(Proceedings, INDIA HYDRO 2005, 19–21 February 2005, New Delhi, pp. 3–9).
Topography of Nepal varies extremely. Snow fed rivers with steep gradients bless Nepal with sufficient amount of hydroelectric potential. The total lengths of all streams and rivulets exceed 45000 kilometers. About 1000 rivers are more than 10 kilometers. 54 rivers are longer than 160 kilometers. The drainage density is closes to about 0.3 kilometers per square kilometer. On the basis of surface flows, the rivers in Nepal are perennial, intermittent or ephemeral. In addition, there are number of glaciers that can be categorized as frozen (ice) streams having extremely slow movement. The river flows are laden with high concentration of sediment during rainy period. Several streams are draining lands with degraded soil on sloping surfaces and so are transporting high amount of sediments annually. Soil erosion, sediment transportation, and deposition process vary with topographical zone and show an increasing trend in the Siwaliks Surface erosion is highly pronounced with high intensity monsoon rain. Sediment transport in streams during pre-monsoon period is higher than in the post monsoon period. The existing sediment monitoring networks in catchments are not sufficient to understand and quantify the sediment transport as well as to assess the sediment yield of catchments in totality.
Steep gradients, Drainage density, Glaciers, River flows, Concentration of sediment, Topographical zone, Sediment transport, Catchments
