Dark zone areas in Tamil Nadu
10 of 38 districts in Tamil Nadu pumped out more groundwater than was recharged in 2025 (over-exploited, the "dark zone"). 2 more were critical and 11 semi-critical. Across the state, 74% of the extractable groundwater was used.
Over-exploited districts (10)
Stage of extraction above 100% in 2025.
Critical districts (2)
Stage of extraction 90–100% in 2025.
Semi-critical districts (11)
Stage of extraction 70–90% in 2025.
What a dark zone means for you
Borewells go deeper every few years and some run dry in summer. New groundwater use for business needs a CGWA NOC with recharge conditions. The fix is to put rain back: at 700 mm of rain a year, a 100 m² house roof recharges about 60,000 litres.
Frequently asked questions
Which areas of Tamil Nadu are in the dark zone?
In CGWB's 2025 assessment, 10 of 38 districts in Tamil Nadu were over-exploited (dark zone): Salem, Tirupathur, Vellore, Chennai, Dindigul, Mayiladuthurai, Namakkal, Perambalur, Karur, Thanjavur.
Is Tamil Nadu's groundwater over-exploited overall?
The state pumped out 74% of its extractable groundwater in 2025, which CGWB classes as semi-critical.
Can I get a new borewell in a dark zone of Tamil Nadu?
Homes usually can, with local registration; some cities restrict new borewells. Industry, infrastructure, mining and commercial users need a Central Ground Water Authority NOC, which in over-exploited areas carries tighter limits and recharge conditions.
Source: CGWB Dynamic Ground Water Resource Assessment 2025, district figures. CGWB classifies blocks (assessment units); a district's figure is the average of its blocks, so a district shown here as safe can still contain over-exploited blocks.