The level of dissolved oxygen in the River Ganga in Varanasi has dipped in the last two years and the river's width has also shrunk considerably in 25 years, a study by the Indian Institute of Technology-Banaras Hindu University (IIT-BHU) has said.
The study, by a team of scientists led by the head of the department of chemical engineering at the IIT-BHU PK Mishra, says the oxygen level in the water of the river once famed for its high purifying quality, has fallen to 4 mg per litre from 6 mg per litre.
"We collected samples of Ganga water from certain stretches in the last two years to examine the oxygen level in the water. Tests revealed depleted dissolved oxygen (DO) level in the Gangajal stood at 5 mg/pre liter around nine months ago," Mishra said.
A dissolved oxygen level of 8 mg per litre in a river is considered healthy, he added.
"Examination of the samples collected around two months ago revealed that DO level in certain stretches of the river dropped to 4 mg per litre which is alarming. It clearly shows that the river struggles to maintain its oxygen level," Mishra said.
"Over-exploitation of the Ganga, discharge of sewage and industrial effluents have caused a serious threat to the health of the river. All three factors are an open secret. However, serious steps to check the flow of industrial wastewater and sewage into the river are yet to take shape," he added.
He said that a complete ban is needed to check the flow of industrial wastewater and drain water into the Ganga.
"It is already too late. Everyone needs to come forward to save the river."
Mishra recently drew a blueprint for saving the Ganga and also informed the Union ministry of water resources, river development and Ganga rejuvenation about it.
Ramji Agarwal, professor emeritus at IIT-BHU and the chief coordinator of the First Ganga Action Plan, also raised the issue of the shrinking width and decreasing depth of the river due to siltation caused by sewage flowing into the river from big drains in the city.
"The Ganga's width in Varanasi was around 360 metres in 1990. In 2015, the width decreased to 270 metres. Besides, the depth is decreasing by 10 to 15 centimetre annually due to siltation. This is a very serious issue. The government needs to take a call on this matter immediately," he said.
Agarwal said the situation could change only if joint efforts are made. He hoped the authorities would take a call on it and the local people would cooperate with them in saving the river.