Assessment and Characterization of Groundwater Quality of Malabar Coast in Kerala, India

Abstract

A study was conducted to assess and characterize the groundwater quality of coastal aquifer of the Vatakara-Koyilandy stretch in the Kozhikode district of Kerala. Mann-Kendall Test was used for analysing the trend in groundwater levels. The Piper diagram was applied to determine the chemical facies of the groundwater and identify the evolution of hydrochemical parameters of groundwater sources. The source of the dissolved ions in the groundwater was described by the Gibbs diagram. The suitability of groundwater for irrigation was determined using the United States Salinity Laboratory diagram. Geostatistical tools were used to describe the spatial variability of groundwater levels and salinity and the ordinary kriging method was used to plot the spatial variability maps. It was found that Na+ was the predominant cation with maximum concentration varying from 455.6 mg/l to 1844 mg/l during pre-monsoon and post-monsoon; respectively. Concentration of Cl- in pre-monsoon and post-monsoon varied from 184 mg/l to 2417 mg/l and 99 mg/l to 714 mg/l; respectively. Other anions in the groundwater were SO42- and HCO3- with an average concentration of 239.79 mg/l and 129.59 mg/l in pre-monsoon and 110.73 mg/l and 75 mg/l in post-monsoon; respectively. The trend in groundwater in confined and semi-confined aquifers showed negative trends whereas eight wells resulted in a significantly negative trend. However, a significant decreasing trend was observed in wells near the coasts. The most dominant cations were (Na+, and K+) and the dominant anions were SO42- and Cl-. The dominant cations and anions were from the mixing of seawater with the groundwater. The Na+ ions were also found to be from the same source. In most of the area, the groundwater was highly to very high highly saline with medium sodium and not suitable for irrigation. In the unconfined aquifer, 25.2% and, in the semi-confined aquifer 24.0% area was found to be unfit for irrigation.