Central Groundwater Board releases the 2024 Annual Groundwater Quality report

The Central Groundwater Board released the 2024 Annual groundwater Quality report in December 2024. This report presents the findings from the nationwide groundwater quality monitoring exercise based on a standardized methodology, following the newly established Standard Operating Procedure (SOP) by the Central Ground Water Board (CGWB). Implemented across India in 2023, this uniform approach aims to establish a comprehensive baseline for groundwater quality, enabling targeted interventions to address emerging concerns.
 
Monitoring and Baseline Establishment: A total of 15,259 groundwater monitoring locations were selected nationwide to assess groundwater quality. These sites form the foundation for future evaluations, offering a clear baseline for ongoing monitoring efforts. To examine trends, 25% of the wells, identified as vulnerable to contamination based on BIS 10500 standards, were chosen for detailed analysis. Groundwater quality was sampled at 4,982 trend stations during pre-monsoon and post-monsoon periods to assess the impact of seasonal recharge on groundwater quality.
The objective of this report was to look into a wide spectrum of inorganic water quality parameters in groundwater used for drinking and agriculture purpose. These parameters consist of physico‐chemical parameters and trace elements.
 

Findings

Significant concerns have emerged from the analysis, particularly the high concentrations of nitrate, fluoride, arsenic, and iron in groundwater. Almost 20% of the samples exceeded the permissible limit for nitrate, while 9.04% of samples had fluoride levels above the limit. Arsenic contamination was found in 3.55% of samples.

Regional Variability and Seasonal Trends: Groundwater quality varies considerably across India. In certain states such as Arunachal Pradesh, Mizoram, Meghalaya and Jammu and Kashmir, 100% of the water samples met the BIS standards. In contrast, states like Rajasthan, Haryana, and Andhra Pradesh faced widespread contamination. Interestingly, the monsoon season showed some improvement in water quality, particularly in areas affected by high electrical conductivity (EC) and Fluoride. Post-monsoon, a modest reduction in EC levels and Fluoride was observed in some regions, indicating that monsoon recharge can temporarily improve water quality by diluting salts. However, certain districts such as Barmer and Jodhpur (Rajasthan) showed a rising trend in EC levels, signalling a deeper issue of groundwater salinization.

Hydrochemical Facies and Salinization: In terms of cation chemistry, calcium dominates the ion content, followed by sodium and potassium. For anions, bicarbonate is the most prevalent, followed by chloride and sulfate. This cation-anion distribution further highlights the role of bicarbonate in contributing to high alkalinity levels, which can exacerbate sodicity when coupled with high sodium concentrations. States like Rajasthan and Gujarat face high chloride concentrations due to the natural hydrochemical processes at play and Na-Cl type formations are prevalent. Over long periods, the aquifers have undergone repeated cycles of wetting and drying. During these cycles, highly soluble Na-Cl salts become concentrated in the aquifers. When groundwater levels drop, these salts become encrusted in the alluvium bed. Upon precipitation or recharge during the monsoon, these encrusted salts re-dissolve into the groundwater, enriching the chloride concentration and contributing to the increasing salinity levels.

Nitrate Contamination: States like Rajasthan, Tamil Nadu, and Maharashtra have some of the highest incidences of nitrate contamination, with over 40% of water samples exceeding the permissible limit. This is primarily linked to agricultural runoff and overuse of fertilizers.

Fluoride Contamination: Fluoride concentrations exceeding the permissible limit are a major concern in Rajasthan, Haryana, Karnataka, Andhra Pradesh and Telangana. Although the monsoon season led to some improvement in fluoride levels in these states, the overall contamination levels remain alarmingly high.

Arsenic contamination: Elevated arsenic levels (>10 ppb) were found in several states, particularly in the floodplains of the Ganga and Brahmaputra rivers. This includes regions of West Bengal, Jharkhand, Bihar, Uttar Pradesh, Assam, and Manipur, as well as areas in the Punjab, and Rajnandgaon district in Chhattisgarh.

Uranium Contamination: A notable concern in the groundwater quality report is the elevated levels of uranium in several regions. 42% of samples with uranium concentrations exceeding 100 ppb came from Rajasthan, and 30% from Punjab, indicating regional hotspots of uranium contamination. Moreover, groundwater samples with uranium concentrations greater than 30 ppb were clustered in areas identified as over-exploited, critical, and semi-critical groundwater stress zones, such as Rajasthan, Gujarat, Haryana, Punjab, Tamil Nadu, Andhra Pradesh, and Karnataka. This overlap points to the exacerbating effect of over-exploitation and deepening water levels on uranium contamination in these regions.