Drainage Basin in Uttarakhand :

The steep relief of the mountains and hills and the high precipitation combine to create a highly active hydrological system, which drains into major river systems, most notably the Rivers Ganges, Yamuna, Kosi and Kali. All these river systems flow North-South from the high mountains to the plains and create distinct basins or watersheds within Uttarakhand.Their configuration is important as the orientation of the valleys determines the quality of views to the high mountains to the north and contains distinct landscapes and natural features. As they are usually defined by extremely high ridgelines, passable only by narrow mountain roads. The drainage basins comprise:

Kali (North East) Drainage Basin: formed by high ridges between Gwaldam/Talwari and the Nanda Devi East National Park and the smaller southern watershed between Gwaldam and Reetha Sahbo via Jageshwar, this basin drains in a eastern/north eastern and south eastern direction towards the Kali River which forms the boundary with Nepal. Beyond this to the east it is hemmed in by the Nepalese mountains. The east-west ridges at Binsar and north of Gwaldam offer spectacular views of the high mountain ranges as well as the wider foothills. As many of the valleys are east-west in direction, their southernmost slopes are well exposed to the high mountains: an example of this is at Munsiyari where spectacular views of the Panchchuli Peaks are afforded from the valley. Important rivers flowing from the ridges (for example Saryu, Ramganga, Panar and Goriganga) as well as the Kali River, offer good opportunities for rafting. 

Southern Basin: The southern basin, which includes Corbett National Park, comprises the generally lower land of the lesser Himalayas and the Bhabar belt. It includes the hill towns of Almora and Nainital. The rivers here, including the Kosi, Ramganga and Gola, flow southwards in the Bhabar belt and beyond towards the plain. This means that views of the Himalayas are largely precluded from towns and villages, although they appear along the ridges north of Almora and in the north-east in Binsar. This southern basin however does offer wide views of the wide plains to the south and offers a different landscape to tourists. 

Ganga (Central) Basin: The central basin, in central Gharwal, is the largest of the watersheds (covering about 50 per cent of the state) and incorporates the River Ganga (called the Bhagirathi north of the confluence with the Alaknanda at Devaprayag). This is part of a major catchment, with many tributaries including the Bhiliganga and smaller streams, all flowing into the Ganga (in the plain, all rivers flow into the Ganga). The critical features of this drainage pattern are that rivers flow in a north-south direction, resulting in more limited views of the high mountains, these being restricted to the valley floors or to the ridges which are orientated north to south (also limiting panoramic views of the higher Himalayas). A particular significance of this basin is that there are few intermediate mountain ranges between the plains and the higher Himalayas. Steep gorges therefore plough directly southwards, avoiding the many micro-climates found further east in Kumaon.

 Yamuna (Western) Basin: The western basin is formed by the Yamuna River system, which also generally flows in a north-south direction. This is a smaller catchment, currently inaccessible to tourists. It contains the source of the Yamuna River at the Bandarpunch Glacier.

Overall Impact of Drainage :

The overall drainage system of the State is responsible for the appearance of its outstanding natural environment. In particular the River Ganga has a major influence on tourism owing to its size, geographical, cultural and religious significance, particularly vis-à-vis its source at the Gangotri Glacier, which attracts many pilgrims. The extensive hydrology of all the major basins, which includes a plethora of mountain streams and fast flowing tributary rivers set amidst deep mountain valleys, and the presence of spectacular waterfalls and rapids, creates a huge potential for adventure and nature tourism. Many of the rivers appear favourable for river rafting and, due to their contrasting physical features, adaptable to both beginners and more experienced rafters. In some of the less aggressive watercourses, kayaking can also be considered. Also as part of the hydrological system, a series of moraine-formed lakes in Nainital district offer distinctive and striking scenery, together with boating opportunities. These are notable due to comparative rarity of lakes in Uttarakhand and indeed other parts of the Indian Himalayas.