Mahananda Basin

The Himalayan mountainous range is 2500 km. in length and 250 to 400 km. in width with a mean elevation of 6000 meters in the Central axial range is the most dominant geographical feature in India.

According to the classification of the Indian rivers, the Ganga, Brahmputra and Meghna river system is known as Eastern Himalayan river system. The main stream of the above river system is Ganga river, which have received a number of tributary rising from various mountainous region and those have enriched the flow of the main stream. In the eastern part, after the river Gandak and the river Kosi meeting with the mighty river Ganga from the north, Mahananda, the most important tributary also meeting the river Ganga from the north.

Mahananda is a typical river system consisting of two different stream, one arising from mountainous region of Himalayas in Nepal traverses through the Indian state of Bihar and out falls in the Ganga in left opposite to Rajmahal in Bihar and is locally named as river Fulahar. The other stream also named as Mahananda rises in downhill in Darjeeling in West Bengal and traverses a distance of about 400 kms. through the district of Darjeeling, West Dinajpur and Malda and enters in Bangladesh territory and ultimately out falls in the Ganga near Godagarighat in Bangladesh just opposite to Lalgola in Murshidabad district of West Bengal. The right channel flow through the state of Bihar in the name of Fulahar. The left channel flow through the district of West Dinajpur and Malda and enters in Bangladesh in the name of Mahananda.

Both the rivers received snow melt in small quantities during non-monsoon month and receive heavy amount of water from the monsoon rains.

Both the streams receive good amount of water from the various tributaries. The average rainfall in the region is about 1400 mm. and 80% of the Annual rain occurs during 4 to 5 months. The catchment area of these two rivers stretched over sub-Himalayan region of Nepal and West Bengal, is the second highest rainfall region in India. As both the streams run very close to each other in sub-Himalayan plains which combine into single river during Peak monsoon months and inundate a huge land area in Bihar and West Bengal. The inundation takes devastating shape particularly when the main stream Ganga is at her Peak when further drainage of water becomes impossible due to obvious reason. A vast area of Bihar and West Bengal get water logged by the pool of water formed by conjunct mass of undischarged water of these two streams of Mahananda. The affected districts are Purnea and Katihar in Bihar and Darjeeling, West Dinajpur and Malda district in west Bengal.

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