The Yamuna in Delhi swelled to 207.55 metres on Wednesday, breaching its all-time record of 207.49 metres set in 1978, government agencies said on Wednesday.
According to the Central Water Commission's (CWC) flood-monitoring portal, the water level at the Old Railway Bridge crossed the 207-metre mark at 4 am, the first time since 2013, and rose to 207.55 metres by 1 pm.
The river is likely to rise further, an official of the irrigation and flood control department said.
As a precautionary measure, the Delhi Police imposed section 144 CrPC in flood-prone areas of the national capital on Wednesday, officials said.
Section 144 CrPC prevents the unlawful assembly of four or more persons and public movement in groups.
Delhi recorded a rapid increase in the Yamuna water level over the last three days.
It shot up from 203.14 metres at 11 am on Sunday to 205.4 at 5 pm on Monday, breaching the danger mark of 205.33 metres 18 hours earlier than expected.
The river had exceeded the evacuation mark of 206 metres on Monday night, prompting the relocation of people residing in flood-prone areas to safer locations and a closure of the Old Railway Bridge for road and rail traffic.
Delhi water minister Saurabh Bharadwaj told the media that the city government was prepared to deal with the situation. "We are monitoring the situation and all possible steps are being taken," he said.
Embankments are being constructed in the low-lying areas to prevent the entry of floodwater into other parts of the capital in case the Yamuna water level rises further.
Major floods in Delhi occurred in 1924, 1977, 1978, 1995, 2010, and 2013. Analysis of flood data from 1963 to 2010 indicate an increasing trend for floods occurring in September, and a decreasing trend in July, according to research.
Bhim Singh Rawat, associate coordinator, South Asia Network on Dams, Rivers, People (SANDRP), attributed the unprecedented rise in the Yamuna water level in Delhi to riverbed elevation due to significant silt accumulation.
"Lack of dredging, more than 20 bridges and three barrages within the 22-km river stretch from Wazirabad to Okhla obstruct the flow, leading to deposition of silt in the riverbed and formation of a lot of mid-stream sandbars," he told PTI.
Locations of these sandbars include beneath the Signature Bridge, between the ITO barrage and Yamunabank, between ISBT Kashmiri Gate and ORB, and between ORB and Geeta Colony Bridge.
Rawat said that in 1978, the river reached a height of 207.49 metres in September after becoming saturated in the monsoon season and it coincided with a flow rate exceeding 7 lakh cusecs from the Tajewala Barrage.
The maximum flow rate this time was 3.59 lakh cusec on Tuesday. An official explained that the sharp rise in water level was due to continuous rainfall in the upper catchment areas and saturated soil from heavy precipitation in Delhi and nearby regions over the weekend.
People living in low-lying areas have been shifted to safer places at higher altitudes, the department said.
It said 45 boats have been deployed for awareness, evacuation and rescue work and NGOs have been roped in to provide relief to the evacuated people.