Context:

Recently, the Union Ministry of Jal Shakti released the Annual Ground Water Quality Report 2024.

About the Report:

• This report was carried out by the Central Ground Water Board (CGWB).
• The report follows the newly introduced Standard Operating Procedure (SOP) established by the CGWB. 
• This report provides a dataset derived from over 15,200 monitoring locations and focused assessments at 4,982 trend stations.
• The objective of this report is to look into a wide spectrum of inorganic water quality parameters in groundwater used for drinking and agriculture purposes. 

Key highlights of the report

The overall water in the country is of calcium-bicarbonate type.

100 per cent of groundwater samples in Northeastern states are in an excellent category for irrigation.

High nitrate levels have been found in the groundwater of 440 districts across India 9.04 per cent of samples had fluoride levels above the safe limit.

• 20 per cent of water samples exceeded the nitrate limit of 45 milligrams per litre (mg/l) (Standard set by the World Health Organisation WHO & Bureau of Indian Standards (BIS) for drinking water)
• High levels of nitrate in the body can cause methemoglobinemia, also known as blue baby syndrome.

As per the report 3.55 per cent of the sample showed arsenic contamination, particularly in the floodplains of the Ganga and Brahmaputra rivers.

• As per the World Health Organisation (WHO) Long-term exposure to arsenic from drinking water and food can cause cancer and skin lesions.

Fluoride concentrations exceeding the permissible limit in Rajasthan, Haryana, Karnataka, Andhra Pradesh, and Telangana.

• Excess fluoride in drinking water leads to Fluorosis, arthritis, bone damage etc.

The report highlights that 42% of samples with uranium concentrations exceeding 100 parts per billion (ppb) came alone from Rajasthan, and 30% from Punjab.

This report evaluates Sodium Adsorption Ratio (SAR) and Residual Sodium Carbonate (RSC) values

• SAR is the ratio of the concentration of sodium (Na⁺) to the concentrations of calcium (Ca²⁺) and magnesium (Mg²⁺) in water.
• SAR in Andhra Pradesh, Gujarat, Haryana, Punjab, Rajasthan and Uttar Pradesh fall in the Very high sodium range and are unsuitable for use in irrigation practices.
• RSC is a measure of the excess amount of carbonate ions in water, which can combine with calcium and magnesium in the soil, leading to soil sodicity (high levels of sodium). 
• 10.43% of samples were found to have RSC values greater than 2.5, making them unsuitable for irrigation due to the risk of sodicity and soil degradation.