A geochemical assessment of coastal groundwater quality in the Varahi river basin, Udupi District, Karnataka State, Indi
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ORIGINAL PAPER
A geochemical assessment of coastal groundwater quality in the Varahi river basin, Udupi District, Karnataka State, India P. Ravikumar & R. K. Somashekar
Received: 9 December 2010 / Accepted: 27 October 2011 / Published online: 27 November 2011 # Saudi Society for Geosciences 2011
Abstract The Varahi Irrigation project site is located at 13°39′ 15″N (latitude) and 74°57′E (longitude) in Hole Shankaranarayana village, approximately 6 km from Siddapura, Kundapura taluk, Udupi district. A total of 59 groundwater samples were collected from dug and tube wells in November 2008 to evaluate hydrochemistry and suitability for drinking and irrigation purposes. The physico-chemical parameters estimated include pH, electrical conductivity (EC), total dissolved solids (TDS), redox potential (Eh), total hardness (TH), total alkalinity (TA), temperature, major cations and anions, besides irrigation quality parameters like boron, sodium absorption ratio (SAR), % Na, residual sodium carbonate (RSC), residual sodium bicarbonate (RSBC), chlorinity index, soluble sodium percentage (SSP), exchangeable sodium ratio (ESR), noncarbonate hardness, potential salinity (PS), permeability index (PI), Kelly index (KI), magnesium hazard (MH), magnesium ratio (MR), index of base exchange. Chloride, sulphate and bicarbonate concentrations classified the groundwater samples into normal chloride, normal sulphate and normal bicarbonate water types, respectively. The Salinity (Class I; 98.3%), Chlorinity (Class I; 100%) and Sodicity (Class 0; 96.6%) indices suggest the suitability of groundwater for irrigation. The Wilcox diagram illustrates that 96.6% of the samples belongs to excellent to good category, while the US Salinity Laboratory (USSL) diagram indicates the low salinity/low sodium content in 86.44% of samples (C1S1). Positive index of base exchange in majority of the samples (91.52%) indicates direct base exchange reaction or chloro-alkaline equilibrium in P. Ravikumar (*) : R. K. Somashekar Department of Environmental Science, Bangalore University, Bangalore 560 056, India e-mail: [email protected] P. Ravikumar e-mail: [email protected]
the study area. The positive value of RSC in majority of samples signifying higher concentrations of HCO3 over alkaline earths indicates that groundwater are base exchange-softened water as there is an exchange of alkaline earths for Na+ ions. Majority of water samples fall in the precipitation dominance field based on Gibbs’ ratio. Keywords Varahi river . Chlorinity index . Sodicity index . Salinity . Kelly index (KI) . Magnesium hazard
Introduction Groundwater is almost globally important for human consumption as well as for the support of habitat and for maintaining the quality of base flow to rivers, while its quality assessment is essential to ensure sustainable safe use of the resources for drinking, agricultural, and industrial purposes. The drastic increase in population, urbanization and modern land use applications (agricultural and industrial), and demands for water sup
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