Districts with excess nitrates in groundwater at seven-year high

Environment

Districts with excess nitrates in groundwater at seven-year high

Excess nitrates are a health hazard, especially for young children; found in groundwater largely due to subsidised fertilizer use; the situation is worsening in central and southern India with highest levels in Rajasthan, Karnataka, T.N.

Updated - January 01, 2025 10:33 pm IST - NEW DELHI

Jacob KoshyJacob Koshy

440 districts with excessive nitrates in their groundwater as of 2023. File | Photo Credit: Getty Images

There are 440 districts with excessive nitrates in their groundwater as of 2023, an increase from 359 such districts in 2017, according to a report by the Central Groundwater Board (CGWB) on Wednesday (January 1, 2025). This is a health hazard, particularly for young children, and a source of environmental toxicity.

The data suggests that about 56% of India’s districts have excessive nitrates — defined as more than 45 mg per litre — in their groundwater, largely due to the use of subsidised, nitrogenous, synthetic fertilizer, a key input for farming.

Of the 15,239 groundwater samples collected from across the country for testing, 19.8% had nitrates or nitrogen compounds above safe limits, according to the report by the CGWB, which comes under the ambit of the Jal Shakti Ministry. This proportion has not shifted much since 2017. In the 13,028 samples analysed in 2017, 21.6% had excessive nitrates.

Concerns in south, central India

Rajasthan, Karnataka, and Tamil Nadu reported the maximum nitrate contamination problem, with 49%, 48%, and 37% of their tested samples respectively reporting numbers beyond the safe limit.

Rajasthan, Madhya Pradesh, and Gujarat have a long-standing nitrate problem with relative levels fairly constant since 2017, the report says. However, regions in central and southern India are reporting an increasing trend, provoking worry. “Maharashtra (35.74%), Telangana (27.48%), Andhra Pradesh (23.5%) and Madhya Pradesh (22.58%) also show notable levels of nitrate contamination, pointing towards growing concern in central and southern regions of India,” the report notes.

Monsoon rainfall tends to increase nitrate levels, with 30.77% of samples contaminated in the pre-monsoon period compared to 32.66% after the rainy season.

Uranium contamination

Other major chemical contaminants affecting groundwater quality are fluoride and uranium. Fluoride concentrations exceeding the permissible limit are “a major concern” in Rajasthan, Haryana, Karnataka, Andhra Pradesh, and Telangana. Rajasthan and Punjab reported the highest number of samples with uranium concentration exceeding 100 ppb (parts per billion).

Anything over 30 ppb of uranium is considered unsafe and several of these samples were predominant in regions of Rajasthan, Gujarat, Haryana, Punjab, Tamil Nadu, Andhra Pradesh, and Karnataka, where more groundwater is being over-exploited, with more water is being drawn out than is being replenished by rains or other means. “This overlap points to the exacerbating effect of overexploitation and deepening water levels on uranium contamination in these regions,” the report adds.

In an accompanying report on the availability of groundwater across India, the CGWB estimates that on the whole, the degree of groundwater extraction across the country is 60.4%, roughly the same as it has been since 2009, when measurements began biennially (and annually since 2022). About 73% of the blocks analysed for groundwater levels are in the ‘safe’ zone, meaning that they are replenished enough to compensate for the water drawn out. This is a sharp rise from the 67.4% in 2022. However, there were 343 fewer blocks analysed for the 2024 assessment, compared to 2022.