The intrusion of seawater into groundwater aquifers, particularly along the coastal areas of Ernakulam district, could be slowly deteriorating groundwater quality, suggests recent research by a team from the Jawaharlal Nehru University (JNU) in New Delhi. Though water is still potable and can be used for irrigation in a majority of the coastal sites where wells were tested for salinity (a sign of seawater intrusion), some regions – including Chellanam and Vypeen – are a cause for concern, according to S. Sreekesh (Associate Professor, Centre for the Study of Regional Development, JNU) who led the research team.
Eroding shoreline
For their research, published recently in the Journal of Climate Change , the team analysed the change in sea level and shoreline along the coasts of Ernakulam district to study its consequent changes on the quality of groundwater in areas nearby. For this, they compiled tide gauge data (a monthly measure of mean sea level) from Kochi between 1971 and 2007, and used satellite imagery between 2002 and 2012 to see how the shoreline changed during this period.
These show that the sea level in the area is rising at 1.8 millimetres per year and that around 30 kilometres of the shoreline – more than 80% of Ernakulam’s coast – is eroding.
These shoreline changes also affected groundwater quality in wells from 27 sites ranging from South Vypeen on the coast to Muvattupuzha further inland. To infer signs of saltwater intrusion, they tested these samples for salinity (by measuring pH values, total dissolved solids, electrical conductivity, etc). While Chellanam’s wells showed high values of electrical conductivity and total dissolved solids (both signs of high salinity), other areas such as Edavanakkad and Pallipuram showed high alkalinity, which is also a sign of saltwater intrusion.
In Vypeen
“However, Vypeen is on the threshold,” said Dr. Sreekesh. “Here, as more wells extract groundwater, it will be replaced by saline water as seawater intrudes into the aquifer. Low-lying areas are particularly at risk.”
It would be wise to regulate further construction in such areas as well as restrict excessive extraction of groundwater if possible, added the scientist. Sea walls and groynes were not a proven solution for sea erosion in the region, he added.
“Saltwater incursion is indeed a grave issue,” said K.T. Damodaran, adjunct faculty at the Cochin University of Science and Technology, who has also written a book chapter on the issue recently. “This is a feature especially in areas near the coastal tract of the Periyar river where there is sand mining,” he added.
