Assessment of groundwater quality for irrigational use: a case study from the coastal tracts of Sindhudurg district, Maharashtra

Abstract

In the present study a total of 36 water samples were acquired from open dug wells, bore wells and hand pumps during the pre-monsoon period in and around Kankavli-Malvan-Vijaydurg, northern part of Sindhudurg district of coastal Maharashtra, to examine the suitability of water quality for agricultural purpose. Irrigation quality parameters namely sodium absorption ratio (SAR), residual sodium carbonate (RSC), soluble sodium percentage (SSP), magnesium adsorption ratio (MAR), Kelly’s ratio (KR), permeability index (PI), percent sodium (%Na) and Chloroalkaline indices (CA) have been calculated along with the corresponding electrical conductivity (EC), total dissolved solids (TDS) and total hardness (TH). The US salinity diagram reveals low to high salinity and low sodium water and thus suitable for irrigation in almost all types of soil, while only one water sample (EC>9000 μS/cm) is unsuitable for irrigation. According to Wilcox classification, all water samples, excepting three, fall under excellent to good class and are acceptable for irrigation purpose. The three samples (well numbers 7, 15 and 32), which are in propinquity to Arabian Sea, divulge high EC values (> 750 μS/cm) and is categorized under the permissible to unsuitable range. It is further observed that based on SSP, MAR, KR and RSC and PI, more than 80% of the water samples are suitable for irrigation. The Chloroalkaline indices of the groundwater in this region signify that normal ion exchange is slightly more than the reverse ion exchange process.