the surface level spreading and other methods are there and creating this artificial mounds recharge mounds or induced recharge and various things are there so which we will be discussing in the next lecture so I thank you and so we will meet for the next lecture thank you bye