Knowledge gap dries up rainfall data

By July 17, monsoon had covered the entire country. But the rainfall has been highly uneven. While some areas have received normal or excess rainfall, many others are deficient, says the Indian Meteorological Department (IMD).

But how dependable are the rainfall data dished out by IMD on a daily basis? Do the weathermen have access to information from the nooks and corners of the country?

The question is important. Excess rainfall in catchment areas may call for dynamic alteration in strategies on agriculture production and disaster management in rain-deficient downstream areas.

And, the only way to track this data is to have a dense network of automatic weather stations (AWS).

The World Meteorological Organisation (WMO) prescribes one such station for every 100 sq km for effective monitoring of weather. But, check the IMD website and you will be surprised to note that they have a fraction of the requisite network.

For example, 12 eastern and north-eastern States, having more than one-third of the country’s population, have about 200 weather stations. According to Angshujyoti Das, CEO of ExpressWeather, a Kolkata-based private weather forecasting agency, this is just 3 per cent of the prescribed network of 6,800 observatories.

“The paucity of weather stations may lead to serious knowledge gaps on actual rainfall data,” said Das. The implications are huge.

Corporates may draw up a flawed strategy, say for Odisha, which reportedly received 31 per cent less rainfall till July 16. Or, there may be flash floods in the rain deficient Mizoram (-50 per cent) and Manipur (-67 per cent).

D Pradhan, Deputy Director General (Eastern Region) of IMD, admits to paucity of weather stations.

As a corrective measure, meteorological authorities recently the ordered setting up of two AWSs and four automated rain-gauges (ARGs) in every district, he said. Orders have been issued for setting up 20 such rain-gauges in West Bengal.

Pradhan, however, ruled out the chance of any major discrepancy in the existing rainfall data as IMD sources also seek information from State Governments and other development agencies (like Damodar Valley Corporation) on a daily basis. Pradhan’s argument is not free from fallacies.

According to Das, most States have a set of primitive observatories, most of which are either defunct or not adequately manned.

Moreover, there is a serious time lag, running into weeks, in information dissemination.

A senior official in the West Bengal Government, that manages 147 weather stations, mostly concentrated in agricultural districts, confirms the infrastructure gap.

Till last year, the State had little clue on rainfall data in the districts, the official said.

As a corrective measure, the State this year replaced the observatories with AWSs. But the data collection and collation procedures are yet to be standardised.

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