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WRD, Danish team to launch second phase of project to map groundwater and reverse seawater intrusion in Minjur
Minjur, a locality in the city's northern fringes that has long battled seawater intrusion into its groundwater aquifers, will soon be the focus of an intensive study aimed at assessing the extent of exploitation and exploring strategies for its reversal.
With the findings of a pilot study on groundwater mapping in Minjur validated, the Water Resources Department would expand the study along with Danish team in the Minjur belt. The phase II of the project will map the groundwater aquifer and arrest seawater incursion in the locality through Managed Aquifer Recharge (MAR).
Officials of the WRD noted that the seawater has moved inland for about 15 km and the water quality has turned saline with a total dissolved solids level exceeding 10,000 ppm in several places.
In a first step towards implementing the second phase of the project, the team from Geological Survey of Denmark and Greenland, WRD's State Ground and Surface Water Resources Data Centre and water resources experts discussed the aspects of MAR technology during a recent meeting.
For many years now, Minjur residents rely on municipal and private water supply for all their needs as salinity ingress has affected coastal aquifer. 'Water drawn from wells in areas close to Kosasthalaiyar riverbank is yellow in colour. Groundwater is availabe at a depth of 40 feet but it has high iron content. Each family spends a minimum of Rs.2,000 on water every month,' said of Minjur.
Noting that water quality has improved in sites along water bodies, residents wanted groundwater recharge projects to be executed on a large scale.
Officials of the WRD said a network of 145 borewells would be sunk across 63 villages at various depths and distance to study the salinised acquifer. Every five km would have piezometers with various instruments like digital water level recorders and water quality sensors. The study would be carried out using s-Tem profiler, a geoscanner tool designed to acquire subsurface data and ideal for mapping groundwater aquifers.
'We are planning to concentrate more on the 15th km with three borewells sunk in each chosen site at various depths to assess the groundwater level and quality. This stretch would have 71 borewells sunk for the study,' said an official.
Some of the villages to be covered include Amoor, Thachoor, Panjetty, Alamathi and old Gummidipoondi. The Rs.10 crore would help identify potential recharge zones to restore the freshwater balance by pushing salinity back towards the coast in five years.
A combination of recharge structures, including recharge shafts, would be established through MAR and identify potential for extraction and recharge, said the official. The project would be scaled up to other over-exploited groundwater zones like Cuddalore and Thoothukudi.
Visiting Faculty, Hydraulics and Water Resources Engineering Group, Department of Civil Engineering, IIT Madras, who was part of the discussion, said Minjur belt is covered by data collection network of various government agencies and the new initiative would help enhance the ongoing efforts.
Several recharge structures like check dams have indicated potential for harnessing groundwater. Citing his study on seawater intrusion in a coastal aquifer, he said largescale measures like interlinking of Araniar and Kosasthalaiyar rivers with a canal to transfer floodwaters and reviving water bodies are essential. Various measures, including interlinking of rivers, would help decrease the extent of seawater incursion by three km in 2030.
