Around 10.5 lakh cusec of water flowed into Hirakud dam due to unabated rains in Chhattisgarh, water level touched 628.5 ft as against the reservoir level of 630 ft, chief engineer of Hirakud reservoir S K Mishra said.
In view of the rising water-level, a total of 55 sluice gates and four crest gates have been opened to maintain a balance between inflow and outflow, he said, adding that about 9.8 lakh cusec of water was being released now.
There are 64 sluice gates and 34 crest gates at the Hirakud dam for discharge of excess water, officials said.
Following discharge of more water from Hirakud dam, about 13 lakh cusec of water was now flowing through Khairmal and it is likely to reach Munduli near Cuttack, water resources department secretary Suresh Mohapatra said.
A high alert has already been sounded in 11 districts while the government apprehends a severe flood threat in Mahanadi delta area comprising four districts of Cuttack, Kendrapara, Jagatsinghpur and Jajpur, sources said.
In addition, districts like Nayagarh, Puri, Sambalpur, Sonepur and Boudh would also be affected due to the flood in Mahanadi river system, they said, adding that people in low-lying areas were asked to move to safe places.
The government is ready to launch relief and rescue operation, while arrangements were being made for air-dropping food and other essential commodities.
Orissa Disaster Rapid Action Force (ODRAF) has also been kept ready for undertaking rescue and relief.
The intensity of the floods, which have already claimed two lives, would be known by tomorrow when the excess water discharged from Hirakud is likely to hit Munduli, Special Relief Commissioner P K Mohapatra said.
While flood waters of Mahanadi had already submerged vast areas in Sambalpur, Burla, Hirakud town, Boudh, Sonepur and other places in western Orissa, the coastal belt is under severe threat, a senior official said.
In 2008, 15.5 lakh cusec of water had flown through Mundali as the flood left a trail of destruction causing 500 breaches on river and canal embankments, a senior official in water resources department said.
This time also about 500 weak points have been identified on river banks and embankments, of which 28 are highly vulnerable to breach. Senior engineers and experts along with police force have been sent there to keep constant vigil, sources said.
District authorities of Sambalpur, Bolangir, Sonepur, Boudh, Nayagarh, Angul, Cuttack, Puri, Jagatsinghpur, Kendrapara and Khurda have been asked to be vigilant.
Instruction has been given to keep boats, dry food, kerosene, flash light, satellite phones, candles, matchboxes and other essentials ready.
Meanwhile, flood situation in Subarnarekha and Baitarani rivers improved with the water receding. Over 1.5 lakh people were affected as these rivers submerged 150 villages in Balasore, Kendrapara and Jajpur districts.
Community kitchens were opened at some of these affected areas for marooned people.