 Welcome to this lecture 25 in ground water hydrology. In this lecture, we will be covering this ground water salinity and samples followed by graphical representations of ground water. So now, let us discuss this. Let us start with this ground water salinity. See almost all ground water contains salts and hence has salinity. And this salt content varies from so this is less than 25 mg per liter to 40,000. So, this is in quartzite spring in quartzite springs 40,000 mg per liter in brines or which are there is a strong solutions of salt, common salt or here. So, this salinity, this type and concentration salts varies with environment then movement that is the movement of salts as well as source from where these salts originate. So, the generally salt concentration in ground water. So, this ground water GW is abbreviation for ground water is much greater than salt concentration in surface water. So, the reason is obvious because in case of ground water the flow velocity is much less. Reason is greater exposure soluble materials in geological state whereas, in case of surface water it may not happen and therefore, especially when the surface is almost impervious. So, in that case, so there will not be any exposure to soluble materials and therefore, the salt concentration will be much less. And here, so the soluble salts in ground water soluble salts in ground water. So, they originate from primarily from rock material solutions and here, so among the anions, so the most common anions are bicarbonates. So, this is derived from CO2 that is released by organic decomposition. On the other hand, the salinity also varies. So, this is the primary anion, anions or HCO3 in ground water, primary anions in ground water or HCO3 and salinity also varies with this surface area of aquifer comma solubility of minerals or mineral solubility and obviously, this contact time. So, each one of them when there more, so then obviously, the salinity also increases and so the salinity is the highest when the ground water movement is the least, is the slowest and generally, so therefore, generally salinity, so it increases with say depth, because as we go down, so the ground water movement slows down and hence the salinity increases. So, this common, this one is the say, suppose this is the ground, so this is the ground level and then, so this is shallow depths, so this is the and then, so this is the, so deeper depths. So, at the shallow depths, so there will be bicarbonate salinity or say HCO3 waters, ground water and at deeper depth and at the deepest depths, so here this is a chloride ground water, so in between the remaining salts filter. So, now, let us go on to the, let us discuss other factors, say for example, this precipitation, this the precipitation which falls on ground, so contains small amounts of dissolved minerals, so once this precipitation reaches ground as precipitation reaches ground, so it reacts with soil minerals and rocks and here, so the type of mineral dissolved depends on the chemical composition, chemical composition of rock, physical structure of rock and also it depends upon the pH and the redox potential. So, these are the four factors which decide the type of mineral dissolved in ground water and here, so this carbon dioxide in solution, so this is assists in solvent action, also solvent action of water and results in the downward movement of ground water. So, in areas with large ground water recharge, say for example, in alluvial streams, channels, artificial recharge areas, so in these areas, so the quality of infiltrating ground water, infiltrating surface water, so this largely influences ground water quality and here, so this locally absorbed gases from gases originating from magma contribute dissolved mineral minerals to ground water. So, this conate water that is soluble compounds of marine sediments that is water with soluble compounds of marine sediments has high mineral content because it is derived from water entrapped in sedimentary strata. Now, let us briefly discuss the geochemical cycle of surface water and ground water, so this is taken from the source, so the USGS water supply paper 1469, here this case, so this is there is evaporation and this evaporation, so and here there is condensation and of course, so here there is atmosphere and while condensation, so here in this, so here it gets nitrogen, oxygen, N2, O2, CO2, so these are dissolved then, so here there will be precipitation and from precipitation, so a small component will go into atmosphere and part of it will move and major part of it will move downwards and here in this precipitation, so this precipitation gets added with, so this is retention in mountains, so here this is it gets added with CO2 dissolved in soil, CA calcium, sodium, magnesium, bicarbonates and then it also gets added with sulphates and it also this conate water, so all these things and then it results, so eventually it is moving as runoff and this part of runoff, so here this is evaporation and again after evaporation it goes into atmosphere then, so here part of this runoff also goes into what is called this soil water, so this is and again in this soil water, so this is CO2 will get added then soil minerals, then carbonic acids that is H2, CO3, then colloidal, Fe, Al, silica, SiO2 etc and again say from this it goes through the, so the soil water is absorbed by the plants and here, so this is transpiration and again say from transpiration it goes into, so this atmosphere and here, so these are the plants and part of it, so here this is the, so this, so after this evaporation, so what are left are the chlorides, sulphates of Na, sodium, magnesium, calcium, so they also get carried and here, so this, so here you have the runoff, so this is and from this runoff you have this to soil water and again, so this is here you have the precipitation and so this part of runoff, so this goes to this ocean outflow and this is here there is ocean and so this part of runoff, so this goes to ground water, so here this is soil water, already you have discussed this soil water and below this soil water we have this ground water and from ground water also there is, so this is the effluent seepage which goes to this ocean outflow and of course there will also be, so subsurface outflow to oceans and this is, so this is the ground water and again, so this the soil water as well as ground water both are absorbed by plants and so from this plants, so this transpiration and again, so it goes to, so this atmosphere and of course from this soil water also, so part of it, so this is evaporation, so from precipitation also, so there will be some evaporation and so here you have this atmosphere, so here you have the atmosphere, so this is the geochemical cycle of surface water and ground water, so now, so this the salts added to the ground water, salts are added to ground water by soil weathering and also by rainfall erosion, so this excess irrigation water contributes substantial salts, substantial amounts of salts, so the moreover the soluble salt materials, I am sorry soluble soil materials, fertilizers, this selective salt absorption from plants alters the salt concentration, the salt concentration in the percolating waters, so we may find high salinity in soils and ground water of arid regions where rain water leaching is not effective, so similarly in poorly drained areas there will be high salt content, so these poorly drained areas, so they are generally referred to as bad lands, so because of poor drainage with low agricultural productivity, so this is how the salinity in soils varies, now we will discuss about the samplings, so the ground water samplings and here, so in the ground water sampling, so this is for quality analysis, so generally the samples are taken in Pyrex glass bottles or this polythene bottles in say 1 to 2 liters is sufficient for normal routine analysis, so this samples need to be stored in cool places for laboratory analysis for prompt lab analysis and samples need to be taken only after ground water pumping for some time, so with each sample records related to well location, sample depth, casing size, then date, sampling date, water temperature, order, color, turbidity say other operating conditions need to be taken down, need to be noted down, so for organic and radiological constituents special sampling and storage techniques are required, storage techniques specific to the ground water pollutants need to be employed, so if the time gap between sampling and analysis is short, the analysis is more reliable, so this temperature analysis related to this temperature, pH, alkalinity, dissolved gases, so is done in the field itself, so cations like Fe plus 2, plus 3, ferrous ferric, Cu, then aluminum, manganese, chromium, zinc are subject to loss by adsorption, samples taken from wells penetrating stratified aquifers may yield different results, different solute concentrations, so in such case, so it is it should be possible to obtain water samples of ground water meeting certain criteria, certain quality criteria, on the other hand samples in individual strata could be entirely could be totally unacceptable because there is only a single strata and then, so it may not be representative, so now we will go to the graphic representation of ground water quality, so here in this graphic representation, so this can be through vertical bar graphs or it can also be through tri-linear diagrams or it can be through radiating vector diagrams, circular diagrams or semi logarithmic diagrams, now let us briefly consider the vertical bar graphs for ground water quality representation, so these vertical bar graphs may have, so these vertical bar graphs and this is taken from M in 1970 and here, so this is the, so this is, so there will be a reference number and in this, so here it could be, so this could be sodium and this could be magnesium, so this could be calcium and likewise, so this could be sulphate, so this could be carbonate and bicarbonate and, so this could be chloride and nitrate like that, so here, so there will be multiple this vertical bar charts, each showing the concentration of different components and then, so each one of them, so there will be a reference number, so next we will go to this tri-linear diagrams, so this tri-linear diagrams essentially, so here there will be three triangles, so the left triangle will have the cation concentration, so this is Na plus k and here this will be Ca and the right side, this one will have anion concentration and here we have the and in between, there will be a diamond shaped diagram which will have which is a combination of both is left triangle and then right triangle, so this is So4 plus Cl, sulphate plus chloride and here this is calcium plus magnesium, so this is a sodium and this one and so like that, so this is a tri-linear diagram and so this is taken from this again from the same source that is hem in 1970 and next it is the radiating vector diagrams, so in case of this radiating vector diagrams, there will be the radiating vectors whose length represent, so this is vector length representing concentration, so in this case, so there are say this is Na Mg Na plus k Mg then HCO3, so we will continue this in the next class, thank you.