Delineation of Watershed:-

Further delineation has been done in 5 (five) stages, following stream hierarchy on the basis of drainage network, starting with Water Resource Regions (1) and their subsequent division into Basins (2), Catchments (3), Sub-catchments (4) and Watersheds (5). This Atlas uses a drainage network on 1:1 million scale.

Various stages of delineation are as under:

Stage-I:- Water Resources Regions (WRR) are segregated and numeric codes 1 - 6 have been assigned to them There are 6 WRR in the country.

Stage-II:- Each WRR is then divided into basins. In some of the cases, where the drainage systems are too large, basin is divided into lower and upper basins or left bank and right bank basins. There are 37 basins in the country.

Stage-III:- These 37 basins are further subdivided into catchments, which mostly pertain to main tributaries or a group of contiguous small tributaries or individual streams. There are 117 catchments in the country.

Stage-IV:- In next stage of delineation, these 117 catchments are further divided into 588 subcatchments which are mainly smaller tributaries and streamlets.

Stage-V:- Each subcatchment has been subjected to further divisions into number of watersheds. There are 3851 watersheds in the country and these are considered as the smallest hydrologic entity on the 1:1000K scale.

A graphical representation of delineation up to watershed on 1:1000K scale in fig. 1 to 5 below:-