Geo-statistical analysis of groundwater quality in an unconfined aquifer of Nethravathi and Gurpur river confluence, India

Abstract

The groundwater quality plays a vital role in domestic, industrial and agricultural water supply. However, seawater intrusion was one of the major problems occur worldwide in the coastal aquifers due to excessive pumping of fresh groundwater. Thus, groundwater gets contaminated due to seawater intrusion, disposal of industrial waste etc. Due to this reason, it becomes necessary for regular monitoring of groundwater quality, in order to take proper measures for avoiding and reducing contamination. Hence, the present study was aimed to assess water quality in Nethravathi and Gurpur river confluence, located on the west coast of India. Groundwater samples were collected for the month of January 2013–May 2017, which was further analysed in the laboratory as per Bureau of Indian Standards (BIS) and World Health Organisation (WHO) standards. The water quality parameters considered for analysis are Potential Hydrogen (pH), Sodium (Na), Potassium (K), Electrical conductivity (EC), Chloride (Cl), Total Dissolved Solids (TDS), Calcium (Ca), Magnesium (Mg), Total Hardness (TH) and Bicarbonate (HCO3). The results of these parameters were further mapped using Geographical Information System (GIS) to visualize spatial distribution. The geo-statistical analysis was also carried out using SPSS tool to know the correlation of these parameters. The regression analysis was carried out with Factor of sea to the chemical parameters such as Bicarbonate (HCO3), Electrical Conductivity (EC), Total Dissolved Solids (TDS), Calcium (Ca), Magnesium (Mg) and Total Hardness (TH). The significant groundwater quality chemical parameters were found by correlation analysis. The significant groundwater quality chemical parameters were further given as input for mapping, prediction and modelling of groundwater quality. The prediction of significant parameters carried out using the monthly groundwater quality data for the year 2013 and 2014. The result of spatial mapping and statistical analysis provides the spatial and temporal variation of groundwater quality in the study area. The results showed that only Panganimuguru and Kunjatbail region is affected by seawater. The modelling results of Cl and TDS shows the spatial occurrence of contamination in the study area of Netravathi and Gurpur river confluence at the various time period. Further, the results of the modelling also show that the contamination occurs up to a distance of 519 m towards the freshwater zone of the study area.