CHAPTER 5 HYDRO CHEMISTRY - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/10079/10/10...77 CHAPTER 5 HYDRO CHEMISTRY 5.1 GENERAL The chemical composition of groundwater varies

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CHAPTER 5

HYDRO CHEMISTRY

5.1 GENERAL

The chemical composition of groundwater varies with many

complex factors. It depends on the size and geography of the aquifer which

yield water to any bore or open well. Groundwater quality can be affected by

the composition and solubility of rock or soil materials in the aquifer, water

temperature, partial pressure of carbon dioxide, acid-base reactions,

oxidation-reduction reactions, loss or gain of constituents as water percolates

through clay layers and mixing of groundwater from adjacent strata. The

extent of each effect is greatly influenced by the duration of the water within

the different subsurface environments. The hydro chemical analysis of water

samples can reveal the quality of the groundwater and its evolution.

5.2 QUALITY PARAMETERS FOR DRINKING PURPOSE

Water samples were collected from 73 locations in clean polythene

bottles during premonsoon and postmonsoon seasons and tested for major

physical and chemical parameters employing the standard methods given by

American Public Health Association (APHA 1998). pH was measured using

pH meter and electrical conductivity (EC) was measured using conductivity

meters. Total dissolved solids (TDS) were computed by gravimetric method.

Carbonate (CO3) and bicarbonate (HCO3) were estimated by titrating with

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H2SO4. Total hardness (TH) as CaCO3 and calcium (Ca) were analysed

titrimerically, using standard EDTA. Magnesium (Mg) was calculated from

Total hardness and calcium. Sodium (Na) and potassium (K) were measured

by a flame photometer. Chloride (Cl) was estimated by standard AgNO3

titration. Sulphate (SO4) and Nitrate (NO3) were analysed using a

colourimeter. Some samples are selected in random manner and tested at

different laboratories. The results are compared to verify the accuracy of the

tests. The quality of the groundwater for drinking purpose was assessed based

on the results of physical and chemical analyses. Its suitability for drinking

purpose is assessed from norms recommended in IS 10500:1991, for both

premonsoon and postmonsoon seasons.

5.2.1 Turbidity

The presence of suspended matters such as clay, organic, inorganic

and microorganisms make water turbid. (ASCE AWWA 1990) Attempts to

correlate turbidity with the concentration of suspended solids are impractical

due to their size, shape and their refractive indices, which are more important

for optical properties. The recent literatures on the subject of water borne

diseases have stressed very strongly the need to reduce turbidity as much as

possible. Viruses, Cysts and Micro organisms associate with suspended

particulate material of water create water borne diseases. It is therefore more

important to have a very low turbidity to qualify as safe drinking water

(Montgomery 1985).

5.2.2 pH

The negative logarithm of the concentration of hydrogen ions in

moles per litre is pH value of a solution. For example, in a pure water sample,

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the disassociated molar concentration of H +

(hydrogen) and OH –

(hydroxyl)

ions are equal, each being 10-7

moles per litre and it is equivalent to a pH of 7.

Hence if pH is less than 7, the water sample is acidic and if pH is higher than

7, the water sample is alkaline. Water with pH value equal to 7 is neutral. The

pH value is dependent on the carbon-di-oxide ~carbonate~bicarbonate

equilibrium. Alkalinity in drinking water will affect the mucous membranes

of human body (IS: 10500 1991). If the value of pH of water is below 6.5, it is

classified as acidic, if it is between 6.5 and 8.5, it is classified as neutral and if

it is above 8.5, it is classified as alkaline.

5.2.3 Total hardness

Hardness is the term relating to the concentrations of certain

metallic ions in water. Total hardness (TH) in natural water is primarily due to

the presence of calcium(Ca) and magnesium(Mg) ions. The relation between

TH, Ca and Mg is given in Equation (5.1). The presence of other ions and

trace elements are ignored for the calculation of TH due to their very poor

concentrations (Syed et al, 2002).

TH = 2.497 Ca + 4.115 Mg (5.1)

where, TH, Ca and Mg are measured in ppm.

Hardness is usually expressed as an equivalent concentration of

dissolved calcite (CaCO3) (APHA 1998). Hard water prevents formation of

lather until excessive soap is consumed and causes yellowing of fabrics and

toughening of vegetables. The classification of groundwater samples based on

hardness is summarized in Table 5.1.

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Table 5.1 Classification of groundwater samples based on hardness

after Tchobanoglous and Schroeder, (1985) and Viessman

and Hammer, (1998).

Total hardness, mg/L as Ca CO3 Classification

0-40 Soft

40-100 Moderately Hard

100-300 Hard

300-500 Very Hard

Above 500 Extremely Hard

5.2.4 Iron

Groundwater containing iron in soluble form (ferrous) is usually

clear and colorless when first drawn. Upon contact with air, they slowly cloud

and finally deposit a yellowish to reddish brown precipitate of ferric

hydroxide in water stored. Iron is an essential element with a suggested daily

intake of 14 mg. The drinking water contributes only a small fraction of daily

needs. For the reasons of aesthetics and taste the iron content in drinking

water is limited. Waters containing iron, stain porcelain fixtures and laundry.

The growth of bacteria in iron-bearing waters may cause pipe clogging

(Syed et al 2002).

5.2.5 Chloride

Chloride bearing rocks minerals and liquid inclusions with very

insignificant fraction of the rock volume are minor sources of chloride in

groundwater. Hence, the chloride content in groundwater is either from

atmospheric sources or from sea water intrusions. The chloride in

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groundwater is present as sodium chloride, but the chloride content may

exceed sodium due to the Base Exchange phenomenon. The presence of

calcium and magnesium chloride is rare in groundwater. Abnormal

concentrations of chloride may result due to pollution by sewage wastes and

leaching of saline residues in the soil (Karnath 1999). Large amount of

chloride along with high sodium concentrations can impart a salty taste to

water. Amounts above 1000 ppm may be physicologically unsafe. High

concentrations also increase the corrosiveness of water (NDWRHA 1993).

5.2.6 Total dissolved solids

Total dissolved solids (TDS) are a measure of the total amount of

dissolved minerals in water. The concentration of TDS in water will depend

on resident time of ground water in aquifers, local geological conditions,

climate and waste discharges (Syed et al 2002). Several processes may cause

an increase in the dissolved solids content of groundwater. These include

movement of groundwater through rocks containing soluble minerals, salt

concentration by evaporation and contamination due to waste water disposal

(Karnath 1999). TDS content beyond the permissible limit will decrease

palatability and may cause gastro intestinal irritation.

5.2.7 Calcium

Calcium is mostly derived from rocks. Calcium is the second major

constituent present in natural water after bicarbonate. It is required as a

nutrient for plants and is a required mineral for human and other animals.

Suggested daily intake is 800 mg for human. The deficiency of calcium may

cause Osteoporosis and its toxicity may cause kidney stones (Syed et al

2002). Excessive presence of calcium cause not only hardness in water but

also it causes encrustation in water supply structures (IS: 10500 1991).

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5.2.8 Sulphate

A wide range of sulphate content in groundwater is due to various

processes during its traverse through rock. Sulphates are also added in

groundwater by the application of sulphatic soil conditioners. Sulphide

minerals when oxidized give rise to soluble sulphates (Karnath 1999). High

concentration of sulphate in drinking water will make the people difficult to

consume. Sulphate rich water may cause laxative action. Medicinal or bitter

taste is produced in water if sulphate content is high (Syed et al 2002).

5.2.9 Nitrate

Nitrogen is a very minor constituent of the rocks. The average nitrate

content in rain water is reported to be 0.2 ppm. Part of the nitrate may be taken

inside the ground by plants before the rain water infiltrates below the root zone.

But the greatest contribution of nitrate to groundwater is from decaying organic

matter, sewage waste and nitrate fertilizers. Groundwater when not polluted

contains less than 5 ppm of nitrates. Nitrate is a non-essential contaminant with

no minimum daily requirement. Excessive content of nitrate in groundwater

may cause infant methemoglobinemia (Syed et al 2002).

5.2.10 Total alkalinity

Alkalinity maintains the pH within the limit. Alkalinity is due to the

presence of bicarbonate, carbonate ions, salts of silica, borate, phosphate,

organic acids and hydroxides. Concentration of alkalinity varies in

groundwater with respect to geographical location and character of the rocks

and soils. Sudden changes in alkalinity in streams are generally due to the

discharge of treated or untreated industrial wastes. Alkalinity results are

needed to calculate the lime and soda ash dosage for water softening and to

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determine the corrosive or scaling action of water. Excessive content of

alkalinity in water tastes unpleasant (IS: 10500 1991).

5.2.11 Fluoride

Flouride occurs in few types of rocks and slightly soluble in water.

Higher fluoride contents occur in aquifers. Both surface water and

groundwater may experience fluoride contamination from certain insecticides,

chemical wastes, airborne particles and gases from aluminum smelting plants.

Flouride is an essential constituent and is utilized in the structure of bones and

teeth. Suggested intake of fluoride per day for infants, children and adults are

0.6, 1.0 and 2.7 mg respectively. A deficiency in fluoride may result in

increased dental cavities. Large intakes of fluoride may cause dental fluorosis

and toxicity (Syed et al 2002).

5.3 DRINKING WATER QUALITY STANDARDS

The water quality limits prescribed by Bureau of Indian standard

specification (IS: 10500-1991) has been followed in this work for the

assessment of water quality. The limits given by IS 10500:1991 are

summarized in Table 5.2.

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Table 5.2 Limits for drinking as per IS 10500-1991

LimitsS.No Parameter Unit

Desirable Permissible

1. Turbidity NTU 5 10

2. pH -- 6.5 8.5

3. Total hardness mg/ L 300 600

4. Iron mg/L 0.3 1.0

5. Chlorides mg/L 250 1000

6 Total dissolved solids mg/L 500 2000

7. Calcium mg/L 75 200

8. Sulphate mg/L 200 400

9. Nitrate mg/L 45 100

10 Total alkalinity mg/L 200 600

11 Flouride mg/L 1.0 1.5

5.4 SPATIAL DISTRIBUTION

Spatial distribution study is an important tool to understand the

spatial distribution of ionic concentrations of hydro-chemical parameters. The

Spatial distribution provides pictorial representation of the spread of ionic

concentration. The sample locations are represented as point feature layer.

Each location is attributed with location identity, physical and chemical

content concentrations. The spatial distribution is presented in three

classifications namely very good, good and poor. The water quality parameter

whose content is within desirable limit is classified as very good and the

water quality parameter whose content is between desirable to permissible

limit is classified as good and the water quality parameter whose content is

above the permissible limit is classified as poor. The limits recommended by

IS: 10500 are followed to define classification.

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5.5 HYDRO CHEMICAL ANALYSIS OF GROUNDWATER

SAMPLES DURING PREMONSOON SEASON

The water samples are tested for physical and chemical parameters.

The results are compared with IS: 10500 recommendations. The chemical and

physical parameters above the permissible limits and below the desirable

limits are discussed here for the samples collected during premonsoon season.

5.5.1 Turbidity

The turbidity values of all the samples are shown in Figure 5.1. The

variations in turbidity values within desirable limit, above permissible limits

and within permissible limits in the study area are presented here in bar chart.

Figure 5.1 Turbidity values of all samples during premonsoon.

78 % of the total samples are free from turbidity contamination.

Out of 73 samples, 57 samples are free from turbidity hazard, 4 samples are

within the permissible limit. Turbidity is high in 12 samples of the study area.

Turbidity varies from 0 NTU to 80 NTU over the study area. The turbidity

has a maximum value of 80 NTU at the sample S17. The turbidity values of

the samples S13, S17, S18, S22, S25, S26, S30, S34, S45, S50, S59 and S63

exceed the permissible limit during premonsoon season.

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5.5.1.1 Spatial distribution of turbidity

The spatial distribution of turbidity values of samples is presented

by dark brown colour and it is shown in the Figure.5.2. From the spatial

distribution diagram, it is understood that the groundwater from the central

part of the study area has groundwater of poor quality with respect to turbidity

during premonsoon season. The distribution of groundwater of poor quality is

found over an area of 732.3 sq-kms, good quality is present over an area of

638 sq-kms and groundwater of very good quality is present over an area of

2034 sq-kms with respect to turbidity during premonsoon season.

Figure 5.2 Spatial distribution of turbidity values of premonsoon

samples

The rainfall during this period (July 2007) is higher than the rainfall

during postmonsoon season (March 2007). The increased turbidity content

during this season may be due to higher rainfall, low slope and rock types

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from surface and subsurface sources. The groundwater in central part of the

study area may have influenced these factors during this season.

5.5.2 pH

The pH values of all the samples are shown in Figure 5.3.The pH

values within the desirable limit, within the permissible limits and above the

permissible limits in the study area are presented here in bar charts. The

results of the chemical analysis revealed that none of the samples is either

neutral or acidic during premonsoon season.

Figure 5.3 pH values of all samples during premonsoon.

7 out of 73 samples collected from the study area are alkaline due

to high pH values above 8.5 and the remaining 66 samples are neutral. The

maximum pH value of the study area is 8.82 at the sample S35.The minimum

pH value of the study area is 7.23 at the sample S62. The variations in the pH

values among the groundwater samples are less and it is understood that the

pH of the groundwater during premonsoon season of the year 2007 was

almost same in the study area. The pH values of the samples S1, S4, S20, S24,

S35, S45 and S49 exceed 8.5 and the groundwater from these locations are

alkaline during premonsoon season.

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5.5.2.1 Spatial distribution of pH

The spatial distribution of pH values of these samples is presented

by dark violet colour and it is shown in the Figure 5.4. From the spatial

distribution diagram, it is understood that the some scattered areas of south

and central part of the study area, contains alkaline groundwater with respect

to pH during premonsoon season. The distribution of groundwater of acidic

quality is not found in any area, neutral quality is present over an area of 3378

sq-kms and groundwater of alkaline quality is present over an area of 26.3

sqkm with respect to pH during premonsoon season.

Figure 5.4 Spatial distribution of pH values of premonsoon samples

The amount of rainfall during premonsoon season (July) is more

than that of postmonsoon season. Increased infiltration due to rainfall may

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pass through carbonate rich rocks and subsequent dissolution of constituents

may be considered as the reason for the increase in pH value of the

groundwater samples in some illustrated portions in Fig 5.4 of the study area

during premonsoon season.


The differences in the TH values of the groundwater samples

during premonsoon season of the year 2007 are presented here in bar chart.

The TH values of all the samples are shown in Figure 5.5.

Figure 5.5 Hardness values of all samples during premonsoon

Out of 73 samples, 14 samples contain TH above permissible value

and 59 samples contain TH within permisible values. None of the water

samples collected in the study area is classified as soft water or moderately

hard. Out of 73 samples, 41 samples are classified as hard, 14 samples as very

hard and 17 samples as extremely hard. But 14 samples are classified as non

potable as per IS: 10500 standards due to TH values exceeding the

permissible limit of 600 mg/L. The maximum value of hardness is 1112 mg/L

as CaCO3 at the sample S61. The TH values of the groundwater samples S3,

S8, S13, S18, S26, S28, S29, S36, S52, S61, S65 and S67 exceed the

permissible limit during premonsoon season.

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5.5.3.1 Spatial distribution of TH

The spatial distribution of TH values of the premonsoon

groundwater samples is shown in the Figure 5.6. TH value above 600 mg/L

are presented by dark bluish green colour and categorized as poor, TH value

between 300 mg/L and 600 mg/L are categorized as good and below 300

mg/L are categorized as very good. The distribution of groundwater of poor

quality is found over an area of 206.5 sq-kms, good quality is present over an

area of 2008.8 sq-kms and groundwater of very good quality is present over

an area of 1189 sq-kms with respect to TH during premonsoon season.

Figure 5.6 Spatial distribution of TH values of premonsoon samples

Higher rainfall during premonsoon season has diluted the

concentration of harness and some parts of the study area contain

groundwater of poor quality. Rest of the area has very good to good category

of groundwater during premonsoon season. From the spatial distribution

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diagram, it is understood that the groundwater from some scattered areas in

central portion of the study area have groundwater of poor quality with

respect to TH during premonsoon season.

5.5.4 Iron

The iron values of all the samples are shown in Figure 5.7. Fe

content in groundwater samples within the desirable limit, within the

permissible limits and above the permissible limits in the study area are

presented here in bar chart.

Figure 5.7 Iron values of all samples during premonsoon

All the groundwater samples of study area contain iron within

permissible limit. Out of 73 samples, iron content is present in 15 samples

only. 58 samples do not contain iron. The sample S54 contains the maximum

iron content of 0.6 mg/L.Due to infiltration in premonsoon season, the values

Fe in the groundwater samples S25, S54 and S57 are above the desirable limit

but within the permissible during premonsoon season.

5.5.4.1 Spatial distribution of Fe

The spatial distribution of Fe values of these samples is presented

by dark pink colour and it is shown in the Figure 5.8. From the spatial

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distribution diagram, it is understood that Fe is seen in some scattered area in

west part of the study area during premonsoon season. The higher rainfall and

therby the higher infiltration during premonsoon season might have made the

iron contents to dissolve and might have mixed in the groundwater.

Figure 5.8 Spatial distribution of Fe values of premonsoon samples

From the geological studies, it is learnt that iron bearing formations

are not found in the study area. Hence it may be considered that leaching of

cast iron pipes of water supply system in these loacaltions is the cause for the

presence of iron in groundwater. The distribution of groundwater of poor

quality is not found in any area, good quality is present over an area of 46.5

sq-kms and groundwater of very good quality is present over an area of

3357.8 sq-kms with respect to Fe during premonsoon season.

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5.5.5 Chloride

The chloride values of all the groundwater samples are presented

here in bar chart. The chloride values within the desirable limit, within the

permissible limits and above the permissible limits are presented here. The

chloride values of all the samples are shown in Figure 5.9.

Figure 5.9 Chloride values of all samples during premonsoon

All the samples have chloride contents within the permissible limit.

52 samples have chloride contents below 250 mg/L and 21 samples contain

chloride between 250 mg/L and l000 mg/L. The chloride content of the study

area varies from 44 mg/L to 588 mg/L. The water sample S54 has a minimum

chloride content of 44 mg/L and the sample S13 has maximum chloride

content of 588 mg/L. The Cl values of the groundwater samples S3, S4, S8,

S13, S16, S18, S26, S27, S28, S29, S32, S36, S44, S45, S48, S52, S61, S65,

S67 and S69 are above the desirable limit but within the permissible during

premonsoon season.

5.5.5.1 Spatial distribution of Cl

The chloride bearing rock minerals are very minor consituets of

rocks. Hence it is presumable that the chloride content in groundwater is

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either from atmospheric sources or due to sea water intrusion. The evaporite

deposits in sedimentary rocks also give rise to high chloride content in

groundwater. Mostly chloride in groundwater is present as sodium chloride

but the chloride content may exceed sodium due to Base Exchange

phenomena and will be present in groundwater. Abnormal concentrations of

chloride in groundwater may result due to pollution by sewage wastes, salting

for some types of trees and leaching of saline residues in the soil (Karnath

1999). The spatial distribution of Cl values of premonsoon samples is

presented by dark algae green colour and it is shown in the Figure 5.10. The

distribution of groundwater of poor quality is not found in any area, good

quality is present over an area of 1176.3sq-kms and groundwater of very good

quality is present over an area of 2228sq-kms with respect to Cl during

premonsoon season.

Figure 5.10 Spatial distribution of Cl values of premonsoon samples

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As the chances for the presence of chloride content in groundwater

due to the above said reasons are equal, the higher infiltration during

premonsoon season weakened the chloride concentration. From the spatial

distribution diagram, it is understood that the groundwater from the central

part of the study area has groundwater with chloride contents within desirable

to permissible limit and the rest part has chloride content below the desirable

limit during premonsoon season.


The TDS values of all the groundwater samples are presented here

in bar chart. TDS values within the desirable limit, within the permissible

limits and above the permissible limits are presented here in the figure.The

TDS values of all the samples are shown in Figure 5.11.

Figure 5.11 TDS values of all samples during premonsoon

20 samples of the study area contain TDS values below the

desirable limit and 47 samples contain TDS values within the permissible

limit. Six water samples contain higher content of TDS. The minimum value

of dissolved solids of the study area is found to be 252.7 mg/L at the sample

S59 and the maximum value is 3501 mg/L at the sample S13. The TDS values

of the groundwater samples S3, S8, S13, S18, S26 and S61 exceed the

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permissible limit during premonsoon season. From the figure, it can be

understood that the TDS content are widely varying across the study area.

5.5.6.1 Spatial distribution of TDS

Several processes may cause an increase in the dissolved-solids

content of groundwater. These include movement through rocks containing

soluble mineral matter, concentration by evaporation and contamination due

to pollutants. The spatial distribution of concentration of TDS values of these

samples is presented by dark blue colour and it is shown in the Figure 5.12.

Figure 5.12 Spatial distribution of TDS values of premonsoon samples

From the spatial distribution diagram, it is understood that the

groundwater from some scattered areas in central north and central south part

of the study area contain groundwater of poor quality with respect to TDS

during premonsoon season. The distribution of groundwater of poor quality is

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found over an area of 60.5sq-kms, good quality is present over an area of

3204.8sq-kms and groundwater of very good quality is present over an area of

60.5sq-kms with respect to TDS during premonsoon season.

5.5.7 Calcium

The Ca values of all the groundwater samples are presented here in

bar chart. Ca values within the desirable limit, within the permissible limits

and above the permissible limits are presented here in the figure.The calcium

values of all the samples are shown in Figure 5.13.

Figure 5.13 Calcium values of all samples during premonsoon.

Water samples from 47 locations of the study area contain calcium

within desirable limit. Samples from 21 locations contain calcium within the

permissible limit. Five water samples contain calcium above permissible

limit. The maximum calcium content of 253.6 mg/L is present in the sample

S61.The minimum calcium content of 20.4 mg/L is present in the sample S10.

The Ca values of the groundwater samples S3, S26, S61 and S65 exceed the

permissible limit during premonsoon season.

5.5.7.1 Spatial distribution of Ca

The spatial distribution of Ca values of these samples is presented

by blue colour and it is shown in the Figure 5.14. From the spatial distribution

diagram, it is understood that the groundwater from some scattered areas in

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central north, west and south part of the study area which contain

groundwater of poor quality with respect to Ca during premonsoon season.

The distribution of groundwater of poor quality is found over an

area of 26.3 sq-kms, good quality is present over an area of 1856 sq-kms and

groundwater of very good quality is present over an area of 1522 sq-kms with

respect to Ca during premonsoon season.

Figure 5.14 Spatial distribution of Ca values of premonsoon samples

5.5.8 Sulphate

The sulphate values of all the groundwater samples are presented

here in bar chart.Sulphate values within the desirable limit, within the

permissible limits and above the permissible limits in the figure presented

here.

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The sulphate values of all the samples are shown in Figure 5.15. 4

samples of the study area contain high sulphate concentrations. 17 samples

contain sulphate content within the permissible limit. The highest value of

sulphate content of the study area during premonsoon season is 522 mg/L and

it is collected from the sample S61.

Figure 5.15 Sulphate values of all samples during premonsoon

The lowest value of sulphate content is 29 mg/L and it is collected

from the sample S55. The SO4 values of the groundwater samples S18, S26

and S61 exceed the permissible limit during premonsoon season.

5.5.8.1 Spatial distribution of SO4

The spatial distribution of SO4 values of these samples is presented

by dark blue colour and it is shown in the Figure 5.16. From the spatial

distribution diagram, it is understood that the groundwater from some

scattered areas in central north, and centre part of the study area have

groundwater of poor quality with respect to SO4 during premonsoon season.


area of 27 sq-kms, good quality is present over an area of 1045.3 sq-kms and

100


respect to SO4 during premonsoon season.

Figure 5.16 Spatial distribution of SO4 values of premonsoon samples

5.5.9 Nitrate

The nitrate values of all the groundwater samples are presented

here in bar chart. Nitrate values within the desirable limit, within the

permissible limits and above the permissible limits are presented here in the

Figure 5.17 Nitrate values of all samples during premonsoon.

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Figure. The nitrate values of all the samples are shown in Figure 5.17. Sixty

samples of the study area contain nitrate within desirable limit. 13 samples

contain nitrate within the permissible limit. The maximum value of the nitrate

content of the study area is 92 mg/L and it is present at the sample S13. The

minimum value of the nitrate content of the study area is 5 mg/L and it is at

the sample S63. The NO3 values of the groundwater samples S3, S8, S13, S18,

S26, S29, S36, S48, S52, S61, S65, S67 and S69 are above the desirable limit

during premonsoon season.

5.5.9.1 Spatial distribution of NO3

The spatial distribution of NO3 values of these samples is presented

by dark brown colour and it is shown in the Figure 5.18. From the spatial

distribution diagram, it is understood that the groundwater from some

scattered areas of central part of the study area has groundwater with NO3

contents within desirable to permissible limit during premonsoon season.

Figure 5.18 Spatial distribution of NO3 values of premonsoon samples

102


area of 1sq-kms, good quality is present over an area of 528.3 sq-kms and


respect to NO3 during premonsoon season.


The TA values of all the groundwater samples are presented here in

bar chart. TA values within the desirable limit, within the permissible limits

and above the permissible limits are presented here in the figure.The total

alkalinity values of all the samples are shown in Figure 5.19.

Figure 5.19 Total alkalinity values of all samples during premonsoon.

Three samples of the study area contain alkalinity above the

permissible limit. 31 samples contain alkalinity within the permissible limit.

39 samples of the study area contain alkalinity below the desirable limit. The

maximum value of the alkalinity is present in the sample S13. The minimum

value of the alkalinity is present in the sample S63. The TA values of the

groundwater samples S8, S13 and S61 exceed the permissible limit during

premonsoon season.

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5.5.10.1 Spatial distribution of TA

The spatial distribution of TA values of these samples is presented

by red colour and it is shown in the Figure 5.20. From the spatial distribution

diagram, it is understood that the groundwater from few scattered areas in

centre part of the study area contain groundwater of poor quality with respect

to TA during premonsoon season.

Figure 5.20 Spatial distribution of TA values of premonsoon samples




respect to TA during premonsoon season.

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5.5.11 Fluoride

Fluoride values of all the groundwater samples are presented here

in bar chart. Fluoride values within the desirable limit, within the permissible

limits and above the permissible limits are presented here.The fluorides

values of all the samples are shown in Figure 5.21.

Figure 5.21 Fluoride values of all samples during premonsoon

Forty one samples out of 73 samples collected from different

locations of study area contain fluoride of very less concentration. The

maximum fluoride content of the study area is present at the sample S2 and it

is found to be 1.2 mg/L and 32 samples of the study area have no fluoride

content in it. The F value of one groundwater sample S2 is marginally above

the desirable limit but it is within the permissible during premonsoon season.

5.5.11.1 Spatial distribution of F

The spatial distribution of F values of the study area is presented in

the Figure 5.22. From the spatial distribution diagram, it is understood that the

groundwater from considerable area of north central part and some scattered

areas of south central part of the study area have groundwater with F contents

within desirable to permissible limit during premonsoon season.

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Figure 5.22 Spatial distribution of F values of premonsoon samples

The distribution of groundwater of poor quality is not found in any

part of the study area, good quality is present over an area of 8.59 sq-kms and

groundwater of very good quality is present over an area of 3395.71 sq-kms

with respect to fluoride during premonsoon season.

5.6 HYDRO CHEMICAL ANALYSIS OF GROUNDWATER

SAMPLES DURING POSTMONSOON SEASON

The groundwater samples collected from all the 73 locations were

tested for physical and chemical parameters for postmonsoon season also. The

chemical and physical parameters of all the groundwater samples with respect

to IS: 10500 limits are compared and presented here for postmonsoon season.

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5.6.1 Turbidity

The variations in turbidity values within desirable limit, above

permissible limits and within permissible limits in the study area are

presented here. The turbidity values of all the samples are shown in Figure

5.23.

Figure 5.23 Turbidity values of all samples during postmonsoon

Out of 73 samples, 53 samples contain turbidity below the desirable

limit. 10 samples contain turbidity within the permissible limit. Turbidity is

high in 10 samples of the study area. Turbidity varies from 0 NTU to 60 NTU

over the study area. The turbidity has a maximum value of 60 NTU at the

sample S35. The turbidity values of the samples S35, S43, S50, S53, S54,

S55, S56, S57, S58 and S59 exceed the permissible limit during postmonsoon

season.

5.6.1.1 Spatial distribution of turbidity

The spatial distribution of turbidity values is presented by dark

brown colour and it is shown in the Figure 5.24. The rainfall during

postmonsoon season (March 2007) is lower than the rainfall during

107

premonsoon season (July 2007). Since the rate of infiltration is low during

this period, the groundwater is not very turbid during this period.

Figure 5.24 Spatial distribution of turbidity values of postmonsoon

samples


groundwater from the north part of the study area has groundwater of poor

quality with respect to turbidity during postmonsoon season. The distribution

of groundwater of poor quality is found over an area of 246 sq-kms, good

quality is present over an area of 505.3 sq-kms and groundwater of very good

quality is present over an area of 2653 sq-kms with respect to turbidity during

postmonsoon season.

108

5.6.2 pH

The pH values of all the samples are shown in Figure 5.25. The

variations in pH values are within the desirable limit or within the permissible

limits or above the permissible limits in the study area are presented here.

Figure 5.25 pH values of all samples during postmonsoon

2 samples of the total 73 samples collected from the study area are

alkaline and their pH values are above 8.5. The maximum pH of value of the

study area is 8.83 at the sample S66. The minimum pH of value of the study

area is 7.45 at the sample S35. The pH values of all the samples are shown in

Figure 5.25. The pH values of the samples S69, S71 and S73 exceed 8.5 and

the groundwater from these locations are alkaline during postmonsoon season.

5.6.2.1 Spatial distribution of pH

The spatial distribution of pH values of these samples is presented

by dark violet colour and it is shown in the Figure 5.26. From the spatial

distribution diagram, it is understood that the some scattered areas of north

part of the study area, contain alkaline groundwater with respect to pH during

postmonsoon season.

109

Figure 5.26 Spatial distribution of pH values of postmonsoon samples

The distribution of groundwater of Acidic quality is found over an

area of 1sq-kms, Neutral quality is present over an area of 23.3 sq-kms and

groundwater of alkaline quality is present over an area of 3380 sq-kms with

respect to pH during postmonsoon season.


The differences in the TH values of the groundwater samples are

during postmonsoon season of the year 2007 are presented here in bar chart.

The TH values of all the samples are shown in Figure 5.27. The classification

of water based on hardness is summarized in Table 5.1. Out of 73 samples, 27

samples are classified as hard, 17 samples as very hard and 29 samples as

extremely hard. The maximum value of hardness is 864 mg/L as CaCO3.at the

sample S26.

110

Figure 5.27 Hardness values of all samples during postmonsoon

The TH values of the groundwater samples S3, S7, S8, S9, S13,


S43, S45, S48, S61, S64, S65, S67, S69 and S72 exceed the permissible limit

during this season.

5.6.3.1 Spatial distribution of TH

The spatial distribution of TH values of these samples is presented

by dark bluish green colour and it is shown in the Figure 5.28. Rainfall is less

during postmonsoon season and it is not sufficient to dilute the concentration

of harness and some parts of the study area contain groundwater of poor

quality. Rest of the area has very good to good category of groundwater

during postmonsoon season.


groundwater from considerable scattered part in central portion of the study

area have groundwater of poor quality with respect to TH during

postmonsoon season. The distribution of groundwater of poor quality is found

over an area of 737.3 sq-kms, good quality is present over an area of 2118 sq-

kms and groundwater of very good quality is present over an area of 549 sq-

kms with respect to TH during postmonsoon season.

111

Figure 5.28 Spatial distribution of TH values of postmonsoon samples

5.6.4 Iron

The iron values of all the samples are shown in Figure 5.29. Fe

content in groundwater samples within the desirable limit, within the

permissible limits and above the permissible limits in the study area are

presented here. Out of 73 samples, 3 samples contain iron content between

0.3 mg/L and 1.0 mg/L, 3 samples contain iron content above 1.0 mg/L, the

remaining 67 samples contain iron below 0.3 mg/L. Sample S35, contains

maximum iron content of 1.8 mg/L. The Fe values of the groundwater

samples S35, S54 and S57 exceed the permissible limit during postmonsoon

season.

112

Figure 5.29 Iron values of all samples during postmonsoon

5.6.4.1 Spatial distribution of Fe

The spatial distribution of Fe values of these samples is presented

by dark pink colour and it is shown in the Figure 5.30.

Figure 5.30 Spatial distribution of Fe values of postmonsoon samples

113


groundwater of these sample locations which contain marginal Fe are seen in

some scattered area and they spread in north part of the study area during


over an area of 17 sq-kms, good quality is present over an area of 240.3 sq-


kms with respect to Fe during postmonsoon season.

5.6.5 Chloride

The chloride values of all the groundwater samples are presented

here in bar chart. Chloride values within the desirable limit, within the

permissible limits or above the permissible limits are presented here. The

chloride values of all the samples are shown in Figure 5.31.

Figure 5.31 Chloride values of all samples during postmonsoon

2 samples of the study area contain chloride content above the

permissible limit. 38 samples have chlorides content below the desirable limit

and 33 samples contain chlorides between 250 mg/L and l000 mg/L. The

chloride content of the study area varies from 72 mg/L to 1316 mg/L. Sample

S63 has a minimum content of chloride 72 mg/L and the sample S13 has a

114

maximum chloride content of 1316 mg/L. The Cl values of the groundwater

samples S13 and S61 exceed the permissible limit during this season.

5.6.5.1 Spatial distribution of Cl

The spatial distribution of Cl values of these samples is presented

by dark algae green colour and it is shown in the Figure 5.32. From the spatial

distribution diagram, it is understood that the groundwater from the north part

of the study area has groundwater with chloride contents above the

permissible limit during postmonsoon season. The distribution of

groundwater of poor quality is found over an area of 13.3 sq-kms, good

quality is present over an area of 2452 sq-kms and groundwater of very good

quality is present over an area of 939 sq-kms with respect to Cl during

postmonsoon season.

Figure 5.32 Spatial distribution of Cl values of postmonsoon samples

115


TDS values of all the groundwater samples are presented here in

bar chart. TDS values within the desirable limit, within the permissible limits

and above the permissible limits are presented here.The TDS values of all the

samples are shown in Figure 5.33. 9 samples of the study area contain TDS

content below the desirable limit and 38 samples contain TDS within the

permissible limit. 26 samples contain higher content of TDS. The minimum

value of TDS of the study area is 322 mg/L at the sample S63 and the

maximum value is 4767 mg/L at the sample S13. 9 samples of the study area

contain TDS content below the desirable limit and 38 samples contain TDS

within the permissible limit. 26 samples contain higher content of TDS. The

minimum value of TDS of the study area is 322 mg/L at the sample S63 and

the maximum value is 4767 mg/L at the sample S13.

Figure 5.33 TDS values of all samples during postmonsoon

116

5.6.6.1 Spatial distribution of TDS

The spatial distribution of TDS values of these samples is presented

by dark blue colour and it is shown in the Figure 5.34.

Figure 5.34 Spatial distribution of TDS values of postmonsoon samples


groundwater from considerable area in central part of the study area contain

groundwater of poor quality with respect to TDS during postmonsoon season.

The distribution of groundwater of poor quality is found over an area of 989.3

sq-kms, good quality is present over an area of 2379 sq-kms and groundwater

of very good quality is present over an area of 36 sq-kms with respect to TDS

during postmonsoon season.

117

5.6.7 Calcium

Ca values of all the groundwater samples are presented here in bar

chart. Ca values within the desirable limit, within the permissible limits and

above the permissible limits are presented here.The Ca values of all the

samples are shown in Figure 5.35.

Figure 5.35 Ca values of all samples during postmonsoon

Groundwater samples from 39 locations of the study area contain

calcium below the permissible limit. Samples from 32 locations contain

calcium below the desirable limit. 2 water samples contain Ca content above

the permissible limit. Maximum content of Ca of value 255.3 mg/L is present

in the sample S2.The minimum value of Ca is 16 mg/L and it is present in the

sample S59. The Ca values of the groundwater samples S3 and S48 exceed

the permissible limit during this season.

5.6.7.1 Spatial distribution of Ca

The spatial distribution of Ca values of these samples is presented

by blue colour and it is shown in the Figure 5.36. From the spatial distribution

diagram, it is understood that the groundwater in small southern part of the

118

study area contain groundwater of poor quality with respect to Ca during


over an area of 12.3 sq-kms, good quality is present over an area of 2852 sq-


kms with respect to Ca during postmonsoon season.

Figure 5.36 Spatial distribution of Ca values of postmonsoon samples

5.6.8 Sulphate

The sulphate values of all the groundwater samples are presented

here in bar chart.Sulphate values within the desirable limit, within the

permissible limits and above the permissible limits are presented here.The

sulphate values of all the samples are shown in Figure 5.37.7 samples of the

study area contain sulphate concentration above the permissible limit. 28

samples contain within the permissible limit. The maximum value of sulphate

content is 517 mg/L in the sample S16 and the minimum value of the sulphate

119

content is 29 mg/L in the sample S63. 38 samples contain sulphate content

less than the desirable limit. The SO4 values of the groundwater samples S13,

S16, S18, S61, S64, S69 and S71 exceed the permissible limit during

postmonsoon season.

Figure 5.37 Sulphate values of all samples during postmonsoon

5.6.8.1 Spatial distribution of SO4

. The spatial distribution of SO4 values of these samples is

presented by dark blue colour and it is shown in the Figure 5.38. From the

spatial distribution diagram, it is understood that the groundwater from some

scattered areas in central north, and centre part of the study area contain

groundwater of poor quality with respect to SO4 during postmonsoon season.

The distribution of groundwater of poor quality is found over an area of 56.3

sq-kms, good quality is present over an area of 1872 sq-kms and groundwater

of very good quality is present over an area of 1476 sq-kms with respect to

SO4 during postmonsoon season.

120

Figure 5.38 Spatial distribution of SO4 values of postmonsoon samples

5.6.9 Nitrate

The nitrate values of all the groundwater samples are presented

here in bar chart. Nitrate values within the desirable limit, within the

permissible limits and above the permissible limits are presented here.The

nitrate values of all the samples are shown in Figure 5.39.

Figure 5.39 Nitrate values of all samples during postmonsoon

121

68 samples of the study area contain nitrate concentration below the

desirable limit. 5 samples contain nitrate within the permissible limit. The

maximum value of the nitrate content of the study area is 73 mg/L in the

sample S13. The minimum value of the nitrate content is 10 mg/L and it is

present in the samples S54, S59, S63. The NO3 values of the groundwater

samples S3, S13, S26, S30, and S61 are above the desirable limit but within the

permissible limits during postmonsoon season.

5.6.9.1 Spatial distribution of NO3

The spatial distribution of NO3 values of these samples is presented

by dark brown colour and it is shown in the Figure 5.40. From the spatial

distribution diagram, it is understood that the groundwater from some scattered

areas in south central part of the study area contain groundwater with NO3

content within desirable to permissible limit during postmonsoon season. The

distribution of groundwater of poor quality is not found in any area, good

quality is present over an area of 947.3 sq-kms and groundwater of very good

quality is present over an area of 2457 sq-kms with respect to NO3 during

postmonsoon season.

122

Figure 5.40 Spatial distribution of NO3 values of postmonsoon samples


TA values of all the groundwater samples are presented here in bar

chart. TA values within the desirable limit, within the permissible limits and

above the permissible limits are presented here.The total alkalinity values of

all the samples are shown in Figure 5.41.

Figure 5.41 Total alkalinity values of all samples during postmonsoon

123

6 samples of the study area contain alkalinity above the

permissible limit. 39 samples contain alkalinity within the permissible limit.

28 samples of the study area contain alkalinity below the desirable limit. The

maximum value of the alkalinity is present in the sample S36. The

maximum value of the alkalinity is 712 mg CaCO3/L. The minimum value

of the alkalinity is present in the sample S59. The minimum value of the

alkalinity is 64 mg CaCO3/L. The TA values of the groundwater samples

S13, S26, S30, S35, S36 and S61 exceed the permissible limit during

postmonsoon season.

5.6.10.1 Spatial distribution of TA

The spatial distribution of TA values of these samples is presented

by red colour and it is shown in the Figure 5.42. From the spatial distribution

diagram, it is understood that the groundwater from few scattered areas in

centre north part and one small portion from south part of the study area

contain groundwater of poor quality with respect to TA during postmonsoon

season.

124

Figure 5.42 Spatial distribution of TA values of postmonsoon samples




respect to TA during postmonsoon season.

5.6.11 Fluoride

Fluoride values of all the groundwater samples are presented here

in bar chart. Fluoride values within the desirable limit, within the permissible

limits and above the permissible limits are presented here.The fluoride values

of all the samples are shown in Figure 5.43.

125

Figure 5.43 Fluoride values of all samples during postmonsoon

4 samples out of 73 samples collected from the study area contain

fluoride above the desirable limit of 1 mg/L. A maximum fluoride content of

1.4 mg/L is present in the samples S12 and S49 and 8 samples do not contain

fluoride. The F value of 4 groundwater samples S7, S12, S13 and S49 are

above the desirable limit but it is within the permissible during postmonsoon

season.

5.6.11.1 Spatial distribution of F

The spatial distribution of F values of these samples is presented by

in the Figure 5.44. From the spatial distribution diagram, it is understood that

the groundwater from considerable area of north central part and some

scattered areas of south central part the study area contain groundwater with F

contents within desirable to permissible limit during postmonsoon season.

The distribution of groundwater of poor quality is not fount in any

part of the study area, good quality is present over an area of 351.3 sq-kms

and groundwater of very good quality is present over an area of 3053 sq-kms

with respect to fluoride during postmonsoon season.

126

Figure 5.44 Spatial distribution of F values of postmonsoon samples

5.7 QUALITY OF GROUNDWATER FOR IRRIGATION

Early irrigation water quality criteria including USSL (1954) have

received strong criticism from the users. It was argued that it was neither

possible nor correct to define clear cut boundaries between different classes of

irrigation water. Because the ionic composition of the water was considered

and the soil properties, salt tolerance of plant species, climatic conditions and

existing irrigation and agronomic practices followed in a region were not

considered. A third class irrigation water in one region may be second or first

quality in another region. Therefore, a general awareness has now reached

among the users, to use water quality criteria as a general guideline. The

awareness has also been reached to consider plant, soil and climatic

conditions to evaluate the final water quality (Kirda 1997).

127

5.7.1 Irrigation hazard

There are two different types of salt problems exist due to irrigation

water. The first type is associated with the salinity and the second type is

associated with the sodium. Soils may either be affected by salinity or by both

salinity and sodium (Fipps 1914).

5.7.1.1 Salinity hazard

Water with high salinity is toxic to plants and poses a salinity

hazard. Soils with high levels of salinity are called saline soils. High

concentrations of salt in the soil can result in a physiological drought

condition. That is, the field may appear to have plenty of moisture but plants

wilt, because the roots are unable to absorb the water. Water salinity is

usually measured by TDS (Fipps 1914). If TDS content in irrigation water is

below 450 mg/L, there is no restriction to use such water for irrigation

purpose and if the TDS content is above 2000 mg/L in irrigation water, severe

restrictions are to be followed to use such water for irrigation (Ayers and

Westcot 1994).

5.7.1.1.1 TDS values of irrigation water during premonsoon season

TDS values of all the groundwater samples are presented here in

bar chart. Excessive amounts of TDS in irrigation water affect plants and

agriculture soil physically and chemically thus reducing productivity. The

physical effects are to reduce osmotic pressure in plant cell and thus

preventing water to reach plant leaves and branches. The chemical effects

disrupt plant metabolism (Yesilnacar and Gulluoglu 2009). Hence regulations

on irrigation water are mandatory to preserve plant and soil. The TDS values

of all the samples for premonsoon season are shown in Figure 5.45.

128

Figure 5.45 TDS values of premonsoon samples with for irrigation

purpose

14 samples of the study area contain TDS values below 450 mg/L

and the groundwater from these sample locations have no restriction for

irrigation use during premonsoon season. 6 samples contain TDS values

above 2000 mg/L during premonsoon season and the groundwaters from these

sample locations have severe restrictions for irrigation use. The representing

samples of high TDS content are S3, S8, S13, S18, S26 and S61. 91.8 % of

the study area did not pose any restriction on its groundwater for irrigation

use whereas 8.2 % of the study posed restriction on its groundwater for

irrigation use during premonsoon season of the year 2007. These 6 sample

locations are not in same locality but spread across the central part of the

study area from north to south directions.

5.7.1.1.2 TDS values of irrigation water during postmonsoon season

The TDS values of all the postmonsoon groundwater samples are

presented here in bar chart.8 samples of the study area contain TDS values

below 450 mg/L and the groundwater from these sample locations have no

restriction for irrigation use during postmonsoon season. 26 samples contain

TDS value above 2000 mg/L during postmonsoon season and the

groundwaters from these sample locations have severe restrictions for

129

irrigation use. The representing samples of high TDS content are S3, S7, S8,


S45, S48, S61, S64, S65, S67, S69 and S72.

Figure 5.46 TDS values of postmonsoon samples with for irrigation

purpose

The TDS values of all the samples for postmonsoon season are

shown in Figure 5.46. 64.4 % of the study area did not pose any restriction on

its groundwater for irrigation use whereas 35.6 % of the study posed

restriction on its groundwater for irrigation use during the postmonsoon

season of the year 2007. These 26 sample locations are not in same locality

but spread across the central part of the study area from north to south

directions except few samples.

5.7.1.2 Sodium hazard

Excessive content of sodium in irrigation water will have effects on

soil and it will cause sodium hazard. The four different indices to assess the

presence excessive sodium are presented here. They are (i) Sodium absorbtion

ratio (SAR), (ii) Residual Sodium Carbonate (RSC), (iii) Soluble Sodium

Percent (SSP) and (iv) Exchangeable Sodium Percentage (ESP).

130

5.7.1.2.1 SAR

SAR is widely used to assess excessive sodium in irrigation water.

It is calculated from the ratio of sodium to calcium and magnesium. The latter

two ions are important since they tend to counter the effects of sodium. (Fipps

1914). SAR gives a clear idea about the absorbtion of sodium by the soils.

Also it is a better measure to understand the reactions of irrigation water with

the soil. The irrigation water with high SAR values will make the soil to

tighten up. The water quality for irrigation based on SAR is summarized in

Table 5.3. The expression for SAR is given as below in Equation (5.2), in

which the concentrations are expressed in meq/L

SAR = Na / ((Ca+Mg)/2)1/2

(5.2)

Table 5.3 Water quality for irrigation based on SAR as per IS: 2296 -

1963

SAR Water Quality

0-10 Excellent

10-18 Good

18-26 Fair

> 26 Poor

5.7.1.2.1.1 SAR values of the premonsoon samples

The SAR values of all the premonsoon groundwater samples are

presented here in bar chart.SAR values of all 73 samples of the study are

below 10, the groundwater from all sample locations is excellent in quality for

irrigation. The minimum value of SAR of the study area is found to be 1.128

at the sample S54 and the maximum value is 9.9882 at the sample S12. The

SAR values of all the samples during premonsoon season are shown in

Figure 5.47.

131

Figure 5.47 SAR values of premonsoon samples

The study area is free from sodium hazard in premonsoon season.

All the groundwater samples have SAR value less than 10 and also the value

of SAR is less than 6 in 70 samples of the study area during this season.

Diluted concentration of chemical elements in the groundwater due to higher

rainfall during this season may be the reason for low SAR value in the

groundwater samples.

5.7.1.2.1.2 SAR values of the postmonsoon samples

SAR values of all the postmonsoon groundwater samples are

presented here in bar chart. SAR values of 71 samples of the study are less

than 10, the groundwater from these sample location are excellent in quality

for irrigation. SAR values of 2 samples are between 10 and 18, the

groundwater quality of these sample locations is good. The minimum value of

SAR of the study area is found to be 2.01 at the sample S54 and the maximum

value is 13.65 at the sample S12. The SAR values of all the samples during

postmonsoon season are shown in Figure 5.48.

132

Figure 5.48 SAR values of postmonsoon samples

The study area is free from sodium hazard in postmonsoon season

as well. All the groundwater samples have SAR value less than 18 and also

the value of SAR is less than 10 in 71 samples of the study area during this

season. But all the samples contain higher value of SAR when compared with

the premonsoon season.

5.7.1.2.2 Residual sodium carbonate (RSC)

In waters containing high concentrations of bicarbonate, there is a

tendency for calcium and magnesium to precipitate as carbonates. This

reaction does not complete under ordinary circumstances but it would

continue. And hence, the concentrations of calcium and magnesium are

reduced and the relative proportion of the sodium is increased. The relative

abundance of sodium due to abundant presence of bicarbonate and carbonate

influence the suitability of water for irrigation purposes. This excess presence

of bicarbonate and carbonate is denoted as Residual Sodium Carbonate (RSC)

and is determined by the formula given in Equation (5.3) (Richards 1954).

RSC = (HCO3 + CO3) – (Ca + Mg) (5.3)

133

where, the concentrations are expressed in epm. If the RSC exceeds 2.5 epm,

the water is generally unsuitable for irrigation. If the value is between 1.25

and 2.5 epm, the water is of marginal quality, while values less than 1.25 epm

indicate the water is probably safe (Karnath 1999).

5.7.1.2.2.1 RSC values of premonsoon samples

The RSC values of all the premonsoon groundwater samples are

presented here in bar chart. RSC values of all 73 samples of the study are

below 1.25 epm. The minimum value of RSC of the study area is found to be

-11.265 epm at the sample S25 and the maximum value is 1.097 epm at the

sample S19. The RSC values of all samples are shown in Figure 5.49.

Figure 5.49 RSC values of premonsoon samples

The study area is free from the risk of precipitation of calcium and

magenesium as carbonates in premonsoon season. And hence the chances for

sodium accumulation in soil due to the presence of carbonates in irrigation

water is nil during premonsoon season. RSC values in 66 groundwater

samples are negative and hence, they can be considered as if they are well

safe against the accumulation of excessive sodium in this season The

groundwaters from 7 sample locations contain poisitive RSC values but less

134

than 1.25 epm. The RSC values in premonsoon samples are higher than the

RSc values of postmonsoon season.

5.7.1.2.2.2 RSC values of postmonsoon samples

The RSC values of all the postmonsoon groundwater samples are

presented here in bar chart. RSC values of all 73 samples of the study are

below 1.25 epm. The minimum value of RSC of the study area is found to be

–8.035 epm at the sample S48 and the maximum value is 0.9423 epm at the

sample S66. The RSC values of all samples are shown in Figure 5.50.

Figure 5.50 RSC values of postmonsoon samples

The study area is free from the risk of precipitation of calcium

and magenesium as carbonates in postmonsoon season. And hence the

chances for sodium accumulation in soil due to the presence of carbonates in

irrigation water is nil during postmonsoon season. RSC values in 66

groundwater samples are negative and hence, they can be considered as if

they are well safe against the accumulation of excessive sodium in this season

as well. The groundwaters from 7 sample locations contain positive RSC

values but less than 1.25 epm. The lower rate of infiltration in postmonsoon

season may be considered as the cause for lower concentrations of

bicarbonates and carbonates and hence reduced values of RSC during

postmonsoon season.

135

5.7.1.2.3 Soluble sodium percent (SSP)

Soluble sodium percent is defined as the ratio of sodium in epm

between total cations in epm as given by the Equation (5.4).

SSP = (Na / (Ca +Mg + K+Na)) x 100 (5.4)

where, the concentrations are expressed in epm. Water with SSP greater than

60 percent may result in sodium accumulations that will cause a breakdown in

the soil’s physical properties (Fipps 1914).

5.7.1.2.3.1 SSP values of premonsoon samples

The SSP values of all the premonsoon groundwater samples are

presented here in bar chart. The SSP values of the premonsoon samples show

that 6 samples of the study area contain SSP values above the permissible

limit. The SSP values of all premonsoon samples are shown in Figure 5.51.

The minimum value of SSP is 29.7 epm in the sample S52 and the maximum

value is 68.4 epm in the sample S10.

Figure 5.51 SSP values of premonsoon samples

136

The representing samples which have SSP above 60 percent are

S9, S10, S11, S12, S13 and S14. 8.2 % of the samples have the risk sodium

accumulations due to SSP and the remaining 97.2 % of the samples have no

risk of sodium due to increase in SSP during premonsoon season. The

increased infiltration during premonsoon season and the consequent dilution

of concentration of ions in the groundwater may be considered as the cause

for the sodium accumulation risk free locations.

5.7.1.2.3.2 SSP values of postmonsoon samples

The SSP values of all the postmonsoon groundwater samples are

presented here in bar chart. SSP values of the postmonsoon samples show that

17 samples of the study area contain SSP values above the permissible limit.

The SSP values of all postmonsoon samples are shown in Figure 5.52. The

minimum value of SSP is 42.9 epm in the sample S13 and the maximum

value is 69.3 epm in the sample S49.

Figure 5.52 SSP values of postmonsoon samples

The representing samples which have SSP above 60 percent are


S71 and S73. 23.3 % of the samples have the risk sodium accumulations due

137

to SSP and the remaining 76.7 % of the samples have no risk of sodium due

to increase in SSP during postmonsoon season. The infiltration due to rainfall

was not sufficient during this season to dilute the concentration of ions in the

groundwater and it may be considered as the cause for the sodium

accumulation risks in 17 sample locations.

5.7.1.2.4 Exchangeable sodium percentage (ESP)

Excessive sodium content in water renders it unsuitable for soils

containing exchangeable Ca and Mg ions. If the percentage of Na to (Ca +

Mg + Na) is considerably above 50 in irrigation waters, soils containing

exchangeable calcium and magnesium will take up sodium in exchange for

calcium and magnesium causing de-flocculation and impairment of the tilth

and permeability of soils (Karnath 1999).

5.7.1.2.4.1 ESP values of premonsoon samples

The ESP values of all the premonsoon groundwater samples are

presented here in bar chart. ESP values of the premonsoon samples show that

23 samples of the study area contain ESP value above the permissible limit.

The remaining 50 samples contain ESP values within the desirable limit. The

minimum value of ESP of the study area is 30.8 epm at the sample S52 and

the maximum value is 71.9 epm at the sample S14. The ESP values of all

samples are shown in Figure 5.53.

The representing samples which have ESP above 50 percent are

S1, S6, S9, S10, S11, S12, S13, S14, S16, S17, S19, S21, S22, S23, S24, S35,

S68, S69, S70, S71, S72 and S73. 31.5 % of the samples have the risk sodium

accumulations due to ESP and the remaining 68.5 % of the samples have no

risk of sodium due to increase in ESP during premonsoon season.

138

Figure 5.53 ESP values of premonsoon samples

The increased infiltration during premonsoon season and the

consequent dilution of concentration of ions in the groundwater may be

considered as the cause for the sodium accumulation risk free locations due to

ESP in premonsoon season.

5.7.1.2.4.2 ESP values of postmonsoon samples

The ESP values of all the postmonsoon groundwater samples are

presented here in bar chart. The ESP values of the postmonsoon samples

show that 61 samples of the study area contain ESP value above the

permissible limit. The remaining 12 samples contain ESP values within the

desirable limit. The minimum value of ESP of the study area is 45.2 epm at

the sample S41 and the maximum value is 72.7 epm at the sample S68. The

ESP values of all samples are shown in Figure 5.54.

The representing samples which have ESP below 50 percent are

S4, S7, S12, S14, S19, S20, S21, S41, S42, S43, S54 and S69. 83.6 % of the

samples have the risk sodium accumulations due to ESP and the remaining

16.4 % of the samples have no risk of sodium due to increase in ESP during

postmonsoon season.

139

Figure 5.54 ESP values of postmonsoon samples

The infiltration due to rainfall was not sufficient during this season

to dilute the concentration of ions in the groundwater and it may be

considered as the cause for the sodium accumulation risks in 61 sample

locations due ESP in postmonsoon season.

5.8 CLASSIFICATIONS OF GROUND WATER SAMPLES FOR

IRRIGATION USE

The suitability of groundwater for irrigation purpose is also known

from the following methods of classifications.

1. USSL classification

2. Doneen’s classification

3. Wilcox’s classification.

5.8.1 USSL classification

Irrigation water quality criteria developed by US Salinity

Laboratory has received wide acceptance in many countries (USSL 1954).

The notations C1, C2, C3, C4 and S1, S2, S3, S4 represents the low, medium,

140

high and very high salinity and alkali hazard. The diagram is divided into 16

divisions by which the water can be categorized as good, moderate and bad

for irrigation.

5.8.1.1 USSL classification of groundwater samples during

premonsoon season

The classification of groundwater for irrigation based on USSL

diagram shows the presence of 5 combination indices of sodium and salinity

hazards in premonsoon samples. These combinations and their respective

categories are summarized in Table 5.4.The USSL diagram for the

premonsoon samples are shown in Figure 5.55.

Figure 5.55 USSL diagram for premonsoon samples

141

Table 5.4 Classification of groundwater samples based on USSL

diagram for premonsoon seasons

ClassificationSuitability for

irrigation

Number of samples during

premonsoon season

C2-S1 Good 23

C3-S1 Good 21

C3-S2 Moderate 15

C4-S2 Moderate 13

C4-S4 Bad 1

From USSL classifications of premonsoon groundwater samples, it

is found that 31.5 % of groundwater samples are medium salinity and low

sodium water category, 28.8 % of groundwater samples are high salinity and

low sodium water category, 20.5% of groundwater samples are high

salinity and medium sodium water category, 17.8% of groundwater samples

are very high salinity and medium sodium water category and 1.4% of

groundwater samples are very high salinity and very high sodium water

category. In general, 60.3% of groundwater samples are good, 24.6% of

groundwater samples are moderate and 1.4% of groundwater samples are bad

for irigation purposes during premonsoon season.

5.8.1.2 USSL Classification of groundwater samples during

postmonsoon season

The classification of groundwater for irrigation based on USSL

diagram shows the presence of 5 combination indices of sodium and salinity

hazard in postmonsoon samples. These combinations and their respective

categories are summarized in Table 5.5. The USSL diagram for the

postmonsoon samples is shown in Figure 5.56.

142

Figure 5.56 USSL diagram for postmonsoon season


diagram for postmonsoon seasons

ClassificationSuitability for

irrigation

Number of samples during

postmonsoon season

C2-S1 Good 21

C3-S1 Good 20

C3-S2 Moderate 16

C4-S2 Moderate 15

C4-S4 Bad 1

From USSL classifications of postmonsoon groundwater samples,

it is found that 28.8 % of groundwater samples are medium salinity and low

sodium water category, 27.4 % of groundwater samples are high salinity and

low sodium water category, 21.9% of groundwater samples are high

salinity and medium sodium water category, 20.5% of groundwater samples

143

are very high salinity and medium sodium water category and 1.4% of

groundwater samples are very high salinity and very high sodium water

category. In general, 56.2% of groundwater samples are good, 42.4% of

groundwater samples are moderate and 1.4% of groundwater samples are bad

for irigation purposes during postmonsoon season.

5.8.2 Doneen’s classification

Doneen (1966) proposed a concept called "permeability index" (PI)

to assess probable influence of water quality on physical properties of soils.

The PI can be calculated using the expression given in Equation (5.5) where

ion concentrations are given in me1-l.

PI = (Na + HCO3) / Cations (5.5)

The major portion of the study area consists of red soil. Alluvial

soil is present along the river banks. Clay loam is also present in some portion

of the study area (PWD 2001). As the permeability of the soils of study area

are less than 2 cm h-1

, Doneen’s chart of part (a) is used. In Doneen’s chart,

the values of PI and TDS are plotted along x and y axes respectively. In

general, water for irrigation propose is good if it is of the class I and class II

of Doneen classification.

5.8.2.1 Doneen classification of groundwater samples for premonsoon

season

The classification of water samples based on Doneen’s diagram

shows that 23 samples belong to class 1, 49 samples belong to class 2 and 1

sample belong to class 3 during premonsoon season. The Doneen’s diagram

for premonsoon sample is shown in Figure 5.57.

144

Figure 5.57 Groundwater samples plotted on Doneen’s diagram for

premonsoon season

From Doneen classification of prmonsoon samples, it is found that

31.5% of the groundwater samples are of the class I, 67.1% of the

groundwater samples are of the class II and 1.45% of the groundwater

samples are of the class III. In general, 98.6% of the groundwater samples are

of good quality and have maximum permeability of 75% and 1.4% of the

groundwater samples are of moderate quality and have a maximum

permeability of 25 %.

145

5.8.2.2 Doneen’s classification of groundwater samples for

postmonsoon season

The classification of water samples based on Doneen’s diagram

shows that 21 samples belong to class 1, 43 samples belong to class 2 and 9

samples belong to class 3 during postmonsoon season. The Doneen’s diagram

for postmonsoon sample is shown in Figure 5.58.

Figure 5.58 Groundwater samples plotted on Doneen’s diagram for

postmonsoon season

From Doneen classification of prmonsoon samples, it is found that

28.8% of the groundwater samples are of the class I, 58.9% of the

groundwater samples are of the class II and 12.3% of the groundwater

samples are of the class III. In general, 87.7% of the groundwater samples are

of good quality and have maximum permeability of 75% and 12.3% of the

groundwater samples are of moderate quality and have a maximum

permeability of 25 %.

146

5.8.3 Wilcox’s classification

Wilcox classified groundwater used for irrigation purpose based on

electrical conductivity and percentage of sodium content (Wilcox 1955). In

Wilcox chart, the values of electrical conductivity and percentage of sodium

content are plotted on x and y axes respectively. The percentage of sodium

content is calculated by the expression given in Equation (5.6).

Sodium percent (Na %) = ( (Na + K ) / ( Ca + Mg + Na + K )) x 100 (5.6)

5.8.3.1 Wilcox’s classification of groundwater samples for premonsoon

season

The classification of water samples based on Wilcox classification

shows that 33 samples belong to very good to good category, 22 samples

belong to good to permissible category, 5 samples belong to permissible to

doubtful category,8 samples belong to doubtful to unsuitable category and 5

samples belong to unsuitable category during premonsoon season. Wilcox

classification for premonsoon samples is shown in Figure 5.59.

From Wilcox’s classification for the premonsoon samples, it is

found that 45.2% of groundwater samples are of good quality and they can be

used for irrigation purposes with out any risk to soil and plant. 31.1 % of

groundwater samples are of moderate quality and good to permissible

category, salinity is little high among these samples. 6.8% of groundwater

samples are of permissible to doubtful category, sodium content is high

among these samples. 11% of groundwater samples are of doubtful to

unsuitable category, salinity is high among these samples. 6.8% of

groundwater samples are of unsuitable category, salinity is very high among

these samples.

147

Figure 5.59 Groundwater samples plotted on Wilcox’s diagram for

premonsoon season

5.8.3.2 Wilcox’s classification of groundwater samples for postmonsoon

season

The classification of water samples based on Wilcox classification

shows that 10 samples belong to very good to good category, 12 samples

belong to good to permissible category, 15 samples belong to permissible to

doubtful category,13 samples belong to doubtful to unsuitable category and

23 samples belong to unsuitable category during postmonsoon season. The

Wilcox classification for postmonsoon samples is shown in Figure 5.60.

148

Figure 5.60 Groundwater samples plotted on Wilcox’s diagram for

postmonsoon season

From Wilcox’s classification for the premonsoon samples, it is

found that 13.7% of groundwater samples are of good quality and they can be

used for irrigation purposes with out any risk to soil and plant. 16.44 % of

groundwater samples are of moderate quality and good to permissible

category, salinity is little high among these samples. 20.55% of groundwater

samples are of permissible to doubtful category, sodium content is high

among these samples.17.8% of groundwater samples are of doubtful to

unsuitable category, salinity is high among these samples. 31.51% of

groundwater samples are of unsuitable category, salinity is very high among

these samples.

149

5.9 CONTROLLING MECHANISM OF HYDRO CHEMISTRY

Rain and snow are the major sources of recharge to groundwater.

The quality of groundwater is altered due to various processes such as

chemical reactions, surface influences, etc. The causes that produce changes

in groundwater quality are discussed here.

5.9.1 Factors influencing groundwater quality

The percolating rain water contains small amount of dissolved

solids and gases such as carbon dioxide, sulphur-dioxide and oxygen. As the

precipitation infiltrates through the soil, biologically-derived carbon dioxide

reacts with the water to form a weak solution of carbonic acid. The reaction of

oxygen with reduced iron minerals is an additional source of acidity in

groundwater. The slightly acidic water dissolves soluble rock material,

thereby increasing the concentrations of chemical constituents’ such as

calcium, magnesium, chloride, iron, and manganese. As groundwater moves

slowly through an aquifer, the composition of water continues to change by

the addition of dissolved constituents (Freeze and Cherry, 1979). A longer

residence time will increase concentrations of dissolved solids. Because of

short residence time, groundwater in recharge areas often contain lower

concentrations of dissolved constituents.

Dissolved carbon dioxide, bicarbonate, and carbonate are the

principal sources of alkalinity or the capacity of solutes in water to neutralize

acid. Atmospheric and biologically-produced carbon dioxide, carbonate

minerals and biologically-mediated sulphate are carbonate contributors to

alkalinity. Noncarbonated contributors to alkalinity are hydroxide, silicate,

150

borate and organic compounds. Alkalinity helps to buffer natural water so that

the pH is not greatly altered by addition of acid. Calcium and magnesium are

the major constituents responsible for hardness in water. Their presence is the

result of dissolution of carbonate minerals such as calcite and dolomite. The

weathering of feldspar and clay is the source for sodium and potassium in

groundwater. Sodium and chloride are produced by the solution of halite

which occurs in the form of grains dispersed in unconsolidated and bedrock

deposits. Chloride also occurs in bedrock cementing material and connate

fluid inclusions (Hem 1991).

Cation exchange is often a modifying influence of groundwater

chemistry. The most important cation exchange processes are sodium-

calcium and sodium- magnesium. Concentrations of sulphide, iron and

manganese depend on amount of dissolved oxygen, pH, minerals available for

solution, amount of organic matter, and microbial activity and geology and

hydrology of the aquifer system. Mineral source of sulphate can include

pyrite, gypsum, barite and celestite. Oxidation-reductions constitute an

important influence on concentrations of both iron and manganese. High

dissolved iron concentrations can occur in groundwater when pyrite is

exposed to oxygenated water or ferric oxide or hydroxide minerals when in

contact with reducing substances (Hem, 1991). Natural concentrations of

nitrate-nitrogen in groundwater originate from the atmosphere and from the

living and decaying organisms. High nitrate levels can result from leaching of

industrial chemicals or decaying organic matter such as animal waste or

sewage.

151

5.9.2 Hydro chemical facies

Hydrochemical facies are defined as water chemistry properties of

distinct zones within an aquifer (Freeze and Cherry 1979). The nature and

distribution of hydro chemical facies can provide information about how

groundwater quality changes within and between aquifers. Trilinear diagrams

are used to graphically illustrate the relationship between the most important

dissolved constituents in a group of groundwater samples.

A scheme for describing hydro chemical facies presented by

Walton (1970) with tri-linear diagram is shown in Figure 5.61. It is based on

the methods used by Piper (1984). This method is based on the dominance of

certain cations and anions in solution.

Figure 5.61 Piper’s tri linear diagram

152

Table 5.6 Basic hydro chemical facies

S.No Hydro chemical

facies

Nature

1 Primary hardness Combined concentrations of calcium,

magnesium and bicarbonate exceed 50 percent

of the total dissolved constituent load in meq/L.

Such waters are generally considered hard and

are often found in lime stone aquifers or

unconsolidated deposits containing abundant

carbonate minerals.

2 Secondary

hardness

Combined concentrations of sulphate, chloride,

magnesium and calcium exceed 50 percent of the

total concentration.

3 Primary salinity Combined concentrations of alkali metals,

sulphate and chloride are greater than 50 percent

of the total concentration. Very concentrated

waters of the hydro chemical facies are

considered brakish or saline.

4 Primary

alkalinity

Combined sodium, potassium and bicarbonate

concentrations exceed 50 percent of the total

concentration. These waters generally have low

hardness in proportion to their dissolved solids

concentrations (Walton 1970).

5 No specific

cation- anion pair

No specific cation-anion pair exceeds 50 percent

of the total dissolved constituent load. Such

water will result from multiple mineral

dissolutions or mixing of two chemically distinct

groundwater bodies.

Cations are expressed as percentage of total cations in meq/L and

plotted as single point in lower left triangle while anions are similarly

expressed as percentage of total anions and plotted as a single point in lower

right triangle. These two points are then projected into the central diamond

shaped area. Distinct hydro chemical facies are defined by specific

combinations of dominant cations and anions. Fundamental interpretations of

153

the chemical nature of a water sample are based on the location of the

projection in the diamond field. If no single cation or anion in water sample

meets this criterion, the water has no dominant ion in solution. The various

interpretations of chemical nature of water are summarized in Table 5.6.

5.9.2.1 Hydrochemical facies based on Piper’s diagram for premonsoon

samples

Cation-Anion concentrations of the groundwater samples of

premonsoon season are plotted on tri-linear diagram for the analysis of

hydrochemical facies. The Piper diagram for premonsoon samples is shown in

Figure 5.62.

Figure 5.62 Piper’s tri-linear diagram for premonsoon season

154

Hydrochemical facies of the premonsoon samples

1. No specific cation anion pair: The facies of no specific cation-

anion pair is found in 43 samples of the study area.

2. Primary salinity: Facies of primary salinity exists in 28

samples. Very concentrated waters of these sample locations

are considered as saline.

3. Primary hardness: One sample out of seventy three samples

consist hydro chemical facies of this type. Water from this

location generally considered hard.

4. Secondary hardness: One sample of the study area consist

facies of this type. In this sample combined concentrations of

anions exceed 50 % of the total dissolved solids.

Cation types in premonsoon samples

1. Sodium or Potassium type: Na or K type cation is present in

30 samples during premonsoon season. This shows that the

concentration of these cation exceed by 50 % than other

cations in these 30 samples.

2. No dominant type: 43 number of samples during premonsoon

season contain no dominating cation. That is, none of the

cations in these 43 samples exceed 50 % of the concentration

of other cations of the solution.

Anion types in premonsoon samples

1. Choride type: Cl type cation is present in 18 samples during

premonsoon season. This shows that the concentration of these

anion exceed by 50 % than other anions in these 18 samples.

155

2. Bicarbonate type: HCO3 type anion is present in 1 sample

during premonsoon season. This shows that the concentration

of this anion exceed by 50 % than other anions in this sample.

3. No dominant type: 54 number of samples during premonsoon

season contain no dominating anion. That is, none of the

anions in these 54 samples exceed 50 % of the concentration

of other anions of the solution.

5.9.2.2 Hydrochemical facies based on Piper’s diagram for postmonsoon

samples

Cation-Anion concentrations of the groundwater samples of

premonsoon season are plotted on trilinear diagram for the analysis of

hydrochemical facies. The Piper diagram for premonsoon samples is shown in

Figure 5.63.

Figure 5.63 Piper’s tri-linear diagram for postmonsoon season

156

Hydro chemical facies of the postmonsoon samples

1. Primary salinity: Facies of primary salinity exists in 65

samples. Very concentrated waters of these sample locations

are considered as saline.

2. No specific cation-anion pairs: The facies of no specific cation-

anion pair exist in 8 samples of the postmonsoon season.

Cation types in postmonsoon samples

1. Sodium or Potassium type: Na or K type cation is present in

67 samples during postmonsoon season. This shows that the

concentration of these cation exceed by 50 % than other

cations in these 67 samples.

2. No dominant type: 6 number of samples during postmonsoon

season contain no dominating cation. That is, none of the

cations in these 45 samples exceed 50 % of the concentration

of other cations of the solution.

Anion types in postmonsoon samples

1. Choride type: Cl type cation is present in 31 samples during

postmonsoon season. This shows that the concentration of this


2. Bicarbonate type: HCO3 type anion is present in 5 samples during

postmonsoon season. This shows that the concentration of these


3. No dominant type: 37 number of samples during postmonsoon

season contain no dominating anion. That is, none of the

anions in these 37 samples exceed 50 % of the concentration

of other anions of the solution.

157

5.9.3 Gibb’s plot

Gibb’s (1970) attempted to predict the contributions of atmospheric

precipitation, rock weathering and evaporation to water chemistry using a plot

of total dissolved salts (TDS) against Na/(Na + Ca) or Cl/(Cl + HCO3). He

had also proposed a diagram to understand the relationship of the chemical

components of water from their respective aquifer lithologies. Three distinct

fields, namely precipitation dominance, evaporation dominance and rock

dominance are shown in the Gibb’s diagram. The Gibb’s ratios are calculated

with the expressions given in Equation (5.7) and in Equation (5.8).

Gibb’s Ratio I (for anion) = Cl / (Cl+HCO3) (5.7)

Gibb’s Ratio II (for cation) = Na+K / (Na+K+Ca) (5.8)

Gibb’s ratios for the samples of the study area are plotted against

their respective TDS as shown in Figure 5.64 to know whether the

groundwater chemistry is due to rock dominance, evaporation dominance or

precipitation dominance.

Water chemistry in the central part of the “boomerang” is

dominated by weathering of silicate minerals. Samples in the upper part of the

boomerang represent progressive evaporation resulting in an increase in TDS

and enrich the water in Na while depleting in Ca. The lower part of the

diagram represents water from precipitation, which would have lower

concentrations of TDS. However, some samples fall outside the boomerang

region that encompasses water of the earth's surface.

158

Figure 5.64 Gibb’s plot

5.9.3.1 Gibb’s plot for groundwater samples of premonsoon season

The plots of Gibb’s ratio for anions and cations of all groundwater

samples during premonsoon season are shown in Figure 5.65.

Figure 5.65 Gibb’s plot for premonsoon season

159

Gibb’s ratio I: Controlling mechanisms of anions in premonsoon samples

a. Rock dominance: The mechanism controlling the

hydrochemistry of anions of 56 samples during premonsoon

season is rock dominance. They occupy the place in central

part of the Gibb’s diagram.

b. Evaporation dominance: The mechanism controlling the


season is evaporation dominance. They occupy the upper part

of the Gibb’s boomerang diagram.

b. Surface influences: The mechanism controlling the


season is surface influences. They occupy the outer part of the

Gibb’s boomerang diagram.

Gibb’s ratio II: Controlling mechanisms of cations in premonsoon

samples


hydrochemistry of 50 samples during premonsoon season is

rock dominance. They occupy the place in central part of the

Gibb’s diagram.



evaporation dominance. They occupy the upper part of the




surface influences. They occupy the outer part of the Gibb’s

boomerang diagram.

160

5.9.3.2 Gibb’s plot for groundwater samples of postmonsoon season

The plots of Gibb’s ratio for anions and cations of all groundwater

samples during postmonsoon season are shown in Figure 5.66.

Figure 5.66 Gibb’s plot for postmonsoon season

Gibb’s ratio I: Controlling mechanisms of anions in postmonsoon

samples


hydrochemistry of anions of 39 samples during postmonsoon

season is rock dominance. They occupy the place in central

part of the Gibb’s diagram.



season is evaporation dominance. They occupy the upper part

of the Gibb’s boomerang diagram.



season is surface influence. They occupy the outer part of the


161

Gibb’s ratio II: Controlling mechanisms of cations in postmonsoon

samples


hydrochemistry of 31 samples during postmonsoon season is

rock dominance. They occupy the place in central part of the

Gibb’s diagram.



evaporation dominance. They occupy the upper part of the




surface influence. They occupy the outer part of the Gibb’s

boomerang diagram.

5.10 RAINFALL AT THE SAMPLE LOCATIONS

The annual rainfall data obtained from the rain gauge stations are

attributed in the GIS software ArcView 3.2a. The rainfall values at the sample

locations are arrived with the help of interpolation grids generated using the

software. The annual rainfall of a year is the total rainfall obtained by the

summation of monthly rainfall in a year from January to December. The total

rainfall for the premonsoon season (July) of the year 2007 is calculated from

the summation of monthly rainfall from July 2006 to June 2007 and the total

rainfall for the postmonsoon season (March) of the year 2007 is calculated

from the summation of monthly rainfall from July 2006 to February 2007.

162

5.10.1 Rainfall during premonsoon season

The rainfall during the year 2007 was taken for the study. The total

rainfall during premonsoon season at the sample locations of the study area are

graphically shown in Figure 5.67. The maximum rainfall during the premonsoon

season (July) of the study area was 939 mm and the maximum rainfall was

recorded at the sample location 9. The minimum rainfall during the premonsoon

season was 512 mm and the minimum rainfall was recorded at the sample S18.

The average rainfall during the premonsoon season was 680 mm.

Figure 5.67 Rainfall during premonsoon season at the sample locations

5.10.2 Rainfall during postmonsoon season

The total rainfall during postmonsoon season at the sample

locations of the study area are graphically shown in Figure 5.68. The

maximum rainfall during the postmonsoon season (March) of the study area

was 723 mm and the maximum rainfall was recorded at the sample location 9.

The minimum rainfall during the postmonsoon season was 431 mm and the

minimum rainfall was recorded at the sample location 18. The average rainfall

during the postmonsoon season was 550 mm.

163

Figure 5.68 Rainfall during postmonsoon season at the sample locations

The rainfall during premonsoon season is invariably higher at all

the sample locations than during postmonsoon season. At the same time, the

concentrations of TDS are lower during premonsoon season than during

postmonsoon season. Hence, it may be considered that the rate of infiltration

has a definite influence in reducing TDs content in groundwater.

5.11 SUBSURFACE PARAMETERS OF THE SAMPLE LOCATIONS

The subsurface parameters such as soil, geology and

geomorphology of the sample locations are known from GIS overlay of

thematic maps and sample locations using ArcView 3.2a. The respective

parameters are summarized in Table 5.7.

164

Table 5.7 Subsurface parameters of the sample locations

Sample. No Soil type Geology Type Geomorphology Type

1 Red Gneissic Rock Shallow pediment


3 Alluvial Gneissic Rock Flood plain


5 Black Dolonite Plateau

6 Red Alluvium Shallow pediment

7 Red Charnockite Shallow pediment

8 Black Alluvium Shallow pediment

9 Black Alluvium Shallow pediment

10 Black Charnockite Shallow pediment

11 Red Charnockite Structural hill






17 Black Gneissic Rock Plateau


19 Alluvial Alluvium Flood plain

20 Alluvial Alluvium Flood plain



23 Brown Gneissic Rock Shallow pediment


25 Red Gneissic Rock Flood plain

26 Alluvial Gneissic Rock Shallow pediment







33 Red Gneissic Rock Structural hill


35 Black Gneissic Rock Shallow pediment



38 Red Gneissic Rock Plateau

39 Red Charnockite Bazada zone

165

Table 5.7 (Continued)

40 Red Charnockite Bazada zone

41 Red Charnockite Plateau

42 Hill Charnockite Structural hill




46 Black Charnockite Structural hill








54 Red Granitoid gneis P Shallow pediment







61 Red Alluvium Shallow pediment


63 Brown Alluvium Flood plain


65 Red Charnockite Structural hill






71 Red Granitoid gneiss P Shallow pediment



166

Table 5.8 Water quality test results of premonsoon samples

Sam

ple

ID

Tu

rbid

ity

( N

TU

)

EC

(

µm

ho

/cm

TD

S

( m

g/

L )

pH

Tota

l alk

ali

nit

y a

s

mg

Ca

CO

3/

L

Tota

l h

ard

nes

s as

mg

Ca

CO

3/

L

Ca

(m

g /

L)

Mg

(m

g /

L)

Na

(m

g /

L)

K

(mg

/ L

)

Fe

(mg

/ L

)

NO

3

(mg

/ L

)

Cl

(m

g /

L)

F (

mg

/ L

)

SO

4

(mg

/ L

)

PO

4

(mg

/ L

)

S1 0 1017 712 8.67 156 252 62.7 30.1 136.7 24.4 0.1 19 180 0 128 0

S2 2 760 532 7.82 120 184 50 25.2 83.7 20 0.2 14 132 1.2 84 0

S3 1 3160 2212 7.86 528 864 202.5 113 367.2 39.4 0.1 48 504 0 346 0

S4 0 1845 1292 8.12 264 412 57 57.7 224.6 47.1 0 30 320 0 259 0

S5 1 718 503 8.1 116 204 21 22 84.4 16.4 0 12 122 0 92 0

S6 1 503 352 8.43 112 120 25.7 11.8 66.3 4.7 0.1 11 72 0.4 52 0

S7 0 1964 1375 8.25 436 536 110 62 199.5 30.1 0.2 35 180 0.7 270 0

S8 1 3180 2226 7.9 706 768 182.3 102.7 316.4 33.6 0 60 428 0.4 364 0

S9 0 1827 1279 8.23 348 440 95.6 51.5 242.2 30.9 0 28 316 0 180 0.1

S10 1 1151 806 8.1 216 176 35 38 160.8 24.6 0 21 182 0.2 140 0

S11 8 729 510 8.03 152 112 20.4 10.6 105.3 10.2 0 12 112 0.6 74 0

S12 0 770 539 8.21 100 120 26.6 16 106.5 17.7 0 15 124 0.7 97 0

S13 24 5000 3500 8.15 916 784 42.2 84 690 60 0 92 588 1 513 0

S14 6 1410 987 7.65 212 220 44.5 23.9 225.3 33.5 0 28 248 0.2 182 0

S15 1 1086 760 8.31 188 156 31 36 156.2 23.1 0 19 184 0.4 126 0

S16 1 2720 1904 8.15 416 628 159.6 97 313.2 37.8 0 32 452 0.6 382 0

S17 80 1588 1112 8.05 332 368 69.2 43.4 201.9 38.5 0 27 224 0.6 192 0.1

S18 60 3120 2184 7.95 516 724 168.5 100 341.4 63.6 0.3 60 420 0 404 0.2

167


Sam

ple

ID

Tu

rbid

ity

( N

TU

)

EC

(

µm

ho

/cm

TD

S

( m

g/

L )

pH

Tota

l alk

ali

nit

y a

s

mg

Ca

CO

3/

L

Tota

l h

ard

nes

s as

mg

Ca

CO

3/

L

Ca

(m

g /

L)

Mg

(m

g /

L)

Na

(m

g /

L)

K

(mg

/ L

)

Fe

(mg

/ L

)

NO

3

(mg

/ L

)

Cl

(m

g /

L)

F (

mg

/ L

)

SO

4

(mg

/ L

)

PO

4

(mg

/ L

)

S19 0 1506 1054 8.41 336 340 45 47 177.3 37 0 27 243 0.2 172 0

S20 1 959 671 8.62 264 224 42.1 27.1 93.5 11.7 0 19 100 0 91 0

S21 4 1524 1067 8.22 424 352 67.3 36.8 164.5 14.6 0 28 156 0.2 158 0

S22 60 1137 796 8.33 284 260 50 32 148 16 0.1 23 176 0 64 0.1

S23 0 690 483 8.07 172 152 34 16 96 6 0 11 112 0 42 0

S24 1 630 441 8.57 104 140 25.1 17 79.8 4.8 0 13 96 0 49 0

S25 50 1492 1044 7.62 360 432 92 51.2 156 16.4 0.5 27 176 0 169 0.3

S26 64 3610 2527 8.25 512 988 244.5 149.1 399.2 49.9 0 69 564 0.2 474 0

S27 1 1965 1376 7.93 256 512 123.5 69.6 233.8 8.2 0 35 312 0.4 216 0

S28 1 2150 1505 8.23 296 644 131.5 81 232.6 36.2 0 41 332 0.8 176 0

S29 0 2800 1960 7.92 412 739 174.2 100 253.7 51.9 0.1 51 312 0.6 362 0

S30 40 1461 1023 8.15 256 384 75.2 47 174 22 0.3 29 196 0.6 166 0.2

S31 1 651 456 7.88 120 164 42.8 21.1 73.7 11.9 0 11 124 1 49 0

S32 1 1975 1383 8.14 224 496 118.4 73.4 225.7 36.4 0 38 320 0.8 236 0

S33 1 806 564 8.1 108 200 48.4 24.7 89.6 13.4 0 14 132 0.6 70 0

S34 24 1038 727 8.41 200 256 55.5 35.5 125.4 17.9 0 21 172 0.4 106 0

S35 1 669 468 8.82 140 168 37 18.3 84.4 10.1 0 11 124 0.6 41 0

S36 0 2800 1960 8.09 360 712 194 119 324 62 0 53 532 0.4 366 0

168


Sam

ple

ID

Tu

rbid

ity

( N

TU

)

EC

(

µm

ho

/cm

TD

S

( m

g/

L )

pH

Tota

l alk

ali

nit

y a

s

mg

Ca

CO

3/

L

Tota

l h

ard

nes

s as

mg

Ca

CO

3/

L

Ca

(m

g /

L)

Mg

(m

g /

L)

Na

(m

g /

L)

K

(mg

/ L

)

Fe

(mg

/ L

)

NO

3

(mg

/ L

)

Cl

(m

g /

L)

F (

mg

/ L

)

SO

4

(mg

/ L

)

PO

4

(mg

/ L

)

S37 1 1639 1147 8.22 360 412 87.6 48.7 188.4 26.6 0 30 188 0 226 0S38 1 875 613 7.56 156 220 50.2 32.4 104.1 14.2 0 18 160 0 79 0

S39 1 774 542 8.28 148 196 48.3 24.6 82.1 11.3 0 13 124 0 66 0

S40 1 1024 717 7.56 196 248 58.6 37.5 112.3 17 0 20 172 0.4 100 0

S41 0 710 497 7.83 136 176 42.1 21 83.4 11 0 12 124 0.2 56 0

S42 2 1138 797 8.41 176 280 62.1 39.4 148.3 18.3 0.2 23 204 0.6 122 0.1S43 1 1654 1158 7.51 320 436 89.6 50 194.2 23.8 0 29 188 0.8 226 0

S44 1 1572 1100 7.59 236 400 91 57 211 27.8 0 30 292 0 183 0

S45 76 1416 991 8.69 216 384 93.7 51.7 171.1 25.7 0 26 252 0.4 154 0.1

S46 2 816 571 7.42 164 212 47.3 30.6 83.5 13.9 0 17 128 0.6 72 0S47 1 720 504 7.73 148 184 44.5 22.4 77.8 11.2 0.1 12 116 0 60 0

S48 2 2700 1890 8.08 468 796 189 115.8 288 45.6 0.1 51 416 0 338 0

S49 2 675 473 8.65 124 192 45.3 23 82.8 10.9 0 12 128 1 52 0

S50 60 588 412 8.49 96 168 38.8 25.6 69.1 10.9 0.2 13 100 0.6 74 0.1

S51 1 1132 792 7.94 212 324 76 41.3 134 17.9 0 20 192 0 116 0S52 0 2640 1848 8.49 364 856 238 145.4 244.1 49.1 0 50 492 0 335 0

S53 1 473 331 8.16 76 152 43.2 21 46.2 7.7 0 8 80 0 58 0

S54 4 362 253 7.45 56 116 24.7 17 32 5.7 0.6 9 44 0 42 0.5

S55 7 416 291 8.15 68 132 37.2 17.5 40.2 7.5 0 6 84 0 29 0

S56 0 463 324 7.67 76 148 35.1 23.4 43.8 8.8 0 10 72 0 57 0

169


Sam

ple

ID

Tu

rbid

ity

( N

TU

)

EC

(

µm

ho

/cm

TD

S

( m

g/

L )

pH

Tota

l alk

ali

nit

y

as

mg

Ca

CO

3/

L

Tota

l h

ard

nes

s as

mg

Ca

CO

3/

L

Ca

(m

g /

L)

Mg

(m

g /

L)

Na

(m

g /

L)

K

(mg

/ L

)

Fe

(mg

/ L

)

NO

3

(mg

/ L

)

Cl

(m

g /

L)

F (

mg

/ L

)

SO

4

(mg

/ L

)

PO

4

(mg

/ L

)

S57 1 1026 718 7.89 164 328 85.3 46.4 110.3 19.8 0.5 18 172 0 137

S58 1 482 337 7.69 72 156 35.2 23.4 40.4 9.5 0 11 60 0 60

S59 10 360 252 8.12 56 112 30.5 13.7 35.8 7.1 0 5 56 0 43 0

S60 1 610 427 7.45 100 184 65.5 42.8 7.8 12.1 0 12 92 0 79 0

S61 1 3680 2576 8.41 612 1112 253.6 147.8 404.7 67.4 0 68 494 0.6 522 0

S62 0 923 646 7.23 140 280 66.2 42.1 97.4 18.3 0 19 168 0.4 88 0

S63 40 365 256 8.12 52 112 32.2 14.5 36.5 7.5 0 5 64 0 41 0

S64 1 1894 1326 8.02 284 572 135.4 83.6 223.3 36 0 36 340 0.6 226 0

S65 1 2600 1820 7.73 352 788 218.3 125.7 276.9 54.3 0 48 504 0.6 324 0

S66 1 606 424 8.47 92 180 42.4 27.8 59.2 12.3 0 13 92 0 74 0

S67 1 2640 1848 7.92 400 784 198.3 114.2 266.4 55.8 0.1 47 392 0 366 0

S68 1 606 424 7.72 96 136 30.3 20.5 78.2 11.8 0 12 104 0.4 74 0.1

S69 2 2450 1715 8.41 340 560 142.3 80.7 327.4 49.4 0 45 460 0 305 0

S70 1 852 596 7.92 128 196 42.3 27.5 112.5 15.8 0 18 136 0 112 0

S71 1 670 469 8.65 100 152 37.7 18.3 80.8 13.5 0 12 124 0.6 51 0

S72 2 1017 712 8.22 152 228 49.1 31.6 128.4 20.1 0 20 176 0.4 102 0

S73 1 480 336 7.73 72 108 28.5 12.7 60.8 13.8 0 8 96 0.4 41 0

170

Table 5.9 Water quality test results of postmonsoon samples

Sam

ple

ID

Tu

rbid

ity

( N

TU

)

EC

(

µm

ho

/cm

TD

S

( m

g/

L )

pH

Tota

l alk

ali

nit

y a

s

mg

Ca

CO

3/

L

Tota

l h

ard

nes

s as

mg

Ca

CO

3/

L

Ca

(m

g /

L)

Mg

(m

g /

L)

Na

(m

g /

L)

K

(mg

/ L

)

Fe

(mg

/ L

)

NO

3

(mg

/ L

)

Cl

(m

g /

L)

F (

mg

/ L

)

SO

4

(mg

/ L

)

PO

4

(mg

/ L

)

S1 0 1931 1352 7.62 216 316 71 33 272 27.6 0 24 256 0 283 0

S2 4 1029 720 7.9 172 228 54 20 126 10.4 0.5 15 164 1 67 0

S3 1 4370 3059 7.78 516 736 255.3 112 392 64 0 49 836 0 274 0

S4 0 2120 1484 7.63 432 492 109 51 196 18 0 26 276 0 167 0

S5 0 1017 712 8.3 180 252 58 20 116 6.3 0 15 121 0 74 0.5

S6 0 735 515 8.1 156 164 48 13 84 15 0 13 132 0.6 46 0

S7 7 2890 2023 8 392 656 159 81 296 84.7 0.5 34 548 1.2 167 0

S8 0 3720 2604 7.72 476 712 180 98 420 36.3 0 41 716 0.8 256 0

S9 0 3280 2296 7.73 424 684 164 79 356 76.1 0 39 496 0 326 0

S10 0 1801 1261 8.4 312 372 87 39 190 15.2 0 23 236 0.4 153 0.3

S11 0 1638 1147 7.73 272 336 82 40 174 47.9 0 22 248 1 173 0

S12 4 1215 851 8.1 296 312 62 26 132 6.1 0.2 17 124 1.4 75 0

S13 1 6810 4767 7.87 696 828 123 78 900 270 0.1 73 1316 1.2 474 0

S14 0 2115 1960 7.7 452 330 67 36 256 132 0 42 372 0.4 273 0

S15 0 2750 1925 7.78 468 584 131 59 316 24.8 0 33 392 0.6 228 0.7

S16 3 3430 2401 8.24 484 680 162 75 384 69.6 0 40 416 1 456 0

S17 0 3970 2779 8.1 552 732 160 70.5 528 30 0 45 536 0 517 0

S18 0 3240 2268 7.93 472 652 149 64 435 46.3 0 37 428 0.6 447 0

171


Sam

ple

ID

Tu

rbid

ity

( N

TU

)

EC

(

µm

ho

/cm

TD

S

( m

g/

L )

pH

Tota

l alk

ali

nit

y

as

mg

Ca

CO

3/

L

Tota

l h

ard

nes

s

as

mg

Ca

CO

3/

L

Ca

(m

g /

L)

Mg

(m

g /

L)

Na

(m

g /

L)

K

(mg

/ L

)

Fe

(mg

/ L

)

NO

3

(mg

/ L

)

Cl

(m

g /

L)

F (

mg

/ L

)

SO

4

(mg

/ L

)

PO

4

(mg

/ L

)

S19 1 2850 1995 7.75 456 644 153 70 292 28 0 32 412 0.4 242 0

S20 0 1480 1036 8.25 348 362 68 35 130 20 0 20 168 0 72 0

S21 0 2790 1953 7.93 452 628 134 70 264 56 0 30 348 0.8 314 0.67

S22 1 2560 1792 7.88 416 556 151 69 268 99.6 0.1 31 416 0.6 332 0

S23 0 1276 893 8.08 164 192 52 13 184 15.6 0 18 216 0 116 0

S24 0 1045 732 7.95 152 184 45 16 156 15..5 0 15 200 0.4 83 0

S25 6 2960 2072 7.91 468 636 159 62 312 50.7 0.3 35 332 0.4 369 0

S26 2 4440 3108 8.2 664 864 189.6 85 544 63 0.1 69 756 0.2 336 0

S27 1 3130 2191 7.72 476 692 139.5 67 425 9.9 0 36 456 0.8 274 0

S28 5 2960 2072 8.12 456 632 146.8 68.2 324 52.2 0.2 35 392 0.8 316 0

S29 1 3140 2198 8.03 512 660 154.8 71.7 328 54.3 0.2 31 480 1 223 0.3

S30 6 4320 3024 8.13 652 708 168.8 79.2 330 164 0.2 48 632 1 352 0

S31 2 1061 743 7.73 148 236 67.3 19 116 23 0.1 16 164 1 92 0

S32 0 3200 2240 7.75 492 684 165.7 77.5 332 68.3 0 37 516 0.8 236 0

S33 2 1375 963 7.69 228 312 78.4 29.5 150 23.2 0.1 19 196 0.6 123 0

S34 2 1965 1376 8.39 332 432 111 37.3 216 30.1 0.1 25 236 0.6 224 0

S35 60 3240 2268 7.45 676 652 143.6 67.9 356 37.4 1.8 37 436 1 264 0

S36 2 3780 2646 7.73 712 728 168 63.5 415 53.2 0.2 42 512 0.4 316 0

S37 1 3030 2121 7.46 536 676 153.6 60.3 405 23.6 0.1 34 424 0.2 328 0

172


Sam

ple

ID

Tu

rbid

ity

( N

TU

)

EC

(

µm

ho

/cm

TD

S

( m

g/

L )

pH

Tota

l alk

ali

nit

y

as

mg

Ca

CO

3/

L

Tota

l h

ard

nes

s

as

mg

Ca

CO

3/

L

Ca

(m

g /

L)

Mg

(m

g /

L)

Na

(m

g /

L)

K

(mg

/ L

)

Fe

(mg

/ L

)

NO

3

(mg

/ L

)

Cl

(m

g /

L)

F (

mg

/ L

)

SO

4

(mg

/ L

)

PO

4

(mg

/ L

)

S38 1 1460 1022 7.83 192 264 66.8 21.3 198 17 0 20 220 0.4 152 0

S39 1 1041 729 8.49 132 164 37 13.9 152 7.2 0 15 176 0.4 81 0

S40 1 1323 926 7.72 168 332 77.9 32.9 172 19.2 0 18 228 0.6 114 0

S41 1 1092 764 7.93 204 296 71.7 37 112 31.4 0 16 136 0.6 172 0

S42 1 1874 1312 7.89 356 452 107.9 41.2 196 19.7 0.1 24 192 1 217 0

S43 13 2820 1974 7.67 416 660 147 70 284 36 0 32 416 1 270 0

S44 4 2640 1848 7.63 452 592 134 61 276 36 0.6 42 356 1 232 0

S45 5 3010 2107 7.77 516 628 142 65 316 40 0.3 35 458 0.8 174 0

S46 2 1037 726 7.62 128 192 46 18 126 16 0.1 15 136 0.8 139 0

S47 0 1005 704 8.13 116 176 46.3 17.2 120 26.4 0 14 176 0.4 82 0

S48 1 3740 2618 8.45 440 816 205.1 92.6 415 97.5 0.1 40 652 0.4 324 0.28

S49 1 1191 834 8.08 196 156 28.6 13.1 188 18.6 0 17 172 1.4 94 0

S50 18 890 623 8.03 152 128 24.5 9.8 136 22.9 0.3 14 136 1 52 0

S51 1 1895 1327 7.78 264 412 105.9 41.7 236 50.7 0.2 24 392 0.8 114 0

S52 2 2780 1946 8.04 444 536 112.9 53.6 344 21 0.1 30 362 0.6 287 0

S53 20 579 405 8.2 84 120 31.7 11.6 64 12.2 0.2 11 84 0.2 57 0.8

S54 30 467 327 8.28 72 112 31.2 9.3 49 9.2 1.3 10 76 0.2 28 0.6

S55 16 538 377 8.07 80 92 27.5 4.7 68 5 0.1 11 84 0.2 35 0.5

S56 18 577 404 8.48 92 84 16.4 7.8 87 11.8 0.2 12 92 0 38 0.7

173


Sam

ple

ID

Tu

rbid

ity

( N

TU

)

EC

(

µm

ho

/cm

TD

S

( m

g/

L )

pH

Tota

l alk

ali

nit

y a

s

mg

Ca

CO

3/

L

Tota

l h

ard

nes

s as

mg

Ca

CO

3/

L

Ca

(m

g /

L)

Mg

(m

g /

L)

Na

(m

g /

L)

K

(mg

/ L

)

Fe

(mg

/ L

)

NO

3

(mg

/ L

)

Cl

(m

g /

L)

F (

mg

/ L

)

SO

4

(mg

/ L

)

PO

4

(mg

/ L

)

S57 42 1469 1028 7.98 152 216 47.5 24.8 196 31.2 1.4 20 232 0.6 165 0

S58 12 555 389 7.95 80 88 19.2 8.2 74 1.7 0 12 84 0.2 37 0.4

S59 20 486 340 7.73 64 76 16 5.9 79 11.8 0.1 10 80 0.2 35 0.3

S60 2 840 588 7.65 132 156 34 12.7 94 19.7 0.1 14 120 0.6 67 0

S61 6 5800 4060 7.72 684 852 163.5 78.3 800 164.7 0.1 64 1164 1 416 0

S62 1 1280 896 7.85 156 176 39 17.5 196 18.4 0.1 18 228 1 129 0.5

S63 0 460 322 8.35 72 88 18.2 7.8 66 1 0 10 72 0.2 29 0.4

S64 8 2950 2065 8.03 532 616 127.8 67.3 316 31.3 0.1 35 236 1 432 0

S65 7 3300 2310 8.27 564 732 162 79 348 44 0 39 436 1 367 0

S66 1 765 536 8.83 92 100 30 6 99 26 0.1 13 112 0.6 86 0

S67 5 3470 2429 8.13 528 760 168 82 388 48 0.1 40 664 1 312 0

S68 0 745 526 8.4 84 96 26 8 116 16 0 12 96 0.8 127 0

S69 3 3000 2100 8.51 468 728 190.7 84 328 89.7 0 34 436 0.4 432 0

S70 0 1143 800 7.85 156 212 55.4 21.7 138 31.4 0 16 136 0.8 192 0.4

S71 0 700 490 8.7 92 104 31.1 8.6 94 18.5 0 12 116 1 416 0

S72 8 3060 2142 8.4 436 628 163.6 74.9 356 104.9 0.1 34 516 1 129 0

S73 0 599 419 8.58 76 92 23.9 9.8 79 17.8 0 11 104 0.2 29 0

174

5.12 RESULTS AND DISCUSSION

The discussion on results of various studies to evaluate the quality

of groundwater for drinking and irrigation purposes and to study the

controlling mechanism of groundwater hydrochemistry is presented here.

5.12.1 Quality of groundwater for drinking purpose

The quality of groundwater samples are estimated for both physical

and chemical parameters based on IS 10500:1991. The water quality

parameters of premonsoon and postmonsoon groundwater samples are

presented here for a comparative analysis. It is found that the water quality

parameters vary between the seasons. The extent of these seasonal variations

of the water quality parameters are explained separately.

5.12.1.1 Turbidity

In some of the samples, the values of turbidity are higher in

postmonsoon season and lower in premonsoon season and vice versa. 21

samples have shown higher turbidity values during postmonsoon season and

lower during premonsoon season. 14 samples have shown turbidity values

higher in premonsoon season and lower in postmonsoon season.

Figure 5.69 Turbidity values during premonsoon and postmonsoon seasons

175

But 6 samples contain turbidity value above the desirable limit and

beyond the permissible limit in both the seasons. The values of turbidity for

both the seasons are shown in Figure 5.69.

5.12.1.2 pH

Invariably all the samples of the study area contain pH value 6.5

during both the seasons. 30 numbers of samples have shown higher pH values

during postmonsoon season and lower during premonsoon season. 43

numbers of samples have shown higher pH values during premonsoon season

and lower during postmonsoon season. But 3 numbers of samples contain pH

value above 8.5 in both the seasons. The values of pH for both the seasons

with the desirable and permissible limits are shown in Figure 5.70.

Figure 5.70 pH values during premonsoon and postmonsoon seasons

5.12.1.3 Total hardness

44 samples have shown high TH values during postmonsoon season

and low during premonsoon season. 29 samples have shown high TH values

during premonsoon season and low during postmonsoon season. But 12

samples contain TH value beyond permissible limit in both the seasons. The

values of TH for both the seasons with desirable and permissible limits are

shown in Figure 5.71. None of the water samples collected in the study area is

classified as soft water or moderately hard during both seasons.

176

Figure 5.71 TH values during premonsoon and postmonsoon seasons

5.12.1.4 Iron

All the samples of study area are safe against iron content. 31

samples have shown higher iron values during postmonsoon season and lower

during premonsoon season. 7 samples have shown higher iron values during

premonsoon season and lower during postmonsoon season. But 35 samples

contain nil or very low value of iron content in both the seasons. The values

of iron for both the seasons with desirable and permissible limits are shown in

Figure 5.72.

Figure 5.72 Iron values during premonsoon and postmonsoon seasons

5.12.1.5 Chloride

61 samples have shown higher chloride values during postmonsoon

season and lower value during premonsoon season. 9 samples have shown

higher chloride values during premonsoon season and lower value during

177

postmonsoon season. 3 samples have no change in their chloride content

during both the seasons. But 2 samples contain chloride value above

permissible limit only in postmonsoon season. The values of chloride for both

the seasons with desirable and permissible limits are shown in Figure 5.73.

Figure 5.73 Chloride values during premonsoon and postmonsoon

seasons

5.12.1.6 Total dissolved solids

6 samples have shown higher TDS values during postmonsoon

season and lower value during premonsoon season. These 6 samples have

TDS content above the permissible limit during premonsoon season also. No

samples have shown higher TDS values during premonsoon season and lower

value during postmonsoon season. But 20 samples contain TDS value above

the permissible limit only in postmonsoon season. The values of TDS for both

the seasons with desirable and permissible limits are shown in Figure 5.74.

Figure 5.74 TDS values during premonsoon and postmonsoon seasons

178

5.12.1.7 Calcium

45 samples have shown higher calcium values during postmonsoon

season and lower values during premonsoon season. 28 samples have shown

higher calcium values during premonsoon seaon and lower value during

postmonsoon season. But only one sample contains calcium value above the

permissible limit in post and premonsoon seasons. The values of calcium for

both the seasons with desirable and permissible limits are shown in Figure 5.75.

Figure 5.75 Calcium values during premonsoon and postmonsoon

seasons

5.12.1.8 Sulphate

45 samples have shown higher sulphate values during postmonsoon


higher sulphate values during premonsoon season and lower value during

Figure 5.76 Sulphate values during premonsoon and postmonsoon seasons

179

postmonsoon season. But 3 samples contain high sulphate value in both

premonsooon and postmonsoon seasons. The values of sulphate for both the

seasons with desirable and permissible limits are shown in Figure 5.76.

5.12.1.9 Nitrate

None of the samples of the study area contain nitrate content above

the permissible limit. 49 samples have shown higher nitrate values during

postmonsoon season and lower value during premonsoon season. 20 samples

have shown higher nitrate values during premonsoon season and lower value

during postmonsoon season. But 4 samples contain same nitrate value in both

postmonsoon and premonsoon seasons. The values of nitrate for both the

seasons with desirable and permissible limits are shown in Figure 5.77.

Figure 5.77 Nitrate values during premonsoon and postmonsoon seasons

5.12.1.10 Total alkalinity

56 samples have shown higher values of total alkalinity during

postmonsoon season and lower values of total alkalinity during premonsoon

season. 16 samples have shown higher total alkalinity values during

premonsoon season and lower total alkalinity values during postmonsoon

season. But 2 samples contain same total alkalinity value in post and

premonsoon seasons. The values of total alkalinity for both the seasons with

desirable and permissible limits are shown in Figure 5.78.

180

Figure 5.78 TA values during premonsoon and postmonsoon seasons

5.12.1.11 Fluoride

57 samples have shown higher fluoride values during postmonsoon


higher fluoride values during premonsoon season and lower value during

postmonsoon season. But 14 samples contain same fluoride value in post and

premonsoon seasons. The values of fluoride for both the seasons with

desirable and permissible limits are shown in Figure 5.79.

Figure 5.79 Total Fluoride during premonsoon and postmonsoon

seasons

181

5.12.2 Suitability of groundwater quality parameters for drinking

purpose

The suitability of groundwater during premonsoon and

postmonsoon seasons for drinking purpose with respect to IS 10500:1991 are

summarized here. The water quality parameters show lower values in their

concentration during premonsoon samples when compared with their values

during postmonsoon samples. The higher rate of dissolution due to rainfall

during the month of July (premonsoon season) can be taken into consideration

for the lower content of water quality parameters in groundwater samples of

premonsoon season.

The value of turbidity is high in more number of premonsoon

samples than in postmonsoon samples. The higher rate of dissolution due to

rainfall during the month of July (premonsoon) is the one of the reasons for

the presence of insoluble sediments in groundwater which has risen the value

of turbidity in premonsoon samples.

The increase in pH of premonsoon samples can be reasoned out

with the following fact. The temperature during premonsoon season (July) is

lower than the temperature during postmonsoon season (March), this change

in temperature can be taken into account for the imbalance in carbon dioxide-

carbonate-bicarbonate equilibrium and it would influence pH value of the

groundwater. No relaxation is permitted in pH value of drinking water.

Higher pH will impart bitter/ soda taste to drinking water. The groundwater

samples with higher pH may be treated by the addition of white vinegar or

citric acid (IS: 10500 1991). pH values of 3 groundwater samples are above

the permissible limit during both premonsoon and postmonsoon seasons. The

groundwater from these sample locations may be used after the treatment

suggested by IS: 10500.

182

TH values of 39.7 % of postmonsoon samples and 19.17 % of

premonsoon samples are above the permissible limits.TH values of 16.44%

samples remain high during both the seasons. The groundwater of theses

sample locations will cause scales in utensils and poor lather with soaps. This

shows the presence of dissolved calcium or magnesium from soil and aquifers

minerals containing limestone or dolomites. The groundwater of these sample

locations may be treated with water softener or ion exchanger or reverses

osmosis (IS: 10500 1991).

Iron content in 3 samples of postmonsoon season are high above

the permissible limits. But none of the samples during premosoon season has

iron content above permissible limits. The higher rate of dissolution due to

rainfall during the month of July (premonsoon) is considered here as the cause

for the reduction in iron concentrations of premosnoon samples. Higher

concentrations of iron will impart metallic taste and brackish colour to the

groundwater. Leaching of cast iron pipes in water distribution system is the

one of the major source for iron in drinking water. Oxidizing filters and green

sand mechanical filters may be used to reduce iron concentrations in

groundwater (IS: 10500 1991). This technique may be used at these 3 sample

locations during postmosnoon season if the groundwater used for drinking

purpose is objectionable due to accumulation of iron concentrations.

Chloride content in 2 samples of postmonsoon season are high

above the permissible limits. But none of the samples during premosoon

season has chloride content above permissible limits. The higher rate of

dissolution due to rainfall during the month of July (premonsoon) is

considered here as the cause for the reduction in chloride concentrations of

premosnoon samples. Higher concentrations of chloride in groundwater will

impart salty taste and it will bring high blood pressure to the users. Fertilizers,

industrial wastes and minerals in aquifer are the major sources for chloride in

183

ground water. Reverse osmosis, distillation and activated carbon methods

may be adopted to reduce chloride concentrations in groundwater (IS: 10500

1991). This technique may be used at these 2 sample locations during

postmosnoon season if the groundwater used for drinking purpose is

objectionable due to accumulation of chloride concentrations.

TDS values of 26 postmonsoon samples and 6 premonsoon samples

are above the permissible limits. Groundwater with high TDS concentrations

will have sediments, cloudy colour and hardness. Also, groundwater with

high TDS will have salty or bitter taste. The sources for high TDS content are

the presence of livestock wastes, septic system wastes, landfills and dissolved

minerals from soil and aquifers. TDS values of 6 samples remain high during

both the seasons. The groundwater of these sample locations may be treated

with reverses osmosis, distillation and deionization by ion exchanger

processes (IS: 10500 1991).

Calcium content in 5 samples of premonsoon season and 2 samples

of postmosoon season are high above the permissible limits. Carbonates and

sulphates of calcium are abundantly present in most of the rocks and its

solubility is found in all groundwater. Dissolution of calcium carbonate

continues as long as the quantity of percolating water is high (Karnath 2001).

The higher rate of dissolution due to rainfall during the month of July

(premonsoon) is considered here as the reason for the presence of higher

calcium content in 5 premonsoon samples. Higher concentrations of calcium

in groundwater will impart poor lathering and deterioration of the quality of

clothes. Incrustation of pipes and scale formation will be seen in water supply

system. Calcium values of 1 sample remain high during both the seasons. The

groundwater of this sample location may be treated with water softener ion

exchanger or reverses osmosis during premonsoon season to reduce the

effects of higher calcium content (IS: 10500 1991).

184

Sulphate values of 7 postmonsoon samples 4 of premonsoon

samples are above the permissible limits. Groundwater with high sulphate

concentrations will have bitter medicinal taste, scaly deposits. Also,

groundwater with high sulphate will have laxative effects. The sources for

high sulphate content are the presence of animal sewage, septic systems,

sewages, industrial wastes and natural deposits or salts. Sulphate values of 3

samples remain high during both the seasons. The groundwater of these

sample locations may be treated with reverses osmosis, distillation and by ion

exchanger processes (IS: 10500 1991).

TA values of 6 premonsoon samples and 2 postmonsoon samples

are above the permissible limits. Alkalinity influences the pH value of the

water. TA values of 2 samples remain high during both the seasons. The

groundwater from these locations contain may be treated with proper

neutralizing agent (IS: 10500 1991) before use.

Nitrate and Flouride contents in all 73 samples are within

permissible limits during both premonsoon and postmonsoon seasons. The

groundwater quality assessment of the study area and the representing

samples which exceed the concentration limits are summarized in Table 5.10.

Table 5.10 Suitability assessment of groundwater

No of samples exceeding the

permissible limitS.

No

Water quality

ParametersPremonsoon Postmonsoon

Representing samples

exceeding

the permissible limits

during both the seasons.

1 Turbidity 12 10 S25,S30,S45,S50,S55,S59

2 pH 7 3 S66,S69,S71

3 TH 14 29S3,S8,S13,S16,S18,S26,S28,

S29,S48,S61,S65,S67

4 Iron Nil 3 Nil

5 Chloride Nil 2 Nil

6 TDS 6 26 S3,S8,S13,S18,S26,S61

7 Calcium 5 2 S3

8 Sulphate 4 7 S13,S18,S61

9 Nitrate Nil Nil Nil

10 TA 6 2 S13,S61

11 Fluoride Nil Nil Nil

185

The samples S3, S8, S13, S18, S26 and S61 contain high

concentrations in more number of chemical parameters during both

premonsoon and postmonsoon seasons. Hence, the groundwaters from these

locations are to be used after proper treatment. However, the samples which

are turbid may be used for drinking purpose after filtering or boiling.

5.12.3 Quality of groundwater for irrigation purpose

The quality of the groundwater for irrigation purpose is analyzed

and assessed by evaluating the chances of irrigation hazards. The

classification of groundwater of the study area for irrigation purpose during

premonsoon and postmonsoon season are carried out in this work. The

irrigation hazard is evaluated separately as salinity hazard and sodium hazard.

5.12.3.1 Salinity hazard

The presence of high salts in irrigation water will produce salinity

hazard. It is evaluated with the help of TDS content in irrigation water. The

TDS content in premonsoon and postmonsoon groundwater samples are

present here to assess salinity hazard.

Figure 5.80 TDS values of all samples for irrigation use during

premonsoon and postmonsoon seasons

186

26 numbers of samples contain TDS value above the permissible limit

in postmonsoon season and 6 numbers of samples contain higher values of TDS in

premonsoon season. 20 numbers of samples become fit during premonsoon season

while they are unfit during postmonsoon season. 8 numbers of samples contain

TDS value less than 450 mg/L during postmonsoon season but this number has

increased to 14 in premonsoon season due to dissolution after rainfall. 39 samples

contain TDS value within desirable to permissible limit during postmonsoon

season and this number has increased to 53 during premonsoon season. The values

of TDS content in all the sample locations during premonsoon and postmonsoon

seasons are shown in Figure 5.80.

5.12.3.2 Sodium hazard

Irrigation water containing large amounts of sodium is dangerous to

soil and it leads to a situation called as sodium hazard. Continued use of water

having high sodium leads to a breakdown in the physical structure of the soil.

Sodium is adsorbed and becomes attached to soil particles. The soil becomes

hard and compact when dry and increasingly impervious to water penetration.

Fine textured soils, especially those high in clay, are most subject to this action.

The values of SAR, RSC, SSP and ESP will help to assess the sodium

accumulation in soil due to irrigation water. The values of theses indices of

premonsoon and postmonsoon groundwater samples are tabulated in Table 5.11.

Influences for salinity are found more in postmonsoon samples than

in premonsoon samples. Indices of sodium accumulations reveal that sodium

accumulation rates remain almost same during both the seasons. The

influences of salinity hazard and sodium hazard are less in premonsoon

season. And hence, the sensitive and susceptible crops are less prone to the

effects of groundwater used for irrigation in premonsoon season than in

postmonsoon season.

187

Table 5.11 The values of indices of sodium accumulation

Indice

sRange Effects

No of

premonsoo

n samples

No of

postmonsoo

n samples

0-10 Excellent for irrigation use 72 71

10-18 Good for irrigation use 1 2

18-26 Fair for irrigation use 0 0SAR

> 26 Poor for irrigation use 0 0

<1.25 epmWater is safe for irrigation

use.72 73

1.25-2.5

epm

Water is of marginal quality

for irrigation use.0 0RSC

>2.5 epm Water is unsuitable for

irrigation use

1 0

< 60 % Safe against sodium

accumulations63 54

SSP

>60 % Not safe against sodium

accumulations

10 19

,< 50% Exchangeable calcium and

magnesium will not take up

sodium for exchange

16 16

ESP

> 50 % Exchangeable calcium and

magnesium will take up

sodium for exchange

57 57

USSL classifications, Doneen classifications and Wilcox

classifications of irrigation water during premonsoon season and

postmonsoon season are summarized in Table 5.12, Table 5.13 and Table

5.14 respectively.About 98 % of the groundwater samples of the study are of

good to moderate in quality for irrigation purposes during both the seasons as

per USSL classification. Groundwater quality for irrigation is good during

premonsoon season when compared with post-monsoon season as per

Wilcox’s classifications. Doneen’s permeability indices reveal that the

probable long time effect of groundwater used for irrigation purposes are

not significant as most of the groundwater samples are of class I and class II

during both the seasons.

188


diagram

Classification

Suitability

for

irrigation

No of samples

during premonsoon

season

No of samples

during postmonsoon

season

C2-S1 Good 23 21

C3-S1 Good 21 20

C3-S2 Moderate 15 16

C4-S2 Moderate 13 15

C5-S4 Bad 1 1

Table 5.13 Groundwater classes for irrigation use according to Doneen

diagram

Water ClassNo of samples

during premonsoon season

No of samples

during postmonsoon

season

Class 1 23 21

Class 2 49 43

Class 3 1 9

Table 5.14 Groundwater classes for irrigation use according to Wilcox

diagram

Water Class No of samples

during premonsoon

season

No of samples

during postmonsoon

season

Very Good to Good 33 10

Good to permissible 22 12

Permissible to Doubtful 5 15

Doubtful to Unsuitable 8 13

189

USSL classification is carried out with the help of both salinity and

sodium hazards. And hence, USSL classification is considered as more

important than any other classifications. In general, the groundwater quality

for irrigation use during premonsoon season (July) is better than during

postmonsoon season (March) in the study area.

5.12.4 Controlling mechanism of hydro chemistry

The phenomenon which alters the groundwater chemistry during

traverse through the substratum can be studied from hydrochemical facies

with the help of Piper’s diagram. The dominant mechanism which plays role

in altering the groundwater chemistry can be studied graphically with the help

of Gibb’s plot. The observations made using these two studies are present

here to understand the controlling mechanisms of premosoon and

postmonsoon groundwater samples of the study area.

5.12.4.1 Hydrochemical facies

There exists a significant change in the hydro-chemical facies in the

groundwater samples during the study period of premonsoon and

postmonsoon seasons. The premonsoon season of the syudy period was July

2007. The predominant hydrochemical facies of this season was of the type

“No specific cation-anion pair”. This is represented by 58.9 % of the total

samples. The other hydro chemical facies present during premonsoon season

was of the type “Primary salinity”. This is represented by 38.4 % of the total

samples. 2.7 % of the remaining samples exhibit facies of “Hardness types”.

The postmonsoon season of the study period was March 2007. The

predominant hydrochemical facies of this season was found to be “Primary

salinity”. This facies is found in 89.04% of the total samples. The other

hydrochemical facies is of the type “No specific cation-anion pair”. This is

represented by 10.6 % of the total samples. The comparative status of

hydrochemical facies of premonsoon and postmonsoon seasons is

summarized in Table 5.15.

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Table 5.15 Hydrochemical facies (Piper’s diagram)

S.NoHydro Chemical

Facies

No of premonsoon

samples

No of postmonsoon

Samples

1 Primary Hardness 1 0

2 Secondary Hardness 1 0

3 Primary salinity 28 65

4 Primary alkalinity 0 0

5 No specific cation-

anion pair

43 8

The results observed from hydrochemical facies show that the

presence of primary salinity is decreased to 28 number of premonsoon

samples from 65 number of samples of postmonsoon samples. At the same

time, the hydrochemical facies of type “No specific cation-anion pair” is

found more in premonsoon season than in postmonsoon season. This shows

that the presence of combined concentrations is more during premonsoon

season. The dissolution of minerals in percolating water may be considered as

one of the reasons for these wide variations in hydrochemical facies of the

groundwater samples between these two seasons. It can also be interpreted

from the results that the groundwater is passing through soluble rocks and the

rock dominance is the controlling groundwater chemistry in the study area.

5.12.4.2 Gibb’s ratio

The cross plots between TDS and Gibb’s ratios I and II are

separately used here to evaluate the contributions of atmospheric

precipitation, rock weathering, and evaporation in anions and cations of

premonsoon and postmonsoon groundwater samples. The mechanisms which

dominate the water chemical composition of premonsoon and postmonsoon

samples are summarized in Table 5.16.

191

Table 5.16 Mechanisms controlling the groundwater chemistry

(Gibb’s diagram)

No of premonsoon

samples

No of postmonsoon

samples

Mechanism

controlling

groundwater

chemistryAnions Cations Anions Cations

Rock dominance 56 50 39 31

Evaporation

dominance

14 15 31 34

Precipitation

dominance

0 0 0 0

Earth’s surface

influence

3 8 3 8

From the results obtained, it is found that the rock dominance is

predominant controlling mechanism of anions and cations of grooundwater in

premonsoon samples. The infiltrations are high during premonsoon season (July).

These higher infiltrations have diluted the TDS content of premonsoon samples

and the effects of salt concentrations in groundwater are also reduced.

From Gibb’s diagram, the controlling mechanism of cations of

groundwater during postmonsoon season is evaporation dominance and the

controlling mechanism of anions of groundwater is rock dominance. Since the

temperature in postmoonsoon season (March) is higher than the premonsoon

season (July), the rate of evaporation is also high during postmosnoon season.

From these analyses, it may be interpretated that the higher values of TDS

concentrations in postmonsoon samples are due to the influences of

evaporation. The earth surface influence is also found in the mechanisms

controlling the groundwater chemistry of anions in 3 different samples and of

cations in 8 different samples during both the seasons.

192

5.12.5 Hydro meteorology

The rainfall and groundwater level are considered here as a major

hydro meteorological parameter to study the groundwater quality. The annual

rainfall data and groundwater level for one decade from 1998 to 2007 are taken

here to understand the rainfall and groundwater level variations in this period.

5.12.5.1 Rainfall

The rainfall was low in the year 2002 when compared with the other

years of the period considered. The rainfall in the year 2005 was high during

this decade. The rainfall hydrograph for this period is shown in Figure 5.81.

(Source: State Groundwater and Surface Water Resources Data Centre, Chennai)

Figure 5.81 Rainfall hydrograph

5.12.5.2 Water level

The well hydrograph from 16 observation wells for the period from

1998 to 2007 is presented in Figure 5.82. The groundwater level from the year

1998 to 2002 was not varying in noticeable difference. The groundwater level

during the year 2004 was very low when compared with the other years of the

period.

193

(Source: State Groundwater and Surface Water Resources Data Centre, Chennai)

Figure 5.82 Well hydrograph

From the rainfall and groundwater level study, it is understood that

the groundwater level in the year 2004 has gone lower due to very poor

rainfall during the year 2002. The groundwater level started rising after the

good rainfall in the year 2005. This shows the recharge potential of the study

area is good. The depletion in groundwater level in the year 2004 was due to

the poor rainfall.

5.12.5.3 Rainfall and TDS content in premonsoon and postmonsoon

seasons

The variations in TDS content at the sample locations with the

rainfall are presented here to discuss the influence of rainfall in the dissolution

of TDS content in the groundwaters of the study area. The total rainfall from

premonsoon season of the year 2006 (July) to premonsoon season of the year

(July) 2007 is considered here to estimate the seasonal variations in TDS

content between the seasons of the year 2007. The chart showing the

194

variations in rainfall at the sample locations during premonsoon and

postmonsoon seasons is given in Figure 5.83

Figure 5.83 Rainfall at sample locations during premonsoon and

postmonsoon season of the year 2007

The rainfall during premonsoon season (July) in all sample

locations were higher than the rainfall during postmonsoon(March) season of

the year 2007. The higher rate of rainfall during premonsooon season may be

taken as the cause for better groundwater quality during premonsoon season

than the groundwater quality during postmonsoon season. The influence of

rainfall on the groundwater quality can further be discuused with the values of

TDS content and rainfall. The values of rainfall and TDS at the rain gauge

stations are taken for the comparison here. The values are summarized in

Table 5.17.

195

Table 5.17 TDS and rainfall during premonsoon and postmonsoon

seasons

Premonsoon (July 07) Postmonsoon (March 07)Rain Gauge

Stations Rainfall

mm

TDS

mg/L

Rainfall

mm

TDS

mg/L

Mohanur 659 1292 560 1484

Senthamangalam 939 1279 723 2296

Namakkal 686 760 609 1925

Paramathi 512 2184 431 2268

Rasipuram 802 727 644 1376

Belukurichi 601 1147 551 2121

Komarapalayam 690 1326 562 2065

Tiruchengode 580 469 434 490

At rain gauge station Mohanur, the rainfall in March 07 was 560

mm and it was increased to 659 mm in July 07. The increased rainfall has

made TDS to decrease from 1484 mg/L in March 07 to 1292 mg/L in July 07.

At the rain gauge station Senthamangalam, the rainfall in March 07 was 723

mm and it was increased to 939 mm in July 07. The TDS content was

decreased from 2296 mg/L in March 07 to 1279 mg/L in July 07. At rain

gauge station Namakkal, the rainfall in March 07 was 609 mm and it was

increased to 686 mm in July 07. The TDS content was decreased from 1925

mg/L in March 07 to 760 mg/L in July 07. At rain gauge station Paramathi,

the rainfall in March 07 was 431 mm and it was increased to 512 mm in July

07. The TDS content was decreased from 2268 mg/L in March 07 to 2184

mg/L in July 07.

At rain gauge station Rasipuram, the rainfall in March o7 was 644

mm and it was increased to 803 mm in July 07. The TDS content was

196

decreased from 1376 mg/L in March 07 to 727 mg/L in July o7. At rain gauge

station Belukurichi, the rainfall in March o7 was 551 mm and it was increased

to 601 mm in July 07. The TDS content was decreased from 2121 mg/L in

March 07 to 1147 mg/L in July 07. At rain gauge station Komarapalayam, the

rainfall in March o7 was 562 mm and it was increased to 690 mm in July 07.

The TDS content was decreased from 2065 mg/L in March 07 to 1326 mg/L

in July 07. At rain gauge station Tiruchengode, the rainfall in March 07 was

434 mm and it was increased to 580 mm in July 07. The TDS content was

decreased from 490 mg/L in March 07 to 469 mg/L in July 07.

The variation of TDS values with rainfall for premonsoon and

postmonsoon seasons is shown in Figure 5.84 for the selected rain gauge

stations of the study area. The changes in TDS content with repect to the

changes in rainfall at the raingauge stations are shown here in bar chart for

better visualization of the changes. The same pattern changes are found in all

stations. From this, it is understood that the higher rainfall reduces the TDS

content in groundwater.

Figure 5.84 Variations in TDS content and rainfall during

premonsoon and postmonsoon season the year 2007

Documents

CHAPTER 5 HYDRO CHEMISTRY - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/10079/10/10...77 CHAPTER 5 HYDRO CHEMISTRY 5.1 GENERAL The chemical composition of groundwater varies