With the implementation of National Waterways Act, 2016 seven rivers of Bihar, namely Ganga, Kosi, Gandak, Ghaghra, Punpun, Sone, and Karamnasa have been declared as National Inland Waterways. The Inland Waterways Authority of India (IWAI) has taken up the work on the Kosi, Gandak an Ganga waterways on a priority basis. In April 2018, the Governments of India and Nepal announced that Kosi and Gandak waterway would be extended into Nepal to convert them into international waterways. Given this, Manthan has taken up a detailed study of the Gandak and Kosi waterways, based on a field visit, meetings with officials, local communities and representatives of civil society, as well detailed study of related documents. This Preliminary Report presents the initial findings and recommendations of the study. Since new developments are taking place at a rapid pace, we are studying these and will come with an updated and revised report in due course.