Monday, 16 September 2019

Indian Monsoon Mechanism: Jet Stream Theory

Indian Monsoon Mechanism – Jet Stream Theory. Role of Sub-Tropical Jet Stream (STJ). Why no south-west monsoons during winter? Why no south-west monsoons in March – May (summer)?

Indian Monsoon Mechanism – Jet Stream Theory

Indian Monsoon Mechanism – Modern Theory: Jet Stream Theory.
  • Jet stream Theory is the latest theory regarding the origin of the monsoons and has earned worldwide acceptance from the meteorologists.
  • To understand how Jet streams affect Indian monsoons, we need to know the basic mechanism of Jet Stream induced weather conditions.

How Jet Streams Affect Weather?

  • Jet streams have distinct peaks (ridges) and troughs.
  • Ridges occur where the warm air mass pushes against the cold air mass. Troughs occur where cold air mass drops into warm air.
  • The region on earth below the trough is at low pressure and the region below ridge is at high pressure.
  • This condition occurs due to weakening of jet stream due to lesser temperature contrast between sub-tropics and temperate region (Our concern is STJ only).
  • Usually the trough region [the region exactly below the jet stream trough] creates cyclonic condition (low pressure) at the surface of earth whereas the ridge regions creates anticyclonic condition.
  • Troughs create upper level divergence which is associated with convergence at the surface (low pressure – cyclonic conditions) and ridges create upper level convergence which is associated with divergence at the surface (high pressure – cyclonic conditions).
  • These ridges and troughs give rise to jet streaks which are also responsible for cyclonic and anticyclonic weather conditions at the surface.
Jet Streams ridge-trough - Weather in Temperate RegionsJet Streams convergence-divergence - Weather in Temperate Regionsconvergence - divergence wind - cyclonic-anticyclonic (Custom)
  • The winds leaving the jet streak are rapidly diverging, creating a lower pressure at the upper level (Tropopause) in the atmosphere. The air below rapidly replaces the upper outflowing winds. This in turn creates the low pressure at the surface. This surface low pressure creates conditions where the surrounding surface winds rush inwards. The Coriolis effect creates the cyclonic rotation (cyclonic vortex) that is associated with depressions [low pressure cells].
  • The winds entering the jet streak are rapidly converging because of the high pressure at the upper level (Tropopause) in the atmosphere. This convergence at upper troposphere leads to divergence (high pressure) at the surface (anticyclonic condition).
  • The Coriolis effect creates the anticyclonic rotation that is associated with clear weather.
But how does this mechanism of jet streams influence Indian Monsoons?

Indian Monsoon Mechanism – Role of Sub-Tropical Jet Stream (STJ)

  • Sub-Tropical Jet stream plays a significant role in both hindering the monsoon winds as well as in quick onset of monsoons.

STJ – Sub-Tropical Jet Stream

  • Sub-Tropical Jet stream is a narrow band of fast moving air flowing from west to east [Westerlies].
  • STJ in northern hemisphere flows between 25° to 35° N in the upper troposphere at a height of about 12-14 km (all this already discussed in previous posts on Jet Streams). (Here we will consider STJ only. Polar Jet has no influence on Indian monsoons).
  • The wind speeds in a westerly jet stream are commonly 150 to 300 km p.h. with extreme values reaching 400 km p.h.
The burst of monsoons depends upon the upper air circulation which is dominated by STJ.

Seasonal Migration of Sub-Tropical Jet Stream – STJ

  • In winter STJ flows along the southern slopes of the Himalayas but in summer it shifts northwards, rather dramatically, and flows along the northern edge of Himalayas in early June and in late summer (July-August) along the northern edge of the Tibetan Plateau.
  • The periodic movement of the Jet stream is often the indicator of the onset (STJ shits to the north of Himalayas in a matter of days) and subsequent withdrawal (STJ returns back to its position – south of Himalayas) of the monsoon.
  • Northward movement of the subtropical jet is the first indication of the onset of the monsoon over India.

Sub-Tropical Jet Stream – STJ in Winter

  • Westerly jet stream blows at a very high speed during winter over the sub-tropical zone.
  • This jet stream is bifurcated by the Himalayan ranges and Tibetan Plateau.
  • The two branches reunite off the east coast of China.
  • The northern branch of this jet stream blows along the northern edge of the Tibetan Plateau.
  • The southern branch blows to the south of the Himalayan ranges along 25° north latitude.
  • A strong latitudinal thermal gradient (differences in temperature), along with other factors, is responsible for the development of southerly jet.

Western Disturbances

  • Meteorologists believe that southern branch of jet stream exercises a significant influence on the winter weather conditions in India.
  • The upper jet is responsible for steering of the western depressions [Western Disturbances] from the Mediterranean Sea.
  • Some of the depressions continue eastwards, redeveloping in the zone of jet stream confluence about 30° N, 105° E (near east coast of China).
  • Winter rain and heat storms in north-western plains and occasional heavy snowfall in hilly regions are caused by these disturbances.
  • These are generally followed by cold waves in the whole of northern plains.
  • The southern branch is stronger, with an average speed of about 240 km compared with 70 to 90 km p.h. of the northern branch.
  • Air subsiding beneath this upper westerly current gives dry out blowing northerly winds from the subtropical anticyclone over northwestern India and Pakistan.

Why no south-west monsoons during winter?

  • Reason 1: ITCZ has left India (the winds that blow over India are mostly offshore –– land to land or land to ocean –– so they carry no moisture).
  • Reason 2: During winter, the southern branch of STJ is strong and is to the south of Himalayas. The ridge of the jet lies over north-western India and is associated with strong divergence of winds and creates a high pressure region (sub-tropical high pressure belt) over entire north India. [This is how the mechanism of jet streams influence Indian Monsoons in winter season]
  • Reason 3: There is already a strong high pressure over Tibet. [High Pressure due to STJ + High Pressure over Tibet = strong divergence = no rainfall]

Sub-Tropical Jet Stream – STJ in Summer

  • With the beginning of summer in the month of March, the STJ [upper westerlies] start their northward march.
  • The southerly branch of STJ remains positioned south of Tibet, although weakening in intensity.
  • The weather over northern India becomes hot, dry and squally due to larger incoming solar radiation and hot winds like loo.
  • Over India, the Equatorial Trough (ITCZ) pushes northwards with the weakening of the STJ [upper westerlies] south of Tibet, but the burst of the monsoon does not take place until the upper-air circulation has switched to its summer pattern.
  • By the end of May the southern jet breaks and later it is diverted to the north of Tibet Plateau and there is sudden burst of monsoons (the ridge moves northwards into Central Asia = high pressure over north-west India moves northwards into Central Asia = makes way for south-west monsoon winds). An Easterly jet emerges over peninsular India with the northward migration of STJ.
  • The upper air circulations are reversed with the emergence of Easterly jet [convergence in upper layers is replaced by divergence == divergence in lower layers is replaced with convergence == high pressure at lower layers is replaced by low pressure system]. The easterly winds become very active in the upper troposphere and they are associated with westerly winds in the lower troposphere (south-west monsoon winds).
  • Western and eastern jets flow to the north and south of the Himalayas respectively. The eastern jet becomes powerful and is stationed at 15° N latitude.
  • This results in more active south-west monsoon and heavy rainfall is caused.

Why no south-west monsoons in March – May (summer)?

  • There is good sun’s insolation from March – May but still there is no s-w monsoons.
Reason: The ridge region of Southern branch of STJ creates strong divergence (high pressure) in north-west India. The diverging air blocks incoming winds and prevents strong convergence of winds along ITCZ.
  • During the summer season in the Northern Hemisphere, low pressure areas develop at the ground surface near Peshawar (Pakistan) and north-west India due to intense heating of ground surface during April, May, and June.
  • As long as the position of the upper air jet stream is maintained above the surface low pressure (to the south of Himalayas), the dynamic anti-cyclonic conditions persist over north-west India.
  • The winds descending from the upper air high pressure [because of the ridge of STJ] obstructs the ascent of winds from the surface low pressure areas, with the result that the weather remains warm and dry.
  • This is why the months of April and May are generally dry and rainless in spite of high temperatures (low pressure on land) and high evaporation
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Mechanism of Indian Monsoons

Indian Monsoons – Factors responsible for south-west monsoon and north-east monsoon formation. Mechanism of Indian Monsoons. Indian Monsoons – ITCZ [Inter-Tropical Convergence Zone].

Indian Monsoons

  • The term monsoon has been derived from the Arabic word mausin or from the Malayan word monsin meaning ‘season’.
  • Monsoons are seasonal winds (Rhythmic wind movements)(Periodic Winds) which reverse their direction with the change of season.
  • The monsoon is a double system of seasonal winds – They flow from sea to land during the summer and from land to sea during winter.
  • Some scholars tend to treat the monsoon winds as land and sea breeze on a large scale.
  • Monsoons are peculiar to Indian Subcontinent, South East Asia, parts of Central Western Africa etc..
  • They are more pronounced in the Indian Subcontinent compared to any other region.
  • Indian Monsoons are Convection cells on a very large scale.
  • They are periodic or secondary winds which seasonal reversal in wind direction.
  • India receives south-west monsoon winds in summer and north-east monsoon winds in winter.
  • South-west monsoons are formed due to intense low pressure system formed over the Tibetan plateau.
  • North-east monsoons are associated with high pressure cells over Tibetan and Siberian plateaus.
  • South-west monsoons bring intense rainfall to most of the regions in India and north-east monsoons bring rainfall to mainly south-eastern coast of India (Southern coast of Seemandhra and the coast of Tamil Nadu.).
  • Countries like India, Indonesia, Bangladesh, Myanmar etc. receive most of the annual rainfall during south-west monsoon season where as South East China, Japan etc., during north-east rainfall season.

Factors responsible for south-west monsoon formation

  • Intense heating of Tibetan plateau during summer months.
  • Permanent high pressure cell in the South Indian Ocean (east to north-east of Madagascar in summer).

Factors that influence the onset of south-west monsoons

  • Above points +
  • Subtropical Jet Stream (STJ).
  • Tropical Easterly Jet (African Easterly Jet).
  • Inter Tropical Convergence Zone.

Factors that influence the intensity of south-west monsoons

  • Strengths of Low pressure over Tibet and high pressure over southern Indian Ocean.
  • Somali Jet (Findlater Jet).
  • Somali Current (Findlater Current).
  • Indian Ocean branch of Walker Cell.
  • Indian Ocean Dipole.

Factors responsible for north-east monsoon formation

  • Formation and strengthening of high pressure cells over Tibetan plateau and Siberian Plateau in winter.
  • Westward migration and subsequent weakening of high pressure cell in the Southern Indian Ocean.
  • Migration of ITCZ to the south of India.
All these will be discussed in detail.

Mechanism of Indian Monsoons

  • The origin of monsoons is not fully understood.
  • There are several theories that tried to explain the mechanism of monsoons.

Classical Theory

  • Monsoons are mentioned in scriptures like the Rig Veda. But these scriptures didn’t make any mention of the monsoon mechanism.
  • The first scientific study of the monsoon winds was done by Arab traders.
  • Arab traders used the sea route to carry out trade with India and monsoon patterns were of prime importance for them.
  • In the tenth century, Al Masudi, an Arab explorer, gave an account of the reversal of ocean currents and the monsoon winds over the north Indian Ocean.
  • In seventeenth century, Sir Edmund Halley explained the monsoon as resulting from thermal contrasts between continents and oceans due to their differential heating.

Modern Theories

  • Besides differential heating, the development of monsoon is influenced by the shape of the continents, orography (mountains), and the conditions of air circulation in the upper troposphere {jet streams}.
  • Therefore, Halley’s theory has lost much of its significance and modern theories based on air masses and jet stream are becoming more relevant.

Indian Monsoons – Classical Theory: Sir Edmund Halley’s Theory

Summer Monsoon
  • In summer the sun’s apparent path is vertically over the Tropic of Cancer resulting in high temperature and low pressure in Central Asia.
  • The pressure is sufficiently high over Arabian Sea and Bay of Bengal. Hence winds flowed from Oceans flow towards landmass in summer.
  • This air flow from sea to land bring heavy rainfall to the Indian subcontinent.
Winter Monsoon
  • In winter the sun’s apparent path is vertically over the Tropic of Capricorn.
  • The north western part of India grows colder than Arabian Sea and Bay of Bengal and the flow of the monsoon is reversed.
  • The basic idea behind Classical theory is similar to land and sea breeze formation except that in the case of monsoons the day and night are replaced by summer and winter.
Drawbacks: The monsoons do not develop equally everywhere on earth and the thermal concept of Halley fails to explain the intricacies of the monsoons such as the sudden burst of monsoons, delay in on set of monsoons sometimes, etc..

Indian Monsoons – Modern theory: Air Mass Theory

  • According to this theory, the monsoon is simply a modification of the planetary winds of the tropics.
  • The theory is based on the migration of ITCZ based on seasons.

Indian Monsoons – Role of ITCZ [Inter-Tropical Convergence Zone]

  • The southeast trade winds in the southern hemisphere and the northeast trade winds in the northern hemisphere meet each other near the equator.
  • The meeting place of these winds is known as the Inter-Tropical Convergence Zone (ITCZ).
Monsoons - periodic windsconvection - thunderstorms ITCZIndian Monsoons -Inter-Tropical Convergence Zone- ITCZ
  • This is the region of ascending air, maximum clouds and heavy rainfall.
  • The location of ITCZ shifts north and south of equator with the change of season.
  • In the summer season, the sun shines vertically over the Tropic of Cancer and the ITCZ shifts northwards.
  • The southeast trade winds of the southern hemisphere cross the equator and start blowing in southwest to northeast direction under the influence of Coriolis force.
  • These displaced trade winds are called south-west monsoons when they blow over the Indian sub-continent.
  • The front where the south-west monsoons meet the north-east trade winds is known as the Monsoon Front (ITCZ). Rainfall occurs along this front.
  • In the month of July the ITCZ shifts to 20°- 25° N latitude and is located in the Indo-Gangetic Plain and the south-west monsoons blow from the Arabian Sea and the Bay of Bengal. The ITCZ in this position is often called the Monsoon Trough [maximum rainfall].
  • The seasonal shift of the ITCZ has given the concept of Northern Inter-Tropical Convergence Zone (NITCZ) in summer (July – rainy season) and Southern Inter-Tropical Convergence Zone (SITCZ) in winter (Jan – dry season).
  • NITCZ is the zone of clouds and heavy rainfall that effect India
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West Flowing Peninsular Rivers: Narmada, Tapti, Sabarmati, Mahi, Luni & Ghaggar

West Flowing Rivers of The Peninsular India

  • The west flowing rivers of the Peninsular India are fewer and smaller as compared to their east flowing counterparts.
  • The two major west flowing rivers are the Narmada and the Tapi.
  • This exceptional behavior is because these rivers didn’t form valleys and instead they flow through faults (linear rift, rift valley, trough) created due to the bending of the northern peninsula during the formation process of Himalayas.
  • These faults run parallel to the Vindhyas and the Satpuras.
  • The Sabarmati, Mahi and Luni are other rivers of the Peninsular India which flow westwards.
  • Hundreds of small streams originating in the Western Ghats flow swiftly westwards and join the Arabian Sea.
  • It is interesting to note that the Peninsular rivers which fall into the Arabian Sea do not form deltas, but only estuaries. {Fluvial Depositional Landforms}
  • This is due to the fact that the west flowing rivers, especially the Narmada and the Tapi flow through hard rocks and hence do not carry any good amount of silt.
  • Moreover, the tributaries of these rivers are very small and hence they don’t contribute any silt.
  • Hence these rivers are not able to form distributaries or a delta before they enter the sea.

Estuary

Estuaries-judson estuary
  • An estuary is a partially enclosed body of water along the coast where freshwater from rivers and streams meets and mixes with salt water from the ocean. [Primary productivity in estuaries is very high. Fishing is a dominant occupation around estuaries. Most of the estuaries are good bird sanctuaries].
  • Estuaries and the lands surrounding them are places of transition from land to sea and freshwater to salt water.
  • Although influenced by the tides, they are protected from the full force of ocean waves, winds, and storms by such land forms as barrier islands or peninsulas. [You know why estuaries make good ports?]
  • Estuarine environments are among the most productive on earth, creating more organic matter each year than comparably-sized areas of forest, grassland, or agricultural land.
  • The tidal, sheltered waters of estuaries also support unique communities of plants and animals especially adapted for life at the margin of the sea.
  • Estuaries have important commercial value and their resources provide economic benefits for tourism, fisheries, and recreational activities.
  • The protected coastal waters of estuaries also support important public infrastructure, serving as harbors and ports vital for shipping and transportation.
  • Estuaries also perform other valuable services. Water draining from uplands carries sediments, nutrients, and other pollutants to estuaries. As the water flows through wetlands such as swamps and salt marshes, much of the sediments and pollutants are filtered out.
  • Salt marsh grasses and other estuarine plants also help prevent erosion and stabilize shorelines [Mangroves].

Narmada River

  • Narmada is the largest west flowing river of the peninsular India.
  • Narmada flows westwards through a rift valley between the Vindhyan Range on the north and the Satpura Range on the south.
  • It rises from Maikala range near Amarkantak in Madhya Pradesh, at an elevation of about 1057 m.
  • Narmada basin extends over states of Madhya Pradesh, Gujarat, Maharashtra and Chhattisgarh having an area ~1 Lakh Sq.km.
  • It is bounded by the Vindhyas on the north, Maikala range on the east, Satpuras on the south and by the Arabian Sea on the west.
  • Its total length from its source in Amarkantak to its estuary in the Gulf of Khambhat is 1,310 km.
  • The hilly regions are in the upper part of the basin, and lower middle reaches are broad and fertile areas well suited for cultivation.
  • Jabalpur is the only important urban centre in the basin.
  • The river slopes down near Jabalpur where it cascades (a small waterfall, especially one in a series) 15 m into a gorge to form the Dhuan Dhar (Cloud of Mist) Falls.
  • Since the gorge is composed of marble, it is popularly known as the Marble Rocks.
  • It makes two waterfalls of 12 m each at Mandhar and Dardi. Near Maheshwar the river again descends from another small fall of 8 m, known as the Sahasradhara Falls.
  • There are several islands in the estuary of the Narmada of which Aliabet is the largest.
  • The Narmada is navigable upto 112 km from its mouth.

Tributaries of Narmada River

  • Since the river flows through a narrow valley confined by precipitous (dangerously high or steep) hills, it does not have many tributaries.
  • The absence of tributaries is especially noted on the right bank of the river where the Hiran is the only exception.
  • The other right bank tributaries are the Orsang, the Barna and the Kolar.
  • A few left bank tributaries drain the northern slopes of the Satpura Range and join the Narmada at different places.
  • The major Hydro Power Project in the basin are Indira Sagar, Sardar Sarovar, Omkareshwar, Bargi & Maheshwar.
West Flowing Rivers

Tapti River

  • The Tapti (also known as the Tapi) is the second largest west flowing river of the Peninsular India and is known as ‘the twin’ or ‘the handmaid’ of the Narmada.
  • It originates near Multai reserve forest in Madhya Pradesh at an elevation of 752 m.
  • Flows for about 724 km before outfalling into the Arabian Sea through the Gulf of Cambay [Gulf of Khambhat].
  • The Tapti River along with its tributaries flows over the plains of Vidharbha, Khandesh and Gujarat and over large areas in the state of Maharashtra and a small area in Madhya Pradesh and Gujarat.
  • The basin extends over states of Madhya Pradesh, Maharashtra and Gujarat having an area of ~ 65,000 Sq.km
  • Situated in the Deccan plateau, the basin is bounded by the Satpura range on the north, Mahadev hills on the east, Ajanta Range and the Satmala hills on the south and by the Arabian Sea on the west.
  • The hilly region of the basin is well forested while the plains are broad and fertile areas suitable for cultivation.
  • There are two well defined physical regions, in the basin, viz hilly region and plains; the hilly regions comprising Satpura, Satmalas, Mahadeo, Ajanta and Gawilgarh hills are well forested.
  • The plain covers the Khandesh areas (Khandesh is a region of central India, which forms the northwestern portion of Maharashtra state) which are broad and fertile suitable for cultivation primarily.

Tributaries of Tapti River

  • Right Bank: the Suki, the Gomai, the Arunavati and the Aner.
  • Left Bank: the Vaghur, the Amravati, the Buray, the Panjhra, the Bori, the Girna, the Purna, the Mona and the Sipna.

Projects on Tapti River

  • Hathnur Dam of Upper Tapi Project (Maharashtra)
  • Kakrapar weir and Ukai Dam of Ukai Project (Gujarat)
  • Girna Dam and Dahigam Weir of Girna Project (Maharashtra)

Industry in the Tapti Basin

  • Important industries in the basin are textile factories in Surat and paper and news print factory at Nepanagar.
Tapti river basin - West Flowing Rivers

Sabarmati River

  • The Sabarmati is the name given to the combined streams the Sabar and Hathmati.
  • The Sabarmati basin extends over states of Rajasthan and Gujarat having an area of 21,674 Sq km.
  • The basin is bounded by Aravalli hills on the north and north-east, by Rann of Kutch on the west and by Gulf of Khambhat on the south.
  • The basin is roughly triangular in shape with the Sabarmati River as the base and the source of the Vatrak River as the apex point.
  • Sabarmati originates from Aravalli hills at an elevation of 762 m near village Tepur, in Udaipur district of Rajasthan.
  • The total length of river from origin to outfall into the Arabian Sea is 371 km.
  • The major part of basin is covered with agriculture accounting to 74.68% of the total area.
  • Rainfall varies from a meager few mm in Saurastra to over 1000 mm in southern part.
  • Left bank tributaries: the Wakal, the Hathmati and the Vatrak.
  • Right bank tributaries: the Sei.
  • Projects: Sabarmati reservoir (Dharoi), Hathmati reservoir and Meshwo reservoir project are major projects completed during the plan period.
indian rivers and lakes
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Industry in Sabarmati Basin

  • Gandhinagar and Ahmedabad are the important urban centers in the basin.
  • Ahmedabad is an industrial city situated on the banks of Sabarmati.
  • Important industries are textiles, leather and leather goods, plastic, rubber goods, paper, newsprint, automobile, machine tools, drugs and pharmaceuticals etc.
  • The industrial city of Ahmedabad poses the danger of water pollution.

Mahi River

  • The Mahi basin extends over states of Madhya Pradesh, Rajasthan and Gujarat having total area of 34,842 Sq km.
  • It is bounded by Aravalli hills on the north and the north-west, by Malwa Plateau on the east, by the Vindhyas on the south and by the Gulf of Khambhat on the west.
  • Mahi is one of the major interstate west flowing rivers of India.
  • It originates from the northern slopes of Vindhyas at an altitude of 500 m in Dhar district of Madhya Pradesh.
  • The total length of Mahi is 583 km.
  • It drains into the Arabian Sea through the Gulf of Khambhat.
  • The major part of basin is covered with agricultural land accounting to 63.63% of the total area
  • Hydro Power stations are located in Mahi Bajaj Sagar dam and at Kadana Dam.
  • Vadodara is the only important urban centre in the basin. There are not many industries in the basin.
  • Some of the industries are cotton textile, paper, newsprint, drugs and pharmaceuticals. Most of these industries are located at Tatlam.

Luni River

  • The Luni or the Salt River (Lonari or Lavanavari in Sanskrit) is named so because its water is brackish below Balotra.
  • Luni is the only river basin of any significance in Western Rajasthan, which form the bulk of arid zone.
  • Luni originates from western slopes of the Aravalli ranges at an elevation of 772 m near Ajmer flowing in South West direction and traversing a course of 511 km in Rajasthan, it finally flow into the Rann of Kachchh (it gets lost in the marsh).
  • Most of its tributaries drain the steep north west of Aravalli hills and join it on left side. Its total catchment area falls in Rajasthan.
  • The peculiarity of this river is that it tends to increase its width rather than deepening the bed because the banks are of soils, which are easily erodible whereas beds are of sand. The floods develop and disappear so rapidly that they have no time to scour the bed.

West flowing Rivers of the Sahyadris (Western Ghats)

  • About six hundred small streams originate from the Western Ghats and flow westwards to fall into the Arabian Sea.
  • The western slopes of the Western Ghats receive heavy rainfall from the south-west monsoons and are able to feed such a large number of streams.
  • Although only about 3% of the areal extent flow swiftly down the steep slope and some of them make waterfalls.
  • The Jog or Gersoppa Falls (289 m) made by the Sharavati river is the most famous waterfall of India.

Ghaggar River – Inland Drainage

  • Some rivers of India are not able to reach the sea and constitute inland drainage.
  • Large parts of the Rajasthan desert and parts of Aksai Chin in Ladakh have inland drainage.
  • The Ghaggar is the most important river of inland drainage. It is a seasonal stream which rises on the lower slopes of the Himalayas and forms boundary between Haryana and Punjab.
  • It gets lost in the dry sands of Rajasthan near Hanumangarh after traversing a distance of 465 km.
  • Earlier, this river was an affluent of the Indus, the dry bed of the old channel is still traceable.
  • Its main tributaries are the Tangri, the Markanda, the Saraswati and the Chaitanya.
  • It contains a lot more water in rainy season when its bed becomes 10 km wide at places.
  • Most of the streams draining western slopes of the Aravalli Range dry up immediately after they enter the sandy arid areas to the west of this range.

Usability of Rivers

  • Source of fresh water, irrigation, hydro-electric production, navigation etc.
  • The Himalayas, Vindhyas, Satpuras, Aravalis, Maikala, Chhotanagpur plateau, Meghalaya plateau, Purvachal, Western and the Eastern Ghats offer possibilities of large scale water power development.
  • Sixty per cent of the total river flow is concentrated in the Himalayan rivers, 16 per cent in the Central Indian rivers (the Narmada, the Tapi, the Mahanadi, etc.), and the rest in the rivers of the Deccan plateau.
  • The Ganga and the Brahmaputra in the north and northeastern part of the country, the Mahanadi in Odisha, the Godavari and the Krishna in Andhra and Telangana the Narmada and the Tapi in Gujarat, and the lakes and tidal creeks in coastal states possess some of the important and useful waterways of the country.
  • In the past they were of great importance, which suffered a great deal with the advent of rail and roads.
  • Withdrawal of large quantities of water for irrigation resulted in dwindling flow of many rivers.
  • The most important navigable risers are the Ganga, the Brahmaputra and the Mahanadi. The Godavari, the Krishna, the Narmada and the Tapi are navigable near their mouths only
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