Saline water is seeping into freshwater bodies that are as far away as 1.4 km from the shore in many parts of the city, especially in regions such as Kunnumpuram, Cheralai, Thundiparambu, Kazhuthumuttu and Pandikudy.
The chloride concentration in groundwater in these areas was found to be 1000 mg per litre against the permissible limit of less than 250 mg in a litre of potable water. The study was carried out during the peak summer months when many city areas are hit by water scarcity and also saline incursion.
Saline incursion is measured from the seashore to areas where chloride concentration is found to be above the 250-mg mark, according to the study. Intrusion levels were marked between March and May, the peak summer months when water availability goes down and consumption shoots up.
The assessment was carried out as part of preparing a water policy for the city.
The researchers at the Water Institute of the SCMS School of Engineering, Kalamassery, carried out a city-specific study as part of the policy documentation.
The assessment revealed that there was little data on borewells and open wells in the city. “Little is also known about the volume of water extracted from these wells though a large number of commercial as well as multi-storied apartment complexes are depending on these for meeting their water needs,” said Ratish Menon, one of the researchers associated with the project.
Besides assessing the saline incursion, predictions on possible fall in groundwater levels were also carried out. The likely water-table levels when proper recharging of groundwater was carried out was also estimated, said Sunny George, director of the Institute.
When the salinity intrusion was analysed for increased pumping rates after 10 years, the water-table was found to be considerably lower.
With the fall in water-table, there would be increased tendency for seawater to flow towards the land to maintain the equilibrium, the policy document said.
