CS(AR)-10/97-98 : Ground water quality monitoring and evaluation in and around Greater Guwahati (Assam) Part-II : Chemical analysis

Abstract

Groundwater quality of greater Guwahati is presented based on the physico- Chemical characteristics of thirty samples collected on grid pattern. The various parameters analysed include pH, Electrical Conductivity, Temperature, DO, TDS, Alkalinity, Hardness, Na+, K+, Ca++, Mg++, N0-3, SO--4, Cl- and F- . The results were compared with water quality standards prescribed by BIS and WHO.

Various parameters like Kelley’s Ratio, Sodium Adsorption Ratios (SAR), Residual Sodium Carbonate. (RSC), Magnesium hazards. Sodium % and Permeability Index were determined to evaluate the suitability of groundwater for irrigation purposes. On the basis of these parameters it is concluded that the water is suitable for irrigation purpose. The study shows that water at some places require treatment before using for drinking purpose.

An attempt has also been made to classify the quality of groundwater on the basis of Stiff pattern diagram. Piper trilinear diagram, USSL classification, Gibbs variation classification, Durove trilinear classification. Doncen's classification and Wilcox classification. As per the Stiff classification, most of the samples were found to be of either Mg-HCO³ type or Mg-Cl type. In the Piper's trilinear diagram, ground water samples of the study area fall in the Ca+Mg-HCO3 and Ca+Mg-SO4+Cl hydrochemical facies. According to the USSL Classification of irrigation water, samples fall under water type C2-S1 (medium salinity and low SAR) and few samples fall under C3-S1 (high salinity and low SAR) and Cl-S1 (low salinity and low SAR) type. Gibbs variation diagrams show that the chemistry of ground water is mainly controlled by the litho units of the area. According to Doneen's classification most of the samples are class-I type for irrigation use. As per the Wilcox classification, most of the samples are excellent to good class and few are good to permissible. Durove's trilinear classification shows that in cation type, majority of the samples are Mg++ and intermediate type while, in anion type, samples fall in HC0-3, Cl-and intermediate category.