60% of Indo-Gangetic basin’s groundwater unfit for drinking, irrigation

An onsite research published in Nature Geoscience, has found contaminants like arsenic, nitrate, faecal pathogens and salinity in Indo-Gangetic basin’s (IGB) groundwater. Up to a depth of 200 meters, 60 per cent of water is highly saline or contaminated by arsenic, according to the study.

Arsenic concentration at toxic level makes water unsuitable for drinking. Long term exposure to arsenic through drinking contaminated water can cause cancer and skin problems, according to World Health Organization. It can also lead to developmental effects, cardiovascular disease and diabetes. On the other hand, as too much salt can damage the crop, water with high level of salinity is not fit for irrigation.

In the IGB, which includes river systems of Indus, Ganga and Brahmaputra, 37 per cent of groundwater has arsenic at toxic concentration. While high level of arsenic in groundwater was found in upper floodplain of southern Bengal basin, in Indus basin concentration levels are lower.

High levels of salinity too has been identified in 23 per cent of the IGB groundwater. It is highest in Indus basin and drier parts of Upper Ganges (Uttarakhand and Uttar Pradesh).

In terms of contributing factors, the report holds natural causes like salinity intrusion, excessive surface water evaporation etc worsened by man-made factors like long term impact of irrigation responsible for the contamination.

Apart from the quality of water, the study also looks into groundwater level in the IGB. In 30 per cent of highly populated areas of North India, the water table is getting depleted. The highest rate of groundwater depletion was recorded in Haryana, followed by Uttar Pradesh and Punjab. However, in areas which are not so heavily populated, the water table was found to be stable or even rising.