The water from the Dhakuria Lakes flooded the walking tracks and the romance benches on Wednesday afternoon. (Bishwarup Dutta)
The depression that brought enough showers in just three days to make this August the rainiest in a decade finally weakened and moved towards Jharkhand on Wednesday.
The skies began clearing in the afternoon as the moisture flow from the sea that sustained the depression stopped, prompting the weather department to signal the end of the incessant rain, which totalled 253mm in 72 hours since Sunday evening.
“The city may continue to get light rainfall here and there on Thursday but there will be no heavy showers,” said G.C. Debnath, director, India Meteorological Department, Calcutta.
The depression had hit the Bengal coast early on Monday and remained stationed north west of Calcutta, drawing moisture from the sea.
“The water vapour a depression draws results in the formation of clouds and heavy rain. But after substantial rain over a prolonged period, the system weakens,” said Ashish Sarkar, who teaches geography at Chandernagore Government College.
The current depression weakened on Wednesday and moved north-west towards Jharkhand, following the law of motion of the wind.
The city got over 30mm of rain in the morning, much less than the almost 100mm it had recorded on each of the previous two days. The advantage of reduced rainfall, however, was offset by a strong tide under whose impact the Hooghly and Kulti Gang rivers swelled so much that the city’s accumulated water could not flow into them.
“The tide would have been stronger had the depression not moved away,” said Debiprosad Duari, director (research and academics), MP Birla Planetarium.
The two rivers are the lifeline to the city’s drainage system — the Hooghly drains out water from the western parts of the city and the Kulti Gang from the eastern parts.
With both rivers in spate, various pockets like Behala and some off the Bypass, including Kasba, remained inundated on Wednesday.
Engineers said the water from these pockets would recede once the water levels in the Kulti Gang and the Hooghly fall, likely from Thursday. On Tuesday and Wednesday, the level of water in the Kulti was higher than that in the canals that drain water into it.
The canals merge into one that flows into the river. Officials said the lockgates at the outfall — 35km from the city, along Basanti Highway — could not be opened for most of Tuesday and Wednesday.
“The lock gates could be opened only in the evening when there was low tide, and the river’s water level was lower than that of the canal. During the day, the rainwater could not be drained out,” said an engineer.
On the other side of the city, the Hooghly almost overflowed. At Babughat, all the steps leading to the river were under water around 1.30pm. “The water level in the Hooghly on Wednesday was 4ft higher than what was recorded during the August 9 new moon. It shows the effect of the tide and the amount of rainfall over last two days,” said the engineer.
August 2013 has smashed records, taking just 21 days to clock 530mm of rain, way beyond the aggregate rainfall recorded in the entire month over the last 12 years.
The record-breaking spell was achieved over the past three days that brought 253mm of rain.
The average August rainfall in Calcutta is 352.4mm, based on a 30-year reading from 1971. As of now, August 2013 has a surplus rainfall of 110 per cent.
The closest competitor is August 2011, which recorded 471.1mm of rain.