Rivers of NepalBuddhi N Shrestha Background
There are about 6,000 rivers, streams, rivulets, brooks and nalas in Nepal. Its total length is approximately 45,000 kilometer. Seventy-six percent of these rivers have been originated in Nepalese territory and the rest have been coming from Tibetan Autonomous Region (TAR) of China. The total watershed area is 191, 000 square kilometer. Density of Nepali rivers is 0.3 kilometer per square kilometer. Nepali rivers produce 225,000 million million cusec water.
Of these, more than 200,000 million cusec of water flows to India from Nepal. According to the Water and Energy Commission, Nepal has wastage of 210,000 cusec water every year. All the river water flowing from Nepal goes to the River Ganges of India and ultimately it reaches to Bay of Bengal.
Length of the rivers
In Nepal, there are 24 rivers which bears near about 500 kilometer in length each. Similarly, there are more than 100 rivers, as its individual length is more than 160 kilometer. Besides, there are near about 1,000 rivers having 11 kilometer long each.
Among the major rivers, Koshi River belongs 721 kilometer long, Karnali 550 km, Gandaki (Narayani) 451 km, Mahakali 223 km and Mechi 80 km in length. Width of these rivers in Tarai plain area is 30 meter to 500 meter. Longest and largest river of Nepal is the Koshi River and the deepest is the River Narayani.
Classification of river
Rivers of Nepal could be classified into three categories on the basis of its source and shape as:
- Large size,
- Medium size and
- Small size.
Koshi, Gandaki, Karnali and Mahakali fall on the large size rivers. Originations of these rivers are the High Himalayas and Tibetan Plateau.
Medium scale rivers are like Biring, Kankai, Kamala, Bagmati, Tinau, Rapti, Babai, Mohana. High Mountain is the area of origination of these rivers.
Similarly, Ratuwa, Lohandra, Budhi, Khando, Balan Hardinath, Jhim, Aruwa, Bhevani, Bhaluyahi, Rohini, Kanchan Kathi, Man, Bhada Nala, Kanara, Dhuraha, Khatiya, Bagmati are the small size rivers. These are originated from Low Mountains.
On the basis of origination and source of the river, there are three types of rivers in Nepal:
- First is the originated from snow capped Himalayan Range,
- Second is originated from the Mahabharat Range, and
- Third is originated from Siwalik Range.
Those rivers originated from the Himalayas are the perennial rivers. The water will be available all the year round from the snow. The rivers which have been originated from the Mahabharat Range have its springs of water, monsoon river water and under ground water. These rivers will have the water all the times, but the volume of water during dry season will be low. Rivers originated from the Siwalik (Churia) Range will have either very low volume of water or no water on the surface during dry season. But during monsoon period, the rivers will have a roaring flood unexpectedly. Such rivers are totally seasonal.
The high mountain rivers have narrow bed and gorges with high slope in the hilly area. But when they come into Tarai plain, it expands its bed right and left banks of the river and it deposits sand and silt. It has its low slope in plain area.
Middle mountain rivers have ups and downs in the volume of water with reasonable slope.
The rivers originated from low mountain of Churia Range, especially of Bhavar region will have no water after two to four hours of stopping the rain. If we dig some meters deep, under-ground water may be available in these rivers. These are the characteristics of the Rivers of Nepal.