The Koshi River is the largest in Nepal and is the most powerful of the Ganga (Ganges) River’s many tributaries. Because of the many smaller rivers that join forces to form the final river, the Koshi is also known as the Sapta Koshi (Seven Koshis).
The Koshi river system is a large and complex one. One of its larger and perennial sub-tributaries (the Bhote Koshi or Tibetan Koshi) is present only a couple of hours driving time away from Kathmandu. In recent years, the Bhote Koshi has gained a worldwide reputation for being one of the best rivers for adventure sports. Tourists from as far away as Chile, Canada and Japan try their luck canoeing or rafting on the river. The rapids are fierce and often not for the faint of heart. At the Last Resort (a privately run adventure company) the brave might even try bungy jumping. The drop is 160 meters.
The Arun is the easternmost tributary of the Koshi and has its origins in the picturesque district of Sankhuwasabha. This is a remote, semi Himalayan district that is known for its stunning scenery. It is also home to Mt. Makalu, the world’s fifth highest peak. The mountainous terrain and the presence of dangerous rapids along the river Arun made Sanskhwasabha a difficult place to get in and out of, and therefore hampered its considerable tourism potential. However, Britain’s DFID has helped to build a bridge across the Arun that should help greatly in connecting the district to the rest of Nepal.
By the time the Koshi reaches the plains, it is no longer the raging stream it is upstream but it generally becomes calm and composed. The only time it loses its composure is during the monsoon season. Eastern Nepal gets more than 2500 mm of rain every year and as a result the river becomes swollen and unpredictable during this time of the year. On many previous occasions the river has burst its banks and caused large-scale flooding. A particularly severe case of flooding occurred in the year 2009, when floods displaced millions of people living in the Indian state of Bihar and, on a smaller scale, inside Nepal itself.
Along the Koshi, the biodiversity is rich. This is especially true of the river when it reaches the plains. This abundance of flora and fauna can be partaken of inside the Koshi Tappu Wildlife Reserve. Lying in the district of Sunsari, this national park contains a wealth of animal and plant life. There are deer, elephants and Asian wild buffalo (arna) present; however Koshi Tappu is most noted for its rich avian diversity and population.
The Koshi barrage is one of the most famous engineering feats in Nepal and it was constructed by India during the 1960s, in a bid to control the region’s flood problems. It is an impressive structure, no doubt, and is more than 700 meters across. However, the persistence of floods even in recent times has led many to conclude that the barrage was either erroneously conceived of or incomplete in some respects.