Vertical variations in physico-chemical characteristics of Bhimtal lake (Uttarakhand)

187Journal of Sustainable Environmental Research, 3 (2): 187-193 (2014)

Vertical variations in physico-chemical characteristics of Bhimtal lake

(Uttarakhand)

Shikha Panwar and D. S. Malik

Department of Zoology & Environmental Sciences

Gurukula Kangri University, Haridwar (U.K.)

Email: [email protected]

INTRODUCTION

Lakes in the Kumaon region have undergone

ecological changes during the last few decades that

have affected water quality, increasing heavy metal

content and algal productivity (Chakrapani 2002;

Das, 2005; Choudhary et al., 2009). Deterioration

of the water quality of Kumaun lakes because of the

intense cultural activities in their catchment areas has

been recognized recently (Das and Pandey, 1978).

In lakes water quality has been highly transformed

due to anthropocene. The vertical distribution of

particular physical-chemical characteristics of water

exhibited a changing magnitude towards bottom of

lakes that which is observed in similar reservoirs not

undergoing such strong pressure. In lakes, the

vertical diversity of physical-chemical characteristics

of water is the largest in summer, during summer

stagnation, and smallest during periods of winter

because ambient temperature is high in the summer

season. It is certainly important for its effects on

different chemical and biological activities in the

ecosystem of different water bodies.

All rights Reserved ��Foundation of Natural Science and Culture (www.nscfoundation.org) [email protected]

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Bhimtal lake receives toxic metals, organic and

inorganic pollutants from different sources like soil

erosion, illegal construction activities and painting of

boat in tourist season every year. The steep hills

surrounding the Bhimtal lake have immature

topography and are prone to landslips and landslides.

The construction in the lake catchment have

substantially have increased the sediment input to

the lake. Because of these anthropogenic activities,

the lake is facing serious problem of eutrophication

and deterioration of water quality of the lake.

Ecological properties of lakes are influenced greatly

by physical and chemical process. Water quality such

as temperature, pH, dissolved oxygen, and the

concentration of nitrates and phosphates are

important ecological indicators of biological

production and its biodiversity. The present study

aimed to investigate the vertical and seasonal

fluctuations of physico-chemical properties mainly

water temperature, pH, dissolved oxygen, BOD,

COD and nutrients in water column of Bhimtal lake.

Abstract: A study was conducted to determine the vertical variations in physico-chemical characteristics of

Bhimtal Lake at Uttarakhand during January to December 2013. Various physico-chemical parameters like water

temperature, pH, dissolved Oxygen (DO), biochemical Oxygen Demand (BOD), chemical Oxygen Demand (COD),

salinity, nitrate and phosphate were monitored along the vertical ecological gradient, to determine trophic variations

in three selected sites in lake. Vertically observed values showed that water temperature decreased with depth

25.80 to 20°C and 16.7 to 10.5°C in summer and winter season respectively, pH was observed alkaline in range,

Dissolved oxygen was observed vertically 7.88 to 6.50mg/l in summer and 8.34mg/l to 6.15mg/l in winter season,

BOD and COD values were showed increasing trends during summer season. The nutrients were accumulated in

lake water from many sources from its catchment basin of Bhimtal lake, hence nitrate and phosphate were

observed 0.068 to 0.041 mg/l, and 0.019 to 0.046mg/l in summer respectively. The physico-chemical values of

water temperature, pH and DO showed a declining trend while and BOD, COD, EC, salinity, nitrate and phosphate

showed a relative increase along the depth of water in Bhimtal lake. The water quality of Bhimtal lake showed a

degrading drift resulting from various anthropogenic activities and results revealed that nutrients pollution loads

were quite higher in summer season in Bhimtal lake.

Key words: Bhimtal lake, Water Quality, Physico-chemical characteristics, Nutrients

ISSN:2278-196X

Received: Oct. 21, 2014; Revised received: Dec. 15, 2014; Accepted: Dec. 16, 2014

188

MATERIALS AND METHODS

Bhimtal lake is situated between 29°21' N latitude

and 79°24' E longitude in Kumaun region in

Uttarakhand state of Indian sub-continent. Bhimtal

Lake is the largest lake approximately 85.26 ha and

located at a distance of 22 km from Nainital. The

lake is warm monomictic under subtropical region.

The physico-chemical characteristics of water of

Bhimtal lake were studied at seasonally January to

December, 2013 by selecting three different sites

(Mallital, Central and Tallital Zone) representing

different region of the lake (Fig. 1). Temperature

and pH were measured on spot. Water samples

were fixed in the field for dissolved oxygen and

brought to the laboratory in an icebox for further

processing. Other physico-chemical parameters

were determined separately from three sampling sites

in the laboratory employing methods described by

APHA, (2005); Trivedi and Goel, (1986).

RESULTS AND DISCUSSION

The results of various physico-chemical parameters

along the water depth from the three sampling stations

of Bhimtal Lake of Kumaun region are given in Figure

2. The Bhimtal lake is warm monomictic and

mesotrophic nature due to its thermal stratification

and nutrient accumulation as the inflow of organic

substances as mentioned by Hutchinson, (1967).

During summer season the major part of mallital zone

got dried due to siltation and sandy soil. The depth

of central zone showed a declined trend by the

maximum lake water drained out through the outlet

for agricultural purposes (Malik and Shikha, 2013).

The vertical profile of physico -chemical parameters

indicated that the oxic epilimnion of lake Bhimtal

ranges from surface to a depth of about 2 m, and

anoxic hypolimnion extends from above of 10 m to

lake bottom.

Panwar and Malik /J.Sust.Env. Res. 3 (2): 187-193 (2014)

Figure1: Map of study area and showing the

sampling sites with depth in winter and summer

season.

(A)

(B)

(C)

189

Temperature is one of the most important physical

factors influencing the aquatic life. It is the basic

environmental factor that effects chemical and

biological reaction in water and maintain the optimum

aquatic biodiversity (Boyd, 1982). Water

temperature, a regular factor for various physico-

chemical as well as biological activities in lake

ecosystems fluctuated markedly with the variations

in air temperature (Sharma and Kumar, 2002). The

depth profile of temperature showed that the lake

water in Bhimtal were circulated during December

to January and remained thermally stratified for

remaining part of the year. Vertically, in summer

season a maximum mean temperature of 25.800C

was recorded at surface water, 24.420C at 5 meter

depth and a least temperature 200C in bottom water

and in winter season maximum mean temperature of

16.70C, at 5meter, 10 meter water depth and bottom

of lake were recorded 15.03 , 11.100C and 10.50C

respectively. These observed values showed that the

water temperature decreased with water depth and

its variations showed that there were wide changed

patterns in water temperature between surface and

bottom layers while the variation between surface

and bottom layers were low value in winter because

sunlight directly interact with the surface water of

lake as while, it heats most readily the top surface

layers of lake water. The sunlight is transmitted by

the water only enough to heat lower levels a little bit.

The high water temperature in summer season was

recorded because of low water level, high air

temperature and clean atmosphere. Sharma et al.,

(2000) observed that water temperature fluctuated

between 21°C to 29°C during limnological studies

of Udaipur lakes.

The water of Bhimtal lake was alkaline throughout

the year at photic depth levels. Vertically, the pH in

summer season maximum 8.80 was recorded at

surface water, 8.40 at 5m, 7.87 at 10m and minimum

6.99 was recorded in bottom water. In winter season

the pH was recorded maximum 7.7 at surface, at

5m, 10m water depth and bottom water of lake as

7.8, 7.6 and 7.3 were recorded respectively. The

pH declined with increasing depth and minimum pH

was recorded in bottom water (hypolimnion) and

showed that pH was higher in epilimnion than

hypolimnion where the surface layer usually is higher

than bottom layer due to changes in photosynthesis

Figure2: Vertically profiles of different param-

eters in summer and winter season in site 1, 2

and 3 of Bhimtal lake (A - G).


(D)

(E)

(F)

(G)

190

activity. The existing pH values are more optimum

for all biological phenomenon in Bhimtal lake. It poses

direct or indirect effect on photosynthesis and growth

in plants. The reduced rate of photosynthetic

activities reduces the assimilation of carbon dioxide

and bicarbonates which are ultimately responsible

for increase in pH, the low oxygen values coincided

with high temperature during the summer month

(Kamble et al., 2009). Higher pH values of studied

lake water during summer could be ascribed to

increased photo synthetic assimilation of dissolved

inorganic carbon by planktons (Goldman, 1972).

Dissolved oxygen is the most crucial ecological factor

for sustain the healthy lake ecosystem and survival

of fishes. Dissolved oxygen is an important measure

of purity for all waters and the productivity of aquatic

systems (Wetzel, 1983). The reduction of DO might

be due to organic load through the municipal,

domestic sewage and nutrients loads during

throughout the year . The limiting factors affecting

the DO content are mainly temperature,

photosynthesis, respiration and decomposition

processes. Warmer temperature during summer

increases the rates of photosynthesis and

decomposition, when all plants die at the end of the

growing season, their decomposition results in heavy

oxygen consumption. In the present investigation

vertically, maximum dissolved oxygen 8.52mg/l were

observed on the surface water 8.21mg/l at 5m,

7.52mg/l at 10m and minimum 5.15mg/l in bottom

water of lake in winter season,. In summer season

maximum DO was observed in surface water as

8.80mg/l, 8.26mg/l at 5m, 7.87mg/l at 10m and

minimum DO 6.21mg/l was observed in bottom

water of lake. It showed that DO was decreased

with depths of water because cumulative respiration

rates of different trophic organisms were more than

present rate of oxygen solubility. The phenomenon

was reversed in summer since the water column

stratified and free oxygen was depleted in bottom

water layer. DO were found lower trends in summer

because higher rate of decomposition of organic

matter and limited flow of water, leading to

consumption of oxygen from water (Jameel, 1998).

The low level of dissolved oxygen in Bhimtal lake

during summer months, reflects richness of organic

matter, which consumes large amount of dissolved

oxygen in the process of decomposition. The surface

water were saturated with dissolved oxygen

throughout the year except during winter at mallital

zone of Bhimtal lake (Malik and Shikha, 2014).

BOD means an essential requirement of oxygen by

all biotic organisms for their metabolic activities in

aquatic system. Biological oxygen demand increases

as the bio degradable organic content increases with

large numbers of consumers occurred in lakes. In

last twenty years, BOD showed increased in summer

season by presence of phosphates, nitrites and

nitrates in Bhimtal lake water through domestic liquid

wastes entering through the inlet at mallital zone of

lake (Malik and Shikha, 2014). BOD above 6 mg/l

in lake water is considered moderately polluted and

high BOD values are attributed to the stagnation of

water body leading to the absence of self-purification

(Iqbal and Katariya, 1995). In Bhimtal lake, BOD

values were noticed vertically in summer season

3.29mg/l at epilimnion, 3.45mg/l at 5m, 3.59mg/l at

10m and maximum 5.28mg/l at hypolimnion. In

winter season minimum value of BOD was observed

at epilimnion 1.30mg/l, 2.26mg/l at 5m, 2.39mg/l at

10m and maximum at hypolimnion 3.03mg/l. The

values of BOD increased with the water depths

because microbial activity was found higher at the

bottom of the lake. The highest value of BOD was

observed in summer season due to high temperature

favors microbial activity while the lowest during the

winter season in all the sampling sites (Tidame and

Shinde 2012; Sachidanandamurthy and Yajurvedi,

2006). COD is the measure of oxygen consumed

during the oxidation of organic matter. High level

COD indicated presence of all forms of organic

matter, both bio degradable and non bio degradable

contributed the degree of pollution in lake water.

COD values were observed higher in summer season

ranged at surface was 5.00 mg/l, at 5m, 10m

5.47mg/l, 5.93mg/l and maximum 7.01 mg/l were

observed at the bottom. In winter COD was

observed minimum 1.74 mg/l at surface, at 5m, 10m

3.02mg/l, 3.33mg/l and maximum 5.65 mg/l at the

bottom water. The higher values of COD in summer

indicated water pollution due to oxidisable organic

matter in lake water, Rasool et al., (2003).

Total concentration of soluble salts in water is

represents the Electrical conductivity. Conductivity

has been used as an important parameter in deciding

whether water resources are suitable for irrigation


191

purpose. Conductivity values showed seasonal

variations. During the study period the EC values

observed minimum 347.69 µ mhos at surface and

maximum 499 µ mhos at bottom in summer season

and in winter season, it was found minimum 258.2 µ

mhos at surface water and maximum 316.9 µ mhos

at bottom respectively. EC values recorded higher

in bottom because adsorption of dissolved salts in

the surface of suspended particles which coming with

water flood and discharged to bottom sediments.

High mineralization of organic matter occurs in

bottom water of lake in summer season so EC values

was recorded less in winter and high in summer.

Salinity is the total concentration of all dissolved salts

in water (Wetzel, 2001). During the study period

Salinity were observed maximum 0.50PSU at surface

water and minimum 20.68 PSU at bottom water in

summer season. In winter salinity was observed

maximum 0.40 PSU at surface water and minimum

was observed 22.03 PSU at the bottom water. It

increased with the depth of water at all the sites

because decrease in temperature with depth of water

increases the water density.

Eutrophication is usually the result of nitrate and

phosphate contamination and is a significant reduction

of water quality. Nitrate and phosphate

concentrations may vary with the depth in lake due

to deeper and shallow zones as per their

bioaccumulation in detritus cycles. At the surface of

the lake, where sun light stimulates algae growth, total

nutrient concentrations may be higher than those

deeper in the lake. These high total concentrations

reflect the increased concentration of organic matter,

because the organisms are utilizing most of the

nutrients that are produced, available nutrient

concentrations may be low. Since decomposition of

organic matter formation of available nutrients from

total nutrients occurs to a larger extent near the

bottom of a lake, available nutrient concentrations

may be higher at depth. The main source of nitrate is

the runoff and decomposition of organic matter. The

higher inflow of water and consequent land drainage

causes high value of nitrate (Thilanga et al., 2005).

The nitrate observed in the present study minimum

0.018 mg/l at surface water, at 5m, at 10m 0.030mg/

l, 0.038mg/l and maximum 0.041 mg/l at bottom

water in summer season. In winter season values

fluctuate between 0.017 mg/l at surface water, at

5m, 10m 0.031mg/l, 0.045mg/l and maximum 0.060

mg/l at bottom water of Bhimtal lake. It increased

along depth gradually at all the sites. The highest value

of nitrate was observed in summer season while the

lowest during the winter season in all the sampling

sites because pollution load was higher in the summer

season. The higher concentration of nitrates is

indication of level of micronutrients in water bodies

and has ability to support plant growth. Higher

concentration of nitrate favored growth of

phytoplankton.

Phosphate content in a lake may be due to release

of phosphate from bottom sediments and organic

load of the water contributing in growth of the

phytoplankton and weeds in the lake (Dhembare,

2011). Total phosphate content distribution in lake

water showed the lowest value at epilimnion 0.019

mg/l, at 5m, 10m 0.028mg/l, 0.037mg/l and high in

hypilimnion 0.046 mg/l in summer season. In winter

season value were observed at epilimnion 0.010 mg/

l, at 5m, 10m 0.019mg/l, 0.029mg/l and maximum

0.040 mg/l at hypolimnion. It showed that phosphate

was higher in summer in comparison to the winter

and it increased with the depth in all the sites. It

showed the deposition of nutrients especially during

summer season in to the downstream of the lake.

Phosphate showed increasing tendencies in

hypolimnion, they were not clearly distinguishable

among the depths. Its highest values were observed

in the summer due to loss of water as a result of

rising temperature and concentration of pollutant

present in lake water.

During the present study the results reveals a

representation of vertically variations in physico-

chemical characteristics of Bhimtal lake in different

parameters as water temperature, pH and DO

showed a declining trend while and BOD, COD,

EC, salinity, nitrate and phosphate exhibited a relative

increase along the depth of water . The present

pollution influx in Bhimtal lake showed that municipal

and domestic pollution loads were accumulated

higher trend towards bottom water . The present

ecological study would be contributed significantly

to know vertical pathway of nutrients cycles in lake

ecosystem and be used a ecological modelling tool

for further ecological assessment in terms of water

quality and their existing aquatic biodiversity in

Bhimtal lake.


192

ACKNOWLEDGEMENT

The authors expressed their thankfulness to Director

and scientists of Directorate of Cold Water Fisheries

Research (ICAR), Bhimtal ,Uttarakhand for their

technical supports and encouragement for the study.

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Vertical variations in physico-chemical characteristics of Bhimtal lake (Uttarakhand)

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