- The drainage pattern of an area is the outcome of the geological time period, nature and structure of rocks, topography, slope, amount of water flowing and the periodicity of the flow
- 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.
It may be grouped into:
- the Arabian Sea drainage; and
- 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.
- 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:
- Major river basins with more than 20,000 sq. km of catchment area. It includes 14 drainage basins such as the Ganga, the Brahmaputra, the Krishna, the Tapi, the Narmada, the Mahi, the Pennar, the Sabarmati, the Barak, etc.
- Medium river basins with catchment area between 2,000-20,000 sq. km incorporating 44 river basins such as the Kalindi, the Periyar, the Meghna, etc.
- Minor river basins with catchment area of less than 2,000 sq. km include fairly good number of rivers flowing in the area of low rainfall
A mighty river called Shiwalik or Indo-Brahma traversed the entire longitudinal extent of the Himalaya from Assam to Punjab and onwards to Sind, and finally discharged into the Gulf of Sind near lower Punjab during the Miocene period some 5-24 million years ago
The remarkable continuity of the Shiwalik and its lacustrine origin and alluvial deposits consisting of sands, silt, clay, boulders and conglomerates support this viewpoint
It is opined that in due course of time Indo– Brahma River was dismembered into three main drainage systems:
- The Indus and its five tributaries in the western part;
- The Ganga and its Himalayan tributaries in the central part; and
- The stretch of the Brahmaputra in Assam and its Himalayan tributaries in the eastern part. The dismemberment was probably due to the Pleistocene upheaval in the western Himalayas, including the uplift of
The Potwar Plateau (Delhi Ridge), which acted as the water divide between the Indus and Ganga drainage systems. Likewise, the down thrusting of the Malda gap area between the Rajmahal hills and the Meghalaya plateau during the mid-Pleistocene period diverted the Ganga and the Brahmaputra systems to flow towards the Bay of Bengal.
The Indus also known as the Sindhu is the westernmost of the Himalayan Rivers in India.
It originates from a glacier near Bokhar Chu (31°15′ N latitude and 81°40′ E longitude) in the Tibetan region at an altitude of 4,164 m in the Kailash Mountain range.
The Panjnad is the name given to the five rivers of Punjab, namely the Satluj, the Beas, the Ravi, the Chenab and the Jhelum.
The Chenab is the largest tributary of the Indus. It is formed by two streams, the Chandra and the Bhaga, which join at Tandi near Keylong in Himachal Pradesh. Hence, it is also known as Chandrabhaga.
The Ganga river system is the largest in India having a number of perennial and non-perennial rivers originating in the Himalayas in the north and the Peninsula in the south, respectively. The Son is its major right bank tributary. The important left bank tributaries are the Ramganga, the Gomati, the Ghaghara, the Gandak, the Kosi and the Mahanada. The river finally discharges itself into the Bay of Bengal near the Sagar Island.
- The Yamuna, the western most and the longest tributary of the Ganga
- Once known as the ‘sorrow of Bengal’, the Damodar has been now tamed by the Damodar Valley Corporation, a multipurpose project
- The Ganga has its minimum flow during the January-June period. The maximum flow is attained either in August or in September. After September, there is a steady fall in the flow. The river, thus, has a monsoon regime during the rainy season.
The discharge is the volume of water flowing in a river measured over time. It is measured either in cusecs (cubic feet per second) or cumecs (cubic meters per second)
The Godavari has the minimum discharge in May and the maximum in July-August.
- After August, there is a sharp fall in water flow.
- The mean maximum discharge of the Godavari at Polavaram is 3,200 cusecs while the mean minimum flow is only 50 cusecs.
PROJECTS:
- Periyar Diversion Scheme
- Indira Gandhi Canal Project
- Kurnool-Cuddapah Canal
- Beas-Satluj Link Canal
- Ganga-Kaveri Link Canal
REASONS:
- No availability in sufficient quantity
- River water pollution
- Load of silt in the river water
- Uneven seasonal flow of water
- River water disputes between states
- Shrinking of channels due to the extension of settlements towards the thalweg.
IAS Platform 