DRAINAGE SYSTEMS NOTES - #CLASS9#GEOGRAPHY
DRAINAGE SYSTEMS NOTES - #CLASS9#GEOGRAPHY
·
Drainage:
Describes the river system of an area.
·
Drainage
Basin: The area drained by a single river system.
·
Water
Divide: An elevated area (like a mountain or upland) that separates two
drainage basins.
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DRAINAGE
SYSTEMS IN INDIA
Indian
rivers are divided into two main groups based on relief features:
1. Himalayan
Rivers
2. Peninsular
Rivers
1.
Himalayan Rivers
o
Most are
perennial (have
water throughout the year)
o
Receive
water from rain and melted snow.
o
Long
courses from source to sea.
o
Perform
intensive erosional activity in upper courses, carrying huge loads of silt and
sand.
o
Form
meanders, ox-bow lakes, and deltas in middle and lower courses.
o
Cut
through mountains making gorges.
·
Major
Himalayan Rivers:
o
Indus River System:
§ Origin:
Tibet, near Lake Mansarowar.
§ Enters
India in Ladakh, forming a picturesque gorge.
§ Tributaries
in Kashmir: Zaskar, Nubra, Shyok, Hunza.
§ Tributaries
joining near Mithankot (Pakistan): Satluj, Beas, Ravi, Chenab, Jhelum.
§ Flows
southwards to the Arabian Sea.
§ Total
length: 2900 km (one of the longest rivers).
§ About
one-third of the basin is in India (Ladakh, J&K, Himachal Pradesh, Punjab).
§ Indus
Water Treaty (1960): India can use 20% of the water for irrigation.
o
Ganga
River System:
§ Headwaters:
'Bhagirathi' (from Gangotri Glacier) and Alaknanda.
§
§
§ Himalayan
Tributaries: Yamuna (rises from Yamunotri Glacier, meets Ganga at Allahabad),
Ghaghara, Gandak, Kosi (rise in Nepal Himalaya, cause floods but enrich soil).
§ Peninsular
Tributaries: Chambal, Betwa, Son (from semi-arid areas, shorter courses, less
water).
§ Flows
eastwards, bifurcates at Farakka into Bhagirathi-Hooghly (distributary) and
mainstream.
§
§ Forms
the Sundarban Delta (world's largest and fastest-growing, home to Royal Bengal
tiger).
§
§ Gentle
slope in plains leads to large meanders.
o
Brahmaputra
River System:
§ Origin:
Tibet, east of Mansarowar lake.
§ Slightly
longer than the Indus; most of its course is outside India.
§ Known
as Tsang Po in Tibet.
§ Enters
India at Namcha Barwa (Arunachal Pradesh) through a gorge, called Dihang.
§ Joined
by Dibang, Lohit, and other tributaries to form Brahmaputra in Assam.
§ In
Tibet, carries smaller volume of water and less silt (cold, dry area).
§ In
India (high rainfall region), carries large volume of water and considerable
silt, forming braided channels and riverine islands.
§ Causes
widespread floods in Assam and Bangladesh due to rising riverbed from silt
deposits.
2.
Peninsular Rivers
·
Characteristics:
o
Mostly
seasonal (flow
dependent on rainfall).
o
Reduced
water flow during dry seasons.
o
Shorter
and shallower courses compared to Himalayan rivers.
o
Drainage
basins comparatively smaller.
·
East
Flowing Rivers (Drain into Bay of Bengal):
o
o
Make
deltas at their mouths.
o
Mahanadi
Basin:
o
o
o
o
·
West
Flowing Rivers (Drain into Arabian Sea):
o
The
Narmada and Tapi are the only long rivers flowing west.
o
Make
estuaries instead of deltas.
o
Narmada
Basin:
o
o
LAKES
·
Vary
in size and characteristics; most are permanent, some seasonal.
·
Formation:
Glacial action, wind, river action, human activities.
·
Types:
o
Ox-bow lakes:
Formed by meandering rivers cutting off.
o
Lagoons:
Formed by spits and bars in coastal areas (e.g., Chilika, Pulicat, Kolleru).
o
Saltwater
lakes: In regions of inland drainage, sometimes seasonal (e.g., Sambhar
Lake in Rajasthan, used for salt production).
o
Freshwater
lakes: Mostly in Himalayan region, often of glacial origin (formed by
glaciers, filled with snowmelt).
o
Tectonic
Lakes: Wular Lake (J&K) is the result of tectonic activity and is the
largest freshwater lake in India.
o
Other
important freshwater lakes: Dal Lake, Bhimtal, Nainital, Loktak, Barapani.
o
Artificial
Lakes: Formed by damming rivers for hydel power (e.g., Guru Gobind
Sagar/Bhakra Nangal Project).
·
Importance
of Lakes:
o
o
Generate
hydel power.
o
Moderate
climate.
o
Maintain
aquatic ecosystem.
o
Enhance
natural beauty.
o
Develop
tourism and provide recreation.
ROLE
OF RIVERS IN THE ECONOMY
·
Basic
Natural Resource: Essential for various human activities.
·