If a flood’s approaching, you may get to know two weeks ahead. Beats a 24-hour notice. | Mint MeidaInsights

With extreme climate events such as flash floods causing large-scale devastation in the country, the Union government is working on a plan to advance the warning mechanism to minimise the loss of life and property.

The water resources department plans to leverage its technical arm, the Central Water Commission (CWC), to issue warnings up to a fortnight in advance of likely floods instead of the current practise of a 24-hour notice, two officials said.

India suffered losses totalling $56 billion on account of weather-related disasters between 2019 and 2023, accounting for a fourth of the $230 billion hit to Asia Pacific countries, according to data from the Center for Research on the Epidemiology of Disasters.

Also, India is the worst flood-affected country in the world, after Bangladesh, and accounts for one-fifth of global death count due to floods, according to the National Flood Commission.

One reason is that nearly 75% of the total Indian rainfall is concentrated during the southwest monsoon months of June to September, forcing a heavy discharge from rivers and causing widespread floods.

This is where the water resources department’s plans would come into play. It proposes using the CWC’s 1,500 surface water monitoring observatory systems and the India Meteorological Department’s 5,000-6,000 rain gauges to track the flow and levels of rivers and streams for more advanced flood warnings rather than only depending on rain forecasts.

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“Currently, we issue flood advisories 24 hours prior. Now the plan is to extend it to 7-15 days in advance,” one of the officials said. “If you are issuing an advisory 24 hours in advance, there is not much time available for the administration to work on. But if it is issued seven days in advance, they can better prepare and can save lives.”

Initially, the advisories will be issued 3-7 days ahead of a likely flood, and gradually increased to up to 15 days, the official said.

The spokesperson and the secretary of the department of water resources and the chairman of the CWC did not reply to Mint’s queries emailed on Thursday.

A new playbook for flood warning

The development of flood forecasting and warning systems is an essential element in regional and national flood preparedness strategies in many countries.

This typically combines a risk assessment in terms of the probability of floods occuring and a vulnerability assessment in terms of the damage that those floods could cause and, therefore, the economic savings to be gained by their reduction, according to a report by the Assam State Disaster Management Authority.

In India, about 40 million hectares of land are liable to floods, and an average of 18.6 million hectares are affected annually, according to the National Flood Commission.

“Flood prediction means understanding which areas could get submerged, which is different from how much the rainfall would be, because there is no correlation between rainfall and flood prediction,” said the second official mentioned above.

“Let’s say there’s rainfall in Maharashtra and the river in the state passes through Karnataka. Because of heavy rain in Maharashtra there could be a higher flow in Karnataka even if there is no rain, no cloud in Karnataka. These are the things that normally create many flooding problems… IMD can’t predict it because it provides forecast area-wise,” the official explained.

Another approach involves assessing a river’s water-carrying capacity and when its waters will likely cross its embankments.

“You must understand (a river’s) natural course of water flow… Suppose there is rain in Haryana towards Yamuna side, there may be possibility of an increased flow in the Yamuna river. (But) how much rainfall is there and how much increase would be there in the flow is difficult to predict as of now,” the second official added.

“We will be closely monitoring streams and rivers and issue advisory to states… The Union water resources department will communicate the information with technical details like water flow, the level, the quantity of flow from CWC.”

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Although the IMD will not be involved directly, the Jal Shakti, or water resources, ministry will keep track of its rainfall forecasts.

“Both Union and state governments have a huge number of observatories, including for surface water flow. Through those observatories we keep getting information about river flow and depending on the increase or decrease in the flow, we will predict flood situations,” the first official said.

A key tool for a longer view

A key tool in the advance flood alerts will be the CWC’s extended hydrological prediction, or EHP, forecasting system to predict monthly or seasonal stream or river flow patterns over a longer period of time.

Currently, the CWC’s EHP project covers three major basins of India—Yamuna in the north, Cauvery in the south, and Narmada in the west. The forecasts are produced at four key locations in each basin using a four-week horizon.

Forecasting such river or stream flow over a multi-week horizon offers a range of benefits to improve water resources planning for flood mitigation, including reservoir pre-positioning, drought planning for shortage allocation, and power maximisation.

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