Environmental Impact on Groundwater of

JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol.77, June 2011, pp.539-548

Environmental Impact on Groundwater of Maheshwaram Watershed, Ranga Reddy District, Andhra Pradesh D. PURUSHOTHAM, A. NARSING RAO*, M. RAVI PRAKASH, SHAKEEL AHMED and G. ASHOK BABU National Geophysical Research Institute, Hyderabad - 500 007 *Geology Department, Osmania University, Hyderabad - 500 007 Email: [email protected] Abstract: Maheshwaram watershed is situated in Ranga Reddy district of at a distance of about 30 km south of Hyderabad. The watershed has an area of 53 km2 and has hard rock aquifers with semi-arid climate. The study area has been expanding at a fast pace and now has the distinction of being one of the fastest growing urban centers, facing the problem of groundwater depletion and quality deterioration due to the absence of perennial source of surface water and also due to over exploitation. Human activities involving industrial and agricultural development and the inadequate management of land and water resources have, directly or indirectly resulted in the degradation of environment viz. water and soil. In the present study chemical analysis of groundwater samples of the study area, collected in pre- and post-monsoon has been carried out. The analysed data is utilized to characterize the hydro chemical process dominant in the area. Various classification methods such as Piper, Back and Hanshaw, Wilcox, U.S. Salinity Laboratory are employed to critically study the geochemical characteristics of groundwater. Keywords: Groundwater, Geochemistry, Anthropogenic, Environment, Watershed, Maheshwaram, Andhra Pradesh.

INTRODUCTION

Groundwater is affected by many factors such as physicochemical characteristics of soil, rainfall, soil erosion, weathering of rocks, chemical reactions sub-surface, role of microorganism, human and agricultural wastes and industrial effluents. Soil serve as a medium through which groundwater is recharged and any constituent added to soil may adversely affect the quality of groundwater. Anthropocentric inputs due to industrial activities are a major source of metal pollution of soils. Regardless of the source, most of the metallic wastes eventually end up in surface and subsurface waters. The movement of contaminated groundwater is controlled by physical and geochemical properties of (i) the contaminant (ii) the groundwater and (iii) the geological system through which the contaminated groundwater is flowing. Presence of some substances beyond certain limits may make it unsuitable for irrigation, domestic or industrial uses. Corrosion or incrustation of tube well screens is another hazard related to quality of groundwater. It also forms bases for groundwater treatment plan, if required. In the present study chemical analysis of groundwater samples of the study area, collected in pre-monsoon and

post-monsoon of 2007-08 has been carried out, to assess its quality. STUDY AREA

The present study is carried out at the Maheshwaram watershed covering an area of 53 km2 (Fig.1). The study area is situated between longitude 78°24'30"E – 78°29'00"E and latitude 17°06'20"N – 17°11'00"N. The region receives on an average annual rainfall of 573 mm from the southwest monsoon. The area can be classified as semi-arid. In general the topography is undulating. A network of 1st and 2nd order streams shows dendritic to sub dendritic type of drainage pattern with no major streams. All streams drain into Mankal tank which ultimately drains into Musi River. GEOLOGY OF MAHESHWARAM

Geology of the area is relatively homogenous comprising of Precambrian granite mostly pink and grey granites (Fig.2). Basic enclaves, aplite, pegmatite, epidote and quartz veins and dolerite dykes frequently traverse the area. Biotite granite covers a major part of Maheswaram with porphyritic

0016-7622/2011-77-6-539/$ 1.00 © GEOL. SOC. INDIA

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D. PURUSHOTHAM AND OTHERS

Fig.1. Location map of Maheshwaram watershed.

Fig.2. Geological map of Maheshwaram watershed. JOUR.GEOL.SOC.INDIA, VOL77, JUNE 2011

ENVIRONMENTAL IMPACT ON GROUNDWATER OF MAHESHWARAM WATERSHED, ANDHRA PRADESH

feldspars. Granites are intruded by quartz and dolerite dykes of several generations and are well exposed in northern and western part of watershed. These dykes form important structural feature controlling the movement of groundwater in the region. Joints are most commonly observed in the study area. Vertical joints act as conduits for transfer of water whereas as horizontal joints help to maintain the lateral continuity of the aquifer. SAMPLING AND CHEMICAL ANALYSIS

In order to study the major ion geochemistry of groundwater and to assess its quality, groundwater samples were collected from the study area and analyzed for various parameters. A random sampling was used to select sampling points (Fig.3). In all, 40 samples collected during premonsoon and post-monsoon seasons of 2007-08 (Table 1). Analysis was carried out for pH, electrical conductivity (Ec), total dissolved solids (TDS), total hardness (TH), calcium

541

(Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), carbonate (CO3–), bicarbonate (HCO3–), chloride (Cl–), sulphate (SO42+) and nitrate (NO3–) ions. GEOCHEMICAL CHARACTERISTICS OF GROUNDWATER

Classification schemes developed are mainly based on the concentrations of various predominant cations and anions or on the interrelationship of ions. In the present study, the methods such as Piper (1994), Back and Hanshaw (1965), Wilcox (1955), and US Salinity Laboratory method Richards (1954) are used to study the geochemical characteristics of the groundwater of the study area. RESULTS AND DISCUSSIONS Hydro-chemical Facies

To identify the water composition in different zones Back

Fig.3. Sample locations in Maheshwaram watershed. 1 - MRO OFF; 2 - QTZ Pul Unitl 3 - TMLR Comm; 4 - Aware; 5 - RNGH Co; 6 - IR Sugr; 7 - BLND Col; 8 - Prnk Oil; 9 - Datr Ashrm; 10 - Santhorm; 11 - JJ Pharm Com; 12 - Rech Site; 13 - Mshrm Com; 14 - Upgd Thnd; 15 - Kbthnd; 16 - Gangaram; 17 - Sirgpr; 18 - KC Thnd; 19 - Mohbt Ngr; 20 - IFP1-9 site. JOUR.GEOL.SOC.INDIA, VOL77, JUNE 2011

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D. PURUSHOTHAM AND OTHERS Table 1. Analytical results of major ions in groundwater samples collected during pre-monsoon and post-monsoon seasons pH

Ec

TDS

TH

Ca

Mg

Na

K

Cl

SO4

HCO3

NO3

Fluoride

Pre-monsson Post-monsoon

6.8 7.08

1260 1978

670 1265

356.55 671.6

53.6 101.2

53.8 101.5

85.3 161.0

22 4.1

143.5 274.7

54 65.8

219.6 909.8

245 194.8

0.85 0.49

SMP-2


6.75 6.99

797 832

424 532

397.1 378.98

89.3 64.7

42 52.6

35.9 44.6

1.6 2

48.9 61.3

12.1 15

292.8 581.6

39.2 43.6

1.0 0.44

SMP-3


6.8 1870 6.77 2.55 MS

1000 1504

768.71 1155.1

217.8 327.6

54.2 81.5

128.1 192.6

3.8 5.7

243.8 366.6

120.4 132.8

298.9 733

383.2 415.1

0.84 0.59

SMP-4


7.43 7.19

1100 997

590 638

284.66 306.77

42.5 45.9

43 46.4

91.9 93.3

1.8 1.9

58.4 63.1

80.5 78.8

320.3 534.2

89.1 107.5

1.8 1.74

SMP-5


6.2 7.15

6450 6250

3500 4000

3134.6 3146.9

705 805.7

223.1 254.9

598.1 684.4

5.7 6.5

2646 3024

2214 215

256.2 711

— —

0.8 1.15

SMP-6


6.3 7.04

2040 2180

1090 1395

908.63 1160.1

213.1 272.7

90.9 116

119.1 152.4

10 12.7

446.8 571.5

184.9 218.8

277.6 473

— —

1.0 1.19

SMP-7


6.65 6.91

1390 1300

740 832

511.26 573.56

97.7 109.8

64.5 72.5

59.7 67.1

1.9 2.1

288.7 324.5

115.4 80.6

336.2 500.6

338.5 229.4

0.85 0.88

SMP-8


6.81 7.5

862 970

459 620.8

417.21 563.43

1011 136.7

39.8 53.8

45 60.8

1.8 2.4

98.8 133.6

127.8 40.8

262.3 536.2

36.8 33.2

0.85 0.92

SMP-9

Pre-monsoon Post monsoon

6.12 6.36

2810 3.66

1500 2342

1566.8 2445.9

427.8 667.9

120.5 188.1

170.3 265.8

4.9 7.6

326.4 509.6

1514.9 1796

280.6 604.7

— 33.8

1.5 1.6

SMP-10


7.05 7.14

790 834

420 534

279.96 355.2

67.6 85.9

26.7 33.9

84.4 107.3

1.9 2.4

23 29.2

10 12.7

503.3 663

15.5 38.1

1.5 1.67

SMP-11


6.71 6.96

744 786

396 503

319.81 406.59

91.3 116.3

22.1 28

50.9 64.6

2.1 2.6

68.9 87.5

18 26.5

289.8 464

14.9 43

1.4 0.53

SMP-12


6.91 7.2

704 845

375 541

259.93 372.09

69.8 100.6

20.4 29.4

70.4 101.5

0.6 0.86

63.8 92

26.9 26.8

509.4 536.8

17.7 8

1.4 0.64

SMP-13


6.54 7.04

1920 1322

1030 846

881.73 720.7

213.1 175

83.6 68.6

99.1 81.3

3.4 2.8

271 222.5

47.6 68.3

241 383.2

86.2 259.7

0.9 0.54

SMP-14


6.75 7.01

1230 1390

660 890

314.5 404.12

67.8 91.4

31.4 42.3

141.9 191.3

2.7 3.6

50 67.4

22.8 38.8

302 699.1

64.5 107.4

1.8 1.27

SMP-15


7 7.1

891 812

475 491

368.13 378.28

88.3 91.2

35.3 36.4

96.2 99.4

1.5 1.5

71.9 74.3

52.2 41.4

308.1 441.3

86.5 64.6

1.6 0.82

SMP-16


6.84 7.12

704 1201

375 768

183.96 375.51

38.8 79.4

20.9 42.8

98.4 201.5

2 4

29.7 60.8

60.6 33.9

396.4 456.8

96.7 161.1

1.5 1.57

SMP-17


6.53 7.14

1150 1124

610 719

457.71 538.54

134.6 158.6

29.1 34.2

76 69.5

3.1 3.6

165.7 195.3

70.8 55.9

170.8 438.5

129.1 76.9

1.72 1.88

SMP-18


6.75 7.15

1230 813

660 520

458.92 359.73

106.3 83.7

46.3 36.4

96.2 75.7

2 1.5

126.5 99.6

55.3 41.9

353.8 379.6

91.2 81.7

1.0 0.6

SMP-19


6.59 7.1

2060 896

1110 573

940.4 484.72

203.6 105.1

104.4 53.8

73.1 37.7

4.4 2.2

305.2 157.5

166.4 54.5

295.3 223.5

238.5 190.2

1.2 1.16

SMP-20


6.75 6.87

1420 1490

760 953

370.57 460.94

55.7 69.8

55.4 69.4

176.1 222.2

1.6 2

154.1 193.2

112.2 87.4

390.4 829.8

6.9 12.6

1.6 1.41

Sample Location

Monsoon Period

SMP-1

and Hanshaw (1965), Morgan and Winner (1962) and Seaber (1962) developed the concept of hydro-chemical facies. Hydro-chemical facies are different zones in an aquifer that differ in their chemical composition. Groundwater of the study area for pre and post-monsoon seasons is classified (Figs.4a and b) using Back and Hanshaw diagram (1965). The percentage of groundwater of the area falling in different groups (Table 2) clearly explains the variation of cation and anion concentrations during pre-monsoon and postmonsoon seasons.

Table 2. Classification of water on the basis of hydrochemical facies Type Cations Ca type (A) Mg type (B) Na/K type (C) No dominant type (D) Anions HCO3 type (E) SO4 type (F) Cl type (G) No dominant type (H)

Pre-monsoon Percent of GW

Post-monsoon Percent of GW

40 Nil 15 45

35 Nil 20 45

60 5 15 20

15 5 5 15

JOUR.GEOL.SOC.INDIA, VOL77, JUNE 2011


(a)

543

(b)

80

80

80

80

80

60

40

20

80

60

40

20

Ca

40

Cl Cl

60

Na + K HCO3 HCO3 Na+K

80

20

40

60

80 Ca Ca

20

H H 60 60 60 H HH H 60 H H HH 40 H 40 40 40 H HH H HH H 20 20 20 20 H - Groundwater H H HH H H HH H Mg Mg SO SO4 Mg SO4 Mg SO4 HHH 4 H H H H H 80 80 80 80 H HH H H H H 60 60 60 60 H H HH 40 HH HH 40 40 H 40 H H H H H H H H H H H HH HH H HH HHHH 20 20 HH 20 20 H HH HH H H H HHHH HH HHH HH HHH H H H H H H H H H H H H H HH H H Na + K HCO3

Cl

Fig.4. Piper Tri-linear Diagram representing the chemical analysis of (a) Pre-monsoon and (b) Post-monsoon. Piper Trilinear Method

The Piper Trilinear Diagram (Piper, 1994) is one of the most useful graphical representations in groundwater quality studies and helps in understanding the geochemistry of shallow groundwater. These Tri linear diagrams are very useful in bringing out chemical relationships than with the other possible plotting methods (Walton, 1970). Chemical composition of analyzed samples of the study area is represented in the Piper diagrams (Figs.4a and b) for pre-

monsoon and post-monsoon seasons. Distribution of the groundwater samples in different subdivisions of the piper diagram reveals the analogies and dissimilarities. Different types of waters are identified and are given in (Table 3). The plot of chemical data on the diamond shaped tri-linear diagram reveals that majority of the groundwater samples fall in the fields of 1,3 and 5 suggesting that alkaline earths exceeds alkalies. Weak acids exceed strong acids and the ions representing carbonate hardness (secondary alkalinity)

Table 3. Characterization of groundwater on the basis of Piper Trilinear diagram Subdivision number ` of the diamond shaped field

Characteristics of corresponding sub division of diamond shaped fields

Pre-Monsoon % of sample

Post-Monsoon % of sample

1

Alkaline Earths (Ca + Mg) exceeds alkalies (Na K)

85

85

2

Alkalies exceeds alkaline earths

15

15

3

Weak acids (CO3 + HCO3) exceeds Strong acids (SO2 + Cl + F)

50

80

4

Strong acids exceed weak acids

50

20

5

Carbonate hardness (secondary alkalinity) exceeds 50% i.e. Chemical properties of the groundwater are dominated by alkaline earths and weak acids

35

65

6

Non carbonate hardness (secondary salinity) exceeds 50% i.e. Chemical properties of the groundwater are dominated by alkalis and strong acids

15

NIL

7

Non carbonate alkali (primary salinity) exceeds 50% i.e. Chemical properties of the groundwater are dominated by alkalis and weak acids

NIL

NIL

8

Carbonate alkali (primary alkalinity) exceeds 50% i.e. Chemical properties are dominated by alkalis and weak acids

NIL

NIL

9

No one cat ion – anion exceeds 50%

45

15

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exceeds 50% respectively (Table 3). From the diagram (Figs.4a and b) it is clear that the hydrochemistry of groundwater is dominated by alkaline earths and weak acids. Classification of Groundwater for Irrigation Purpose

The suitability of groundwater for irrigation purposes depends upon its mineral constituents. The salts present in the water affect the soil structure, permeability and aeration, which indirectly affect the plant growth. The sodium concentration in irrigation water by the process of Base Exchange replaces calcium for soil, there by reduces the permeability of soil. Wilcox (1955) has classified groundwater for irrigation purposes based on percent sodium and electrical conductivity. Eaton (1950) has recommended the concentration of residual sodium carbonate for determining the suitability of water for irrigation purposes. According to the US Salinity Laboratory method Richards (1954), electrical conductivity and sodium adsorption ratios are considered in determining the suitability of water quality for irrigation. Classification by Percent Sodium

The sodium in irrigation waters is usually denoted as

percent sodium and can be determined by the following formula (Wilcox, 1955) %Na = {(Na+ + K+) x 100}/{Ca2++Mg2++Na++K+}

1

Where, the quantities of Na, Ca, Mg, and K are taken in meq/l. The classification of groundwater samples with respect to percent sodium and electrical conductivity is shown in Figs.5a and b. It is observed that during pre-monsoon season, 75% of the groundwater is confined to the good to permissible class, while (10) % fall in the excellent to good class and another (15)% in the doubtful to unsuitable class (Fig.5a). Hence 85% of the groundwater fall between permissible to excellent class and is suitable for irrigation purposes. Whereas for the post-monsoon period 90% of the groundwater is confined to the good to permissible class, and 10% in the doubtful to unsuitable class (Fig.5b). Classification by Residual Sodium Carbonate (RSC)

The sodium hazard to the crops increase significantly with rise in bicarbonate concentration. Water containing high concentrations of carbonate and bicarbonate ions tends to precipitate Ca and Mg as their carbonates. As a consequence the relative proportion of sodium increases and gets fixed in the soil, there by decreasing, the soil permeability.

Fig.5. Classification of groundwater based on Ec and Na% (Wilcox) of (a) Pre-monsoon. (b) Post-monsoon. JOUR.GEOL.SOC.INDIA, VOL77, JUNE 2011

ENVIRONMENTAL IMPACT ON GROUNDWATER OF MAHESHWARAM WATERSHED, ANDHRA PRADESH Table 4. Classification of groundwater during Pre-monsoon and Postmonsoon on the basis of RSC Suitability for irrigation

No. of samples PrePostmonsoon monsoon

RSC (meq/L)

Safe for irrigation

< 1.25

13

9

Moderate for irrigation

1.25 – 2.5

0

1

Unsuitable for irrigation

> 2.5

7

10

Residual sodium carbonate is calculated by the following equation (Eaton, 1950). RSC = (CO32- + HCO3–) – (Ca 2++ Mg2+)

2

where all the concentrations are expressed in meq/L. On the basis of RSC (Table 4), it is observed that 65% of groundwater is safe for irrigation and 35% is unsuitable for irrigation purposes during pre-monsoon season. Whereas for the post-monsoon, it is observed that 45% is safe for irrigation, 5% is moderate and 50% is unsuitable for irrigation purposes Classification of Groundwater by U.S. Salinity Laboratory Method

The U.S. Salinity Laboratory (Richards, 1954) proposed a diagram for studying the suitability of groundwater for irrigation purposes based on sodium adsorption ratio (SAR) and electrical conductivity (Ec). SAR measures the alkali/ sodium hazard for crops. SAR can be estimated by taking individual values of Na+, Ca+2 and Mg+2 in milli-equivalents per litter and substituting in the below expression SAR = [ Na+ ] / [ v( Ca2+ + Mg2+ )/2 ]

C1 250

C2

750

C3

The chemical parameters of the groundwater of the area are represented in the U.S.S.L. Diagram (Figs.6a and b) and the results are shown in Table 5. During pre-monsoon season, it is observed that 15% of the groundwater fall under (C2S1) class indicating medium salinity, low-sodium waters; 80% under (C3S1) class indicating high salinity and low sodium waters, 5% under (C4S1) class indicating very high salinity – low sodium waters. During postmonsoon season, it is observed that 100% of the groundwater fall under (C3S1) class indicating high salinity and low sodium waters. It is observed that 95% of the groundwater samples, for both pre-monsoon and postmonsoon fall in the fields of C2S1 and C3S1 class, indicating high salinity and low sodium water type. This type of water can be used for irrigation with little care of exchangeable sodium. Groundwater samples collected from the study area during pre-monsoon and post- monsoon seasons have been analyzed for various ionic and non ionic parameters to assess its quality for drinking and irrigational purposes (Table 1). Parameters for assessment of groundwater quality compared with Standards as per World Health Organization (WHO, 1993) and Bureau of Indian Standards (BIS, 1991) Table 5. It is observed that 7.5% of the samples come under brackish water (TDS >1000 mg/l). Excessive TDS leads to gastrointestinal irritation. The pH is varying between (6.12– 7.5), and is within the desirable limits. The Electrical conductivity varies between (704 - 6450) µs/cm at 25°C (acceptable limit is 1500 µs/cm) was observed between 17.5% (as per WHO) of the groundwater samples and this

C1 250

2250C4

32

H Groundwater 26 Sodium Sodium(Alkali) (Alkali)hazard hazard:

S4

19

13 S3 6

H HHH H HH H HHHH HH HH H HH

0 100

1000

Salinity Hazard (Cond)

S2 S1

S1: Low S2: Medium S3: High S4: Very high Salinity hazard: C1: Low C2: Medium C3: High C4: Very high

C2

750

C3

26 S4

19

13 S3 6

HHH HH HH H H H H HHH H

0 100

1000

Salinity Hazard (Cond)

Fig.6. Classification of groundwater based on USSL of (a) Pre-monsoon and (b) Post-monsoon. JOUR.GEOL.SOC.INDIA, VOL77, JUNE 2011

2250C4

32

Premonsoon

Sodium Hazard (SAR)

Sodium Hazard (SAR)

3

545

S2 S1

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D. PURUSHOTHAM AND OTHERS Table 5. Drinking water quality standards Parameter

BIS (1991)

pH Ec (µs/cm)

6.5 - 8.5 -

TDS (ppm) TH (ppm) Ca (ppm) Mg (ppm) Na (ppm)

WHO (1993)

Analysed Samples Range

% of samples exceeding desirable limits as per BIS (1991)

6.5 - 8.5 400 - 2000

6.12 - 7.5 704 - 6450

500 - 2000 600 75 - 200 30 - 100 -

500 - 1000 500 100- -200 30 - 50 20 - ‘175

274 - 4000 156.7 - 3146.9 38.8 - 805.7 19.5 - 264.9 35.9 - 684.4

K (ppm)

-

10 - 12

0.6 - 12.7

HCO3 (ppm) Cl (ppm) SO4 (ppm) NO3 F (ppm)

300 - 600 250 - 1000 200- 400 45 - 100 1.0 – 1.5

25 - 600 25 - 250 -

170.7 - 909.8 23 - 3024 10 – 1796 5.6 – 415.1 0.44 - 1.95

17.5% (as per WHO) 7.5% 28% 25% 17.5% 20% (as per WHO) 5% (as per WHO) 17.5% 5% 7.5% 30% 17.5%

may be attributed to high salinity in groundwater. Excess salinity reduces the osmotic activity of plants and thus interferes with the absorption of water and nutrients from the soil. Total hardness of groundwater of the study area is varying from (156.7 – 3146.9) mg/l, nearly 28% of the groundwater of the area exceeded the desirable limits (>600 mg/l). The hardness of water is due to the presence of alkaline earths such as calcium and magnesium. Among the cationic (Ca, Mg, Na, K) concentrations, the order of abundance is Ca>Na>Mg>K, The concentration of Ca, Mg, Na in the groundwater is due to the weathering of pyroxenes, plagioclase feldspars, apatite and sphene present in the granites and alaskites of the study area. The Ca of groundwater of the study area varies from 30.1-805. Around 25% samples exceed the desirable limit (BIS, 1991). The sources of Ca2+ consists mainly of carbonate rocks containing calcite CaCO3 and dolomite CaMg(CO3)2. The Mg of groundwater of the study area varies from 19.5264.9mg/l, nearly 17.5% exceeding the desirable limit (BIS, 1991) Mg-silicate minerals, chiefly amphiboles, pyroxene, olivine, biotite and dolomite constitute the main source of Mg, Berner and Berner (1987). Excess of magnesium affects the quality of soil, which results in poor yield of crops. The high concentration of magnesium and calcium impair the potability of water and may cause encrustation in the water supply structure. Apart from natural sources, human activities have significant influence on the concentration of sodium in groundwater. Sewage, industrial effluents, the use of sodium compounds for corrosion control and water softening processes has contributed to Na concentrations in groundwater of the study area. The sodium concentrations

of the groundwater is varying from (35.9–684.4) mg/l of the area, around 20% of the samples exceed the desirable limit (175mg/l) (WHO, 1993). Sodium can deteriorate quality of the soil and damage the sensitive crops because of its phyto-toxcity when present in higher concentrations. The K of groundwater of the study area varies between 0.6-12.7mg/l. 5% of the samples exceed the desirable limit (12 mg/l) (WHO, 1993). High K-values may cause nervous and digestive disorders. Among the anionic (HCO 3, SO 4, Cl, NO 3 and F) concentrations, the order is HCO 3 >Cl>SO 4>NO 3 >F. Bicarbonate concentrations are varying from (170.8 - 909.8) mg/l in the groundwater of study area. 17.5% of samples exceed the desirable limit (600mg/l) (BIS, 1991). The Maximum concentration of bicarbonate 909.8 mg/l is observed at the Mandal Revenue Office, near Maheshwaram. Bicarbonate, usually the primary anion in groundwater, is derived from the carbon dioxide released by the organic decomposition in the soil (Todd, 1980) CO2 + H2O = HCO3– + H+

4

According to Subba Rao et al. (2002), groundwaters saturated with CaCO3 leads to precipitation of CaCO3,. This indicates the occurrence of kankar in the soil zone. The precipitation of CaCO 3 could decrease the Ca +2 and carbonates (HCO3 and CO3) in the ground waters, but leaching of CaCO3 from the kankar can increase them and consequently increases the level of pH, Hem (1991) as H2O + CaCO3 = HCO3– + Ca+2 + OH–

5

In the present analysis the HCO3 has increased during JOUR.GEOL.SOC.INDIA, VOL77, JUNE 2011


post monsoon period, hence leaching of CaCO3 from the kankar has taken place. Sulfate concentrations are varying from (10 - 1796) mg/l, around 7.5% of the samples exceed the desirable limit of (400 mg/l) (BIS, 1991). It is observed that the high concentrations of sulfate in groundwater are distributed at Dattatreya Ashram, near Maheshwaram. The distribution of sulfate is due to sulphur minerals, sulfides of heavy metals, which are common occurrence in igneous rocks and metamorphic rocks. Apart from these natural sources, sulfates can be introduced through the application of sulfuric soil conditioners (Karanth, 1987). Sulphates are also discharged into the groundwater from different industrial effluents. Excessive sulphate concentration causes laxative effect. The source of chloride in groundwater is due to the weathering of phosphate mineral apatite present in granites of the study area. Apart from natural sources, domestic sewage and industrial effluents also contribute for chloride in groundwater (Karanth, 1987; Craig and Anderson, 1979). Similar sources are expected to cause the increase in chloride concentration in the groundwater of the study area. Chloride concentrations are varying from 23 - 3024 mg/l. It is observed that nearly 5% of groundwater from the area exceeds the desirable limit (1000 mg/l) (BIS, 1991). Excessive chloride concentration leads to salinity, which deteriorate the soil. Nitrate concentrations vary from (5.6 415.1) mg/l, 33% of water sample exceed the permissible limit of 100 mg/l (BIS, 1991). Numerous sources in the environment contribute to the total nitrate content of natural waters (Handa et al. 1982) viz., atmosphere, geological sources, soils, atmospheric nitrogen fixation and anthropogenic sources which include (a) industrial wastes containing N-compounds (b) human and animal wastes and agricultural activities. Urea (NH2)2CO and ammonium nitrate NH4NO3 are the most commonly used fertilizers contributing nitrates to the ground water. Although commercial fertilizers are suspected as major source of nitrate in groundwater, researchers have also identified natural organic nitrogen, livestock, septic tank and atmospheric inputs in contributing to the absence of fertilizer application and geological deposits, in high nitrate concentrations observed may be attributed to the anthropogenic sources like leakage of septic tanks, sewer pipes and improper disposal of domestic and industrial wastes (Sudarshan and Sravanthi, 1996; Sravanthi et al. 1997). Presence of high concentrations of nitrate in drinking water (>45 mg/l) not only causes methemoglobinemia in infants, but has also been reported to cause cancer (Dissanayake and Weerasooriya, 1987). Nitrate acts in the JOUR.GEOL.SOC.INDIA, VOL77, JUNE 2011

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blood to convert hemoglobin to methemoglobin, a form that does not carry oxygen to the body cells, which in large amounts can lead to death from asphyxiation (Ozha et al. 1993). Fluoride concentration varies from 0.44 – 1.88 mg/l. 17.5% of sample exceeds the limit of 1.5 mg/l (BIS, 1991). High fluoride content in groundwater leads to dental and skeletal fluorosis such as mottling of teeth, deformation of ligaments and bending of spinal cord. Maximum concentration of F (1.88) mg/l is observed in the groundwater collected from a bore well located in SMP-17 Sirgiripur area. Fluorite (CaF2) is the main solid phase fluoride in rocks. F– ions are released when CaF2 reacts with carbonate waters, Saxena and Ahmed (2001) CaF2 + Na2CO3 = CaCO3 + 2F - +2Na+

6

CaF2+2NaHCO3(aq) = CaCO3+2Na++2F–+H2O+CO2(aq) 7 The NaHCO3 rich water accelerates the dissolution of CaF2 and thereby releases fluoride into groundwater. High fluoride concentration in the groundwater may be attributed to the presence of fluorine bearing minerals like biotite, apatite and sphene from the granites of the study area and due to use of the phosphatic fertilizers (Fluoroapatite Ca 5[PO 4] 3[F,Cl]), Handa (1975), at these areas were predominantly used for agricultural activities before settlements. Most of the industries in the study area are steel, chemical industries (Uma Organic Ltd, Sai Teja Electroplating etc., at SMP-5) , brick tiles, oil refineries and other anthropogenic activities which contribute to the fluoride concentrations. The fluoride concentrations increased at some places (SMPS 5-10, 16 and 17 = 40%) and decreased in the rest (60%) during post-monsoon season. The presence of fluoride is due to lithology as well as due to pollution by chemical industries. The tri-linear plot in the piper diagram suggests that alkaline earths exceed alkalis, weak acids exceed strong acids and the secondary alkalinity exceeds 50%. The Wilcox diagrams reveals that 85% of the groundwater samples fall between permissible to excellent class and another 15% in the doubtful to unsuitable class for irrigation purposes. On carrying out Residual Sodium Carbonate analysis, it is observed that 35 % of groundwater of the area is unsuitable for irrigation purposes during pre-monsoon season. Whereas for the post-monsoon, it is observed that 50% is unsuitable for irrigation purposes. From the U.S. Salinity Laboratory diagrams, it is observed that 95% of the groundwater samples, for both pre and post- monsoon fall in the fields of C2S1 and C3S1 waters, indicating high salinity and low

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sodium water type. This type of water can be used for irrigation with little danger of exchangeable sodium. CONCLUSIONS

Maheshwaram watershed is facing the problem of over exploitation and deterioration of groundwater quality due to rapid urbanization and industrialization. In the absence of perennial source of surface water and inadequate rainfall the problems are increasing year after year. Water quality has deteriorated considerably due to unscientific disposal of waste and improper waste management practices of industries. Change in land use pattern resulted in the degradation of hydro-geological environment. Weathered zone has become dry, the existing wells tap the fractured and fissured aquifers (Hashimi and Engerrand, 1999). The anthropogenic activities like poultry farms, various industries including chemical and pharmaceuticals, indiscriminate use of fertilizers/pesticides, release of sewage and reactive pollutants into the atmosphere by chemical industries are the main cause for deterioration of air, water and soil quality in the watershed. The groundwater in the study area is slightly alkaline in nature. Based on the TDS, about 8% of groundwater samples exceed the desirable limits of the drinking water. The Wilcox

diagram reveals that 15% of the groundwater samples are in doubtful to unsuitable class for irrigation purposes. From the RSC analysis it is observed that 42.5% of samples are unsuitable for irrigation purpose. About 27% of samples exceed the desirable limits for Na, Mg, Cl and HCO3 concentrations together. Excess of Na, Mg, Cl and HCO3 concentrations deteriorates the soil quality and damage sensitive crops. Hence these soils require gypsum treatment to improve permeability of soils and yields of the crops. It is observed that more than 33% of samples exceed the desirable limits for NO 3 concentrations. Salinity and pollution problems of the study area should be solved by installing distillation plant, adopting rain harvesting method and by providing proper drainage facilities. Practice of drip irrigation to prevent leaching and weathering. There are zones of high fluoride exceeding the prescribed limit water in such areas should not be allowed for drinking purposes. It is also recommended to have a periodical monitoring of the environment in this area and mitigative measures be implemented to avoid further deterioration of the Environment for Sustainable Development. Acknowledgements: We are thankful to Dr. Y.J. Bhaskar Rao, Director, NGRI for his encouragement and permission to publish this paper.

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