Chemical characteristics of tsunami-affected groundwater and lagoon on the east coast of Sri Lanka

Previous studies have shown that groundwater on the east coast of Sri Lanka was heavily impacted by salinization due to the Dec. 26, 2004 tsunami. This study follows up on these initial studies to investigate the effect of the onset of the first rainy season after the tsunami on groundwater quality in the same areas. The results show that approx. 620 mm of rain falling between September and November 2005 improved the water quality with respect to salinity, decreasing the average well water salinity levels from 1250 to 950 μS/cm. A slight elevation in salinity levels in flooded vs. non-flooded wells (1240 vs. 780 μS/cm) in November indicated prolonged salinity impacts in the tsunami-affected areas. As opposed to salinity, groundwater quality deteriorated significantly with the first rains following the dry season with respect to nutrient content. Average well nitrate concentration was doubled (from 7.7 to 17.0 mg/l), with number of wells exceeding the WHO standard of 50 mg/l increasing from 2 to 9% with the rains.