Current World Environment

Introduction

Water - the main source of life and one of the most important natural resource of the ecosystem.¹ Lakes are the major sources of drinking and domestic usage for rural and urban population of India. A lake is a watershed area in which its quality depends upon every component of that ecosystem. The health of lakes and their biological diversity are directly related to health of almost every component of the ecosystem.² Topography of the surrounding area, soil, geology and vegetation determine the kind of materials entering into lake which indicates the water quality.³ In present scenario, the contamination and degradation of lake ecosystems has increased manifold due to various anthropogenic activities like urbanization, industrialization, discharge of domestic sewage, untreated industrial effluents, idol immersion and encroachment of Lake Watershed area. The effects of water pollution are not only devastating to people but also to animals, fish and birds⁴ and causing serious disturbance to the biodiversity of the lake environment.

Water quality assessment has become a critical issue in the last decades. ^{5, 6, 7, 8, 9, 10, 11, 12} Therefore regular monitoring of the lake water in terms of quality assessment is mandatory to control the pollution to earliest either experimentally or through mathematical modeling. Water quality index is one of the most effective tools to communicate information on the quality of any water body.¹³ It is basically a dimensionless number that combines multiple water-quality factors into a single number by normalizing values to subjective rating curves. It is a widely used communication tool which summarizes water quality data in an effective and understandable way for to the general public.¹⁴

The present study was undertaken to enumerate water quality of the three lakes viz., Hussain Sagar, Fox Sagar and Kattamysamma lake of Hyderabad city using mathematical aggregation of water quality index (WQI) as an indicator of the environmental quality and to classify based on the Indian standards. There is no previous classification study based on the WQI scores on these Lakes.
 

Figure 1: Location Map of the study area Click here to View figure

Materials and Methodology

Sample Collection

Three different lakes such as Hussain Sagar Lake, Fox Sagar Lake and Kattamysamma Lake in Hyderabad, Telangana State, India were selected for study (Figure.1). Hussain Sagar Lake is located 17°25’22”N, 78°28’28”E at an elevation 510 m in the heart of twin cities of Hyderabad and Secunderabad. It is, built during 1550-1580 AD.¹⁵ It is 3.2 km long and 2.8 km wide; its depth ranging from 2.5 to 12.5 m with a surface area of 446 hectares. Fox Sagar Lake local name is Jeedimetla cheruvu or Kolla Cheruvu is the fifth largest lake in India spreading about 2 km.² Situated (17°30’–17°20’N and 78°30’–78°20’E) 1 km west of Hyderabad-Nizamabad road at Jeedimetla near Kompally in Hyderabad.^1,16 Kattamysamma Lake is also known as Gandimysamma Lake is situated between 17°33’–17°42’N and 78°26’–78°20’E near Medak highway in Sooraram, Hyderabad. Systematic sampling (sixteen samples from each lake which covers entire lake) was carried during monsoon season (September-October) in the year 2014.

Study of Physico-Chemical parameters

The physico-chemical parameters were analyzed as per the Standard Methods for Examination of Water and Wastewater¹⁷ and Guide manual: Water and Waste water analysis.¹⁸ In situ measures such as pH, EC of the water samples were determined on the spot using pH meter and conductivity meter respectively. The laboratory analyses such as cations Calcium (Ca²⁺) and Magnesium (Mg²⁺) were analyzed by complexometric titration method using ethylene diamine tetra acetic acid (EDTA). Sodium (Na⁺) and Potassium (K⁺) were analyzed using flame photometry. The anions Carbonate (CO₃^2-) and Bicarbonate (HCO₃^-) were analyzed by acid-base volumetric titration using sulfuric acid (H₂SO₄) and the chloride ions (Cl⁻) were analyzed by argent-metric titration using silver nitrate (AgNO₃). Nitrates (NO₃^2-) and Fluoride (F^-) were analyzed by using nitrate and fluoride ion selective electrodes respectively. Sulphates (SO₄^2-) analyzed by using UV-Visible spectrophotometer.

Calculation of Water Quality Index (WQI)

In the present study, for the calculation of WQI, ten physico-chemical parameters viz.,  pH, TDS, TH, TA, Ca²⁺, Mg²⁺, NO₃^2-, SO₄^2-, F^- and Cl^- were chosen. The WQI has been calculated by using water quality guidelines for drinking purpose.¹⁹ The Weight Arithmetic Water Quality Index method has been used for calculation WQI of three lakes.

The overall WQI is determined by using Eq. (1)
WQI= a⁰ WiQi / a⁰W_i

The unit weight (W_i) for each water quality parameter is calculated by using the following expression:
Wi = K/ S_i

Where, K is proportionality constant and is determined by using the following formula:
K=1/a⁰ [1/S_i]

S_i is the standard permissible value of the i th parameter.

The quality rating (Q_i) of Eq. (1) is calculated as under:
Q_i = 100 [(V_i- V₀/ S_i-V₀)]

Where, V_i is estimated concentration of the i th parameter in the analyzed water and V₀ is the ideal value of this parameter in pure water. All ideal values are taken as zero for drinking water, except pH = 7.0.

Results and Discussion

In this study, WQI for three lakes was evaluated to assess the water quality of these lakes. The results of various physicochemical parameters and their standard values (BIS 2012) were presented in Table.1. WQI for Hussain Sagar, Fox Sagar and Kattamysamma Lakes were presented in Table.2, Table.3 and Table.4 respectively. WQI and status of Water quality were presented in Table.5. The graphical representation of WQI for three lakes is shown in Figure.2.

TDS, TH, TA, F^-, Cl^- values in all the three lakes, Ca²⁺ in Hussain Sagar and Kattamysamma lakes, Mg²⁺ in Fox Sagar and Nitrates in the Hussain Sagar were found to be exceeding the acceptable limit.¹⁹

The WQI values of Hussain Sagar, Fox Sagar and Kattamysamma Lakes were 132.43, 113.09, and 104.29 respectively. The highest value of WQI was observed in Hussain Sagar while lowest value was observed in Kattamysamma Lake. WQI of all three lakes, falling under E grade and unsuitable for drinking purpose category (WQI > 100) (Table.5).

Discharge of untreated municipal sewage, industrial waste water into these lakes and religious activities like immersion of Gods and Goddess idols made by Plaster of Paris (POP) are responsible for the contamination of these three lakes.

Table 1: Physico-Chemical parameters of three lakes and comparison with standard values

Table 2: Calculation of Water Quality Index (WQI) for Hussain Sagar lake

Table 3: Calculation of Water Quality Index (WQI) for Fox Sagar Lake

Table 4: Calculation of Water Quality Index (WQI) for Kattamysamma Lake

Table 5: Water Quality Index (WQI) and status of Water quality

Figure 2: Graphical representation of WQI of three lakes Click here to View figure

Conclusion

Water quality index proposed in this work use ten parameters to evaluate the water quality of three lakes and this can be used as a useful tool for watershed management and aquatic body monitoring. On the basis of the above discussions, it is concluded that the WQI for all the three lakes were found as unsuitable for drinking purpose.

Acknowledgment

I extend my special thanks to University Grants Commission (UGC), for providing financial assistance through RGNF for doctoral research work. I am thankful to Head of the Department and Dr. M. Ramana Kumar, Dept. of Applied Geochemistry, University College of Science, Osmania University for his enormous support in the laboratory during analysis.

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