Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

N. Subba Rao ¹, J. Prakasa Rao ¹, A. Subrahmanyam ²

Affiliations
1 Department of Geology, Andhra University, Visakhapatnam-530003, IN
2 Department of Geology, Hindu College, Guntur - 522 003, IN

Abstract

Principal component analysis (PCA) of the chemical variables of groundwater is employed to interpret the relationships with specific processes that control the quality of water. Groundwater samples collected from the Guntur urban area, Andhra Pradesh were analyzed for major ion chemistry. The PCA separates the chemical variables into three principal components, which together account for 77.20% of the total variance. The principal component-I (PC-I) is dominated by TDS, Na⁺, Cl^-, SO₄^2- and K⁺. The principal component-II (PC-II) is influenced by pH and CO₃^2-. The principal component-III (PC-III) is governed by NO₃^-. These three principal components are identified with the processes of salinity, alkalinity and pollution, which are considered as lithologically and non-Lithologically controlled factor, lithologically controlled factor and non-Lithologically controlled factor, respectively.

Areal distribution of the principal component scores show that the higher positive scores of PC-I, PC-II and PC-III are randomly distributed, but do not coincide with one another, which suggest the local modifications of PC-I due to the regional flow system of groundwater, whereas PC-II and PC-III are the pathways of recharge zones via soil and anthropogenic activity operated independently, following the natural environmental hydrogeochemical evolution of groundwaters. Identification of these zones helps to take appropriate management measures to improve the quality of groundwater for sustainable development of the area.

Keywords

Principal Component Analysis, Groundwater Quality, Hydrogeochemical Processes, Guntur Urban Area, Andhra Pradesh.

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N. Subba Rao ¹, J. Prakasa Rao ¹, D. John Devadas ¹, K. V. Srinivasa Rao ¹

Affiliations
1 Department of Geology, Andhra University, Visakhapatnam - 530 003, IN

Abstract

This paper describes the results of hydrogeochemistry and groundwater quality to generate baseline information on groundwater resources in the developing urban area of Guntur, Andhra Pradesh. The area falls under a semi-arid type of climate and consists of charnockites and alluvium. Groundwaters are mostly brackish type, having Na⁺:Cl^--facies, that are of meteoric origin. The waters are subjected to evaporation/evapotranspiration process under climatic influence aided by gentle slope, intensively irrigated lands and continued re-use and re-cycling of waters. This process tends to remove ions from the waters for formation of new clay minerals and precipitation of CaCO₃.The soils in the area appear to have the ability to pick up these ionic species during the pre-monsoon season. In the subsequent post-monsoon period, the waters become more saline, which suggests that the ions are leachzd from soils by the infiltrating recharge waters and are added to the groundwater body. In accordance with the domestic and industrial water quality standards, these groundwaters are not safe. The urban authorities of the area, therefore, should take necessary ameliorative steps to overcome the adverse effects caused by the inferior quality of groundwater.

Keywords

Hydrogeochemistry, Groundwater Quality, Urban Semi-Arid Region, Guntur, Andhra Pradesh.

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