Insufficient rainfall and a prolonged spell of dry weather have taken a toll on the groundwater resources in and around the city.
The water table is now at an average of four metres below the ground. This is a metre less than the level recorded at this time last year, according to data of State Ground and Surface Water Resources Data Centre, a wing of Water Resources Department.
Residents of several areas, particularly the suburbs, who are dependent on groundwater, are already feeling the heat as the water level in their open wells has come down by a few feet. Prema Sriraman, a resident of Villivakkam, said the kind of decline in water levels seen now usually occurred in peak summer.
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The water is also turning saline in many areas.
The declining water level has only increased the burden on residents who are already staring at a water crisis as water levels in major reservoirs supplying drinking water to the city has come down.
Hydrogeologists in the WRD said that the localities in the southern parts of the city are worst affected as groundwater resources are over-exploited. Besides burgeoning population, indiscriminate extraction of groundwater by private water suppliers has also led to the fall in the water table.
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The total dissolved solids in water ranges between 500 parts per million to 1,200 ppm across the city according to the soil condition.
The Adyar creek is one area where the TDS level is as high as 3,000 ppm due to tidal action.
The permissible limit for drinking water is 500 ppm.
A succession of years with good monsoons helped sustain the groundwater table despite growing demand and over-extraction.
Seawater incursion, though, is still at manageable levels, said officials. Seawater has however intruded up to few hundred metres in areas close to the coast such as Besant Nagar and Thiruvalluvar Nagar, Thiruvanmiyur. In northern areas such as Minjur, seawater intrusion is observed upto 13 km from the coast.
Water experts said that the lack of enforcement of both Tamil Nadu Groundwater (Development and Management) Act, 2003 and norms on sinking and depth of borewells has affected the deep aquifers, which take longer time to recharge.
There is an urgent need to save the vanishing water bodies from encroachments and pollution and increase their storage capacity to recharge groundwater. Coastal Regulation Zone norms must be strictly enforced to regulate activities in coastal areas and prevent seawater intrusion, they said.