Heavy and very heavy rainfall is expected today 19 July and until 22 July in Bihar, eastern Uttar Pradesh and sub-Himalayan West Bengal. The India Meteorological Department has issued a heavy rainfall alert for these regions.

These are the districts which will be the most affected:
In Bihar – Paschim Champaran, Gopalganj, Purbi Champaran, Siwan, Chhapra, Muzaffarpur, Sitamarhi, Madhubani, Darbhanga, Supaul, Saharsa, Madhepura, Purnia, Katihar, Kishanganj, Araria.
In Uttar Pradesh – Pilibhit, Shahjahanpur, Kheri, Hardoi, Sitapur, Shrawasti, Bahraich, Gonda, Balrampur, Basti, Sidharthnagar, Sant Kabir Nagar, Gorakhpur, Deoria, Maharajganj, Kushinagar.

These are the five river sub-basins of the Ganga basin which are affected:
Gomti – including the Kathna, Sarayan, Kalyani rivers. Cities in this sub-basin – Sitapur, Hardoi, Lucknow, Rae Bareli, Sultanpur, Jaunpur.
Ghaghara – including the Saryu, Rapti, Chhoti Gandak rivers. Cities in this sub-basin – Lakhimpur, Shrawasti, Gonda, Faizabad, Basti, Gorakhpur, Kushinagar, Deoria, Siwan, Ballia.
Ghaghara confluence to Gomti confluence – including Chhoti Saryu and Mangal rivers. Cities in this sub-basin – Faizabad, Nizamabad, Azamgarh, Mau, Ghazipur, Buxar, Bhojpur, Chandauli.
Kosi – including Kamala, Pipra, Dhemra rivers. Cities in this sub-basin – Sheohar, Sitamarhi, Darbhanga, Supaul, Madhepura, Saharsa, Kishanganj, Khagaria.
Bhagirathi – including Fariyani Nadi and Kamla rivers. Cities in this sub-basin – Araria, Purnia, Sahibganj, Malda (West Bengal).

In the Middle Ganga plains, the water drainage lines govern the human occupancy of land, particularly the agricultural land and settlements. The rivers meet at acute angles and several tributaries form parallel or sub-parallel lines to the main stream. The major rivers that meet the main stream in the middle plain are the Gandak, the Kosi, the Sone and other small tributaries of Ganga like the Tons, the Karmansa, the Chatar, the Jargo, the Karnauti, the Khejuri on the west of the Sone and those on the east of the Sone are the Punpun, the Mohini and the Chandan.

Floods are recurring feature in this region particularly in the North Ganga plains. Almost all rivers in this middle plain develop a capacity to spill over in the monsoon period and are notoriously dynamic in character, particularly the Rapti, the Ghaghara, the Gandak, the Kosi, the Sone and the main Ganga itself.