Salem, Thanjavur worst-hit by groundwater exploitation in TN, finds Central survey

CHENNAI: Taluks in Salem have topped the list of most affected by high levels of groundwater extraction, according to the Central Ground Water Board's (CGWB) 2025-26 assessment. The report noted that 56 of 111 taluks across 13 districts in Tamil Nadu have exceeded sustainable extraction limits. Another 11 taluks have been classified as critical, indicating that extraction is nearing the assessed annual groundwater availability.

Salem has 13 of its 14 taluks in the overexploited category, while six of the nine taluks in Thanjavur, a key Cauvery delta district, have crossed the threshold. The findings highlight mounting pressure on groundwater resources used for agriculture, domestic consumption and other needs.

CGWB classifies an area as overexploited when annual groundwater extraction exceeds 100 per cent of the assessed annual resource available for extraction. Areas where extraction is above 90 per cent fall under the critical category.

In Salem, Thalaivasal recorded the highest extraction at 228.6 per cent, followed by Gangavalli at 192.5 per cent, Salem West at 172.3 per cent and Attur at 167.3 per cent.

Mettur, a key location along the Cauvery's course, was also classified as overexploited, with extraction at 119 per cent. Hill station Yercaud was the only taluk in the district not listed in the overexploited category.

The figures indicate that extraction in several taluks has substantially exceeded the assessed annual availability, raising concerns over the long-term sustainability of groundwater supplies and the vulnerability of local water sources to fluctuations in rainfall and recharge.

In Thanjavur, Tiruvidaimarudhur recorded groundwater extraction of 124.8 per cent, followed by Tiruvaiyaru at 110.9 per cent, Kumbakonam at 109.6 per cent and Orathanadu at 108.2 per cent. Papanasam and Pattukkottai were marginally above the threshold at 100.7 per cent and 100.1 per cent, respectively. Thanjavur taluk was classified as critical, with extraction at 92.3 per cent. This classification for an agrarian district is quite significant.

However, the assessment does not establish the extent of groundwater decline in individual wells or identify the specific causes of overexploitation in each taluk.

PR Pandian, general secretary of the Tamizhaga Cauvery Vivasayigal Sangam, told DT Next that around 13 lakh acres of agricultural land in Thanjavur, Nagapattinam, Mayiladuthurai and Tiruvarur districts depended on the Cauvery, while only around 2.5 lakh acres relied on groundwater.

Cauvery was the primary source of groundwater recharge in the delta, which lacked large lakes capable of supporting recharge on a substantial scale, he said. With a deficit in the southwest monsoon and inadequate Cauvery water releases this year, prospects for Samba cultivation had become uncertain, he added.

Pandian also expressed concern over hydrocarbon exploration by the Oil and Natural Gas Corporation (ONGC), which involves drilling to depths of around 10,000 feet in the delta. He alleged that such activities could contribute to concerns over seawater intrusion into groundwater in Nagapattinam district.

He urged the government to implement the Nadanthai Vaazhi Cauvery project to protect the Delta's agricultural resources and improve water management.

Sundaresh Prasanna Chandran, climate activist and founder of Neer Vazhvu (neervazhvu.org), said Salem's groundwater stress underscored the need to improve access to surface water for irrigation.

Although the Mettur dam is located in Salem district, farmers in several parts of the district do not directly benefit from its water and remain heavily dependent on groundwater, he said, adding that this dependence was among the factors contributing to the high number of overexploited taluks in the district.

Chandran called for immediate measures, including the construction of a new canal to supply water to farmers in Salem. He also urged the government to promote water-efficient agricultural practices, including drip irrigation and the cultivation of crops requiring less water.

With the possibility of a strong El Niño event raising concerns over rainfall patterns and the risk of a dry summer in 2027, the government should act in advance to protect groundwater resources and prevent further depletion, he said.

The assessment underscores the need for district-specific water management measures, including improved groundwater recharge, tighter monitoring of extraction and greater access to sustainable irrigation sources to protect agriculture and long-term water security in Tamil Nadu.