Groundwater Contamination in India: Nitrate and Chemical Pollutants
12-01-2025
06:30 AM
1 min read

What’s in today’s article?
- Why in News?
- Central Ground Water Board (CGWB)
- Excessive Nitrate in Groundwater: A Growing Concern
- Regional Analysis of Nitrate Contamination in Groundwater
- Other Major Chemical Contaminants in Groundwater
- State of Groundwater in 2024

Why in News?
- An assessment of India’s groundwater by the Central Ground Water Board (CGWB) found that several States are grappling with a serious problem of nitrate contamination.
Central Ground Water Board (CGWB)
- About
- The Central Groundwater Board (CGWB) is a key organization under India's Ministry of Jal Shakti, responsible for monitoring, managing, and regulating groundwater resources.
- It maintains a vast network of observation wells to assess groundwater quality and availability.
- It also provides technical guidance, promotes sustainable practices, and formulates policies to address groundwater-related challenges across the country.
- Head quarter - Bhujal Bhawan, Faridabad, Haryana
- Organization Setup: The Board is headed by the Chairman and has five members.
- Measurement of Groundwater Levels: Observation Network
- Current Network: The Central Ground Water Board (CGWB) uses 26,000 observation wells to manually measure groundwater levels.
- Digital Integration: Since 2023, 16,000-17,000 piezometers equipped with digital water level recorders transmit real-time data to a central system.
Excessive Nitrate in Groundwater: A Growing Concern
- Increase in Nitrate-Contaminated Districts
- The number of districts with excessive nitrate in groundwater increased from 359 in 2017 to 440 in 2023, impacting nearly 56% of India’s districts.
- Excessive nitrate levels are defined as concentrations above 45 mg/l.
- Groundwater Testing and Trends
- 2017 Findings: 13,028 samples were analyzed, with 21.6% showing excessive nitrate levels.
- 2023 Findings: Of 15,239 samples tested, 19.8% had nitrate levels above safe limits.
- While the percentage of affected samples has not substantially changed, the number of contaminated districts has risen.
- Health Concerns
- Excessive nitrate in groundwater causes methemoglobinemia, reducing the ability of red blood cells to carry oxygen, particularly affecting infants and vulnerable populations.
- Environmental Impact
- Elevated nitrate levels in groundwater can lead to algal blooms in lakes and ponds, severely degrading aquatic ecosystems by depleting oxygen and harming biodiversity.
- Sources of Nitrate Contamination
- Agricultural Practices: Farmers use fertilizers such as ammonium nitrate, calcium nitrate, urea, and diammonium hydrogen phosphate, leading to nitrogen leaching into groundwater.
- Forms of Dissolved Nitrogen in Groundwater:
- Nitrate (NO3-)
- Ammonium (NH4+)
- Ammonia (NH3)
- Nitrite (NO2-)
- Nitrogen gas (N2)
- Nitrous oxide (N2O)
- Organic nitrogen
Regional Analysis of Nitrate Contamination in Groundwater
- States with the Highest Proportion of Contaminated Blocks
- Rajasthan: 49% of tested samples exceeded permissible nitrate levels.
- Karnataka: 48% of tested samples were contaminated.
- Tamil Nadu: 37% of tested samples showed excessive nitrate levels.
- States with Persistent Nitrate Issues
- Rajasthan, Madhya Pradesh, and Gujarat: These states have had a long-standing nitrate problem with contamination levels remaining relatively constant since 2017.
- Emerging Nitrate Concerns in Central and Southern India
- Increasing nitrate contamination has been observed in blocks in central and southern India, raising alarm.
- States with notable levels of contamination:
- Maharashtra: 35.74%
- Telangana: 27.48%
- Andhra Pradesh: 23.5%
- Madhya Pradesh: 22.58%
Other Major Chemical Contaminants in Groundwater
- Key Contaminants
- Arsenic, Iron, Fluoride, and Uranium: These chemicals significantly affect groundwater quality alongside nitrate contamination.
- Fluoride Contamination: 9.04% of tested groundwater samples had fluoride levels exceeding the permissible limit.
- High-Risk States: Rajasthan, Haryana, Karnataka, Andhra Pradesh, and Telangana reported high fluoride concentrations, making it a “major concern.”
- Uranium Contamination: Several samples had uranium concentrations exceeding 100 ppb (parts per billion), far above the safe limit of 30 ppb.
- High-Risk States: Rajasthan and Punjab reported the maximum number of contaminated samples. Other affected states include Gujarat, Haryana, Tamil Nadu, Andhra Pradesh, and Karnataka.
- Cause
- Predominantly observed in regions with over-exploited groundwater (where water withdrawal exceeds replenishment).
State of Groundwater in 2024
- Groundwater Extraction: The country’s groundwater extraction rate stands at 60.4%, consistent since 2009.
- Safe Zones: Approximately 73% of blocks are classified as ‘safe,’ indicating sufficient replenishment to balance water withdrawal.
Q.1. What are the main contaminants in India’s groundwater?
Nitrate, fluoride, arsenic, iron, and uranium are the primary contaminants affecting groundwater. Excessive nitrate levels, particularly in Rajasthan, Karnataka, and Tamil Nadu, lead to health issues and environmental damage.
Q.2. How is groundwater quality monitored in India?
The Central Groundwater Board (CGWB) monitors groundwater quality using a network of 26,000 observation wells and digital piezometers, providing real-time data on contamination and availability.