Delhi floods 2023: Local factors impacted forecast accuracy, CWC tells NGT

Delhi recorded its highest flood level ever in the monsoon of 2023, with the river’s water level touching 208.6mm — a record high on July 13, 2023.

The Central Water Commission (CWC) has informed the National Green Tribunal (NGT) that its forecasts during the 2023 Delhi floods were largely inaccurate due to local factors in the capital, including the presence of silt islands in the river Yamuna and the disposal of muck at locations where bridges were being constructed in the river.

A view of Yamuna Khadar near Mayur Vihar Phase I in July 2023 during the monsoon floods. (HT Photo)

The commission also said that some gates at the ITO barrage were not open, which may have contributed to some forecasts missing their mark.

The NGT had in May last year taken cognisance of a news report which said CWC’s forecasts were largely inaccurate for the flood and sought clarity from agencies.

In an affidavit, dated January 4, CWC said its forecasts are based on gauge-to-gauge correlation graphs, which are updated every year by incorporating previous year’s monsoon data. It said to make accurate forecasts, a free-flowing condition was needed in Delhi between the Wazirabad barrage and Okhla barrage.

“But for such a high flood, it was observed later that, the free flow condition did not exist in Delhi due to non-opening of all gates at ITO barrage: formational of islands of silt deposits; growing trees in river course and muck disposal at various locations due to bridge construction activities,” the submission read, stating all these factors led to congestion in the river.

“The free flow condition of the channel was compromised and the forecast issued will mismatch with the actual forecast,” it added.

NGT noted that as per the news report, between July 10, 2023, and August 1, 2023, out of the 52 forecasts issued by the CWC, 16 were revised later.

Delhi recorded its highest flood level ever in the monsoon of 2023, with the river’s water level touching 208.6mm — a record high on July 13, 2023. This was over a metre higher than the previous record of 207.49 metres in 1978, submerging large parts of the capital for several days, damaging property and leading to loss of life.