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Discriminant analysis for characterization of hydrochemistry of two mountain river basins of contrasting climates in the southern Western Ghats, India

  • Jobin Thomas
  • Sabu Joseph
  • K. P. Thrivikramji
Article

Abstract

Discriminant analysis (DA) was performed on river hydrochemistry data for three seasons (i.e., monsoon (MON), post-monsoon (POM), and pre-monsoon (PRM)) to examine the spatio-temporal hydrochemical variability of two mountain river basins (Muthirapuzha River Basin (MRB) and Pambar River Basin (PRB)) of the southern Western Ghats, India. Although the river basins drain tropical mountainous terrain, climate and degree of anthropogenic disturbances show significant differences (i.e., humid, more disturbed MRB vs semiarid, less disturbed PRB). In MRB, TDS, Na+, pH, Mg2+, and K+ are the attributes responsible for significant hydrochemical variations between the seasons, while Cl, TH, and Na+ are the predictors in PRB. The temporal discriminant models imply the importance of rainfall pattern, relative contribution of groundwater toward stream discharge and farming activities in hydrochemistry between the seasons. Inclusion of hydrochemical attributes (in the temporal discriminant functions) that can be derived from both natural and anthropogenic sources suggests that ionic enrichment strongly depends on the seasons, and is mainly due to the variability in the intensity of anthropogenic activities as well as fluctuations in river discharge. In spatial discriminant models, Cl is the only variable responsible for hydrochemical variations between the basins (during MON), whereas Si discriminates during POM and PRM, implying the role of atmospheric supply, anthropogenic modifications as well as intensity of weathering. In the spatial discrimination models, misclassification of hydrochemistry data between MRB and PRB can be attributed to the overlapping effect of humid climate of MRB extending toward the upstream of (semiarid) PRB. This study underscores the versatility of DA in deciphering the significance of climatic controls on hydrochemical composition of tropical mountain rivers.

Keywords

Discriminant analysis Hydrochemistry Muthirapuzha Pambar Western Ghats 

Notes

Acknowledgments

The first author (JT) is indebted to late Dr. R. Satheesh (SES, Mahatma Gandhi University, Kerala) for his moral support during the early stages of research career. JT is also thankful to Ms. Manjusree, T.M. (Department of Environmental Sciences), the HOD (Department of Geology), Dr. Manoj Chacko (Department of Statistics), University of Kerala and the Director, Central Ground Water Board, Thiruvananthapuram, for the assistance rendered during chemical and statistical analyses. Financial support from Kerala State Council for Science, Technology, and Environment, Thiruvananthapuram, and permission and logistics for the field studies in the protected areas by Kerala Forest Department are also delightedly acknowledged. We are also grateful to the anonymous reviewers for their critical and helpful comments, which significantly improved the quality of the manuscript.

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Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  • Jobin Thomas
    • 1
  • Sabu Joseph
    • 1
  • K. P. Thrivikramji
    • 2
  1. 1.Department of Environmental SciencesUniversity of KeralaThiruvananthapuramIndia
  2. 2.Center for Environment and DevelopmentThiruvananthapuramIndia

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