The Koshi spoke during the monsoon of 2008. She opened a new path, just as Dinesh Mishra predicted. The river breached an apparently ill-constructed and certainly ill-maintained embankment. A photo taken as the flood began shows the ridge of sand dissolving as water poured through a widening gap in the embankment and flowed southeast. In both Nepal and Bihar, villages and farms that had not seen a flood for the past half century were devastated. The embankments on the Koshi had already breached seven times at various spots downriver. This time the entire river below the Siwalik range in Nepal, where the land flattens, had essentially jumped out of its straitjacket and returned to one of its old channels—one it had flowed down two centuries ago. In Nepal the Koshi River is known as the Saptakoshi, or “seven Koshis,” because seven Himalayan rivers merge to create it. The Tamur flows down from Kanchenjunga in eastern Nepal near its border with Bhutan and India; the Arun comes down from Tibet. Out of the Khumbu comes the Dudh Koshi, the milky blue river that entranced me on the way up to Gokyo. The Dudh Koshi joins the Sun Koshi, which is also fed by the Tama Koshi, which in turn receives water from the Rolwaling Khola and Tsho Rolpa, the threatening glacial lake I visited during the monsoon of 2006. From farther west, toward Kathmandu, come the Likhu and the Indrawati. The latter receives the as yet undiverted waters of the Melamchi Khola. These seven tributaries of the Saptakoshi drain more than a third of the Nepal Himalaya, the wettest and highest of the great range, which includes the Khumbu and Ngozumpa glaciers. The Koshi drains almost thirty thousand square miles. It is Nepal’s largest river and one of the largest tributaries of the Ganga. Less than ten miles above the plains, three of these great rivers come together in a final merging: the Sun Koshi from the west, the Arun from the north, the Tamur from the east.
Impact analysis of small hydropower construction on river connectivity on the upper reaches of the great rivers in the Tibetan Plateau