CHAPTER - V

STUDIES ON WATER QUALITY OF MANANCHIRA LAKE

1.0 INTRODUCTION

A lake may be defined as a body of standing water, occupying a

basin and lacking continuity with the sea. Welch (1952) regards all large

bodies of standing water as lakes, eliminating in his definition, ponds as

smaller water bodies. Fore1 (1901) was the first to--propose a generally

accepted classification of the lakes of the world into polar, temperate and

tropical lakes according to their thermal characteristics.

Depending upon the productivity, lakes may be grouped into

different trophic states. It may range from eutrophic (well nourished) and

mesotrophic (moderately nourished) to oligotrophic (little nourished).

Eutrophication is the result of increase in essential plant nutrients like

nitrogen, phosphorous, iron etc. Usually eutrophic lakes have good supplies

of all essential plant nutrients fkom nutrient rich inflows and recycling. In

contrast, oligotrophic lakes are poorly supplied with nutrients. Some lakes

pass through different trophic states, beginning with the lower fertility or

oligotrophic and gradually arriving at a moderately productive or

mesotrophic state. In many lakes, eroded sediments may anive in sufficient

quantities, which subsequently may change the depth of the lake

significantly. This, when combined with rising fertility due to

anthropogenic activities may result in a highly productive or eutrophic state.

In fact, consideration of all lakes throughout the world leads to the

conclusion that the idea of oligotrophic to mesotrophic to eutrophic to

exinct is one of several possible routes in lake evolution.

Lakes are created or destroyed by geologic or climatic events. Chief

modes for lake origin are through glacial action, land slides, dissolution of

soluble rocks of the substratum, crystal movements of the earth, volcanic

action, wind action and river meanderings (Jhingran, 1982). Lakes of

Pongong valley, Dal and Anchar lakes of Kashrnir are formed by glacial

action. Many small lakes in the limestone tracts of Khasi and Jaintia Hills

of Assam are believed to be solution lakes. Tectonic lakes are formed due

to the movements of earth.

There exists amazing variability between lakes in tropical and

humid tropical regions. Taub (1984) reported lakes that have pH values

less than 2.0 as well as those that have seasonally high pH values exceeding

9.0; lakes that have complete daily vertical mixing like lake Gatien and

Panama and lakes that never have complete vertical mixing like the lake

Wald Sea, Canada and lakes that have permanently frozen surface such as

lakes Bonney and Vanda. Thus lakes are not only very different fiom each

other but may vary fiom season to season and from year to year. This

mutability is possible because many of the organisms are short lived and

that a variety of species are available at each trophic level. At any given

time one or a few species of a trophic level are dominant, where many

competitors are simultaneously present but at lower densities. Most

planktonic organisms (Algae and Zooplankton) have a high potential

reproductive rates and also often have high death rates from grazing,

settling or predation. Species dominance can shift rapidly with changes in

nutrient availability, turbulence, temperature, predation, pressure etc.

Hence, the information on various lakes is not always comparable, since

considerable changes appear in the ecology of the lakes. Regional

limnology is influenced by the dominant features of the locality. For

example, in polar region temperature and ice are important considerations.

In certain lakes, due to cultural enrichment, importance is given to nutrient

cycles. For some of the tropical lakes, nutrients have been ignored while

limnologists have concentrated on productivity, species relationship and the

like.

A scientific approach to lake and environment management is

concerned with the study of structures and hnctions of aquatic ecosystems.

The study of physical, chemical and biological parameters reveal the

importance of structures for understanding the functions of the ecosystem.

Structure includes distribution of nutrients in the water column besides the

diversity and quantity of phytoplankton and zooplankton. From the

functional point of view the primary production along with available

nutrients play an important role in maintaining aquatic productivity. Thus,

the biological process in a lake ecosystem includes primary producers,

primary consumers, secondary consumers, tertiary consumers and

decomposers. Primary productivity is also affected by the benthic

community of the lake and this serves as a major source of food for the

nektonic community.

Physical condition of the water includes depth, temperature,

turbidity and light ~enetration' of the lake. Chemical conditions of lake

water depends on the gases, solids, nutrients, pH, EC, Total hardness and

the like. Gases like ammonia and hydrogen sulphide are harmful to aquatic

organisms like fishes. Dissolved oxygen content in the lake water reflects

the physical and biological processes prevailing in the waters, pH is also an

important factor in determining the chemical quality of the lake water.

Trace elements like calcium, magnesium, copper, zinc are also significant

in determining the quality of water.

Littoral zones of lakes represent the most complex ecotones, with

extremely sensitive land-water fiinges. In lakes where distinct zonations

like epi, supra, eu-, infralittoral have developed, a slight impact may result

in profound changes. The destruction of such a fragile section of the littoral

zone followed by the sudden eruption of the lake behind it may be released

by earth quakes, excessive precipitation, and volcanic or other rock fall into

the lake (Loffler, 1988). Floods, water-movement from seiches and waves

are the most common parameters which may either improve the littoral

zonation and its persistence or which exert destruction tendencies on man

made establishments such as terrestric agriculture, roads, different sites of

recreation (swimming, boating) etc. Other serious consequences may

involve erosion or silting which often result in dramatic changes in the

littoral morphology frequently combined with the alteration of the plant

communities and of the general littoral aspects (Loffler, 1979). Loss of lake

-littoral zone is one of the most significant man made impacts contributed

mostly by his recreational activities. Many of the lakes suitable for

swimming, boating, yachting and holiday housing have lost their littoral

communities as in the case of Lake Atitlan, Guatemala. Loss of littoral

zone also leads to imbalance in the maintenance of genetic diversity.

Introduction of exotic species, for example fishes for pisciculture leads to

catastrophic effects on the endemic fish fauna of the lake. Examples are

stocking of Lake Titicaca with rainbow trout and Lake Victoria with nile

perch. Similarly the introduction of Chinese grass carp has often led to the

complete destruction of submerged macrophytes in shallow lakes and

littoral zones (Jorgensen and Loffler, 1990).

In Kerala Sastharnkotta lake in Quilon district is the largest fresh

water lake, having an area of 3.75 sq.km. Other natural fresh water lakes

are Pookot lake, Thariyod lake etc in the Western Ghats of Wyanad. The

lakes are extremely sensitive to the environmental changes in the

watershed. Deterioration in the lake environment is caused by changes due

to land use patterns, alterations to the natural vegetation, increase in

population, industrial development and other anthropogenic impacts. This

may lead to deterioration of water quality, fisheries and species extinction

through habitat destruction (Tatuokira and Hidehiko Sazuunami, 1997).

The Mananchira lake in Calicut corporation of Kerala state is

highly susceptible to pollution from the municipal sewage and domestic

waste. Increasing urbanization and certain textile based industries near the

lake add to pollute this drinking water resource. During rainy season

contamination of lake is higher through leaching of pollutants. In addition,

impacts from other developmental activities like construction of roads,

buildings, recreational activities like musical fountains is also higher,

leading to upset the ecology of the lake. In the long run, these

anthropogenic activities if not monitored and checked on time would

convert this virgin lake into a eutrophic, barren lake, causing

ecodegradation in its floral and faunal composition. In this study an attempt

has been made to compare the water quality status of Mananchira lake

through seasonal sampling and analysis. Hence the present study serves as

a base-line for future Environmental Impact Assessment (EIA) studies.

2.0 STUDY AREA

The Mananchira lake having an area of 3.49 acres is located in the

heart of Kozhikode city in Kerala State. The Mananchira is an enclosed

manmade lake (Fig. 17) surrounded by laterite on all sides and is connected

by well built up roads. There is a children park with a musical fountain

nearby and hence it is of particular attraction to the people and is used as a

picnic spot due to its beautiful surroundings. A map showing area of study

and sampling locations is given in Fig. 18 and 19. Rain water is the major

source of recharge to the lake. This lake is a major drinking water source

for Calicut city. The salient feature of the lake are shown in Table. 24.

Table: 24 Salient feature of Mananchira Lake, Calicut

3.0 METHODOLOGY

1

2

3

4

5

6

Water samples were collected seasonally from four comers of

Mananchira Lake (Fig.19) These samples were analyzed for various

physical, chemical and bacteriological parameters. The samples were

analyzed for pH, Temperature, Colour, Turbidity, Electrical Conductivity,

Total Dissolved Solids, Chloride, Total Hardness, Calcium, Magnesium,

Dissolved Oxygen, Bio-Chemical Oxygen Demand etc. The samples were

also analyzed for Total Coliform Bacteria and Faecal Coliform besides

nutrients like nitrates and phosphates.

Temperature and pH were measured in situ using a portable field

kit. Turbidity was measured using Nephelometric techniques, Hardness by

EDTA method, Chloride by Argentometric method, Nitrates and

Phosphates by Spectrophotometric method DO and BOD by Winklers

Azide modification method as per the Standard methods given in APHA

(1998).

Length

Breadth

Average depth

Average capacity

Slope

Lake strata

140M

118M

3 .OM

17000 M'

Towards north

Lime stone

Fig. 17 A view of Mananchira Lake

Microbiological analysis involved the determination of total

coliform bacteria besides faecal coliform which is an indicator of organic

pollution. The values were compared with the specifications of Bureau of

Indian Standards for Drinking Water (BIS, 199 1)

3.1 Temperature

Temperature measurements are required in studies of self-

purification of water bodies. Temperature measurements are made 'insitu'

with mercury-filled thermometer graduated at 0 . 1 ' ~ increments in Degree

Celsius. The measurement was done by dipping the thermometer for

sufficient time to obtain the value. It is expressed in degree centigrade ( O C )

3.2 Colour

The determination of colour is rapid one and is useful in detecting a

change in the characteristics of water. When waters from the same source

are being regularly examined (as from a river), the variations in colour often

serve as indices of quality. German make SQ 118 Photometer was used for

the determination of colour. It is expressed in Hazen Unit.

3.3 Turbidity

Turbidity is an important parameter for characterizing water

quality. The SQ 118 Photometer was used for the measurement of

turbidity. The unit of turbidity is NTU (Nephelo Turbidity Unit).

3.4 Dissolved Oxygen (DO)

Dissolved oxygen is the most important limiting factor in aquatic

ecosystems because most organisms other than anaerobic microbes perish

rapidly when oxygen levels in water fall to zero. The Principle behind DO

is oxygen in the sample rapidly oxidizes the ~ n ~ + to a higher state of

valance under alkaline conditions and that manganese in higher states of

valance, is capable of oxidizing iodide ions to free iodine under acidic

conditions. The free iodine thus released is equivalent to the dissolved

oxygen originally present in the sample and is measured by titration with

standard sodium thiosulphate solution In the presence of starch as indicator.

Procedure

To 300 ml of sample taken in the BOD bottle which is devoid of air

bubbles, 2 ml of MnS04 and 2 ml of alkali azide reagent are added. A

brown precipitate was obtained which was allowed to settle. Then 2 ml of

Conc. &So4 was added to dissolve the precipitate. Then this sample is

immediately titrated against Sodium thiosulpahte with starch as indicator.

At the end point the initial dark blue colour changes to colourless.

Calculation

DO, mg/l = (ml X N) of Sodium thiosulphate X 8 X 1000

Volume of sample taken

3.5 Biological Oxygen Demand (BOD)

Biological oxygen demand refers to the quantity of oxygen required

by bacteria and other microorganisms in the biochemical degradation and

transformation of organic matter under aerobic conditions. The basic

,principle underlying the BOD determination is the measurement of the DO

content of the sample before and after 5 days of incubation at 20' C. BOD

is a test of great value in the analysis of sewage, industrial effluents and

grossly polluted water.

Procedure

Samples in duplicate were taken and one set was fixed immediately

with Winkler's reagent and the initial DO is measured titrimetrically. The

other set of samples was kept in BOD incubator at 2 0 ' ~ fot 5 days and then

analyzed for final DO.

Calculation

BOD mg/l = D l - DZ

Where, Dl = Initial DO of the sample

D2 = DO of the sample after 5 days

4.0 RESUTS AND DISCUSSION

The results of the analysis of water samples are presented in Tables

25-27. The results of the physico-chemical analyses of water samples are as

follows:

The pH value of the samples collected from Mananchira, varied

from 6.97 to 8.26 during pre-monsoon, 6.03 to 6.95 during monsoon and

8.12 to 9.07 during post-monsoon. The samples were found to be highly

alkaline during pre-monsoon and post-monsoon. he rise in pH during pre-

and post-monsoon indicated high pollution due to the mixing of sewage and

other wastes especially when rate of flow of water was low. This is in

agreement with the findings of Mishra and Saksena (1991). The seasonal

variation of pH in the waters of Mananchira lake is given in Fig.20.

4.2 Electrical conductivity

Electrical conductivity of the samples varied from 71.4 to 74.4

during pre-monsoon, 71.3 to 137.2 during monsoon and 67.0 to 70.4 during

post-monsoon. The high Electrical conductivity was noticed in sample

number 4 during monsoon which could be attributed to the leaching of ionic

substances from the nearby drainage.

4.3 Total dissolved solids

Total dissolved solids indicate the general nature of water quality or

salinity. The total solids in the waters of Mananchira lake ranged from 45.5

mg/l to 47.62 mg/l, 46.0 mgA to 88.0 mg/l and 42.1 1 mg/l to 45.06 mg/l

during pre-monsoon, monsoon and post-monsoon respectively. The

seasonal variation of TDS in Mananchira is depicted through Fig.21.

4.4 Chlorides

Chloride values of the water samples varied from lO.Omg/l to

12.0mg/l during pre-monsoon, 8.0mgIl to 22.0mgA during monsoon and

8.0mg/l to 16.0mgA during post-monsoon. The values are within the

permissible limit as per BIS.

4.5 Turbidity

Turbidity is mainly due to the silt, clay and suspended particles

present in the water. The turbidity was noticed to be within the permissible

limit set by BIS in all the seasons. The seasonal variation of turbidity in

Mananchira lake waters is presented in Fig.22.

4.6 Colour

Colour of the sample is mainly due to the metallic substance

present in the water. The colour of the lake water samples were found to be

within the acceptable limit except during post-monsoon. The seasonal

variation of the colour in the waters of Mananchira lake is presented in

Fig. 23.

4.7 Nitrate-Nitrogen

Seasonal variation of nitrate-nitrogen in the waters of Mananchira

lake is illustrated through Fig.24. The mean values of nitrate -nitrogen

varied from 1.88mgfl fo 3.0 mgA during pn-monsoon, 0.88 mgfl to 1.66

mg/l during monsoon and 1.50mgA to 1.84 mgA during post-monsoon. The

highest value was observed during pre-monsoon at both the stations No 1

and 2. This could be explained that under aerobic conditions, bacterial

action decomposes organic refuse, releasing ammonia, which is ultimately

oxidized to form nitrates. Nitrate in water is responsible for the growth of

blue green algae (Abdul Jarneel, 1998). The permissible limits of water

quality parameters (BIS, 1991) and the ill effects beyond the specified

limits are presented in Table.28.

Table: 28 Water Quality Parameters and their Significance

structures and adverse effects on

i 6 I

I 7

8

9 -

Chloride, mg/l

Calcium, mg/l

Nitrate- nitrogen mgA Total colifoims, MPNI 100mlmg/l

250

75.0

10

10

Beyond this limit taste, corrosion and palatability are affected Encrustation in water supply structures and adverse effects on domestic uses Beyond this methaemoglobanemia

Beyond this waterborne diseases

Phosphate concentrations varied from 0.036mgA to 0.045mg/l

during pre-monsoon, 0.023mg/l to 0.028mgll during monsoon and

0.027mg/l to 0.032mgll during post-monsoon. However sample No. 1 and

2 showed slightly higher concentration during pre-monsoon which indicates

that the lake is tending towards eutrophication. The major source of

phosphates in Mananchira lake waters is sewage. The seasonal variation of

phosphates in the waters of Mananchira lake is given in Fig. 25.

4.9 Calcium

Calcium concentration in the water samples of Mananchira lake

ranged from 4.80 mg/l to 8.0 mg/l, 6.40 mg/l to 12.80 mg/l and 4.0mg/l to

5.60mg.11 during pre-monsoon, monsoon and post-monsoon respectively.

The seasonal variation of calcium concentrations is presented through given

Fig.26.

4.10 Magnesium

Magnesium content varied from 1.0 mgA to 3.0 mgll, 1.46 mgA to

2.92 mg/l and 1.45 mg/l to 3.40 mgll during pre-monsoon, monsoon and

post-monsoon respectively. The seasonal variation of the magnesium

content in the water samples is presented in Fig. 27.

4.1 1 Dissolved Oxygen (DO)

The seasonal distribution of DO in the waters of Mananchira lake is

illustrated in Fig. 28. The DO ranged from 7.60mg/l to 8.30mg/l during pre-

monsoon, 7.90mgll to 8.50mg/l during monsoon and 6.90mg/l to 7.20mg/l

during post-monsoon. The DO values found to be higher during monsoon

are attributed as due to the influence of rain water.

4.12 Bio-Chemical Oxygen Demand (BOD)

According to Central Pollution Control Board, BOD values

for drinking and bathing water should not exceed 3.0 mg/l. The BOD value

were found to be less in all seasons which indicated that lake is not

organically polluted (Singh & Singh, 1995). The seasonal variation of BOD

In the water samples of Mananchira lake is given in Fig.29.

4.1 3 Total Hardness

Total hardness of the waters samples varied from 22.0mg/l to

28.0mg/l, 16.0mg/l to 32.0 mg/l and 20.0 mgA to 24.0mgA during pre-

monsoon, monsoon and post-monsoon respectively. Total hardness in the

water samples was found to be within the permissible limit as per BIS in all

sampling stations during all the three seasons. The seasonal variation of

total hardness of the water samples is represented in Fig.30.

4.14 Total Coliforms

Seasonal variation of total coliforms in Mananchira lake waters is

represented in Fig.3 1. The coliforms varied from 23MPN/100ml to

1 100MPN/100ml during pre-monsoon, 460MPNflOOml to

7500MPN/lOOml during monsoon and 4.OMPN/100ml to 93MPN/100ml

during post-monsoon. From the present investigation it was observed that

all the samples were bacteriologically polluted in all the seasons. Bacterial

counts indicated considerable variation in the samples collected from

different sampling locations of the lake. Depending on the degree of

contamination influenced by various anthropogenic activities some

locations indicated high bacterial contamination while others indicated

comparitively less. The high coliform density during monsoon is

attributable to the municipal effluents pouring through drains.

4.15 Correlation between Total Coliforrn count and faecal

coliform count

Total coliforms have shown a positive relationship with faecal

coliforms (Fig.32). When total coliforms increased during monsoon, faecal

coliforms also increased and when total coliforms decreases during pre-

monsoon, also faecal coliforms decreased indicating a linear correlation

between the two. The seasonal and spot-wise distribution of total coliforms

and faecal colifonns are presented in Table.29.

6 0

1 0 15 20 2 5 3 0 3 5 4 0 satnpll~ StabOnS

Fig20 Seasonal variations of pn in the waters of Mananchira lake

-I- Pre-monsoon 0 Monsoon A Post-monsoon

sampling stations Fig.21 Seasonal variations of TDS in the waters of Mananchira lake

m Monsoon

7.5 - 7.0 - 8.5 - 6 0 -

I 5.5! * 5.0 -

8 4 5 -

3 4 0 -

3 5 - 30-

2 5 .

o ! , . , . , . , . l . l . l . I .O 1 5 2.0 2.5 3 0 3.5 4.0

FIg.23 ~erson%%!#d??o~ur in the wetem of Mananchira lake

b

/ /'

I I A /" A \. -..,d,' ,,'

, . , . , . , . , . , . , r 1 .O 1 5 2 0 2 5 3 0 3 5 4 0

samplng station Fig22 Seasonal variations of turbidity in the waters of Mananchira lake

in the waters of Mananch~ra lake - Monsoon

10 1 5 2:0 3:0 3'5 4'0 sampling stations

Fig.25 Seasorurl variations of in l tm wstsns of Menenchira Iake

lake

13.5 13 0 12 5 12 0 11 5 11 0

2 :xx g s 5

.$ ;g - 0 8 0

7 5 7 0 6 5 6 0 5 5 5 0 4 5 4 0

+ , . , . , . , . , . , . 1 .

1 0 1 5 2 0 2 5 3.0 3 5 4 0

sampling shlionrr Fig.27 Seasonalvariations d Magnt#iium in me waters of Mananchira take

. _/ --- -I

I----- ,

, & * A

I

I . I ' I . I '

1 0 1 5 2 0 2 5 3 0 3 5 4 0

sarnphng stabons F ~ 2 6 seasonal vanations of caburn in the waters of Mananchira

- - Monsoon

sarnpbng stations Fig.28 Seasonal varialon of DO in the waters of Mananchira lake

post-monsoon A

-!P%"o- Fy1.28 Segonal valrPdion of BOD in the waters of Mnnanchlre leks

I I post-monsoon

sPmpling.tntions Fii.30 Seasonal variabons of Total Hardness in the watenr of hhnan~hits lake

8000- post-monsoon

7m: 0

I -: a 2- -- € 4WO- ,O = 8 NW- - 3 xm: I-

1mo-

0 1 2 3 4

sampling staf on8 Fii.31 Seasonal variations of Total Cofiformo in the waters of Mananchira kke

Sampling stations Fig.32 Correlation between total cobforms and faecal coliforms

inthe waters of Mananchira lake

Table: 29 Seasonal and spot-wise distribution of Total coliforms and Faecal Coliforms

&,on I Pre-Monsoon / Pre-Monsoori / Monsoon 1 Monsoon I Post-Monsoon / Post-Monsoon 1

TC- Total Coliforms. FC- Faecal Coliforms

last \onh \\ est /

South \\ est - south

5.0 CONCLUSIONS

Results of the present investigation confirm that the

(f2.0) 150

(f 5.0) 23

(k3.0) 1100

microbiological contamination of Mananchira lake is throughout the year

l a s t i

with monsoon season recording the highest bacterial count. Understanding

(kt .O) 82

(f3.0) 10

(kl.0) 150

the distribution and seasonal variation of bacteria that pollute the water

(f5.O)

body, help to adopt effective measures that could prevent the spread of

(f3 .O) 7500 (f9.0) 460

(rt5.0) 4600

water borne diseases, besides protecting the lake from eutrophication and

(f l5)

future resource extinction. However it was found that lake waters were

(k 5 .O) 2400 (f10) 150

(k4.0) 1100

alkaline during pre and post monsoon seasons Mananchira lake waters

(f7.0)

especially station No.1 and 2 were found to be enriched with nutrients like

(k1 .O) I S

(f2.0) 93

(24.0) 43

nitrates and phosphates in all the seasons leading to eutrophication.

(f 1.0) 6

(k2.0) 43

(k2.0) 25

(f 2.0)

Main findings of Mananchira lake

1. Fluctuations In pH value

( e . 0 )

The pH of the lake water varied from 6.97 to 8.26 during pre.

,

monsoon, 6.03 to 6.95 during monsoon and 8.12 to 9.07 during post-

monsoon. The rise in pH during pre and post- monsoon indicated high

pollution due to the mixing of sewage and other wastes especially when the

rate of flow of water was low (Mishra and Saksena, 1999).

2. Bacteriological contamination

Bacteriological analysis of water samples of Mananchira lake

indicated that water was polluted by faecal contaminants to the extent that it

was not potable for drinking purposes and hence needed thorough

impoundment. The total coliforms were found to be beyond the permissible

limit. Total coliforms varied from 23.0 MPN/100ml to 1 100 MPN1100ml

dur~ng pre-monsoon, 460 MPN1100ml to 7500 MPN1100ml during

monsoon and 4.0 MPN/IOOml to 93.0 MPN/100ml during post-monsoon.

The order of degree of contamination in different seasons is as follows:

Monsoon > Pre-monsoon >Post -monsoon

3. Nutrient enrichment

Nitrates and phosphates are found to be present in all the sampling

stations in all seasons, tending the lake towards eutrophication. Kerala in

spite of receiving heavy average annual rainfall of about 3,000 rnm is facing

severe water scarcity and drought. Rehabilitation of the dried up fresh

water lakes, tanks and ponds, besides conservation of the rainwater are the

needed measures t o meet the water demands of that area.