 Welcome to this lecture number 5 of this groundwater hydrology course. In this lecture we are starting with the second chapter that is on occurrence and movement of a groundwater. And we know that this groundwater, so initially it appears in the below the ground and then it moves below the ground also in various locations. So, all these aspects will be studied in this chapter. So, here so first of all we need to know where and how this groundwater exists. Next we need to, so the geologic zones which facilitate the storage and or movement of groundwater. So, when we are when we need to know where and how groundwater exists obviously, we our focus is shifted to the geologic zones or formations which exist below the ground. And so not all the geological zones below the ground are conducive for the occurrence and for groundwater. So, only certain selected geological zones facilitate the storage as well as movement of. So, we need to study them. And here, so the next is, so the water holding and water yielding properties of these geologic zones or formations. So, and of course, therefore, the here, so we cannot exclude the role of geology from groundwater hydrology. So, as the this groundwater hydrology implies, so the study of water the quantitative the predominantly quantitative study of water below the ground or below the surface. And here when we talk of this one the groundwater hydrology. So, we have to consider the geology also. And there are some special cases also such as say the, so here let me write. So, geology is an important part of geology has an important role in groundwater hydrology. And here, so let us also let me mention here springs hydrothermal phenomena hydrothermal phenomena water in permanently frozen ground constitute special groundwater occurrences. So, these springs may be releasing water either at the normal temperature or they may be releasing water at a higher temperature or a lower temperature due to various hydrothermal phenomena wherein. So, the groundwater which is getting released through the springs it is either getting heated or sometimes it is also getting cooled down. So, as well as, so there may be some water which is permanently frozen. So, all these constitute the special cases of the occurrence of groundwater. Now, let us come to the origin and age of groundwater. So, here I would like to explain this origin and age of groundwater with the help of this diagram consisting of these 6 blocks. So, let us start with the newest among them which is represented at the top and which is denoted as which is known as juvenile water. So, that is new water and next below that is the magmatic water. So, this magmatic water of course, also includes plutonic. So, this magmatic water is in or from magma which is in the deeper strata and here and if it is in very deep strata. So, then it is known as so this is plutonic is. So, this is a very deep strata. Next is this meteoric water. So, that is atmospheric water and from this atmospheric water of course, so there is also I am sorry. So, here so there is also so this from magmatic water there is a connection to oceanic water which is the water in the ocean and here there is a two way link between oceanic water and meteoric water which is essentially the atmospheric water which is you can say it is recent water. Then there is also another two way link between oceanic water and this conate. So, which is also known as fossil water, conate water and here there is another one which is metamorphic water is the water which exists in the metamorphic rocks or rocks undergoing change in it their form. Again from this metamorphic water to conate water there is a two way flow and also here say from this metamorphic water and magmatic water there is a two way interaction. So, this is this figure is taken from the geologic geological society of America in 1957. So, essentially here we have say six types of water depending upon their occurrence as well as age and here as you can say so this juvenile water as well as this meteoric water. So, they are the most recent ones this is atmospheric water, meteoric water also means and this conate water which is the oldest one. Conate water and also you can say this plutonic water which is existing in the deeper strata. So, and in between so there is magmatic water there is metamorphic water and also this oceanic water and of course oceanic water it is a mixture of all because the ocean water right at the top. So, it must have it might have been at the ocean surface maybe it could be very recent whereas the ocean water at deeper depths it could be almost as old as say conate water or say the plutonic water and so on. So, essentially what I am trying to tell you is the age of ground water depends upon the various factors the location from where it has come as well as the depth of this the depth below the ground where this ground water is existing. Now, so essentially as I was mentioning so there are these six forms of water and it is this there is a two way interaction between magmatic water and metamorphic water. There is also a two way interaction between conate water and metamorphic water as there is another two way interaction between conate water and oceanic water. There is one more two way interaction between oceanic water and meteoric or atmospheric water. So, essentially so this ocean water is in two way interaction with meteoric or atmospheric water as well as conate water. And metamorphic water is in two way interaction with conate water as well as magmatic water. And this magmatic as well as conate water they have two way interaction with only this conate water has two way interaction with oceanic water as well as metamorphic water, whereas this magmatic water it has two way interaction with only metamorphic water. So now let us come to the age determination, age of ground water. So here in this while determining the age, so it is the isotope hydrology helps in ground water age determination and when I talk of isotopes, so two important isotopes are there, that is a tritium which is H3, that is hydrogen 3, so essentially hydrogen with two proton additional proton molecules, proton particles and then there is carbon 14 and this tritium 3 it has a half life period, so these are the two isotopes, both these are isotopes, so this has a half life period 12.3 years and this carbon 14 it has a half life period 5730 years. So here, so because, so the half life period in case of tritium is relatively small, while that for carbon 14 is relatively large. So these two are used in determining the age of the ground water in various geological formations and here so this tritium is used for estimating ground water residence times up to say 50 years and this C14, that is the carbon 14 used to or used for estimating ground water residence times from several hundred years, 50,000 years and here we should also remember that the equation which is A is equal to A0 into e to the power minus gamma t, where A is the radio activity at time t, the observed radio activity and A0 is the radio activity when the ground water enters the, when the water enters the aquifer and this lambda is the decay constant and t is the time and generally it is the time is measured in years. So with this and it is also mentioned here that this the carbon 14 isotope is present in ground water as a dissolved bicarbonate originating from biologically active layers of soil where carbon dioxide is generated. So basically wherever this, there is a dissolved bicarbonate which generates carbon dioxide by root respiration and humus decay. So there, so this carbon 14, this isotope generally exist and so these two isotopes, these mainly these two isotopes that is tritium which is hydrogen 3 as well as carbon 14. So they have been used to determine the age of this ground water samples all the way up to say 20,000 to 30,000 years in the Middle East such as the United Arab Republic which is basically the Russia, I am sorry Egypt, it was previously known as Egypt along with I believe say another North African country. So they were together known as a United Arab Republic. So essentially in Saudi Arabia and Egypt, so these two isotopes have been used to determine the ground water samples having a ages of say 20,000 to 30,000 years. Now let us come to the next part of the next article which is the rock properties which affect the ground water. And here when I talk of this rock properties, rock or soil properties implies those properties which facilitate the storage and movement of ground water. Here so before going for this rock properties, so we should know certain terminologies such as aquifer. So this aquifer it has the synonyms that is the ground water reservoir, so this is or with an underline that means one and the same it is synonym. So it is a water bearing formation. So basically so this aquifer it is this soil or rock formation or layer wherein so there is enough of wide spaces for the ground water to get stored as well as to move. And here so because of the capability of storage as well as the movement of ground water within the aquifer, so these aquifers so they are basically they yield significant amount of ground water to springs and wells for the simple reason that so there are lots of empty or wide spaces in which the ground water gets stored and because of the hydraulic gradient so this ground water also starts moving from a higher gradient to from a higher head to lower head wherever there is a slope or a gradient. So the ground water starts moving and eventually so these aquifers yield significant amount of ground water to various wells which may be open wells or tube wells or even to springs where say many small streams and other these water bodies so they originate. And these aquifers generally have a confining bed say suppose this is an aquifer it is so let me represent this as a so this is an aquifer so these represent the wide spaces in them and then so here so they may have either a fully confining bed or they may have a semi confining bed so this could be fully confining bed and then so this could be here you can say impervious and this is a semi pervious confining bed so when it is semi pervious so then this ground water leaks through this semi pervious confining layer so this is the so this is the ground water leakage you can say and so now let us also note little bit about 3 more terminologies that is aquifuge, aquitard and then aquiclude so here aquiclude, aquitard, aquifuge so here let us understand the meaning of this so we can remember this as aqua exclude so water is excluded from movement that is aquiclude so basically here so this is an impervious material practically not yielding so example for aquiclude is say clay so clay is soil with the finest particle size so therefore the amount of wide spaces is very limited so therefore this clay behaves like an aquiclude next it is the aquitard which is a saturated but less permeable stratum which retards ground water movement and here the examples for this aquitard is a sandy clay well the example for aquiclude is a clay so because clay is consists of fine finest soil particles with practically no wide spaces or empty spaces on the other hand the sandy clay it will have some empty spaces through which so there is less permeability and so it is saturated also so therefore it retards so it yields very limited quantities of ground water next is this aquifuge so this is a relatively impermeable formation not containing and not transmitting water that is an aquifuge so here we can give an example of a hard rock such as granite other hard rock so they form aquifuge so now we learnt about aquifer which is basically a water bearing stratum which can be interpreted as a ground water reservoir and also followed by this aquitard which is essentially which retards the ground water movement then it is the aquiclude which is practically an impervious material not yielding ground water such as clay and lastly aquifuge which is a hard rock so this clay will contain water this aquiclude will contain water but this aquifuge does not contain and it does not transmit also what so these are the four the soil or rock formations and out of this for our case the aquifer is the most important in case of ground water hydrology as well as this aquitard so this is we have to exploit we have to harness ground water using the aquifers and we should ensure that so these aquifers should have a proper confining layer either at the bottom or in the sides so that so this ground water is stored and it is not leaked to so undesirable locations. Now the most important property of the rock or soil is known as porosity and this porosity so if you denote it as alpha then this is volume of interstices divided by the total volume since just to distinguish this from velocity I am using the V hatch notation so this V i is the volume of voids interstices that is voids and this V is the total volume of soil or rock so this porosity it ranges from say 0 to 50 percent and in case of say this aquifuge so the porosity will be 0 percent and in case of aquiclude the porosity will be very low and then in case of aquitard the porosity will be even more and aquifer will have the highest porosity so here so this porosity can also be expressed as 1 minus rho D divided by rho m so this rho D is the mineral particle density or grain density and this rho m I am sorry so this is a so this rho m is the mineral particle density and this rho D so this is the bulk density so this porosity can also be expressed as 1 minus the bulk density divided by the grain density so this mineral particle density also known as grain density and depending upon whether these void spaces are primary or secondary so there can be we can also define this primary porosity and secondary porosity now let us come to this the ground water column so in this we discuss about the ground water which exists at various depths right from the ground below so here so there is a very important interface and that interface is known as water table it is also known as so in case of piezometric surface or say chaotic surface essentially suppose this is the ground and water table is denoted by W T it represents that layer that horizontal layer below the ground below which the entire soil or rock layer is saturated and above which the soil or rock layer is either partially saturated or unsaturated so that is the water surface and here so accordingly so this whole thing is known as a ground water column so suppose I represent this as a column then the the soil column above water table is known as zone of aeration and there is other name also and the water present in this is known as weido's water water which may be present many times if it is fully dry if it is fully unsaturated then there may not be any this one at all and the the soil or rock column below the water table so this is known as zone of saturation and the water which is available there is known as the ground water and again this zone of aeration so it has 3 zones the top one is known as the soil water zone so this corresponding to so here this corresponds to root zone depth and the bottom one is known as capillary zone or it is also known as capillary fringe wherein even though it is above the water table in the zone of aeration due to capillary action taking place through the thin capillary tubes as well as slots so some water rises up to the this capillary is up to the top of this capillary zone by the action of capillarity due to surface tension of water and in between the soil water zone and the capillary zone so there is what is known as the intermediate weido's zone so this intermediate weido's zone is below the soil water zone wherein we will find the root depths of plants and it is above the capillary zone to the top of which we will find the capillary rise of water so essentially the soil water zone intermediate zone and weido's zone I am sorry capillary zone together constitute what is known as the zone of aeration which is above the water table and here so this zone of saturation at the bottom of this zone of saturation we have impermeable layer and again so this zone of saturation may contain few impermeable layers few impermeable or semi permeable layers within them and so accordingly it may contain say one or more aquifers so here the aquifer which is just below the water table is known as the unconfined aquifer or the water table aquifer and the aquifer which is bound at the top as well as bottom by this confining layers it is known as the confined aquifer and here let me also represent how the water is held in this weido's zone suppose say these are the soil particles these are the soil or rock and then so this is a soil or rock particles and in between say this is the air particle and here due to the attraction between water and the soil or rock particles so this water so this is weido's water so which is held between the soil rock particles as well as the air particle so like this so in the unsaturated zone so there may be weido's water if it is in the unsaturated or partially saturated zone and coming to this capillary zone so here obviously the height of this capillary zone so depends upon the capillary rise if this is h and it is given by 2 sigma cos theta divided by r gamma so the sigma is the surface tension of water and theta is the angle of contact and r is the so the radius of capillary tube and this gamma is the specific weight of water so based on these 4 parameters that is the surface tension which is measured as force per unit length and then this theta the angle of contact so r the radius of the capillary tube and if it is a slot in that case it is the semi width of the slot as well as the specific weight of water so based on this the capillary rise the height of the capillary rise can be determined which determines the depth of the capillary zone or capillary range so we will stop here and then we will continue about further on this the various zones that is zone of aeration zone of saturation thank you.