Application of Water Quality Index for Assessment of Surface Water Quality Status in Goa

Water quality index (WQI) is valuable and unique rating to depict the overall water quality status in a single term that is helpful for the selection of appropriate treatment technique to meet the concerned issues. Thirty Six surface water samples were collected from in and around mining talukas of Goa (India). The quality of surface water were evaluated by testing various physico-chemical Oxygen Demand (BOD). The WQI for all samples were found in the range of 34 to 107. The highest value of WQI was observed during the monsoon season while the lowest value was during the post monsoon season. Most of the water samples within study area were found within Good to moderate categories.


INTRODUCTION
Water is addressed as a necessary resource and life preservative.It is required for most human activities like -drinking, cooking bathing, washing, agriculture, industry, recreation, navigation and fisheries etc.About 75% of the world's surface area is covered with water.Out of which 97% of the earth's water is in the ocean, not fit for human use due to its high salt content.Remaining 2% is locked in polar ice caps and only 1% is available as fresh water in rivers, lakes, streams reservoirs and ground water, suitable for human consumption.Now-a-day, water quality issues have become a significant concern due to the growth of population, urban expansion and technological development.Water can be easily contaminated in different ways through unregulated or regulated but not well designed and monitored disposal practices.In India's case, the future is a bit more-worse, since we have only 2.45% of the word's landmass supporting 16% of the world's population and our freshwater resource does not exceeding 4% of the global water resources (Kumar 2005).Apart from availability, continuous water pollution due to disposal of sewage, industrial and mining wastes also threatens to reduce the available quantity of usable water and more and more of our ground and surface water resources including lakes, ponds and rivers are being categorized as polluted (Subramanian et Singh et al. 2013).Access to safe drinking water remains an urgent necessity, as 30 % of urban and 90 % of the rural Indian population still depends completely on untreated surface or groundwater resources (Kumar et al. 2005).Access to drinking water in India has increased over the past few decades with the tremendous adverse impact of unsafe water for health (Singh et al. 2013).Scarcity of clean and potable drinking water has emerged in recent years as one of the most serious developmental issues in many parts of West Bengal, Jharkhand, Orissa, Western Uttar Pradesh, Andhra Pradesh, Rajasthan and Punjab (Tiwari and Singh 2014).
Water quality index (WQI) is defined as a technique of rating that provides the composite influence of individual water quality parameter on the overall quality of water (Singh et al. 2013).Water Quality Index, a technique of rating water quality, is an effective tool to assess quality and ensure sustainable safe use of water for drinking (Tiwari et al. 2014).Water quality index is one of the most effective tools to communicate information on the quality of any water body (Rizwan and Gurdeep 2010).WQI is an a superior way to the understanding of water quality issues by integrating complex data and generating a score, which ultimately describes the water quality status (Tiwari et al. 1985; Singh, D. F. 1992; Rao, S.N; 1997; Mishra et al. 2001).One of the major advantages of WQI is that, it incorporates data from multiple water quality parameters into a mathematical equation that rates the health of water quality with number (Yogedra and Puttaiah 2008).
Mining is one of the major activities causing water pollution and threatens the quality surface water.Water pollution in mining areas is mainly due to overburden (OB) dumps, surface impoundments, mine water, industrial effluents, acid mine drainage, tailing ponds etc. (Singh et al. 2013).River and other streams are not far from the mining industries and it contaminate continuously from point as well as nonpoint source.Waste generation due to the operation and expansion of mining and industrial activity in Goa is going to be a serious negative impact on the water resource in near future.The problems of water quality degradation and its adverse impacts on availability of potable and irrigation water, soil quality and agricultural productivity, and biodiversity in the area have been attracting increasing attention of people.The aim of this study is to assess the quality of surface water for the suitability of drinking and domestic purpose in Goa mining region.

Study area
Goa is the 25 th State of India, attaining statehood in May 1987.It lies between the latitudes 14°53'54" N & 15°40'00" N and longitudes 73°40'33" E & 74°20'13" E with geographical area of 3,702 km 2 and coastline of 105 km.The study area comprises of 5 mining Talukas namely Bicholim, Sattari, Dharbandora, Quepem and Sanguem encompassing an area of 1513 km 2 .Study area entails all the areas wherein mining activities of Goa are encompassed along with a belt of five km from the lease boundary (Fig 1).

MATERIALS AND METHODS
The water samples were collected from thirty six (36) different locations in all two seasons, Pre-monsoon post-monsoon season.Sampling locations were selected on the basis of different land use pattern (agricultural, mining, residential and barren etc.).Care was taken to collect subsequent samples from same location in all season.The Samples were taken from 10 to 15cm below the water surface using acid washed plastic container to avoid unpredictable changes in characteristic as per standard procedures (APHA, 2005).Details of sampling locations along with their latitude and longitude are illustrated in (table 4).

Water Quality Index
WQI's aim at giving a single value to the Water quality of a source reducing great amount of parameters into a simpler expression and enabling easy interpretation of monitoring data (Singh et al. 2013).Water Quality Index (WQI) is a technique of rating that provides the composite influence (let there be n water parameter and quality rating or sub index (q n ) corresponding to n th parameter is a number reflecting the relative value of this parameter in the polluted water with respect to its standard permissible value) Quality rating for the n th water quality parameter V n = Estimated value of the n th parameter at a given sampling station S n = Standard permissible value of the n th parameter V io = Ideal value of n th parameter in pure water.(i.e., 0 for all other parameter except the parameter pH and Dissolved oxygen (7.0 and 14.6 mg/l respectively) Unit weight was calculated by a value inversely proportional to the recommended standard value S n of the corresponding parameter.
where W n = Unit weight for the n th parameters, S n = Standard value for n th parameters, K = Constant for proportionality.The overall water quality index was calculated by aggregating the quality rating with the unit weight linearly: ... (3) Different levels of water quality index and their respective water quality status were given in Table -1.Various parameters and their unit weight were calculated and summarized in Table -2 with their standards and recommended agencies.

RESULTS AND DISCUSSION
The World Health Organization (WHO), Bureau of Indian Standards (BIS), and Indian Council for Medical Research (ICMR) for the drinking water together with its corresponding status categories of WQI are given in Tables 1, Table 2, Table 3 and Table 4, respectively.The WQI of water samples were found in the range of 34 to 83 in post monsoon, 28 to 81 in winter, 34 to 86 in summer and 23 to 107 in monsoon season.The WQI for all samples were found in the range of 34 to 107.Almost 94% of the total water samples were found in range of good and medium except SW2 and SW35 which were found to be in poor categories.Out of 36 water samples only two (6%) were found within poor category, it is due to transportation of iron ore and mining activities.Huge overburden dumps are piled in and around mining areas were suffered during monsoon seasons due to leaching.Among all the of the water samples, the percentage (%) of WQI categories Good (47.22%),Moderate (47.22) and Poor (5.56%) were observed in all four the seasons (Fig. 2).

CONCLUSION
On the basis of the above discussions, it may be concluded that the WQI for all samples were found in the range of 34 to 107 in the four seasons.

Table . 1: Descriptive category of WQI values Water Quality Water Quality Status Index Level
Fig. 2: WQI Categories of Samples (%)