Patna, Aug. 31: The Ganga should not be blamed for posing the threat of floods to Patna.

Based on scientific observations, hydrologists and water experts say that overflowing of the river water in central and north Bihar is due to excessive siltation in the riverbed caused by man-made factors such as construction of dams in the upstream.

In simple terms, more and more accumulation of sand because of the weak flow of water has raised the level of the riverbed. Thus, even a marginal increase in the flow of water, as observed over the past few weeks, is leading to overflowing of the river.

The level of water at the two ghats in Patna — Digha and Gandhi Ghat — remained constant over the past 24 hours. But it is expected to witness a rising trend over the next 24 hours. (See graphic)

R.C. Sinha, chairman of the state-level Environment Impact Assessment Authority, who has done several researches on the Ganga, claimed that the capacity of the river to hold water has become very weak along Patna.

“The flow of the Ganga from the upstream has become low owing to various man-made obstructions in its way, including numerous dams in Uttarakhand and hydro-power plants at Haridwar. As the river enters Bihar through Buxar, its flow is observed to be extremely weak till Ara, located west of Patna. The poor flow has led to heavy siltation in the riverbed along Patna. The excessive siltation in turn, has reduced the capacity of the Ganga to hold water. Thus, the river overflows even with a marginal rise in the flow of water from the upstream as is being observed these days,” said Sinha.

Experts from the Centre for Flood Management Studies at the National Institute of Hydrology (NIH)-Patna corroborated the claims of flooding in the river due to excessive siltation. “Though we have not yet prepared any supporting data as such but siltation coming from the upstream in Ganga and also from its tributaries is one of the major factors behind the floods in Bihar. In fact, it is due to the heavy siltation that the main flow of the Ganga is now almost restricted till Allahabad only. The flow thereafter is mostly contributed by its tributaries — Ghagra, Sone and Gandak — and remains very low. However, even this low flowing water gets displaced from its original course as soon as it hits the heavy silt in the riverbed, flooding the areas near the river bank,” said Biswajit Chakravorty, head, NIH-Patna.

The problem of heavy siltation along Patna has also been supported by those who operate vessels in the river. “It is becoming increasingly difficult for us to operate the floating restaurant — MV Ganga Vihar — because of heavy siltation in the Ganga along Patna. There have been countless occasions when our vessel got stuck somewhere mid-way due to excessive silt in the river,” said Naveen Kumar, deputy general manager, Bihar State Tourism Development Corporation.

The heavy siltation along Patna has also turned out to be a bane for Inland Waterways Authority of India that carries out dredging in the river. Gurmukh Singh, director, IWAI-Patna, told The Telegraph on Saturday: “The Ganga is joined by three of its tributaries — Ghagra, Sone and Gandak — along Patna and the silt deposited by them is much more as compared to that coming from the upstream of the river. IWAI carries out dredging in the main channels of the river after conducting a hydrographic survey. In case of Patna, we have to conduct a survey every year after the floods due to heavy discharge of silt. Whatever has been done in the previous years has become zero now because of fresh discharge of voluminous silt in the river along the city.”