D RAINAGE S YSTEM C H A P T E R Important Drainage Patterns The drainage pattern resembling the branches of a tree is known as “dendritic” the examples of which are the rivers of northern plain. When the rivers originate from a hill and flow in all directions, the drainage pattern is known as ‘radial’. The rivers originating from the Amarkantak range present a good example of it. (iii) When the primary tributaries of rivers flow parallel to each other and secondary tributaries join them at right angles, the pattern is known as ‘trellis’.
(iv) When the rivers discharge their waters from all directions in a lake or depression, the pattern is know as ‘centripetal’. Find out some of the patterns in the topo sheet given in Chapter of Practical Work in Geography– Part I (NCERT, ) . Figure . : A River in the Mountainous Region Figure .
: Major Rivers of India 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. There is, however, a slight difference between a river basin and a watershed. Watersheds are small in area while the basins cover larger areas.
River basins and watersheds are marked by unity. What happens in one part of the basin or watershed directly affects the other parts and the unit as a whole. That is why, they are accepted as the most appropriate micro, meso or macro planning regions. 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: (i) the Arabian Sea drainage; and (ii) the Bay of Bengal drainage. They are separated from each other through the Delhi ridge, the Aravalis and the Sahyadris (water divide is shown by a line in Figure . ). Nearly 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