Water Resources of Nepal: Types and Major River Systems
Before the rise of the Himalayas about 58 million years ago Nepal was under the Tethys Sea. All the land mass was divided in into Two land masses:
- The southern land masses was Gandowana and laying with the present African Continent; and
- The Northern was Euro- Asian.
(About Jurassic time – 205 million years ago)-
Mahabharata and Churia Rivers started after the raise of Mahabharata and Churia hills (Siwalik). During Pleistocene a worldwide glaciations occurred and in this process the Himalayas were also involved. After the Ice age the rivers started carrying the monsoon rainfall and also melt water of glaciers. For this Nepal Himalayas were drained by four major river basins: the Koshi, Gandaki, Karnali and Mahakali form east to west respectively.
Types of Water Resources in Nepal
In Nepal all the sources of water come from the annual precipitation by monsoon July- September and also by westerly. About 96 % rainfall is from monsoon and remain 4 % is from westerlies. On the physical basis water resources can be divided into four categories:
- Snow cover/ Glacier Lakes
- Surface Water ( Rivers, Lakes, Ponds, Spout and Springs), and
- Ground Water (Deep and Shallow).
- Ground Water (Deep and Shallow).
Major River System and their Tributaries in Nepal
- Sapta Koshi River Basin
Tributary– Indrawati, BhoteKosi, TamaKosi, Likhu Khola, DudhKosi, Arun, and Tamur.
- Gandaki River Basin
Tributary– Kaligandaki, , Madi, Marsyangdi, Darondi, Trissuli, Bhurigandaki, and AndhiKhola
- Karnali River Basin
Tributary– West Seti, Budhi Ganga, Humla Karnali, Tila, Mugu Karnali, Thulo Bheri, and Sano Bheri
- Mahakali River Basin (Sarada Barrage) Western Boundary River of Nepal
Tributary– Chamalya, Surnaya, Rangoon Khola, Khuti Yankti Nepal, Dhauli Ganga, Saryu and Landhiya (India)
- Southern Rivers of Nepal
- Meechi River (Eastern boundary with India);
- Kankai River;
- Trijunga River;
- Kamala River;
- Baghmati River;
- Rapti( east) River;
- Tinau River;
- Rapti( west) River;
- Babai River;
- Khutia River;
- Mohana River.
- The SaptaKosi Basin
The river derives its name after a sage Rishi Kaushik who mediated his entire life in the worship of God on the bank of this river. The ‘Sapta’ word means seven. The SaptaKosi is the biggest river of Nepal and is believed to be next to Indus and Brahmaputra. A large area of its basin falls in the Tibetan autonomous region of China. The basin has oval shape with a protruding projection in the Saptakosi area of Chatara. After the Tribeni confluence the river is called Saptakosi, before it is called after the name of three tributaries i.e. Sunkosi, Arun and Tamur. The basin has 270 Km N-W, S-E length and width is about 145 Km N-E, S-W. The catchment area is about 25600 Sq. KM morphologically. The Sunkosi which consist of Indrawati, Bhotekosi, Tamakosi, Likhukhola, stretches longer in its NW-SE direction. Most of its tributaries are parallel to each other and flow in SW direction to meet the main trunk of the Sunkosi.
From the Tribeni the river starts its south westerly journey. The total length is 50 KM up to the India border. The river joined by Kokaha a small river coming from the east at Barahachetra. The Barahachetra is a holy place of worship of such God of Hindus. From Chatara the Kosi flares into two channels. The Kosi, before barrage at Bharda was built, was a river of sorrow of South Asia and the uncontrolled river flowed east of Purnia 2oo years ago. Now it is flowing 160 KM west of original course.
Sapta Gandaki System
Gandaki river is called Narayani in the plains sometimes Gandaki. It drains the area between Dhaulagiri and Gosainthan. It starts as Kaligandaki from photomaps of Mustang area of northern Tethyan zone. At Devghat it is joined by Trisuliganga which has consisted Seti, Marsyangdi, Budhi Chepe, Ankhu and Trisuli as main tributaries. It become Saptagandaki after Devghat and cuts the Churia hill at Tribeni and flows SW in India. A barrage has been built at Balmikinagar to contain the river in the course.
It meets E-W flowing East Rapti River and joins at Meghauli. It makes two major oxbow types bands in siwalik before Tribeni Bazar. From Tribeni the course is westerly and then it change to south easterly in India plains.
Karnali River System
The Karnali River system has Seti, Bheri and Karnali threat Major River and its starts from Tibet, North West of Taklakot, and passes through Himalaya draining Mount. Gurla, and in the east it drains out Langu valley near Muktinath through its Bheri Tributary. It then flows the South-Eastern direction and firms four bands before entering Churia hill where the gorge of Chisapani is located.
Karnali is one of the Major River systems of Nepal, lying in the western region of Nepal. It is called Ghagra in India. The rover rises in the glaciers of Mapchadunga and starts its journey from the south of Mansarovar and Rakas Lakes, and enters Nepal at Khojarnath, flowing in the south eastern direction. In Nepal it is named as Humla Karnali. It makes a sharp bend at Naralagna Himal. It makes a deep and picturesque gorge while cutting the Great Himalayan ranges.
From there is direction is towards east and south east at Nimapiplang, where it is joined by Mugu Karnali and the Kharte Khola meets it at Sukhadik. It makes two channels make a delta of triangular shape and again join before entering India. It is joined by Mahakali at Beharmghat in India and is called there as Ghaghara. It passes by the famous city Ayodhya where Lord Rama was supposed to be born.
Mahakali River System
Mahakali makes western border with India and originates from Milan glacier from India and also Lipylekh of Nepal. Mahakali basin is more or less rectangular in shape expect that Sarju River has some protrusion in 160 KM, north of Churia Hill or Siwalik.
The main tributaries from south to north are as follows:
Eastern bank of Nepal:
- Rangun Khola;
- Sunaigad; and
- Chimliya River.
Western bank of India:
- Ladhiya Khola;
- Sarju River;
- GoriGanga; and
The Mahakali makes western shift due to fault at Poornagiri and then it follows in stew trend till it reaches Tanakpur and Sharada barrage, where it is considerably wider. Bellow the barrage, Mahakali makes N-S bend and finally it follows parallel to Nepal border to easterly course in Indian Territory as Sharada River.