The Central Ground Water Board’s (CGWB) annual report reveals for 2025 that Delhi’s groundwater is among the most contaminated in India, with high levels of uranium, lead, nitrate, and other toxic metals.

Key Findings from the Report

• Toxic Metals in Groundwater: Delhi’s groundwater exhibits some of India’s highest levels of uranium, lead, nitrate, and fluoride, as well as salinity-related indicators, with several contaminants exceeding national drinking water standards.
• Lead Contamination: Delhi has the highest proportion of lead-contaminated groundwater samples in India, with 9.3% of pre-monsoon samples exceeding the Bureau of Indian Standards (BIS) limits.
• Uranium Levels: Around 16% of groundwater samples nationwide exceeded the permissible fluoride limit.
• • Delhi ranks third nationally (after Punjab and Haryana) in uranium contamination, with 13–15% of samples exceeding permissible limits. 
  • Northwestern India, particularly Punjab, Haryana, Delhi, and parts of Rajasthan and Uttar Pradesh, emerged as hotspots for uranium contamination
• Fluoride: Nearly 18% of groundwater samples nationwide exceeded the permissible fluoride limit.
  • The fluoride contamination is largely geogenic, meaning it occurs naturally, with Rajasthan showing the highest levels of contamination.
• Nitrate: Nitrate contamination is the most widespread pollutant in India, with approximately 25% of groundwater samples exceeding the WHO and BIS limits of 45 mg/L.
  • The primary sources of nitrate contamination are anthropogenic activities such as the use of fertilizers, and the infiltration of sewage and animal waste into groundwater.
• Salinity: EC, which indicates total dissolved solids and salinity, remains a major concern in Delhi’s groundwater, with 33.33% of samples exceeding permissible limits in 2025.
• Sodium Adsorption Ratio (SAR): SAR levels, which determine irrigation suitability, are among the worst in India, with 34.8% of samples exceeding the permissible limit of 26.
  • Delhi topped the nation with 51.11% of samples exceeding the permissible RSC limit (2.5 meq/L), indicating severe alkalinity hazards affecting soil fertility and crop yield.

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