Assessment of groundwater quality using multivariate statistical methods at Nagadeepa area in Badulla district, Sri Lanka

Abstract

The study area, Nagadeepa is situated in Badulla District within the dryer parts of the country. Groundwater is the main drinking water source in the area. The study was carried out from 2013 to 2016 and the main objective of the study was to examine the chemical status and pollution levels by examining of 25 water quality parameters namely Na+, K+, Mg2+, Ca2+, Pb Mo, Cr, Cd, Mg, Hg, As, Al, Zn, Se Cl-, F-, NO3-, HCO3-, SO42-, PO43-, DO, pH, temperature, electrical conductivity and water hardness in 28 wells. The results of the factor analysis indicated that conductivity, alkalinity, hardness, Calcium, Fluoride, Mo, Cr and Cd have a strong impact on the water quality compared to the categories of moderate and weak loadings. The parameters namely; Mg, Na, As and Al, Zn, Se and Water Level, Se, Cl, pH and DO, Pb have a moderate impact on water quality based on the moderate loadings indicated by the PC analysis. The weak impact on water quality is indicated by Cl-, SO22- and K, PO4, Hg, Se and Hg, Se, Al and Temperature, Cl-, pH and PO43-. Analysis indicated that; (i) significant and positive correlation with alkalinity, hardness, Ca2+ and Mg2+, (ii) positive and significant correlation only with hardness and Ca2+, (iii) Hardness shows positive and significant correlation only with Ca2+, (iv) Fluoride has a positive and significant correlation with Mo2+ and (v) Na+ has a positive and significant correlation only with Mg2+. Cluster analysis indicated, cluster 1 with less polluted water in 9 wells, cluster 2 with moderately polluted water in 11 wells, cluster 3 with highly polluted water in 7 wells, and cluster 4 with very highly polluted water in one well. Factor analysis indicated that pH, conductivity, alkalinity, hardness, dissolved oxygen, chloride, and sulfate are the major factors that affect the quality of the water. In the majority of the sampling wells, the correlation coefficient revealed a geogenic nature. Cluster analysis revealed that 29% of wells are unsuitable for drinking purposes.