New Delhi,  The already rain-battered areas of north Bihar are likely to witness increased flood due to heavy rainfall in the catchment of transboundary rivers in Nepal, officials said on Tuesday.

The Central Water Commission (CWC) has issued an orange alert for north Bihar areas. The India Meteorological Department (IMD) data showed that there was a very heavy rainfall over Bihar and sub Himalayan West Bengal during the last 24 hours ending at 8.30 a.m. on Tuesday.

"Heavy rainfall reported in the catchment of Kosi and Bagmati in Nepal territory. Water level in these transboundary rivers may rise in North Bihar," said a CWC official.

The IMD has also forecast extremely heavy rainfall likely over Bihar on Wednesday and over Sub-Himalayan West Bengal and Sikkim this day itself.

Officials said there was a moderate risk over some watersheds and neighborhoods of Uttarakhand, north Bihar and Sub-Himalayan West Bengal and Sikkim in the next 24 hours.

"Surface runoff / inundation may occur at some fully saturated soils and low-lying areas due to expected rainfall occurrence in the next 24 hours," another official said.

As per the CWC, river Kosi at Basua in Supaul district of Bihar continued to flow in severe condition this morning at a level of 48.69 m with steady (0.0 mm/hour) trend. This is 0.94 m above its danger level of 47.75 m and 0.55 m, but below its previous high flood level of (HFL) of 49.24 recorded on August 13, 2017.

In the same district, the Kosi river at Birpur continued to flow at severe situation in the morning at a level of 75.3 m with steady (0.0 mm/hour) trend, which is 0.60 m above its danger level of 74.7 m and 0.72 m and below its previous HFL of 76.02 m on July 13, 2019.