Seasonal Analysis of Groundwater Samples from Borewells to Identify the Water Quality Index and its Comparative Statistical Analysis of Hunsur Taluk, Mysuru District, Karnataka, India.


 Management and identification of groundwater quality are vital for the maintenance of freshwater sources in semi-arid and arid areas, which is important for sustainable development. Depending on the quality of the groundwater in various areas, the water quality control authorities can regulate the usage of water for either agriculture or drinking implementations since nearly 85% of India’s population is dependent on groundwater for their domestic and irrigation demand, particularly as a source of drinking in rural areas. This study is to explore and identify suitable areas for pumping groundwater for drinking and agricultural harvest from Hunsur taluk, Mysore district, Karnataka, India. A study of groundwater quality was conducted by analyzing the Water Quality Index (WQI) determined from 30 wells during two seasons of the year 2019 namely Pre-Monsoon and Post-Monsoon. The identification of the quality of water resources for irrigation and drinking purposes can be determined with the help of the Water Quality (WQI) index. The WQI index can be useful for the classification of the quality of drinking water as excellent, good, poor, very poor, or unsuitable for drinking. By using the Weighted Arithmetic Index methodwas calculated using the collected data, the analysis concludes that most of the groundwater samples harvested from the study area are ‘excellent water’, ‘good water’, and ‘poor water’. The IWQ index average for the study area is reported to be in the range of 17.35 to 65.64.


Introduction
Water is important for sustenance of life on earth. It could be present as surface or groundwater. Groundwater availability is subject to the hydro-geological terrain speci cs of a region. India is said to host many aquifer systems formed from precipitation of surface runoffs in uphill regions and discharged in the lowlands. Renewable water supplies below 1700 m 3 /capita /year indicate water stress which turns chronic when the gure drop below 1000 m 3 /capita /year (Falkenmark and Widstrand 1992; MoWR 2015). The natural system of groundwater in ow and discharge has been greatly altered by anthropogenic and geogenic activities in recent decades. The issue of groundwater availability is critical as one-third world population uses it for drinking purposes (Nickson et al. 2005). Increased population density, industrialization, agricultural practices, disposal of domestic sewage, industrial runoffs all contaminate the groundwater and water resources in general (Chandra et al. 2015). India's agricultural and drinking water requirements are partly met by aquifers and groundwater that supply roughly 62% towards irrigation, 85% towards water supply in rural areas and 45% in urban areas. (Vijay Shankar et al. 2011). This dependence however has stressed the groundwater resources immensely.
The groundwater aquifers in Karnataka fall geographically in the most predominant hard rock or crystalline zone where rock porosity is acquired through processes of weathering, fractures and joints over time. However the groundwater tables are declining gradually leading to drying up of wells and giving rise to severe water crises. Therefore understanding the mechanics of aquifers systems and their pollution will not only educate us to protect the groundwater better but also devise new strategy to sustain them better.
Assessment of groundwater quality and well locations that are suitable for drinking purpose is imperative to qualify them for drinking purposes. Water studies and researches should assist in highlighting the impending problems with the waters used in the region. Many methods have been employed in the past to test water samples both qualitative and quantitatively. One of them is the water quality index (WQI) method that rates water quality effectively in terms of the overall quality of water (Horton 1965, Brown et al. 1970, Mishra and Patel 2001. In this regard, WQI data highlights the overall quality of water numerically in simple and easy denomination (Ambiga K.et al., 2013). WQI technique translates the intricate statistics on water quality derivations into simple ratings in the form of comprehensive conclusions as good, best, poor or excellent for the public assessment. This helps them further to manage their groundwater resources prudently for the near future (Chauhan et al. 2010).
The current research work was undertaken to identify groundwater areas that were suitable for pumping to meet the drinking and agricultural requirements in Hunsur taluk of Mysore district in Karnataka India. Groundwater quality was analyzing using the Water Quality Index (WQI) from 30 handpumps during pre and post-monsoon seasons of the year 2019. The results of each parameter were compared to the guidelines and standards set by the WHO (2004) and BIS (2012). The results of our study showed that most of the groundwater samples harvested from Hunsur taluk study area were excellent or good water both in terms of WQI and SAR values and therefore it can be used for drinking and irrigation purposes.

Study Location and Climate
Hunsur taluk, Mysuru District falls in the survey of India toposheet Nos. 57D/ 3, 4, 7, 8 and 11. The taluk is bounded by north latitudes 12 0 05' 00" -12 0 26' 00" and east longitudes 76 0 05' 00" -76 0 32' 00, covering an area of 897 sq km receives an annual average rainfall of 873 mm. This taluk belongs to the Mysuru district of the state of Karnataka and is bordered by Piriyapatna taluk on the north-east, Kodagu district on the south-east, Krishnarajanagara taluk on the north, Mysore taluk on the west, and Heggadadevankote on the south. The rainfall is highly variable in its distribution over space and time. The southwestern monsoon contributes more than 60% of the annual rainfall from June to September. During October and December, the northeastern monsoon and depressions either in the Bay of Bengal or the Arabian Sea bring rainfall to the area. The area is covered with hilly terrain and contains red-shallow gravelly soils.
Geologically, the Hunsur area is covered by the Archean basement complex of gneisses, younger granites, and rocks of the Dhawar Group. Like in other places of India, in Hunsur also, agricultural, domestic and industrial sectors are competing more and more for a limited supply of water. Although the agricultural and industrial demands are increasing as the sectors continue to grow, domestic needs claim only a small portion of the annual water withdrawals, as access to adequate water and sanitation supplies remains low throughout. Greater access and an improvement in the socio-economic situation in Hunsur will result in high demand for water from the domestic sector in coming years.

Materials And Methods
Groundwater from 30 handpumps of Hunsur taluk, Mysore district, Karnataka, India was analyzed during both pre and post-monsoon seasons of 2019. The major objective of the study was to explore and identify suitable areas that could be used for pumping groundwater for drinking and agricultural purposes. Water quality was assessed for both physical and chemical parameters of the water and results were summarized by using the Water Quality Index (WQI), Sodium Adsorption Ratio (SAR), and Pearson's correlation studies to determined the quality of water.
Samples were either refrigerated at 4°C or immediately analyzed as per the requirement. Physical or chemical (organic/inorganic) constituents of water were analyzed following protocols from standard procedures (Basett, 1978 WQI re ects the quality of groundwater for use in domestic and agricultural chores and is calculated employing four steps (Hortan 1965). In the rst step weight (Wi) of each water quality parameter is calculated by assigning them values between (4-2) depending on the manner in which they would in uence the water quality for drinking purpose holistically (Mu d al -hadithi, 2012). Second step involves calculations for the relative weight (Wi) using protocols from Manzoor, 1988, Brown et al., 1972). Third step, involves calculations for quality rating scale (Qi) for all parameters and fourth step is SI determination for the chemical parameters, after which WQI is determined Equations used in the WQI calculations for all steps are as following

Sodium adsorption ratio (SAR)
Salinity affects water quality negatively making it un t for domestic and agricultural purposes. Sodium adsorption ratio (SAR) de nes the sodium quantity relative to calcium and magnesium ions in groundwater sample. Mathematically SAR can be expressed for all the well water samples following equation where, Na + , Ca 2+ and Mg 2+ denotes the concentration of sodium, calcium, and magnesium particles in water, respectively as

Statistics
Samples from 30 handpumps were reported as Mean ± SD, SAR and WQI values and analyzed statistically using Pearson's correlation test for multiple-comparisons and interdependence between groups with signi cance set at p < 0.05. Correlation coe cients ranged between -1 to +1.

Results
The analysis of the 30 handpump samples from groundwater were compared to the water quality guidelines set by WHO (2004)   The regression analysis was carried out for the following parameters i.e. Mg vs TDS, where Mg was taken on X axis (independent variable) TDS on Y axis: Y = 10.71*X + 179.9 was obtained; Cl vs EC, where Cl was taken on X axis (independent variable) EC on Y axis: Y = 6.310*X + 638.3 was obtained; TDS vs EC, where TDS was taken on X axis (independent variable) EC on Y axis: Y = 1.535*X + 189.3 was obtained, TDS vs Cl, where TDS was taken on X axis (independent variable) Cl on Y axis: Y = 0.1839*X -17.38 was obtained.

SAR
Sodium adsorption ratio (SAR) de nes the irrigation potential of sodium affected water and soils sources.
The SAR values of hundpump samples ranged from 0.720 to 2.35 (avg. 1.6) in the pre-monsoon season and 0.6 to 1.9 (avg. 1.3) in the post-monsoon season. The higher SAR value of the handpump water was present in the pre monsoon season as compared to the post-monsoon season as shown in Tab. 7, 8 & 9 and Fig. 7. According to SAR(meq/l) classi cation, <10 is considered as excellent, between 10-18 SAR(meq/l) as good, between 18-26 SAR(meq/l) as fair and >26 as poor.

Discussion
The current research throws light on the quality of handpump water suitability for drinking and agricultural The pHof water indicates the equilibrium between bicarbonate, carbon-di-oxide, carbonate of a water sample and therefore reporting its status is of utmost importance. In our study, pH of the 30 handpump samples showed an average shift from 7.77 to 7.05 between pre to post monsoon seasons re ecting that they were within the permissible limits (6.5-8.5) of the BIS (2012)   Sodium adsorption ratio (SAR) de nes the irrigation potential of sodium affected water and soils sources.
The SAR values of hundpump samples ranged from 0.720 to 2.35 (avg. 1.6) in the pre-monsoon season and 0.6 to 1.9 (avg. Conclusively, our study of 30 handpump samples taken from Hunsur taluk clearly reiterates that Hunsur taluk can be exploited for ground water pumping for domestic, drinking and irrigational purposes based upon the WQI, and SAR analysis of the samples studied there.

Conclusion
In the present study, the computed WQI values ranges from 53.69 to 26.785. Very poor quality water has been observed in the analysis samples of the study area. It has been observed that 97% of samples indicate a good water quality around the study area. Analysis of results reveals the fact that WQI pertaining to the groundwater of the area needs some degree of treatment before consumption. 24 sample of location Table -5 has been observed to be best in quality for drinking and all the parameters are well within the acceptable limit prescribed by BIS for drinking water. The results of the correlation analysis