Water flow in the Ganges is declining: Study

The water flow in the two trans-border rivers the Indus and the Ganga, which feed agriculture ecosystem in India, Pakistan and Bangladesh, are moving in opposite hydrological directions, says a study by Indian scientists and published in peer-reviewed Earth's Future, a publication of the American Geophysical Union.

The study cites data from 1980 to 2021 and found that over the past four decades, the Indus Basin water flow has increased by 8%, while water flow in the Ganga Basin has declined by 17%.

According to the study, western disturbances and changing monsoon patterns are the primary causes of the rapid increase in water levels in the Indus River system and its western tributaries, such as the Jhelum and Chenab.

While the flow in the Indus has been going up due to increased rainfall, the opposite is noticed in the Ganges, said the study.

The peer-reviewed research, using high-resolution physical models, concluded that decreased rainfall is not the only reason for decreasing water flow in the Ganga river basin.

While rainfall in the Gangetic region has decreased by about 10%, the major cause of the decline is the indiscriminate exploitation of groundwater for irrigation, according to the study.

Several parts of the Ganga basin, an estimated 50% to 70% of the river flow is generated by groundwater recharging and water reaching the rivers. This declines when excessive groundwater is pumped out primarily due to drought, the study said, noting that the situation is critical in parts of upper Ganga where the river water itself is getting absorbed into the dried up underground aquifers.

The drying up of the Ganga is considered the fastest decline in the last 1,300 years, which could impact the lives of millions of people, the research warns.

Declining rainfall, including during monsoon, is cited as the main reason for groundwater pumping, further reducing rechargeable water in the Ganga basin, said the study.