| Bio-Mapping of Rivers, March 1999
|
RIVER
BASINS
A river during its course of flow has definite
basin area. The basin area is the geographical extent in thee catchment of the
river from where precipitator water joins the river. It includes tributaries and
the drains. Indian rivers have been divided into three categories depending upon
basin area. Major rivers are those rivers which have basin area - 20,000 sq km
or more. The rivers having basin area between 2000 and 20000 sq km are grouped
as medium rivers and rest rivers are minor rivers. There are 13 major river basins
and as a group, these basins cover 80% population and 85% of total river discharge.
Among the 45 medium river basins, four are international and eleven are interstate
river basins. A total of 17 rivers having a combined basin area of 63500 sq km
join, the Arabian sea, while remaining 24 rivers having a combined basin area
of 210596 sq km, joins Bay of Bengal. The four rivers are originated in India
but cross the national boundry, thus incorporate international river basin. Medium
river basins occupy 8% of total basin area and about 119940 million cubic meter
water flows through these. There are fifty five minor river
basins having a combined basin area of about 2 lakh sq km. Most of these originate
from Eastern and Western Ghats. The total area of minor basins is about 9% of
total basin area of Indian rivers.
River Basin Pollution
With
increasing population pressure and associated activities, the rivers are affected
both in terms of water quality and quantity. The flowing water have significant
self-purification capacity which self purify and diluted during course of travel
of river water to some distance. After the construction of a barrage or dam or
development of irrigation canal network on a river, downstream stretches of river
does not get enough water. As a result the pollutants discharged through several
drains, sewage streams and effluents joining the rivers are not diluted. It affect
the self purification capacity of the rivers and thus river stretches are polluted.
