Hydrochemistry of tropical springs using multivariate statistical analysis in Ithikkara and Kallada river basins, Kerala, India

Abstract

Spring waters are the most important natural resource used for drinking by many people around the world, especially in arid and semi-arid areas. This resource cannot be optimally used and sustained, unless the quality of groundwater is assessed. The main objective of this study is to understand the quality and hydrochemistry of spring water sources of two important river basins of Southern Western Ghats—the Ithikkara and the Kallada river basins draining Kollam district of Southern Kerala as an example. Water Quality Index (WQI) values are used to assess the drinking suitability of spring water samples. Multivariate statistical approach (factor analysis and principal component analysis) allow driving hidden information from the data set about their possible influences of the environment on water quality. Multivariate analysis was performed on matrix of hydro-geochemical data. To study the influences of the environment on water quality, multivariate statistical approach is applied. A total of 57 samples were collected and analyzed for major cations and anions for pre-monsoon, monsoon and post-monsoon seasons of 2011–2012 periods from lowland and highland regions of the study area. The results of the WQI values show that majority of the samples fall in Excellent to Good category rendering these water samples suitable for drinking purposes. From the statistical analysis, it is inferred that in catchments rich with pyrite in rocks and clays, drainage of sulphuric acid may significantly contribute to acidity. The negative loading in pH and DO is due to anaerobic conditions in the spring source from the loading of high-dissolved organic matter, which results in the formation of ammonia and organic acids leading to a decrease in pH. The positive loading of SiO2 reflects the dissolution of silica minerals and high temperature. The evaluation of the saturation index of the water samples in highland regions indicted that water was oversaturated with respect to iron minerals and undersaturated with fluorite minerals. The chemistry of the spring waters favors kaolinization and subsequent leaching of mobile elements like alkali and alkaline earth elements. The study is helpful in understanding the relationship between individual ions and for the classification of groundwater types.