Impact of agriculture practices on water quality parameters of ground water from Valikamam area in Jaffna district, Sri Lanka

Abstract

The Jaffna Peninsula largely depends on groundwater resources for domestic as well as agricultural purpose. The quality of ground water is a vital concern for mankind since its directly linked with human welfare. In this study the water quality parameters of ground water were analysed in Valikamam area of Jaffna and samples collected from agriculture wells and domestic wells near the agricultural areas during the period of February 2019 to March 2019. 32 samples were analysed with random sampling for physical characteristics (turbidity, pH, colour, electrical conductivity, salinity, TDS) and chemical characteristics (nitrate, sulphate, phosphate, fluoride, chloride, calcium, magnesium, sodium, potassium, total hardness and total alkalinity). All the samples have higher alkalinity (1069.5 - 494.5 ppm), electric conductivity (5380 S/cm- 675 S/cm) and total hardness (514.56 - 196 ppm) than desirable level compared to Sri Lankan standards (SLS). 87.5% of samples showed higher amount of calcium and 88.2% samples showed high magnesium contents. Sodium, magnesium, salinity, TDS, and chloride contents were found to be very highin samples collected close to sea water. Sulphate (200 – 21.2 ppm) and phosphate (1.24 – 0.02 ppm) contents are found to be within SLS acceptable level but in the case of nitrate, 28.85% of samples exceeded the permissible level (50 ppm) including domestic wells and it was in the range of 5.7 to 93.1 ppm. The wells are in agriculture land as well as domestic wells showed higher content of nitrate. This is due to excessive usage of nitrate fertilizers in the agricultural land where the intensive cultivation is practised throughout the year.