Indian Drainage System

Watershed

A river drains the water collected from a specific area,which is called its 'catchment area'. An area drained by a river and its tributaries is called a drainage basin. The boundary line separating one drainage basin from the other is known as the watershed. The catchments of large rivers are called river basins while those of small rivulets and rills are often referred to as watersheds.Watersheds are small in area while the basins cover larger areas.
Indian drainage system may be divided on various bases.On the basis of discharge of water(orientations to the sea),it may be grouped into

1.The Arabian Sea Drainage .
2. The Bay of Bengal Drainage

They are separated from each other through the delhi ridge, the Aravalis and the Sahyadris Nearly 77 per cent of the drainage area consisting of the Ganga, the Brahmaputra,the Mahanadi,the Krishna etc is oriented towards the Bay Of Bengal while 23 per cent comprising the Indus,the Narmada,the Tapi, the Mahi and the periyar systems discharge their waters in the Arabian Sea.

On the basis of the size of the watershed, the drainage basins of India are grouped into three categories:
1.Major river basins with more than 20,000 sq km of catchment area. It includes 14 drainage basins such as the Ganga, the Brahmaputra,etc.
2.Medium river basins with catchment area between 2,000-20,000 sq km incorporating 44 rivers basins such as the Kalindi,the Periyar etc.
3.Minor river basins with the catchment area of less than 2,000 sq km include fairly good number of rivers flowing in the area of low rainfall.
On the basis of the mode of origin, nature and characteristics,the Indian drainage may also br classified into the Himalayan drainage and the Peninsular drainage.

DRAINAGE SYSTEM OF INDIA

Indian drainage system consists of a large number of small and big rivers. It is the outcome of the evolutionary process of the three major physiographic units and the nature and characteristics of precipitation.

Comparison between the Peninsular River and the Himalayan

Place of origin Peninsular plateau and central highland,Nature of flow Seasonal; Dependent on monsoon rainfall, Type of drainage Super imposed, rejuvenated resulting in trellis, radial and rectangular patterns, Nature of river smaller, fixed course with well-adjusted valleys, Catchment area relatively smaller basin, Age of the rivers with graded profile, and have almost reached their base levels.

Himalayan mountain covered with glaciers Perennial; receive water from glacier and rainfall Antecedent and consequent leading to dendritic pattern in plains long course Flowing through the rugged mountains experiencing head ward erosion and river capturing ;In plains meandering and shifting of course very large basins Young and youthful Active and deepening in the valleys

Highlights of India's National Water Policy, 2002

The National Water Policy 2002 stipulates water allocation priorities broadly in the following order:

Drinking water,irrigation, hydro-power, navigation, industrail and other uses. The policy stipulates progressive new approaches to water management .

Key features include:

1. Irrigation and multi-purpose projects should invariably include drinking water component, wherever there is no alternative source of drinking water.
2. Providing drinking water to all human beings and animals should be the first priority.
3. Measures should be taken to limit and regulate the exploitation og groundwater.
4. Both surface and ground water should be regularly monitored for quality. A phased programme should be undertaken for improving water quality.
5. The efficiency of utilisation in all the diverse uses of water should be improved.
6. Awareness of water as a scarce resource should be fostered.
7. Conservation consciousness should be promoted through education,regulation,incentives and the disincentives.

In India, the rivers can be divided into main two groups:

• Himalayan Rivers
• Peninsular Rivers