Water woes: On the state of India’s groundwater
India needs to deal with rising levels of nitrate in groundwater
An annual assessment by the Central Ground Water Board (CGWB) on the state of groundwater, and its quality, has some worrying portents. First, the number of districts with excessive nitrate in their groundwater has risen from 359 in 2017 to 440 in 2023. This translates to a little more than half of India’s 779 districts having excessive nitrate, or more than 45 mg/L (milligram per litre). There are two major concerns with excess nitrate content: first, methemoglobinemia, or a reduced ability of red blood cells to carry oxygen. This sometimes causes ‘Blue Baby Syndrome,’ in infants. The bigger problem is environmental: once nitrates in groundwater rise to the surface and become part of lakes and ponds, algal blooms throttle the health of aquatic ecosystems. What the CGWB found, from analysing 15,239 groundwater samples across the country, was that close to 19.8% samples had nitrates — nitrogen compounds — above safe limits. However, this proportion has not shifted much since 2017, when 21.6% had excessive nitrate (13,028 samples).
Rajasthan, Karnataka and Tamil Nadu reported the largest extent of nitrate contamination, with 49%, 48% and 37% of the samples reporting numbers beyond the limit. Rajasthan, Madhya Pradesh and Gujarat have a perennial nitrate problem, primarily from geological factors, with relative levels fairly constant since 2017, the report says. However regions in central and southern India are reporting a rise, which is a reason for worry. Through the years, several studies have established the correlation between elevated nitrate levels and the practice of intensive agriculture. Other significant chemical contaminants affecting groundwater quality were fluoride and uranium. Fluoride concentrations exceeding the permissible limit were “a major concern” in Rajasthan, Haryana, Karnataka, Andhra Pradesh and Telangana. The report drew attention to the fact that States with over-exploited groundwater blocks — where extraction is more than replenishment — were more likely to have excessive chemical contaminants. Overall, the country’s degree of groundwater extraction is 60.4%, or roughly the same as it has been since 2009. 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. While it is a good sign that India now has a robust, scientific system of assessment to monitor the health of groundwater blocks annually, efforts are lacking in getting States to act on these findings. There needs to be more concerted awareness programmes led by the highest levels of leadership to contain the crisis.