MATERIALS AND METHODS - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/25968/14... · Materials and Methods Studies on Physico-chemi cal characteristics, Plankton diversity

Chapter - 2

MATERIALS AND METHODS

2.1 History of Idukki Reservoir 2.2 Description of Study Area 2.3 Sampling for Analysis of Physico-Chemical Parameters 2.4 Phytoplankton Sampling and Analysis 2.5 Zooplankton Sampling and Analysis 2.6 Fish Sampling 2.7 Statistical Analysis

2.1 History of Idukki Reservoir

The Idukki hydro-electric project is the biggest man made project in

Kerala. The works started in 1966 with the cooperation of the Canadian

Government and the project was dedicated to the nation on 12th February 1976

by the then prime minister Smt. Indira Gandhi. This project is the main source

of electricity for Kerala state and all water is used for the power generation

and irrigation purpose.

The Western Ghats, which constitutes an almost continuous mountain

wall on the eastern side, forms the high land region in Kerala. Idukki district is

situated in this region beneath the corridors of Sahyadris and about 97% of the

total area of the Idukki district is covered with rugged mountains and forests.

Idukki means ‘constricted’. The dam site selected on Periyar river at Idukki

gorge is a place of great constriction hardly 30 feet wide at the bottom. On

either side of this narrow gorge were the wild, un-trodden, untamed, bare and

massive steep rocky hills (Kuravan and Kurathi hills). The tribes who are the

Chapter 2

24 Studies on Physico-chemical charact eristics, Plankton diversity and I chthyofauna of Idukki reservoir, Kerala, India

aborigines of the forests have interesting tales to tell as to how these rocky

hills came to be called Kuravan and Kurathi. They believe that a tribal couple

Kuravan and Kurathi was cursed by Sree Rama in His fury for their

mischievous behaviour while He with his spouse Seetha was enjoying a dip in

Periyar. The curse transformed the tribal couple into two high rocks and then

the Periyar river deflected its course and started flowing in between Kuravan

and Kurathi separating them. Geologically the formation of Idukki gorge is

believed to have taken place during the tertiary age.

2.2 Description of Study Area

The Idukki reservoir is roughly ‘V’ shaped, situated at an altitude of

693 m above sea level. When it full will have a water spread area of 23.1 sq.

miles (59.83 sq.km) with depth varying from 50 to 80 m and this storage

regulates the yield of over 250.7 sq.miles (1649.3 sq.km) of Periyar and

Cheruthoni catchments. The Idukki hydro-electric project encompasses 3

dams. They are Idukki arch dam (090 50” 30’N latitude and 760 58” 40’E

longitude) across Periyar, the largest river in Kerala, at Idukki gorge;

Cheruthoni a straight concrete gravity dam (090 50” 48’N latitude and 760 58”

00’E longitude) across the tributary River Cheruthoni and Kulamavu dam (090

47”15’N latitude and 760 51” 20’E longitude) across Kilivallithodu (Fig.2.1

and Plate I).

2.2.1 Dams and Reservoir

The details of the reservoir and the dams are given in the Table 2.1

Materials and Methods

Studies on Physico- chemi cal charact eristics, Plankton diversity and I chthyofauna of Idukki reservoir, Kerala, India 25

Fig

2.1

Sate

llite

imag

e of

Iduk

ki R

eser

voir

Chapter 2


Table 2.1 The morphometric f eatures of the Idukki reservoir

I. RESERVOIR Full reservoir level +2,403ft

Maximum reservoir level +2,408.5ft

Gross storage at F RL 70,500 Mcft

Gross storage at MWL 74,400 Mcft.

Dead storage below MDDL of + 2,280 ft 18,957 Mcft

Water spread area at FRL 23.1 sq.miles

II. IDUKKI DAM Type Double curvature thin parabolic concrete arch dam

Crest Length 1200 ft

Width at bottom 65 ft

Width at top 25 ft

Maximum height 555 ft

Concrete quantity 16,950 cu.yds

III. CHERUTHONI DAM Type Straight concrete gravity dam

Crest length 2150 ft



Discharge capacity of Permanent outlets 30,000 cu.ft/sec

Spillway capacity 150,000 cu.ft/sec with 5 radial gates

Concrete quantity 2,252,392 cu.yds

IV. KULAMAVU DAM Type Masonry and concrete gravity dam

Crest length 1265 ft



Discharge capacity 1600 cu.ft/sec

Volume of masonry and concrete 620,300 cu.yds



Fig

2.2

Diag

ram

sho

win

g di

ffer

ent

sam

plin

g st

atio

ns in

Iduk

ki r

eser

voir

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Idukki reservoir receives water from the catchments of a number of

rivers and minor streams. Maximum inflow and out flow details are given

Table 2.2.

Table 2.2 The details of the maximum inflow and outflow of t he Idukki res ervoir

Sl.No Maximum inflow Cusecs Maximum outflow Cusecs 1 From Mullaperiyar flood 122000 Powerhouse discharge 5011

2 Idukki catchment maximum flood 283000 Spillway discharge 128800

3 From Azhutha diversion 393 Through outlet gates 38770

4 From Erattayar diversion 2398 Valve dispersion 1817

5 From Kuttiyar diversion 247

6 From Vaz hikadavu diversion 162

7 From Vadakkepuzha 92

8 From Narakakkanam 81

9 Total inflow 408373 Total outflow 174398

The present investigation was carried out to study the physico-chemical

characteristics, seasonal distribution and diversity of plankton (zooplankton

and phytoplankton) and fish in Idukki reservoir for a period of 3 years from

February 2007 to January 2010. Sampling for water quality parameters and

plankton analysis were done bimonthly, during the early hours between 6 am

to 10 am and always collected at the same time on every sampling day. Water

samples for the analysis of physico-chemical parameters, phytoplankton and

zooplankton were collected from 16 stations in the reservoir (Table 2.3,

Fig.2.2 and Plate II) with the help of inspection boat of K.S.E.B -‘Periyar’.



Table 2.3 Details of sampling stations

Sl. No Name of station Details

1 Idukki – Cheruthoni Dam

2 separate dams. Distance between these two dams is only ½ km.

One side of the Idukki dam is huge rock and the other side is

Cheruthoni dam. The other side of the Cheruthoni dam is forest.

2 Narakakkanam One side is rock and the other side is forest

3 Vettilappara One side is rock and other side is deep forest

4 Vazhavara Both sides of this station are deep forest

5 Anchuruly A deviation from Vazhavara. This station receives water from

Erattayar tunnel. Both sides are forest.

6 Kochidukki One side is small rock and other side is forest.

7 Kallarthodu Two sides are forest

8 Ayyappankovil Periyar river mouth enters the reservoir bed. Forest area.

9 Meenmutty Forest area

10 Cherry Both sides are forest

11 Vyramani ”

12 Venghanam ”

13 Kappakkanam ”

14 Mullakkanam ”

15 Nellickappara ”

16 Kulamavu Dam This dam constructed at the end of a channel from Vyramani. Water for electricity generation is taken from here. One side is PWD road and other side is forest.

N.B: Stations 1-8 are in River Periyar and 9-16 are in River Cheruthoni. The distance between two stations is approximately 3.5Kms.

2.3 Sampling for Analysis of Physico-Chemical Parameters

Different stations of Idukki reservoir was visited bimonthly for a period of 3 years (February 2007 to January 2010) to study the various physico-chemical parameters such as atmospheric temperature, water temperature, transparency, turbidity, electrical conductivity (EC), total dissolved solids (TDS), pH, dissolved oxygen (DO), free carbon dioxide (free CO2), total alkalinity, chloride, total hardness, calcium, magnesium, chemical oxygen

Chapter 2


demand (COD), biological oxygen demand (BOD), sodium, potassium, nitrate, phosphate, sulphate and iron (Table 2.4). Surface water (< 0.05m) was collected from all the 16 sampling stations, in the first week of the month. The samples in well labelled and tightly capped polyethylene bottles having 1 litre capacity were brought to the laboratory in an ice box and kept in a freezer for further analysis. The parameters such as atmospheric temperature, water temperature, transparency and pH were recorded on the spot.

Table 2.4 Details of the physico-chemical paramet ers studied

Sl.No Parameters analysed Unit Method/Instruments Reference 1. Atmospheric temperature 0C Mercury thermometer -

2. Water temperature 0C Mercury thermometer -

3. Transparency cm Secchi disc -

4. Turbidity NTU Turbidity meter APHA, 1998

5. Electrical conductivity µS/cm Conductivity meter -

6. Total dissolved solids ppm TDS meter -

7. pH - pH meter -

8. Dissolved oxygen mg/l Titrimetry APHA, 1998

9. Free Carbon dioxide mg/l Titrimetry Saxena, 1987

10. Total alkalinity mgCaCO3 /l Titrimetry ,,

11. Chloride mg/l Argentometry Trivedi and Goel, 1984

12. Total hardness mg/l EDTA titrimetry Saxena, 1987

13. Calcium mg/l Titrimetry ,,

14. Magnesium mg/l Titrimetry ,,

15. Chemical oxygen demand mg/l Open reflux method APHA, 1998

16. Biological oxygen demand mg/l Titrimetry ,,

17. Sodium mg/l Flame photometry ,,

18. Potassium mg/l Flame photometry ,,

19. Nitrate mg/l Brucine method ,,

20. Phosphate mg/l Stannous chloride method ,,

21. Sulphate mg/l Turbidimetric method ,,

22. Iron mg/l Spectrophotometer ,,



2.3.1 Atmos pheric temperature

Atmospheric temperature of each sampling station was measured by

using a standard mercury thermometer.

2.3.2 Water temperature

Water temperature at each sampling station was recorded on the spot by

using a standard mercury thermometer.

2.3.3 Transparency

Transparency (cm) was measured with a Secchi disc of 20 cm diameter.

2.3.4 Total Dissolved Solids (TDS)

Total dissolved solids were measured by using a digital TDS meter.

The instrument was calibrated using 0.01M KCl.

2.3.5 Electrical Conductivity

Electrical conductivity is a measure of the concentration, dissociation

as well as the migration of ions in the solution. It was measured by

conductivity meter.

2.3.6 Turbidity

Turbidity is caused by suspended colloidal matter such as silt, finely

divided organic matter and inorganic matter, plankton and other microscopic

organisms. Turbidity is an optical property that results from the scattering and

absorption of light by colloidal or suspended particles in the samples.

Turbidity is measured using Nephlometric Turbidity Meter. The Instrument

was calibrated using standard solution having turbidity 40 NTU.

Chapter 2


2.3.7 pH

pH is one of the most important and frequently used test in water

chemistry. It is a measure of intensity of acidity or alkalinity. The principle of

electronic pH measurement is the determination of the Hydrogen ions by

potentiometric measurements using a standard hydrogen electrode with buffer

solutions of pH 9.2 and 4.

2.3.8 Total Alkalinity

Total alkalinity is the measure of the capacity of the water to neutralize

a strong acid. Alkalinity is mainly imparted by the salts of carbonate,

bicarbonate, phosphate, nitrates, borates, silicates, etc. Total alkalinity,

carbonates and bicarbonates are estimated by titrating the sample with a strong

acid (Sulphuric acid, 0.02N), first to a pH 8.3 using Phenolphthalein as

indicator and then between 4.2 and 5.4 with Methyl orange.

2.3.9 Total Hardness

Total hardness of the water samples were determined by titrimetric

method with Ethylene Diamine Tetraacetic Acid (EDTA, 0.01N) as titrant and

Erichrome Black-T as an indicator.

2.3.10 Calcium

EDTA titrimetric method was adopted. The water sample with sodium

hydroxide solution and murexide indicator titrated against the EDTA solution

until the pink colour turns purple.

2.3.11 Magnesium

Total hardness and calcium hardness of water samples were determined

as discussed above and from the difference of these two values the magnesium

content was calculated.



2.3.12 Chloride

Chloride was estimated using Argentometric method with standard

silver nitrate (0.02N) as titrant and Potasssium chromate as the indicator

solution. Silver Chloride is precipitated quantitatively before red silver

chromate is formed, reported as mg CaCo3/l.

2.3.13 Free Carbon dioxide (Free CO2)

Free CO2 was estimated by titrating samples against 0.2272N sodium

hydroxide using phenolphthalein and methyl orange as indicators and thus the

bicarbonate alkalinities were calculated.

2.3.14 Dissolved Oxygen (DO)

For the estimation of dissolved oxygen (DO), water samples were taken

carefully into 250 ml reagent bottles avoiding air bubbles. The samples

collected were fixed separately by using Winkler’s method in the field itself.

Manganous sulphate and alkaline potassium iodide reagents were added soon

after the collection of water samples and the bottles were transported to the

laboratory for further estimation. Later the D.O was estimated in the

laboratory dissolving the precipitate by adding concentrated sulphuric acid and

then by titrating the samples against sodium thiosulphate (0.025N) solution

using starch as an indicator and the result has been expressed in mg/l.

2.3.15 Biological Oxygen Demand (BOD)

BOD was analysed by incubation of water sample for 5 days in a BOD

bottle. Incubation is done in a BOD incubator at 20 +50C. On the 5th day, the

DO of the sample was analyzed. The difference of the initial and the final DO

was calculated as BOD5.

Chapter 2


2.3.16 Chemical Oxygen Demand (COD)

The sample is refluxed with K2Cr2O7 and H2SO4 in presence of mercuric

sulphate to neutralize the effect of chlorides and silver sulphate catalyst. The

excess of K2Cr2O7 is titrated against ferrous ammonium sulphate using ferroin

as an indicator. The end point is indicated by a colour change from blue to

reddish brown. The amount of K2Cr2O7 used is proportional to the oxidisable

organic matter present in the sample.

2.3.17 Nitrate

In water, the forms of nitrogen are of greatest interest in the order of

decreasing oxidation state - nitrate, nitrite, ammonia and organic nitrogen.

Nitrate was determined by the Brucine method. Nitrate and Brucine react to

produce a yellow colour, the intensity of which can be measured

colorimetrically at 410 nm.

2.3.18 Phosphate

Phosphorous is present in natural water almost solely as phosphates.

These are classified as ortho, pyro, meta and other phosphates and organically

bound phosphates. Acid hydrolysis of boiling water temperature converts

dissolved and particulate condensed phosphate to dissolved ortho phosphate.

As phosphorous may occur in combination with organic matter, a digestion

method was used which oxidizes organic matter effectively releasing

phosphorous or ortho phosphates. The nitric acid - sulphuric acid was used for

the digestion of the sample. After digestion liberated orthophosphate is

determined by the colorimetric method, (specifically stannous chloride

method). Molybdophosphoric acid is reduced by stannous chloride to intensely

coloured molybdenum blue, which is more sensitive.



2.3.19 Sulphate

The sulphate ion is one of the most universal anions that occur on

natural waters. Sulphate ions have a tendency to precipitate out as barium

sulphate on reaction with barium chloride under acidic medium. This tendency

of sulphate ion increases in the presence of a conditioning reagent. The

concentration of sulphate can be determined from the absorbance of light at

420 nm by barium sulphate and then comparing it with a standard curve.

2.3.20 Sodium

Filter the sample through filter paper and find out the concentration of

sodium using flame photometer. Calibration curve is prepared by using the

various standard solutions of sodium.

2.3.21 Potassium

The concentration of potassium also determined flame photometrically,

where the sample is nebulised in to a gas flame and the emission of light

intensity is measured at specified wavelength.

2.3.22 Iron

All the iron is converted into ferrous state by boiling with hydrochloric

acid and hydroxylamine. After cooling, ammonium acetate buffer and

phenonthroline solutions added. The reduced iron chelates with 1, 10-

phenonthroline at pH 3.2-3.3 to form a complex of orange-red colour. The

intensity of this colour is proportional to the concentration of iron and can be

determined colorimetrically.

2.4 Phytoplankton Sampling and Analysis

For the analysis of seasonal variation of phytoplankton, 40 litre of the

surface water (< 0.5m) samples were taken from each stations, bimonthly over

Chapter 2


a period of 3 years from February 2007 to January 2010. Phytoplanktons were

collected by filtering water through plankton net made up of bolting silk (No:

25, Mesh size 40µm). The final volume of the filtered sample was 100 ml

which was transferred to plastic bottle and labelled mentioning the time, date

and place of sampling. The samples were preserved on the field with 2 ml of

4% formalin and added Lugol’s iodine solution @1ml/100 ml of sample to

arrest cell activity, for sedimentation and better staining. The sample bottles

were then transported to the laboratory for plankton analysis and the preserved

sample was reduced to 10 ml. 1ml was pipetted out from the 10 ml (after it has

been shaken) and qualitative and quantitative estimation of phytoplankton was

carried out with the help of ‘Sedgwick Rafter’ counting cell under an optical

microscope (100x magnifications) (Trivedi and Goel, 1984). The systematic

identification of the phytoplankton up to the level of species was done

adopting the standard keys of Desikachary (1959), Edmondson (1959),

Whitford and Schumacher (1973), Prescott (1973), Palmer (1980) and Anand

(1998). Average of 10 replicates for each sample was taken into account and

the density of phytoplankton was expressed in number of organisms per litre.

2.5 Zooplankton Sampling and Analysis

For the study of zooplankton, samples were collected from the surface area

of the reservoir on bimonthly basis for a period of 3 years (from February 2007 to

January 2010). 40 litre of water from each station was filtered through plankton

net of No: 25 bolting silk with a mesh size of 55 µm. Filtered water samples were

collected in well labelled 100 ml plastic bottles and preserved on the spot by add

of 4% formalin and few drops of glycerine. The bottles were carried to the

laboratory and kept aside overnight for better sedimentation. Supernatant plankton

free water was removed and settled concentrated sample to 10 ml were

enumerated by Sedgwick-Rafter Cell method (Trivedi and Goel, 1984).



Identification of zooplankton was done up to species level under microscope

using keys of Ward and Whipple (1959), Tonapi (1980), Battish (1992), and

Dhanapathi (2000). Average of 10 counts for each sample was taken into account

and expressed as number of organisms/liter of water of the reservoir.

2.6 Fish Sampling

For the study of ichthyofauna diversity in the reservoir, fishes were

sampled bimonthly from 16 stations with the help of fishermen using gillnets.

The gillnets with mesh size of 14 mm and 26 mm(2m height, 100m length)

were set close to the shore (depth < 3m) and nets of 40 mm mesh size (3.5m

height, 100 m length) were set in the deeper part of the reservoir. Nets were set

in late afternoon (17:00-19:00 hours) and retrieved the following morning

(5:00-7:00 hours) in order to ensure a constant fishing effort. The collected

specimens were measured for total length (cm) and total weight (gm) and

preserved in 10% formalin for further identification. The collected fishes were

brought to the laboratory and identified by using standard references such as

Day (1967), Jhingran (1983), Datta Munshi and Shrivastava (1988), Talwar

and Jhingran (1991), and Jayaram (1999).

2.7 Statistical Analysis

In order to account all the major seasonal environmental fluctuations of the study area, the bimonthly measurements done were grouped into averages of three seasons such as the premonsoon season (February, March, April and May), monsoon season (June, July, August and September) and postmonsoon season (October, November, December and January). Stationwise analysis and comparison of different data reveals the difference in them on different parts of the reservoir system. Comparison of different parameters in identical stations as well as in similar seasons between the three years of study explains the degree of fluctuation in these parameters. Bimonthly mean differences of

Chapter 2


each particular parameter across stations and that over seasons were calculated using the ANOVA. The variations are significant if P < 0.05 and non significant if P > 0.05. Calculations were performed using Microsoft Excel and SPSS software package (version 12 SPSS Inc.) The correlation (Pearson correlation coefficient) and level of dependence between the physico-chemical parameters, total phytoplankton, phytoplankton groups, total zooplankton and zooplankton groups with the physico-chemical factors were calculated. The species diversity indices, viz., Shannon-Weiner diversity index (H’), Species richness (S), Margalef’s richness (d) and Pielou’s evenness index (J’) were computed for plankton and fish using Primer v5 (Plymouth Routines in Multivariate Ecological Research, Clarke and Warwick, 2001).

1. Shannon-Weiner (Shannon and Weaver, 1949), diversity index was used to emphasize species richness.

H’ = −∑i pi loge (p i) where p i is the proportion of the total count arising from the ith species. The natural logarithm is used for biological interpretation.

2. Margalef’s index was used to measure the number of species present for a given number of individuals.

d = (S-1) / Log N, where S is the total number of species and N the total number of individuals.

3. Evenness of the community was calculated using Pielou’s evenness index (Pielou, 1984)

J’ = H’ / H’ max = H’/ log S where H’ max is the maximum possible value of Shannon diversity and S is the total number of species

4. Species richness was defined as the number of species (S) caught at a sampling station on each sampling date.

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MATERIALS AND METHODS - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/25968/14... · Materials and Methods Studies on Physico-chemi cal characteristics, Plankton diversity

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