Water quality and dissolved inorganic fluxes of N, P, SO 4 , and K of a small catchment river in the Southwestern Coast of India

Environ Monit Assess (2012) 184:1541–1557DOI 10.1007/s10661-011-2059-x

Water quality and dissolved inorganic fluxes of N, P, SO4,and K of a small catchment river in the SouthwesternCoast of India

D. Padmalal · S. I. Remya · S. Jissy Jyothi ·B. Baijulal · K. N. Babu · R. S. Baiju

Received: 10 March 2010 / Accepted: 8 April 2011 / Published online: 5 May 2011© Springer Science+Business Media B.V. 2011

Abstract The southwestern coast of India is drainedby many small rivers with lengths less than 250 kmand catchment areas less than 6,500 km2. These ri-vers are perennial and are also the major drinkingwater sources in the region. But, the fast pace ofurbanization, industrialization, fertilizer intensiveagricultural activities and rise in pilgrim tourism inthe past four to five decades have imposed markedchanges in water quality and solute fluxes of manyof these rivers. The problems have aggravatedfurther due to leaching of ionic constituents fromthe organic-rich (peaty) impervious sub-surfacelayers that are exposed due to channel incisionresulting from indiscriminate instream mining forconstruction-grade sand and gravel. In this con-text, an attempt has been made here to evaluatethe water quality and the net nutrient flux of oneof the important rivers in the southwestern coastof India, the Manimala river which has a length ofabout 90 km and catchment area of 847 km2. Theriver exhibits seasonal variation in most of the

D. Padmalal (B) · S. I. Remya · S. Jissy Jyothi ·B. Baijulal · K. N. Babu · R. S. BaijuCentre for Earth Science Studies,Thiruvananthapuram 695031, Kerala, Indiae-mail: [email protected]

water quality parameters (pH, electrical conduc-tivity, dissolved oxygen, total dissolved solids, Ca,Mg, Na, K, Fe, HCO3, NO2-N, NO3-N, P-inorg,P-tot, chloride, SO4, and SiO2). Except for NO3-N and SiO2, all the other parameters are generallyenriched in non-monsoon (December–May) sam-ples than that of monsoon (June–November). Theflux estimation reveals that the Manimala rivertransports an amount of 2,308 t y−1 of dissolvedinorganic nitrogen, 87 t y−1 dissolved inorganicphosphorus, and 9246 t y−1 of SO4, and 1984 t y−1

K into the receiving coastal waters. These togetherconstitute about 23% of the total dissolved fluxestransported by the Manimala river. Based on thestudy, a set of mitigation measures are also sug-gested to improve the overall water quality ofsmall catchment rivers of the densely populatedtropics in general and the south western coast inparticular.

Keywords Manimala river ·Small catchment rivers · Solute fluxes ·South western coast of India · Water quality

Introduction

The demand of fresh water is rising exponentiallyover the years to meet the ever-increasing humanneeds for drinking, agriculture, and industries.Among the various natural agents at work, rivers

1542 Environ Monit Assess (2012) 184:1541–1557

Fig. 1 Drainage map of the study area showing sampling locations

are the most important sources of drinking waterin tropics and subtropics. But in the past four tofive decades, there has been a drastic reduction inthe quality of water in many rivers of the world conse-quent to various kinds of anthropogenic activities(Walling 1980; Berner and Berner 1987; Naimanand Bilby 1998; Subramanian 2000; Jennerjahanet al. 2004). Although many studies have beencarried out on the chemical composition and themechanisms of water quality changes in the world’smajor rivers (Meybeck 1976; Subramanian 1987;Sarin et al. 1989; Goolsby et al. 2000; Liu et al.2003), only very limited investigations (Bajpayeeand Verma 1999; Maya et al. 2007; Raj andAzeez 2009) have been made in the small catch-ment rivers (i.e., the rivers with catchment area<10,000 km2, Milliman and Syvitzki 1992) thatare more responsive to episodic events (Milliman1995) and drains the densely populated regionsin tropics like that in the southwestern coast ofIndia. Furthermore, many such regions are grow-

ing fast over the years due to rapid economic andindustrial developments (Leeuw et al. 2009). Asrivers are one of the most sensitive ecosystems andperhaps the first to hit a negative economic growth,many of the small catchment rivers draining thesouthwestern part of India are severely impairedby human activities threatening even the ruralwater supply schemes attached to these systems(Padmalal et al. 2008). In this context, an attempthas been made in this paper to examine the waterquality and dissolved fluxes of N, P, SO4, and Kin one of the important rivers in Kerala State inthe southwestern coast of India, the Manimalariver—originating from the Western Ghat MountainRanges (Fig. 1).

Study area

The Manimala river is one of the important riversin Kerala with a length of about 90 km and a

Environ Monit Assess (2012) 184:1541–1557 1543

catchment area of about 847 km2. The river basinlies between north latitudes 9◦20′–9◦40′ and eastlongitudes 76◦25′–77◦0′. The river drains throughhighly varied geologic and geomorphic provincesof the State. Geologically, the Manimala riverbasin is composed of Precambrian crystallinebasements comprising charnockites, charnock-ite gneisses and hypersthene–diopside gneisses.These rocks are intruded at many places by py-roxene granulites and quartzite (GSI 1995). In thedownstream, the river flows through laterites aswell as coastal sands and alluvium (Fig. 2). Theriver basin falls under three broad physiographicdivisions of Kerala such as (1) the lowlands (<8 mabove msl), (2) the midlands (8–75 m above msl),and (3) the highlands (>75 m above msl). The to-tal population and population density of the riverbasin are 587, 541 (2001 census) and 693 inh km−2

respectively. The density of population exhibits anincreasing trend towards the coast. The lowlandsnear the river mouth account for a density ofpopulation of 1,585 inh km−2, which is three timeshigher than the highlands. The average annual wa-ter discharge computed for the period 1990–2000for Mundakkayam (highland), Manimala (mid-land), and Thondara (lowland) gauging stations inthe river are 385, 1,082, and 1,568 Mm3, respec-tively. The average monthly discharges computedfor these three gauging stations of the Manimalariver are depicted in Fig. 3. Atmospheric tem-perature varies between 23◦C and 32◦C with anaverage of 27.5◦C. The river basin receives anaverage rainfall of 2,581 mm, a major portion(i.e., >80%) of which is contributed by the mon-soon season. The area enjoys a tropical humidclimate.

Fig. 2 Geology of the study area (After GSI 1995)


0

100

200

300

400

500

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Wat

er d

isch

arge

(M

m3 )

Mundakkayam

Manimala

Thondara

Fig. 3 Average monthly discharge of water throughManimala river during the period 1990–2000. The peakdischarge in July is contributed by the southwest monsoonand October is contributed by the north east monsoon

Methodology

A systematic fieldwork was carried out for thecollection of primary and secondary data from theManimala river basin. Water discharge data hasbeen collected from the gauging stations of Irriga-tion Department, Government of Kerala. Further,a total of 26 water samples were collected fromthe river channel during the month of May (non-monsoon season) and August (monsoon season;Fig. 1). The pH and electrical conductivity of thesamples were determined at the time of samplingusing a portable water quality analyzer (Multi-lane F/SET-3, WTW). Dissolved oxygen (DO)content in the sample was estimated by Winklermethod with azide modification. Estimations ofDO, hardness, HCO3, chloride, SO4, NO2-N,NO3-N, P, SiO2, Ca, Mg, Fe, and TDS concen-trations were carried out following standard meth-ods (APHA 1995). All colorimetric analyses wereperformed using a UV–visible spectrophotometer(Shimadzu, UV 160A). The Na and K concentra-tions were determined by flame photometer.

Results

Table 1 shows the physico-chemical parametersestimated for the water samples collected from the

Manimala river during non-monsoon (May 2009)and monsoon (August 2009) seasons. The down-stream variations of the physico-chemical param-eters along the master channel of the river aredepicted in Fig. 4. Table 2 summarizes the aver-ages and ranges of physico-chemical parametersestimated for the tributaries, main channel (high-land, midland, and lowland), and distributary.

The river water is slightly acidic throughoutthe year with pH ranges of 6.29–6.94 during non-monsoon and 5.9–6.5 during monsoon seasons. Onan average, the monsoon water shows marginallyhigher acidity (6.26) than non-monsoon (6.56)water. The electrical conductivity (EC) and totaldissolved solids (TDS) exhibit an increase towardsdownstream (Table 1). The non-monsoon valuesof both the parameters (EC: av. 47.76 μS/cm,range 26.64–65.13 μS/cm; TDS: av. 28.62 mg/l,range 14.92–42.98 mg/l) are markedly higherthan that of monsoon season (conductivity: av.35.76 μS/cm, range 22.4–47.2 μS/cm; TDS: av.21.85 mg/l, range 13.66–28.79 mg/l). All the sta-tions record DO values of over 5 mg/l duringmonsoon (range 5.54–6.66 mg/l; av. 6.06 mg/l) andnon-monsoon (range 6.28–7.77 mg/l; av. 7.03 mg/l)seasons with slightly higher values in the lat-ter period. Although the DO values in mon-soon show a general decreasing trend towardsdownstream especially in the monsoon season(Table 2), the non-monsoon values exhibitfluctuation with marked decrease in the Centralzone around Manimala (Stn. 12) and Koratti (Stn.18) stations where the local people as well asthe pilgrimage tourists reaching the area in con-nection with festival of Sabarimala temple (thefamous hill temple in South India) use the riverfor bathing and washing.

The river water exhibits low hardness val-ues during the monsoon season (av. 8.5 mg/l;range 5–12 mg/l) than non-monsoon season (av.11.08 mg/l; range 2–16 mg/l). The hardness val-ues generally show an increasing trend towardsdownstream. Among the cations, Ca content inthe Manimala river exhibits an increasing trendtowards downstream with notable fluctuations innon-monsoon season. The ranges of Ca duringnon-monsoon and monsoon seasons are 1.6–4.01 mg/l (av. 2.63 mg/l) and 0.8–3.2 mg/l (av.2.25 mg/l), respectively. The fluctuations are more


Tab

le1

Phy

sio-

chem

ical

para

met

ers

esti

mat

edin

the

wat

ersa

mpl

esof

the

Man

imal

ari

ver

Sam

plin

gpH

EC

(μs/

cm)

TD

S(m

g/l)

DO

(mg/

l)H

ardn

ess

(mg/

l)H

CO

3(m

g/l)

Chl

orid

e(m

g/l)

Sulf

ate

(mg/

l)N

itra

te(μ

g/l)

stn.

no.

NM

MN

MM

NM

MN

MM

NM

MN

MM

NM

MN

MM

NM

M

Stn.

16.

306.

0261

.60

42.5

037

.58

25.9

26.

885.

5414

.00

8.00

16.0

05.

6013

.59

9.00

5.09

2.77

251

1022

Stn.

26.

666.

1261

.71

43.3

238

.26

26.4

26.

715.

7314

.00

10.0

010

.00

6.60

12.6

29.

507.

872.

6630

799

1St

n.3

6.67

6.27

63.0

747

.20

40.3

628

.79

7.14

5.72

14.4

012

.00

12.0

07.

8011

.65

9.50

13.7

52.

0533

996

6St

n.4

6.69

6.37

65.1

342

.15

42.9

826

.71

7.15

5.80

14.0

010

.00

10.0

05.

4012

.62

9.00

9.34

3.68

689

1284

Stn.

56.

626.

2359

.28

42.3

335

.57

25.8

27.

136.

0214

.00

10.0

010

.00

5.20

9.71

8.50

7.45

3.28

706

1215

Stn.

66.

575.

9061

.93

39.4

238

.39

24.0

46.

775.

9014

.00

9.00

8.00

5.40

10. 6

88.

009.

872.

4610

4611

93St

n.7

6.55

6.44

62.1

339

.30

39.1

423

.97

6.28

6.09

14.0

09.

008.

005.

4010

.19

8.50

10.0

82.

2510

5710

77St

n.8

6.59

6.16

54.0

840

.53

32.4

424

.72

7.63

5.97

16.0

010

.00

8.00

6.00

9.22

9.50

7.98

2.05

942

1097

Stn.

96.

466.

1043

.58

39.1

525

.71

23.8

86.

765.

918.

008.

006.

005.

407.

766.

001.

151.

4384

810

78St

n.10

6.41

6.48

42.1

735

.85

24.6

721

.86

6.53

6.18

12.0

07.

008.

005.

608.

748.

500.

630.

7279

810

86St

n.11

6.54

6.30

43.7

739

.22

25.4

723

.92

6.56

6.08

12.0

09.

008.

005.

808.

259.

501.

680.

3110

6572

8St

n.12

6.43

6.14

48.4

136

.10

29.0

422

.02

6.77

6.34

12.0

010

.00

8.00

5.00

8.74

8.50

3.88

0.51

1185

1124

Stn.

136.

296.

5545

.04

33.7

026

.57

20.5

56.

946.

4212

.00

10.0

07.

006.

008.

259.

003.

250.

1012

2574

1St

n.14

6.48

6.26

61.6

239

.20

37.5

823

.91

6.32

6.31

10.0

010

.00

13.0

06.

0011

.65

10.5

00.

630.

1036

656

4St

n.15

6.55

6.27

44.5

536

.23

26.0

622

.10

6.82

6.66

10.0

08.

007.

004.

008.

748.

501.

470.

3110

9310

81St

n.16

6.45

6.44

39.2

436

.20

22.3

622

.08

7.02

6.57

8.00

9.00

7.00

5.00

7.77

7.00

0.52

2.25

1071

1158

Stn.

176.

536.

4657

.76

47.2

034

.66

28.7

97.

015.

8812

.00

10.0

012

.00

6.60

10.6

810

.00

0.73

0.72

779

1043

Stn.

186.

606.

2843

.53

33.9

225

.68

20.6

97.

356.

4910

.00

9.00

8.00

4.60

4.85

7.50

15.3

20.

6111

8011

19St

n.19

6.58

6.30

39.9

329

.77

22.7

618

.16

7.67

6.40

10.0

06.

0010

.00

0.80

7.28

7.00

1.47

0.31

1171

906

Stn.

206.

576.

1741

.30

38.3

023

.95

23.3

67.

086.

072.

008.

008.

009.

807.

777.

000.

420.

5110

6510

99St

n.21

6.59

6.28

35.9

424

.75

20.4

915

.09

7.77

5.93

12.0

06.

007.

004.

407.

777.

000.

320.

1010

2970

7St

n.22

6.50

6.10

35.9

728

.17

20.5

017

.18

7.35

5.56

8.00

7.00

6.00

4.00

8.74

7.50

2.20

0.10

1164

1250

Stn.

236.

486.

1133

.98

24.7

519

.20

15.0

97.

246.

3110

.00

5.00

8.00

4.20

8.74

7.00

0.42

0.10

824

497

Stn.

246.

786.

4534

.60

24.3

619

.89

14.8

67.

426.

208.

005.

008.

004.

608.

747.

000.

840.

1063

843

7St

n.25

6.69

6.42

26.6

422

.40

14.9

213

.66

7.09

5.81

10.0

05.

006.

004.

608.

256.

000.

520.

1062

450

1St

n.26

6.94

6.15

34.7

523

.80

19.9

814

.52

7.32

5.70

8.00

6.00

8.00

4.80

7.77

8.00

1.36

0.31

609

441


Tab

le1

(con

tinu

ed)

Sam

plin

gN

itri

te(μ

g/l)

P-i

norg

(μg/

l)P

-tot

al(μ

g/l)

Silic

ate

(μg/

l)C

a(m

g/l)

Mg

(mg/

l)N

a(m

g/l)

K(m

g/l)

Fe

(μg/

l)st

n.no

.N

MM

NM

MN

MM

NM

MN

MM

NM

MN

MM

NM

MN

MM

Stn.

14.

541.

8158

.30

40.0

699

.33

77.9

248

6596

253.

212.

401.

460.

492.

61.

92.

10.

614

2.6

8.68

Stn.

24.

543.

7685

.51

38.0

510

2.02

73.1

947

2699

573.

213.

211.

460.

492.

82.

82.

20.

813

3.0

46.2

8St

n.3

4.84

2.71

58.3

744

.06

110.

0794

.44

5020

1125

43.

393.

211.

520.

972.

92.

82.

20.

837

.034

.71

Stn.

413

.01

1.88

64.1

340

.06

142.

2980

.28

5756

9276

3.21

2.81

1.46

0.73

3.0

1.7

2.4

0.7

236.

02.

89St

n.5

3.33

1.51

75.7

942

.06

150.

3473

.19

6107

9126

4.01

2.40

0.97

0.97

3.7

1.8

2.2

0.6

88.0

28.9

3St

n.6

15.4

41.

8869

.96

42.0

612

8.86

89.7

265

9893

594.

012.

810.

970.

493.

71.

82.

30.

793

.02.

89St

n.7

7.26

1.51

71.9

136

.05

136.

9287

.36

5838

8944

3.21

2.40

1.46

0.73

3.7

1.7

2.3

0.6

53.0

17.3

6St

n.8

6.96

0.31

89.4

038

.05

155.

7180

.28

6745

1005

73.

213.

211.

950.

493.

51.

82.

00.

648

.049

.18

Stn.

93.

331.

8869

.96

40.0

615

3.03

80.2

864

7599

412.

402.

810.

490.

242.

81.

91.

70.

632

.014

.46

Stn.

102.

421.

2177

.44

36.0

516

9.13

96.8

079

5596

091.

602.

401.

950.

242.

91.

71.

40.

664

.037

.61

Stn.

115.

450.

3181

.62

44.0

614

4.97

75.5

581

0296

253.

212.

400.

970.

732.

92.

11.

50.

774

.098

.36

Stn.

1211

.20

2.19

89.4

038

.05

174.

5099

.16

8495

9658

1.60

2.40

1.95

0.97

3.2

1.8

1.7

0.6

103.

012

7.28

Stn.

133.

030.

6010

2.99

44.0

614

2.29

63.7

568

9210

623

2.40

2.40

2.43

0.97

3.1

2.1

1.5

0.6

66.0

83.8

9St

n.14

3.63

1.88

27.9

938

.05

67.1

299

.16

4938

9592

3.21

2.81

0.49

0.73

0.2

2.4

3.2

0.7

93.0

2.89

Stn.

156.

362.

7141

.99

48.0

777

.86

106.

2570

2398

742.

402.

400.

970.

493.

11.

81.

50.

611

4.0

11.5

7St

n.16

4.24

3.31

99.1

140

.06

150.

3496

.80

7522

1034

02.

402.

400.

490.

732.

61.

51.

40.

758

.060

.75

Stn.

175.

150.

3110

1.06

40.0

613

9.60

103.

8866

9694

423.

212.

810.

970.

693.

22.

72.

00.

811

9.0

11.5

7St

n.18

10.8

93.

0125

.99

44.0

611

6.78

75.5

572

6010

124

2.00

2.00

1.22

0.97

3.0

1.6

1.3

0.6

60.0

86.7

8St

n.19

0.61

2.19

147.

740

.06

189.

2787

.36

7456

1037

32.

002.

001.

220.

242.

81.

51.

00.

460

3.0

11.9

6St

n.20

1.82

1.57

106.

8942

.06

163.

7787

.36

9713

1022

43.

212.

400.

970.

492.

92.

11.

10.

715

4.0

56.8

3St

n.21

2.12

1.51

106.

8936

.05

115.

4492

.08

9475

1019

11.

600.

801.

950.

972.

21.

30.

70.

466

.029

.91

Stn.

225.

150.

3110

6.89

42.0

612

0.81

70.8

394

5110

456

2.40

1.60

0.49

0.73

2.3

1.4

0.7

0.4

53.0

47.8

6St

n.23

0.91

0.63

110.

7738

.05

123.

5087

.36

9182

9076

1.60

1.20

1.46

0.49

2.2

1.2

0.6

0.3

24.0

173.

49St

n.24

1.51

0.31

116.

6040

.06

128.

8696

.80

7301

9442

2.40

1.20

0.49

0.49

2.2

1.2

0.6

0.4

53.0

2.99

Stn.

250.

610.

3110

1.06

46.0

613

1.55

108.

6187

5610

489

1.60

0.80

1.46

0.71

2.0

1.2

0.5

0.4

74.0

2.99

Stn.

260.

910.

3097

.17

38.0

511

5.44

92.0

851

9296

431.

601.

200.

970.

732.

21.

20.

60.

382

.071

.79


10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80 90

Distance (km) from RM

EC

(µs

/cm

)

NM M

RM

4

5

6

7

8

9

0 10 20 30 40 50 60 70 80 90


DO

(m

g/l)

RM

NM M

5.5

6

6.5

7

7.5

0 10 20 30 40 50 60 70 80 90


pH

NM M

RM

0

5

10

15

20

0 10 20 30 40 50 60 70 80 90


HC

O3

(mg/

l)

NM M

a

Fig. 4 a Downstream variations of pH, DO, EC, andHCO3 along the profile of the main channel of Manimalariver. RM River mouth, NM Non-monsoon, M Monsoon.b Downstream variations of chloride (Cl), sulfate (SO4),

NO2-N, NO3-N, P-inorg and SiO2 along the profile of themain channel of the Manimala river. c Downstream varia-tions of Hardness, Na, Ca, K, Mg, and Fe along the profileof main channel of the Manimala river

pronounced in the case of Mg, although thenon-monsoon values (av. 1.24 mg/l; range 0.49–2.43 mg/l) are slightly higher than that of monsoon(av. 0.65 mg/l; range 0.24–0.97 mg/l). Magnesiumcontents in the water samples are lower thanthe corresponding Ca values. The alkali metals,Na and K, show marked increase towards down-stream. But the trend is more pronounced for Kthan Na. Monsoon water generally shows low Naconcentrations (av. 1.81 mg/l; range 1.2–2.8 mg/l)than non-monsoon water (av. 2.76 mg/l; range 0.2–3.7 mg/l). The ranges of K in non-monsoon andmonsoon seasons are 0.5–3.2 mg/l (av. 1.57 mg/l)and 0.3–0.8 mg/l (av. 0.58 mg/l), respectively. Theconcentration of Fe in the river water registershigher values in non-monsoon season (range 24–

603 μg/l; av. 104.72 μg/l) than monsoon season(range 2.89–173.49; av. 43.23 μg/l). In both the sea-sons, the content of Fe shows a fluctuating trendalong the profile of the river. Dissolved Fe con-centration shows wide spatial variations. Samplescollected from Vallakkadavu bridge (Stn. 19) ex-hibit fairly high Fe values in non-monsoon seasonwhile Station 23, located upstream of Kootikkal,records elevated levels of Fe during the monsoonseason.

In general, the HCO3 content exhibits an in-creasing trend towards downstream. Also, mon-soon water exhibits low HCO3 values (av.5.33 mg/l; range 0.8–9.8 mg/l) than that of non-monsoon (av. 8.73 mg/l; range 6–16 mg/l) seasons.Chloride averages 8.19 mg/l (range 6–10.5 mg/l) in


0

40

80

120

160

0 10 20 30 40 50 60 70 80 90


P-i

norg

(µg

/l)

RM

NM M

0

3

6

9

12

15

18

0 10 20 30 40 50 60 70 80 90


NO

2-N

(µg

/l)

RM

NM M

0

500

1000

1500

0 10 20 30 40 50 60 70 80 90


NO

3-N

(µg

/l)

RM

NM M

0

4

8

12

16

0 10 20 30 40 50 60 70 80 90


SO4 (

mg/

l)

RM

NM M

3

6

9

12

15

0 10 20 30 40 50 60 70 80 90


Cl (

mg/

l)

RM

NM M

0

5000

10000

15000

20000

0 10 20 30 40 50 60 70 80 90


SiO

2 (µ

g/l)

RM

NM M

b

Fig. 4 (continued)

monsoon and 9.26 mg/l (range 4.85–13.59 mg/l) innon-monsoon seasons. The chloride values showa fluctuating trend till Stn. No. 8 (Komalam),and thereafter, the non-monsoon values domi-nate over the monsoon season. The SO4 con-tent in the water samples of the monsoon sea-son (av. 1.15 mg/l; range 0.1–3.68 mg/l) is lowerthan non-monsoon season (av. 4.16 mg/l; range0.32–15.32 mg/l). Water sample collected fromKoratti (15.32 mg/l; Stn. 18) and Velium kadavu

(13.75 mg/l; Stn. 3) stations exhibit high SO4 val-ues in non-monsoon season. The average SO4

content in Manimala river is low compared todrinking water standards. The content of NO2-N in Manimala river is several folds lowerthan that of NO3-N values. The water sam-ples in the study area exhibit wide variation ofNO2-N during non-monsoon season (range 0.61–15.44 μg/l; av. 4.97 μg/l). During the monsoon sea-son, the variation of NO2-N is comparatively low


0

5

10

15

20

0 10 20 30 40 50 60 70 80 90

Distance (km) from RMRM

NM M

0

1

2

3

4

5

0 10 20 30 40 50 60 70 80 90


Na

(mg/

l)

Har

dnes

s (m

g/l)

RM

NM M

0

1

2

3

4

5

0 10 20 30 40 50 60 70 80 90


Ca

(mg/

l)

RM

NM M

0

1

2

3

4

0 10 20 30 40 50 60 70 80 90


K (

mg/

l)

RM

NM M

0

1

2

3

0 10 20 30 40 50 60 70 80 90


Mg

(mg/

l)

RM

NM M

0

50

100

150

200

0 10 20 30 40 50 60 70 80 90


Fe

( µg

/l)

RM

NM M

c

Fig. 4 (continued)

(av. 1.53 μg/l; range 0.3–3.76 μg/l). The NO2-Nconcentration shows an increasing trend towardsdownstream. Water collected from Manakkachirabridge (13 μg/l; Stn. 4) and Kalloopara Check dam(15.44 μg/l; Stn. 6) in the downstream records sub-stantially high NO2-N values during non-monsoonperiod. Unlike the other parameters, averageconcentration of NO3-N in monsoon season ishigher (range 437–1284 μg/l; av. 939 μg/l) thanthat of non-monsoon water (range 251–1225 μg/l;av. 849 μg/l). The highland stations show only

marginal seasonal difference in NO3-N contentsthan the other stretches. Maximum NO3-N valueis observed at Manakkachira bridge (Stn. 4) andManimala upstream (Stn. 13) in both the seasons.In general, the NO3-N concentration in monsoonseason increases towards downstream, whereas areverse trend is observed during the non-monsoonseason.

Inorganic P records an average concentrationof 40.59 μg/l (range 36.05–48.07 μg/l) in monsoonseason and 84.09 μg/l (range 26–147.7 μg/l) in


Table 2 Averages and ranges of physico-chemical parameters in the tributaries, distributaries and main channel of theManimala river

Parameters Season Tributaries Main channel Distributarya

Upstream Midstream Downstream

pH NM 6.56 (6.48–6.69) 6.63 (6.48–6.94) 6.52 (6.29–6.69) 6.49 (6.30–6.67) 6.60M 6.38 (6.26–6.46) 6.22 (6.10–6.45) 6.28 (5.90–6.55) 6.15 (6.02–6.27) 6.12

EC NM 48.67 (26.64–61.62) 36.64 (33.98–41.30) 50.22 (39.24–65.13) 62.34 (61.60–63.07) 61.71(μs/cm) M 36.27 (22.40–4 7.20) 27.70 (23.80–38.30) 38.01 (33.70–42.33) 44.85 (42.5–47.2) 43.32

TDS NM 29.05 (14.92–37.58) 20.97 (19.20–23.95) 30.31 (22.36–42.98) 38.97 (37.58–40.36) 38.26(mg/l) M 22.12 (13.66–28.79) 16.89 (14.52–23.36) 23.26 (20.55–26.71) 27.36 (25.92–28.79) 26.42

DO NM 6.67 (6.32–7.01) 7.56 (7.08–7.77) 6.89 (6.28–7.63) 7.01 (6.88–7.14) 6.71(mg/l) M 6.00 (5.81–6.31) 6.02 (5.56–6.40) 6.19 (5.80–6.66) 5.63 (5.54–5.72) 5.73

HCO3 NM 10.33 (6.00–13.00) 7.86 (6.00–10.00) 7.92 (6.00–10.00) 14.00 (12.00–16.00) 10.00(mg/l) M 5.73 (4.60–6.60) 4.66 (0.80–9.80) 5.29 (4.00–6.00) 6.70 (5.60–7.80) 6.60

Hardness NM 10.67 (10.00–12.00) 8.29 (2.00–12.00) 12.00 (8.00–16.00) 14.20 (14.00–14.4) 14.00(mg/l) M 8.33 (5.00–10.00) 6.14 (5.00–8.00) 9.08 (7.00–10.00) 10.00 (8.00–12.00) 10.00

Ca NM 2.67 (1.60–3.21) 2.12 (1.60–3.21) 2.74 (1.60–4.01) 3.30 (3.21–3.39) 3.21(mg/l) M 2.14 (0.80–2.81) 1.49 (0.80–2.40) 2.5 (2.00–3.21) 2.81 (2.40–3.21) 3.21

Mg NM 0.97 (0.49–1.46) 1.08 (0.49–1.95) 1.33 (0.49–2.43) 1.49 (1.46–1.52) 1.46(mg/l) M 0.71 (0.69–0.73) 0.59 (0.24–0.97) 0.67 (0.24–0.97) 0.73 (0.49–0.97) 0.49

Na NM 1.80 (0.20–3.20) 2.40 (2.20–2.90) 3.17 (2.60–3.70) 2.75 (2.60–2.90) 2.80(mg/l) M 2.10 (1.20–2.70) 1.41 (1.20–2.10) 1.79 (1.50–2.10) 2.35 (1.90–2.80) 2.80

K NM 1.90 (0.50–3.20) 0.76 (0.60–1.10) 1.78 (1.30–2.40) 2.15 (2.10–2.20) 2.20(mg/l) M 0.63 (0.40–0.80) 0.41 (0.30–0.70) 0.63 (0.60–0.70) 0.70 (0.60–0.80) 0.80

Fe NM 95.33 (74.00–119.00) 147.86 (24.00–603.00) 83.77 (32.00–236.00) 89.80 (37.00–142.60) 133.00(μg/l) M 5.82 (2.89–11.57) 56.40 (2.99–173.49) 47.84 (2.89–127.28) 21.69 (8.68–34.71) 46.28

Chloride NM 10.19 (8.25–11.65) 8.12 (7.28–8.74) 8.89 (4.85–12.62) 12.62 (11.65–13.59) 12.62(mg/l) M 8.83 (6.00–10.50) 7.21 (7.00–8.00) 8.31 (6.00–9.50) 9.25 (9.00–9.50) 9.5

Sulfate NM 0.63 (0.52–0.73) 1.01 (0.32–2.20) 5.59 (0.52–15.32) 9.42 (5.09–13.75) 7.87(mg/l) M 0.31 (0.10–0.72) 0.22 (0.10–0.51) 1.54 (0.10–3.68) 2.41 (2.05–2.77) 2.66

Nitrate NM 589.6 (366–779) 928.6 (609–1171) 992.7 (689–1225) 295.0 (251–339) 307.0(μg/l) M 702.7 (501–1043) 762.4 (437–1250) 1075.4 (728–1284) 994.0 (966–1022) 991.0

Nitrite NM 3.13 (0.61–5.15) 1.86 (0.61–5.15) 7.15 (2.42–15.44) 4.69 (4.54–4.84) 4.54(μg/l) M 0.83 (0.31–1.88) 0.97 (0.30–2.19) 1.72 (0.31–3.31) 2.26 (1.81–2.71) 3.76

P-inorg NM 76.70 (27.99–101.06) 113.27 (97.17–147.70) 73.82 (25.99–102.99) 58.34 (58.30–58.37) 85.51(μg/l) M 41.39 (38.05–46.06) 39.48 (36.05–42.06) 40.98 (36.05–48.07) 42.06 (40.06–44.06) 38.05

P-tot NM 112.76 (67.12–139.60) 136.73 (115.44–189.27) 141.77 (77.86–174.50) 104.70 (99.33–110.07) 102.02(μg/l) M 103.88 (99.16–108.61) 87.69 (70.83–96.80) 84.99 (63.75–106.25) 86.18 (77.92–94.44) 73.19

Silicate NM 6797 (4938–8756) 8253 (5192–9713) 6982 (5756–8495) 4943 (4865–5020) 4726(μg/l) M 9842 (9443–10490) 9916 (9077–10457) 9736 (8944–10623) 10440 (9625–11255) 9958

Ranges are given in parenthesisNM non-monsoon, M monsoonaOnly one sample has been analyzed

non-monsoon season. The sample collected fromthe Vallakkadavu bridge (Stn. 19) exhibits highphosphorous value during the non-monsoon pe-riod. A wide difference in P-inorg is noticed dur-ing both the seasons. The upstream stretchesof Manimala river basin show substantially lowphosphorous concentrations in non-monsoon sea-son. All the sampling stations record elevated

P-tot in monsoon season (range 63.75–108.61 μg/l;av. 87.54 μg/l) than the corresponding non-monsoon counterparts (range 67.12–189.27 μg/l;av. 132.68 μg/l). In natural waters, silica occurs asSiO2 and is exclusively used by diatoms. Monsoonwater exhibits high SiO2 (range 8944–11255 μg/l;av. 9859 μg/l) values than the correspond-ing non-monsoon waters (range 4726–9713 μg/l;


av. 7059 μg/l). Spatial analysis reveals that theSiO2 values show an increasing trend towards up-stream of the Manimala river.

Discussion

Water entering a river environment is derivedmainly from three important sources—surfacerun-off, through flow and interflow, and base flowor ground water flow (Walling 1980; Petts andForster 1985). All these three sources have a di-rect influence on the net chemical compositionof river waters. River water is generally a diluteaqueous solution whose chemical qualities are ac-quired from atmospheric, soil, and rock sources,the relative contributions of which is a function ofclimate modified by human activities both directlyby effluent discharges and indirectly by agricul-tural activities, land-use/land-cover changes andpollutant discharges (Berner and Berner 1987;Moldan and Cerney 1994; Jennerjahan et al. 2004;Maya et al. 2007; Buda et al. 2009).

Factors responsible for water quality changes

Most of the chemical parameters with the excep-tion of NO3-N, SiO2 and Na in the tributariesare concentrated in the non-monsoon waters(Table 1, Fig. 4). It is to be noted in this contextthat the average annual discharge in the monsoonseason (1,598 Mm3) is four times higher com-pared to non-monsoon season (360 Mm3; also seeFig. 3). The observed inverse relationship betweensolute concentrations and stream flow could beexplained in terms of dilution of solute rich baseflow with shorter residence time and thereforelower solute concentrations (Walling 1980). Stud-ies by Basak (1998) reveal that the peculiar phys-iography of the study area with towering WesternGhat mountains in the eastern boundary of theManimala river basin having an elevation of over1,400 m amsl accelerates the stream flow dur-ing monsoon season which in turn considerablyreduces the residence time of the solute fluxes.Therefore, the river water with solute contentsreaches the sea within a few days. In short, at-mospheric precipitation is the prime natural factorin determining the general water quality of the

Manimala river as revealed by the average saltconcentration in the river, 22 mg/l in monsoonseason and 29 mg/l in non-monsoon season (Gibbs1970). The plots of Na/Na+Ca and Cl/Cl+HCO3

against TDS shows distinct clustering in the at-mospheric precipitation dominance sector of theGibb’s diagram (Fig. 5), which reiterate the factthat atmospheric precipitation plays a major rolein determining the fate and dispersal of the ionicconstituents of the Manimala river. Non-monsoonseason, on the other hand, is characterized by leanwater flow (Fig. 3), high evapotranspiration andexcessive contribution of solute rich waters fromvarious sources especially in the uplands. This, inturn, enhances the solute concentrations in watersamples.

The increase in the concentration of NO3-N(except the case of highlands), SiO2 and Na intributaries during monsoon season indicates therole of surface run-off in bringing the ions from ur-ban and agricultural areas, a feature also observedelsewhere (Webb and Walling 1974; Berner andBerner 1987; Boyer et al. 2002). The deviationof NO3-N in the highland stations from the gen-eral trend of the non-monsoon season could bedue to its excess contribution from anthropogenicsources. The anthropogenic effects are reflectedin the case of Na, NO2-N, and P-tot and P-inorg

as well. The uplands (i.e., highland and part ofthe midland reaches) of the Manimala and alsothe adjoining Pamba river basins host many fa-mous temples, the prominent one is the templeof Lord Ayyappa at Sabarimala in the Pambariver basin. It is estimated that over 20 milliondevotees visit the temple every festival seasonfrom November to January (Business Line 2009).As some of the important rituals in connectionwith the Sabarimala festival begins at Erumeliin the Manimala river basin (near Koratti; Stn.18), a good proportion of the devotees use theManimala river for bathing (holy dipping), wash-ing, etc. This, along with excessive drainages fromhotels and restaurants in the area, could con-tribute a substantial quantity of NO3-N, P-inorg, Naetc., to the Manimala river during non-monsoonseason. In an earlier study, Babu and Sreebha(2004) reported anomalously high concentrationof total coliforms (240–1500 CFU/ml) and fecalcoliforms (8–24 CFU/ml) in areas affected by


Fig. 5 Plots of total dissolved solids (TDS) againstNa/Na+Ca and Cl/HCO3 for monsoon and non-monsoonseasons, after Gibbs (1970)

pilgrim tourism than the other reaches of the river.BOD was also higher in the tourism hot spots. Butduring the monsoon season, these parameters ex-hibit substantially lower values. All these reiteratethe human source of pollution in Manimala riverduring non-monsoon season. The lack of adequatelaws to contain inflow of pilgrimage tourists inenvironmentally sensitive, fragile ecosystems is amajor constraint challenging the performance ofregulatory systems on one hand and mitigation ofhuman-induced pollution threats on the other.

From the land-use map of the Manimala riverbasin (Fig. 6), it is evident that over 70% of thetotal drainage area of the river is used for agri-cultural activities. Analysis of relevant data forthe period 2000–2005 reveals that on an average,3,000 t y−1 of N, 1,650 t y−1 of P, and 2,350 t y−1

of K are applied in the drainage area of the riverthrough fertilizer sources. Additionally, a substan-tial quantity of pesticides, herbicides, fungicidesand biogenic fertilizers are also applied in theagricultural lands of the river basin the estimateof which is unavailable at present. Figure 7 showsthe exponential rise in the quantity of N–P–Kfertilizers used in the Manimala river basin duringthe period 1961–2005 for raising the agriculturalproductivity. It is a fact that a substantial pro-portion of the unused nutrients would reach theManimala river through surface and ground waterpathways especially in the monsoon season.

Water quality assessments

The averages and ranges of the water qualityparameters estimated for the Manimala river isgiven in Table 3 along with the standards pre-scribed by WHO and BIS for drinking water.During the monsoon season, the pH of most ofthe water samples is slightly lower than the wa-ter quality standards. Except for the sample col-lected from Stn. No.1, at Panachimoottil kadavu,all the samples record slightly higher Fe values.Further, the indiscriminate sand mining activity inthe alluvial reaches of the midlands and lowlands,anthropogenic interferences in the uplands, etc.,could enhance the organic particulates in riverwater, this in turn reduces the DO levels in thewater column. All the other parameters are wellwithin the WHO (1997) and BIS (1991) standards


Fig. 6 Land-use/land-cover map of the study area

(Table 3). In general, the chemical quality of thewater in the Manimala river is almost agreeableand only little correction is required especially inthe case of pH in the monsoon season for vari-ous human uses. The report of the bacteriologicalanalysis by Babu and Sreebha (2004) reveals thatthe Manimala river water is contaminated withtotal coliforms and fecal coliforms. The numbercounts of these bacteriological forms are at el-evated concentrations in the uplands comparedto downstream reaches. As per the classificationsof the Central Pollution Control Board, Govern-ment of India (http://www.cpcb.nic.in), the watersamples of the midlands fall in the Category ‘C’which is good for drinking only after conventionaltreatment and disinfection. At the same time, thewater in the other reaches falls within the Cat-egory ‘B’ which is suitable for outdoor bathing(organized).

Flux computations—DIN, DIP, SO4, and K

Monsoon contributes more than 90% waterdischarge in the Manimala river and hence, asubstantial proportion (>70%) of the elementaltransfer takes place in monsoon season. Estimatesshow that the Manimala river transfers an amountof 58166 t y−1 of total dissolved salts to thereceiving coastal environments. In non-monsoonseason, the total dissolved salts exhibit 4 timesthe enrichment at Manimala gauging station lo-cated in the midstream and 13 times enrichmentat Thondara station in the downstream.

Table 4 shows the dissolved nutrient flux (dis-solved inorganic nitrogen (DIN), dissolved inor-ganic phosphorus (DIP), SO4, and K) recordedat the Mundakkayam, Manimala, and Thon-dara gauging stations of the Manimala river.The total dissolved nutrient flux into the coastal

http://www.cpcb.nic.in


0

500

1000

1500

2000

2500

3000

3500

4000

1961

-196

2

1970

-197

1

1980

-198

1

1982

-198

3

1984

-198

5

1986

-198

7

1988

-198

9

1990

-199

1

1992

-199

3

1994

-199

5

1996

-199

7

1998

-199

9

2000

-200

1

2002

-200

3

2004

-200

5

Year

Qua

ntit

y (t

y-1 )

N

P

K

Fig. 7 Quantity of nitrogen (N), potassium (K) and phos-phorus (P) fertilizer consumption in the Manimala riverbasin during the period 1961/62–2004/05 (Source: Agricul-tural Department, Government of Kerala)

environments through the Manimala river is esti-mated to be 2,308 t y−1 for DIN, 87 t y−1 for DIP,9,246 t y−1 for SO4, and 1,984 t y−1 for K. Thefour dissolved nutrients (DIN, DIP, SO4, and K)

together constitute just 23% of the total dissolvesalts. The dissolved inorganic flux of phospho-rus is very meager as the major pathway of Pfrom land to sea is in particulate form (Brobergand Persson 1988; Padmalal and Seralathan 1995;McClain et al. 1998; Kroger et al. 2008; Buda et al.2009). During the non-monsoon season, DIN andDIP exhibit three to four times enrichment inManimala gauging station compared to its con-tents in the Mundakkayam station in the high-land. From thereon, the increase of DIN and DIPare only marginal. This could be due to theirexcess contribution from urban centers and/orhuman sources, especially the pilgrimage touristsreaching the area during festival season. However,both these parameters show a marked increase inlowlands during monsoon season which could beexplained in the light of contributions non-pointsources by surface run-off.

The quantity of SO4 shows anomalous highvalues in the lowlands during monsoon as wellas non-monsoon seasons. The lowland and theadjoining parts of midlands that act as the storagezones of the Manimala river is subjected to indis-criminate extraction for construction-grade sandand gravel. This activity not only lowers the riverbed level, but also exposes the sub-surface MiddleHolocene carbonaceous clay (often peaty) con-taining iron sulfide minerals. Oxidation of sulfide

Table 3 Averages and ranges of water quality parameters of the Manimala river along with standard limits prescribed byWHO (1997) and BIS (1991)

Sl. no. Parameters Manimala river WHO BIS IS:10500

NM M Max. Highest Max. Highestdesirable permissible desirable permissible

1 pH 6.56 (6.29–6.94) 6.26 (5.90–6.55) 7.0–8.5 6.5–9.2 6.5–8.5 8.5–9.22 EC (μS/cm) 47.76 (26.64–65.13) 35.76 (22.40–47.20) 750 1500 – –3 TDS (mg/l) 28.62 (14.92–42.98) 21.85 (13.66–28.79) 500 1500 500 20004 DO (mg/l) 7.03 (6.28–7.77) 6.06 (5.54–6.66) 5.0 – 5.0 –5 HCO3 (mg/l) 8.73 (6.00–16.00) 5.33 (0.80–9.80) 200 600 200 6006 Ca (mg/l) 2.63 (1.60–4.01) 2.25 (0.80–3.21) 75 200 75 2007 Mg (mg/l) 1.24 (0.49–2.43) 0.65 (0.24–0.97) 30 150 30 1008 Na (mg/l) 2.76 (0.20–3.70) 1.81 (1.20–2.80) 50 200 – –9 K (mg/l) 1.57 (0.50–3.20) 0.58 (0.30–0.80) 100 200 – –10 Fe (μg/l) 104.72 (24.00–603.00) 43.23 (2.89–173.49) 1000 – 1000 –11 Chloride (mg/l) 9.26 (4.85–13.59) 8.19 (6.00–10.50) 250 600 250 100012 Sulfate (mg/l) 4.16 (0.32–15.32) 1.15 (0.10–3.68) 200 600 200 40013 Nitrate (μg/l) 848.88 (251–1225) 938.65 (437–1284) 45000 50000 45000 100000

Ranges are given in parenthesisNM non-monsoon, M monsoon


Table 4 Dissolvednutrient flux (t y−1)through the Manimalariver

Gauging station Season DIN DIP SO4 K TDS

Mundakkayam NM 54 5.4 21 55 1201M 355 13.6 165 226 7543Annual 409 19.0 186 281 8744

Manimala NM 219 18.3 91 267 4728M 674 40.0 578 545 18667Annual 893 58.3 669 819 23395

Thondara NM 253 23.1 3365 865 15483M 2054 64.0 5881 1119 42683Annual 2308 87.1 9246 1984 58166

minerals under exposed/partially exposed condi-tions could contribute SO4 ions in higher amounts(Chen and Morris 1972) to the river water. This,along with contributions from agricultural landsand decomposition of litter fall (Bilby 1981) fromthe dense riparian vegetation that covers the riverbanks in the lowlands and midlands, could en-hance SO4 loading in the overlying waters.

Potassium shows high loading in the river reachdown to Manimala gauging station where a goodand continuous baseflow charged with substan-tially high content of K and other cations (Ca,Mg, and Na) derived from weathering of feldsparsand biotite minerals in the host rock occurs. AtMundakkayam, about 80% of the K contributiontakes place during the monsoon season; whereasin Manimala and Thondara stations, the non-monsoon season also contributes a substantialproportion (35–45%) of the K ions through baseflow that trickles through the weathered subsoilsin the off-channel areas.

Summary and recommendations

The hydrochemical parameters estimated in theManimala river basin show marked seasonal aswell as spatial variations. The pH of the riverwater is slightly acidic. The low electrical conduc-tivity and TDS indicate the role of atmosphericprecipitation as a major natural determinantin changing the solute concentrations in theManimala river. However, indications of humaninterventions are also well registered in the watersamples, especially in the uplands around Koratti–Chenappadi river reaches. The uplands (i.e., high-land and adjoining part of the midlands) of theManimala river host many religious places (tem-

ples) and townships. Pilgrim tourism in connec-tion with the hill temple at Sabarimala attainsits peak during the non-monsoon season. It isestimated that over 20 million devotees visit thehill temple at Sabarimala every festival season(November–January); a good proportion of thedevotees use the Manimala river for bathing,washing, etc. This, together with contaminant dis-charges from nearby urban centers, could sig-nificantly change the overall water quality ofthe Manimala river during the non-monsoon sea-son. Agricultural activities contribute a substantialproportion of N and P in river waters during themonsoon season trough surface run-off.

Manimala river transports an amount of58166 t y−1 of dissolved salts to the receivingcoastal environments. Out of the total solute dis-charge, a greater part (∼70%) of the ionic fluxtakes place during the monsoon season as thesurface run-off and the base flow componentscould contribute various cationic and anionic con-stituents to the river water in dissolved form. Theflux of DIN, DIP, SO4, and K are 2,308 t y−1,87 t y−1, 9,246 t y−1, and 1,984 t y−1, respec-tively. DIN and DIP exhibit high loading in theManimala gauging station in the midland indicat-ing its contribution from human sources as wellas nearby urban centers. Sulfate ions are loadedheavily in the lowlands where the river bed hasbeen lowered due to indiscriminate extraction forsand and gravel. The mining activity exposes theunderlying organic-rich peaty layers containingiron sulfide minerals which, upon oxidation, couldcontribute SO4 ions to the overlying waters. De-composition of litter fall from the dense ripar-ian vegetation that covers the river banks andcontribution from agricultural lands are the othersources of SO4. Markedly high K loading in the


lowlands and adjoining part of midlands could beattributed from base flow contributions.

The following are some of the recommenda-tions made to enhance the overall water qualityof small catchment rivers over-stressed by humanactivities, like the Manimala river in the southwestern coast of India.

(a) Direct disposal of liquid and solid wastes intothe river should be banned. Instead, sci-entific waste management practices are tobe adopted strictly to minimize pollutionthreats from urban centers.

(b) A check dam has to be constructed in thehighland part of the Manimala river andflush out the contaminant river water of non-monsoon season at regular intervals aftergiving warning signals.

(c) Regulate inflow of pilgrimage tourists withinthe carrying capacity limits of the area. Ex-tend the period of festival season to morenumber of days.

(d) Enhance the assimilative capacity of thetourism hotspots through adoption ofenvironment-friendly technologies and/orupgrading infrastructural facilities.

(e) Minimize the residence time of the pil-grimage tourists in the area by upgrading/modernizing the transit facilities.

(f) Steps are to taken to evolve a new crowdmanagement strategy exclusively for pilgrim-age tourists. Enforce the strategy throughappropriate legislation.

(g) Sand mining in small rivers may be regulatedbased on Environment Impact Assessmentstudies.

(h) Limit the use of chemical fertilizers by pro-moting bio-manures for raising agriculturalcrops in the river basin.

(i) Create awareness on nature conservationand the imminent need for environment-inclusive development strategies.

Acknowledgements We thank Director, Centre of EarthScience Studies (CESS), Thiruvananthapuram for encour-agements and supports. Thanks are also due to Dr. K.Maya, Scientist, Environmental Sciences Division, CESSfor all her helps during the course of this study. Thefinancial support from Revenue Department, Governmentof Kerala is gratefully acknowledged.

References

APHA (1995). Standard methods for the examination ofwater and waste water. Washington: American PublicHealth Association.

Babu, K. N., & Sreebha, S. (2004). Evaluation of nutrientbudget of the rivers and adjoining back water–nearshore systems of Kerala (unpublished report). Centrefor Earth Science Studies, Thiruvananthapuram.

Bajpayee, S. K., & Verma, A. (1999). Distribution ofcarbon and phosphorus in River–Backwater systemof Kerala, India. In V. Ittekkot, V. Subramanian,& S. Annadurai (Eds.), Biogeochemistry of riversin tropical south and southeast Asia (pp. 219–233).Sonderband: SCOPE.

Basak, P. (1998). Water resources of Kerala—Myths andrealities. In E. J. James, K. N. Remani, & P. S.Harikumar (Eds.), Water scenario of Kerala (pp. 1–6).India: State Committee on Science, Technology andEnvironment, Government of Kerala.

Berner, K. B., & Berner, R. A. (1987). The global watercycle: Geochemistry and environment (p. 397). NewJersey: Prentice Hall.

Bilby, R. E. (1981). Role of organic debris dams in regulat-ing the export of dissolved and particulate matter froma forested watershed. Ecology, 62, 1234–1243.

BIS (1991). Bureau of Indian Standards—Indian standardspecif ication for drinking water. IS:10500.

Boyer, E. W., Goodale, C. L., Jaworski, N. A., & Howaith,R. W. (2002). Anthropogenic nitrogen sources andrelationships to riverine nitrogen export in the northeastern USA. Biogeochemistry, 57(58), 137–169.

Broberg, O., & Persson, G. (1988). Particulate and dis-solved phosphorus forms in fresh water: Compositionand analysis. Hydrobiologia, 170, 61–90.

Buda, A. R., Kleinman, P. J. A., Srinivasan, M. S., Bryant,R. B., & Feyereisen, G. W. (2009). Effects of hydrol-ogy and field management on phosphorus transport insurface runoff. Journal of Environmental Quality, 38,2273–2284.

Business Line (2009). Medical and sanitary facilities atSabarimala ‘woefully inadequate’. The Hindu group ofPublications.

Chen, K. Y., & Morris, J. C. (1972). Kinetics of oxidationof aqueous sulfide by oxygen. Environmental Scienceand Technology, 6, 529–537.

Gibbs, R. J. (1970). Mechanisms of controlling world waterchemistry. Science, 170, 1088–1090.

Goolsby, D. A., Buttaglin, W. A., Aulenbach, B. T., &Hooper, R. P. (2000). Nitrogen flux and sources in theMississippi river basin. Science of the Total Environ-ment, 248, 75–86.

GSI (1995). Geological and mineralogical map of Kerala.Calcutta: Geological Survey of India.

Jennerjahan, T. C., Ittekkot, S., Klopper, S., Adi, S.,Nugroho, S. P. Sudiana, N., et al. (2004). Biogeochem-istry of a tropical river affected by human activities inits catchment: Brantas river estuary and coastal watersof Madura Strait, Java, Indonesia. Estuarine CoastalShelf Science, 60, 503–514.


Kroger, R., Holland, M. M., Moore, M. T., & Kooper, C. M.(2008). Agricultural drainage ditches mitigate phos-phorus loads as a function of hydrological variability.Journal of Environmental Quality, 37, 107–113.

Leeuw, J., Shankman, D., Wu, G., Boer, W. F., Burnham,J., He, Q., et al. (2009). Strategic assessment of themagnitude and impacts of sand mining in PoyangLake, China. Regional Environmental Change. doi:10.1007/s10113-009-0096-6.

Liu, S. M., Zhang, J., Chen, H. T., Wu, Y., Xiong, H., &Zhang, Z. F. (2003). Nutrients in the Changjiang andits tributaries. Biogeochemistry, 62, 1–18.

Maya, K., Babu, K. N., Padmalal, D., & Seralathan, P.(2007). Hydrochemistry and dissolved nutrient flux oftwo small catchment rivers, south western coast ofIndia. Chemistry and Ecology, 23, 13–27.

McClain, M. E., Bilby, R. E., & Triska, F. J. (1998). Nu-trient cycles and responses to disturbance. In R. J.Naiman, & R. E. Bilby (Eds.), River ecology andmanagement: Lessons from Pacif ic Coastal Ecoregion(pp. 347–369). New York: Springer.

Meybeck, M. (1976). Total dissolved transport by worldmajor rivers. Hydrological Science Bullettin, 21, 265–289.

Milliman, J. D. (1995). Sediment discharge to the oceanfrom small mountainous rivers: The New Guinea ex-ample. Geo-marine Letters, 15, 127–133.

Milliman, J. D., & Syvitzki, J. P. M. (1992). Geomorphic/tectonic control of sediment discharge to the ocean:The importance of small mountainous river. Journalof Geology, 100, 525–544.

Moldan, B., & Cerney, J. (1994). Small catchment research.In B. Moldan & J. Cerney (Eds), Biogeochemistry ofsmall catchments: A tool for environmental research(pp. 1–24). SCOPE, England: Wiley.

Naiman, R. J., & Bilby, R. E. (1998). River ecology andmanagement: Lessons from the Pacif ic Coastal Ecore-gion (p. 705). New York: Springer.

Padmalal, D., & Seralathan, P. (1995). Organic carbonand phosphorus loading in recently deposited riverineand estuarine sediments—A granulometric approach.Indian Journal of Earth Sciences, 22, 12–28.

Padmalal, D., Maya, K., Sreebha, S., & Sreeja, R. (2008).Environmental effects of river sand mining: A casefrom the river catchments of Vembanad lake, South-west India. Environmental Geology, 54, 879–889.

Petts, G., & Forster, I. (1985). Rivers and landscape(p. 274). London: Arnold.

Raj, N., & Azeez, P. A. (2009). Spatial and temporal vari-ation in surface water chemistry of a tropical river,the river Bharathapuzha, India. Current Science, 96(2),245–251.

Sarin, M. M., Krishnaswami, S., Dilli, K., Somayajulu,B. L. K., & Moore, W. S. (1989). Major ion chem-istry of the Ganges—Brahmaputra river system—Weathering process and fluxes to the Bay of Bengal.Geochemica Cosmochimica Acta, 53, 997–1009.

Subramanian, V. (1987). Environmental chemistry ofIndian river basins—A review. Journal of GeologicalSociety of India, 29, 205–220.

Subramanian, V. (2000). Water quality—Quantity perspec-tive in South Asia (p. 125). Surreg: Kingston.

Walling, D. E. (1980). Water in the catchment ecosystem.In A. M. Grower (Ed.), Water quality in catchmentecosystems (pp. 1–47). New York: Wiley.

Webb, B. W., & Walling, D. E. (1974). Local variation inbackground water quality. Science of the Total Envi-ronment, 3, 141–153.

WHO (1997). Guidelines for drinking-water quality, V.1, rec-ommendations. Geneva: World Health Organization.

http://dx.doi.org/10.1007/s10113-009-0096-6

http://dx.doi.org/10.1007/s10113-009-0096-6

Documents

Water quality and dissolved inorganic fluxes of N, P, SO 4 , and K of a small catchment river in the Southwestern Coast of India