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.
