Classification of Southern Basin shore water by multivariate statistical techniques of Lake Biwa, Japan

Abstract

Lake Biwa provides drinking water for about 15 million people in the Kansai region, Japan. Its Southern Basin shores have not been fully investigated. Thus, the aim of our study was to classify the Southern Basin shore, offshore and inflow river waters of lake using major ions. During the period from June 2006 to July 2008, from 18 sites of the Southern Basin shore and inflow water rivers positions 216 water samples were collected. Major ions (Na+, K+, Ca2+, Mg2+, Cl−, SO4 2−, HCO3 − and NO3 −) were determined. Thereafter, to classify the Southern Basin shores, different analysis techniques like hexadiagrams, correlation, principal components analysis (PCA) and hierarchical cluster analysis (HCA) were implemented. Further generated data have been plotted using the Gibbs, hexadiagrams and multivariate statistical techniques. These methods provided exhaustive information of the Southern Basin shore and inflow river water quality. Three water types were identified: (1) (Na+ + K+)–HCO3 −, (2) Ca2+–HCO3 −, and (3) (Na+ + K+)–Ca2+–HCO3 −. The hexadiagrams were resulted the dominance of (Na+ + K+)–Ca2+–HCO3 − type. The spatial–temporal patterns of major ions and its controlling factors for the selected shores and inflowing rivers were also discussed. The periodic data analysis was indicated that some inflow rivers including Okami and Kusatsu Rivers contained relatively high concentration of ions in comparison to Mano and Fujinoki Rivers. Sampling stations 15 and 60 showed significantly high concentration of ions compared to other sampling stations. The results of physico-chemical parameters and multivariate method indicate enhanced information of the Southern Basin shore and inflow river water quality.