BHUBANESWAR: Even as Ganjam continues to reel under an unprecedented flood, an assessment by the Water Resources department has found that despite water storage being lowered in 10 dams across the region well ahead of Cyclone Arnab, the extreme rainfall event drove the flood.
The sheer intensity of rainfall topped all previous records – from precipitation in the river catchments to peak discharge volume.
First, the month of October received a staggering 401 mm rainfall, around 2.14 times more than normal rainfall of 187.9 mm. Around 70.8 pc of this was received in just two days on October 28 and 29 under the impact of the very severe cyclonic storm.
After India Meteorological Department (IMD) warned of severe cyclonic conditions and very heavy rainfall, steps were initiated for advance reservoir depletion and direction to this effect was issued by the principal secretary to the Water Resources department Subha Sarma on October 23.
Accordingly, the storage was lowered from 67.95 pc to 62.57 pc in Godhahado , 79.09 pc to 72.81 pc in Harbhangi, 84.67 pc to 81.09 pc in Bhanjanagar, 92.11 pc to 86.34 pc in Soroda, 65.43 pc to 63.15 pc in Badnalla, 69.56 pc to 66.70 pc in Baghua, 70.37 pc to 65.50 pc in Baghalati, 72.25 pc 66.51 pc in Daha, 88.98 pc to 85.76 pc in Dhanei and 45.46 pc to 41.15 pc in Ghatakeswar. Releases and gates were regulated as inflows rose.
However, on October 29, Patrapur recorded 546 mm rain, the fourth-highest 24-hour figure in Odisha, followed by 462 mm in G Udayagiri, 458 mm in Mahendragarh, 388 mm in Sanakhemundi, 375 mm in Sorada, 306 mm in Chikiti, 261 mm in Rangeilunda, 252 mm in Digapahandi and 209 mm in Kukudakhandi, Rout said.
The Eastern Ghats enhanced the rainfall making it more severe than Cyclone Titli. Engineer-in-chief of Water Resources department Dillip Kumar Rout said the Rushikulya basin recorded 338.74 mm rainfall under the impact of Cyclone Arnab, around 30 pc higher than the 260.4 mm rains that it had received during Cyclone Titli in 2018.
Following the intense spell of rain, the peak flows stood at approximately 4,197 cumec at Janivilli, 4,439 cumec at Aska and a staggering 6,908 cumec at Purushottampur on October 29. The flood discharge at Purushottampur was almost two times more than its actual carrying capacity of 3,500 cumec, officials said.
Compared to during cyclones Titli and Phailin, higher levels were observed at Sorada (82.34 m), Aska (36.87 m), Janivilli (55.73 m), Hiradharabati (26.59 m), Purushottampur (19.26 m), Kabisuryanagar (34.71 m) and Gokulapur (138.20 m), while Janivilli, Hiradharabati and Kabisuryanagar anicuts even exceeded their listed historical highest flood levels.
Under the impact, officials said about 90 metre of Janivilli weir was washed away, affecting water supply arrangements in Berhampur, while damage to Rushikulya irrigation under-tunnel drain has affected around 34,000 hectare irrigation area. Bahuda and Rushikulya canals that overtopped at multiple locations also resulted in substantial damage. The preliminary assessment pegs the total damage at more than `50 crore.
Principal secretary Sarma also made a two-day on-ground assessment and field functionaries of Ganjam and other potentially affected districts have been directed to ensure prudent reservoir management and close monitoring of the situation.
Officials said keeping the damage in view, the department has already taken a series of measures to address the emerging situation and minimise public inconvenience.
The department has assisted the Housing and Urban development department for expeditious restoration of the disrupted water supply system in Berhampur town. Simultaneously, repair and restoration work of the severely damaged Janivili anicut has been also been taken up on a war footing to restore the infrastructure at the earliest, the department informed.
