Long-Term Management of Kosi River Basin

Abstract

Kosi River starts from Tibet in China, gains momentum in Nepal, enters India to join the Ganges. Kosi is a young river. Chatara as nodal point, Kosi had shifted westward for about 120 km in past 250 years showing a cone (80 km long and 150 km wide alluvial fan) building activity, prior to its embankment in 1959. The major aim of Kosi barrage was to control flood in Bihar; irrigation, hydroelectricity generation, land reclamation, fishing and navigation were less important. Although it prevented major floods in Bihar for about 50 years, the Project was disputed. Some scholars also raised environmental and safety concerns. Kosi is a heavy sediment carrying river (80 million m3/year). So far no effective method has been developed to avoid siltation upstream of the barrage. The riverbed continued to rise at about 0.05 m per year leading to a situation when it was 4–5 m above the land outside the embankments. Due to sloping landscape, Kosi breached eastern bank in its weakest part and followed some of its old channels. The 2008 flood took 527 lives, inundated 116,000 ha of land and left 234,000 people homeless. The 2008 Kosi flood has been considered as manmade for failure to address the sedimentation problem upstream of the barrage with effective counter measures, no regular repair and maintenance work of the upstream embankments and delay in opening the barrage gates. As a solution, India is lobbying for Kosi 269 m high dam 40 km north of present barrage. The proposal first suggested in 1937 has been opposed by Nepalese scholars. Scientific researches on the ways to reduce the sediment load from upstream and to increase the silt clearing capacity downstream are needed. Nepal–China–India trilateral close cooperation is called for producing a long-term solution.