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Incorporating Factor Analysis in GIS for Assessment of Groundwater Quality for Irrigation Use

P. Kabbilawsh and R. Rajkumar

The study was conducted to assess the quality of groundwater in 35 wells in the Dusi Mamandur tank command area which is located in Thiruvanamalai district of Tamilnadu, using Factor analysis, Cluster analysis and Spatial Techniques. The physiochemical parameters exhibited wide variability. Since most of the groundwater sample lie at thelower triangle part of the diamond in the Piper diagram, therefore the quality of water is ALKALI CARBONATE in nature .Factor analysis indicated the data is a four component system explaining 80% of the total variance. Factor 1 explains 31.754% of the total variance and shows higher positive loadings for K+ (0.772), Na+(0.625). The contribution of Na+ and K+ can be attributed to cation-exchange processes at Soil-Water interface and dissolution of Sodium Bearing Minerals. Factor-2 explains 23.29% of the total variance and shows moderate loadings for four parameters Na+(0.335), K+(0.456), HCO3 -(0.498) and CO3 2- (0.467). This component can be considered to explain the Water Type (i.e. Alkali carbonate in nature). It is analogous with the Piper diagram.Factor-3 has higher loading for pH (0.677) and Ca2+ (0.443). The pH of water is mainly governed by the dissociation of H2CO3 (H+) and by the hydrolysis of bicarbonate (OH-). Conversion of Adenosine into kaolinite present in Clay soil would account for moderate loading of Ca2+. Factor-4 has higher loading for Mg2+ (0.841), the reason can be attributed to Base Exchange reaction.Cluster analysis categorized the sampling locations into four spatially dissimilar groups. The natural hydrochemistry of the groundwater appears to explain much of variability of the data. Spatial plot of Cluster-3 and Factor score-1 helped in narrowing down the area with moderate Sodic hazard which could be treated by appropriate management practices.