Patna: The water released from Bansagar dam in Madhya Pradesh travelled down the Sone river into the Ganga near the border of Patna and Bhojpur districts on Monday, resulting in the water level showing a rising trend and renewing the flood threat to the state capital.

The Ganga was flowing 18 cm above the danger level at Digha Ghat and 87 cm above the danger level at Gandhi Ghat in the state capital.

"As per our information, rains are continuing in various parts of Madhya Pradesh and it is currently releasing over 2.1 lakh cusec water from Bansagar into Sone river. As this excess water is draining into the Ganga, it will increase the water level in river," a senior water resources department (WRD) official told The Telegraph on Monday under cover of anonymnity.

One cusec or 'cubic feet per second' is around 28.32 litres of water per second.

"We are hoping that Madhya Pradesh doesn't face a situation in which it has to release higher volume of water from Bansagar dam because it will increase the possibility of flood along the Sone and the Ganga," the official added.

The Ganga is currently flowing above the danger level throughout its length in Bihar, including Patna, Samastipur, Bhagalpur and Katihar districts. It was 2.15 metres above the danger level at Sultanganj in Bhagalpur.

The Kosi is also flowing 65 cm above the danger level at Kursela in Katihar district. The river is expected to swell further as the discharge from the Birpur barrage has crossed 1 lakh cusec.

The flood threat is emerging in Kishanganj district as the Western Kankai river is flowing 31 centimetres above the danger mark at Kochadhaman. The district administration said it was a result of increased water discharge into the Mahananda from a barrage located near Siliguri in north Bengal.

If water discharge in various important rivers in Bihar was not enough, weather scientists are predicting the return of moderate to heavy rainfall as the axis of the monsoon trough line has oscillated towards the state.

"The axis of monsoon trough, which was running south of its position, has now oscillated towards north and across Bihar. Good rains are expected to make a comeback to the state in the next couple of days. This will continue, especially in north Bihar districts till September 13," said a scientist with the India Meteorological Department.

If the rain is moderate to heavy, it could increase the flood threat in Sitamarhi, Madhubani, Supaul, Araria, Kishanganj, East Champaran and West Champaran districts. If the rainfall is very heavy, chances of flash floods like in 2017 could emerge.

The Dheng river in Sitamarhi and the Budi Gandak in Khagaria districts were also flowing above the danger mark.