River System in India

INTRODUCTION #

The Indian economy and society is facing daunt- ing challenges in the water sector. The demands of a rapidly industrialising economy and urbanising soci- ety come at a time when the potential for augmenting supply is limited, water tables are falling and water quality issues have increasingly come to the fore. As we drill deeper for water, our groundwater gets contaminated with fluoride and arsenic. Both our rivers and our groundwater are polluted by untreated effluents and sewage continuing to be dumped into them. Climate change poses fresh challenges with its impacts on the hydrologic cycle. More extreme rates of precipitation and evapotranspiration will exacerbate impacts of floods and droughts. It is no wonder then that conflicts across competing uses and users of water are growing by the day. Meanwhile, water use efficiency in agriculture, which consumes around 80 per cent of our water resources is only around 38 per cent, which compares poorly with 45 per cent in Malaysia and Morocco and 50–60 per cent in Israel, Japan, China and Taiwan.

DEMAND AND SUPPLY OF WATER IN INDIA #

Estimates of the annual flow of water available for human use after allowing for evapotranspiration and minimum required ecological flow vary con- siderably. The water budget based on Ministry of Water Resources estimates shows utilisable water of 1,123 billion cubic metres (BCM) against current water demand of 710 BCM, suggesting more than adequate availability at the aggregate level given current requirements. The Standing Subcommittee of the Ministry of Water Resources estimates total

water demand rising to 1,093 BCM in 2025, which reaffirms a comfortable scenario at the aggregate level even in 2025.

However, more recent calculations, based on more realistic estimates of the amount of water lost to the atmosphere by evapotranspiration, are less reassuring. Since the amount of water available is more or less constant, rising demands due to increas- ing population and economic growth will strain the demand–supply balance. The 2030 Water Resources Group (2009) estimates that if the current pattern of demand continues, about half of the demand for water will be unmet by 2030.

DRAINAGE SYSTEMS OF INDIA #

India is blessed with hundreds of large and small rivers, which drain the length and breadth of the country. The annual yield of water in the rivers of the country is 18, 58,100 million cubic meters, 1/3rd (33.8%) of which is contributed by the Brahmapu- tra followed by the Ganga (25.2%), the Godavari (6.4%), the Indus (4.3%), the Mahanadi (3.6%), the

Krishna (3.4%), and the Narmada (2.9%).

On the basis of the origin of rivers, the Indian drainage system can broadly be divided into–

• The Himalayan river system including Indus,

Brahmaputra, Ganga and their tributaries, and

• The Peninsular river system which include Mahanadi, Godavari, Krishna, Cauvery, Nar- mada, Tapi and their tributaries.

Similarly on the basis of orientation to the sea, the Indian drainage system can be divided into-

• The Bay of Bengal drainage
  • The Arabian sea drainage.

About 77% of the drainage area of the country is oriented towards the Bay is Bengal and it consists of large numbers of rivers like Ganga, Brahmaputra, Mahanadi, Godavari, Krishna, Cauvery, Penneru, Vaigai etc. while 23% of the country’s drainage area is oriented towards the Arabian sea including the Indus, Narmada, Tapi, Sabarmati, Mahi and large number of swift flowing western coast rivers descending from the Sahyadris. Over 90% of the water carried by the Indian rivers is drained into the Bay of Bengal and rest into the Arabian Sea or forms inland drainage. Water-divide plays an important role in deciding the direction of the river flow.

HIMALAYAN RIVER SYSTEMS #

Important features #

• Himalayan rivers are typical example of antecedent drainage, i.e. they were in exist- ence before the uplift of the Himalayas. It is evident from the deep gorges of the rivers like Indus, Satluj, Alaknanda, Bhagirathi, Brahmaputra and Kosi. Also, most of them are not consequent to the Himalayan relief.
• Because these rivers are fed by extensive snow cover of the Himalayas, they are per- ennial in nature. During the monsoon season they receive heavy Rainfall and reach to their maximum discharge.
• The geologically unstable condition and friable nature of the terrain causes consider- able meandering or drastic changes in their courses and uncertainty and capriciousness in their behaviour.
• The valleys are in immature stage of develop- ment and, therefore, they are characterized by a number of rapids, waterfalls, and cascades.

EVOLUTION OF THE HIMALAYAN DRAINAGE #

Geologists believe that a mighty river called Shiwalik or Indo-Brahma traversed the entire lon- gitudinal extent of the Himalayas from Assam to Punjab and onwards to Sind, and finally discharged into the Gulf of Sind near lower Punjab during the Miocene period. The remarkable continuity of the Shiwalik and its lacustrine origin and alluvial

deposits consisting of sands, silt, clay, boulders and conglomerates support this viewpoint. It is opined that in due course of time Indo-Brahma river was dismembered into three main drainage systems:

• the Indus and its five tributaries in the west- ern part;
• the Ganga and its Himalayan tributaries in the central part; and
• the stretch of the Brahmaputra in Assam and its Himalayan tributaries in the eastern part.

The dismemberment was probably due to the Pleistocene upheaval in the western Himalayas, including the uplift of the Potwar Plateau (Delhi Ridge), which acted as the water divide between the Indus and Ganga drainage systems. Likewise, the downthrusting of the Malda gap area between the Rajmahal hills and the Meghalaya plateau during the mid-Pleistocene period, diverted the Ganga and the Brahmaputra systems to flow towards the Bay of Bengal.

THE INDUS SYSTEM #

This is one of the largest river basins of the world, covering an area of 1,178,440 sq. km (in India 321,290 sq. km) and a total length of 2,880 km (in India 709 km). The Indus, also known as the Sindhu, is the westernmost of the Himalayan rivers in India.

The Indus originates from a glacier near Bokhar Chu (31°15’ N latitude and 81°40’ E longitude) in the Tibetan region at an altitude of 5,182 m in the Kailash Mountain range. In Tibet, it is known as ‘Singe Khamban’ or Lion’s mouth until it is joined by the Dhar. It enters India and continues to flow in the northwest direction between Ladakh and Jaskar ranges. In India, the Indus flows only through the Leh district in Jammu and Kashmir. The gradient of the river is very gentle (30 cm per km). It receives a number of tributaries such as the Shyok, the Gilgit, the Gortang, the Zaskar, the Hunza, the Nubra, the Shigar, the Gasting and the Dras.

Indus enters Pakistan near Chillar in the Dardis- tan region and finally emerges out of the hills near Attock where it receives the Kabul river on its right bank. The other important tributaries joining the right bank of the Indus are the Khurram, the Tochi, the

Gomal, the Viboa and the Sangar. They all originate in the Sulaiman ranges. The river flows southwards and receives ‘Panjnad’ a little north of Mithankot. The Panjnad is the name given to the accumulated water of the five rivers of Punjab namely the Jhelum, the Chenab, the Ravi, the Beas and the Satluj. Indus finally discharges into the Arabian Sea, east of Kara- chi. The average annual flow of water in the Indus river is 110,450 million cubic meters at Kalabagh.

The Jhelum, an important tributary of the Indus, rises from a spring at Verinag situated at an altitude of 4900 m in the south-eastern part of the valley of Kashmir. It flows northward through Srinagar and the Wular lake. At Muzaffarabad, the river takes a hairpin bend southwards and receives river Kishen- ganga on its right bank. Thereafter, it forms the India- Pakistan boundary for 170 km and emerges at Potwar plateau near Mirpur. Its main tributaries are the Lidar, the Sind, and the Pohru from Kashmir Himalayas. The average annual flow of water in the Jhelum river is 27,890 million cubic meters at Mangala. It joins the Chenab at Trimmu near Jhang in Pakistan.

The Chenab, the largest tributary of the Indus, originates near Bara Lacha Pass and is formed by two streams, the Chandra and the Bhaga, which joins at Tandi near Keylong in Himachal Pradesh. Here, it is also known as Chandrabhaga. It flows towards northwest through Pangi valley and enters Jammu and Kashmir. At Akhnur, the Chenab enters the plain. The river flows for 1,180 km before entering into Pakistan. The average annual flow of water in the Chenab river is 29,000 million cubic meters at Marala. It joins the Satluj at Panchnad in Pakistan.

The Ravi has its source in the Kullu hills near Rohtang Pass in Himachal Pradesh. Flowing in the northwest direction, it drains the area lying between the Pir Panjal and the Dhauladhar ranges. It enters Punjab plains near Madhopur and enters Pakistan 26 km south of Amritsar. It debouches into Chenab at Sarai Sindhu near Rangpur. Its annual flow at Madhopur is 8,000 million cubic meters.

The Beas originates from the Beas Kund near the Rohtang Pass at an elevation of 4,000 m above the mean sea level. The river flows through the Kullu valley and forms gorges at Kati and Lorji in the Dhauladhar range. It enters the Punjab plains

near Pong. Then it takes southwesterly direction and meets the Satluj near Harike. The average annual flow of the Beas at Mandi is 15,800 million cubic meters.

The Satluj, an antecedent river, originates from the Mansarovar-Rakas Lake near Darma Pass at an altitude of 4,570 m in Tibet where it is known as Langchen Khamban. It flows almost parallel to the Indus for about 400 km before entering India through the Shipki La Pass. It has created a 900 m deep gorge in Nari Khorsan province of Tibet. Its main tributary Spiti joins it at Namgia. It is a very important river as it feeds the canal system of the Bhakra Nangal project. After entering the plains at Rupar, it turns westward and is joined by the Beas at Harike. From Ferozepur to Fazilka, it forms the boundary between India and Pakistan for 120 km. Out of its total length of 1,450 km, it flows for 1,050 km in India. Its average annual flow at Rupnagar (Rupar) is 16,600 million cubic meters.

THE GANGA RIVER SYSTEM #

The Ganga originates as the Bhagirathi from the Gangotri glacier at Gaumukh, at an elevation of 7,010 m. Alaknanda, the other headstream of Ganga, has its source in the Satopanth glacier near Badrinath. The Alaknanda consists of the Dhauli and the Vishnu Ganga which meet at Joshimath. The Alaknanda river meets

• The Dhauliganga river at Vishnuprayag,
• The Pindar river at Karnaprayag,
• The Mandakini or Kali Ganga at Rudraprayag, and finally
• The Bhagirathi river at Devprayag.

At Devprayag Ganga gets its name. After traversing 280 km from its source, Ganga debouches on the Gangetic Plain at the pilgrimage town of Haridwar. Here, some of its waters is diverted to the Ganges Canal, which irrigates the Doab region of Uttar Pradesh. The Ganges, whose course has been roughly southwestern until this point, now begins to flow southeast through the plains of northern India. The river follows a 770 km curving course passing through the city of Kanpur before being joined from the southwest by the Yamuna at Allahabad. Joined by numerous rivers such as the Kosi, Son, Gandak

and Ghaghra, the Ganges forms a formidable current in the stretch between Allahabad and Malda in West Bengal. On its way it passes the towns of Varanasi, Buxar, Patna and Bhagalpur. At Bhagalpur, the river meanders past the Rajmahal Hills, and begins to run south.

At Pakur, the river begins its attrition with the branching away of its first distributary, the Bhagi- rathi-Hooghly, which goes on to form the Hooghly River. Near the border with Bangladesh the Farakka Barrage, built in 1974, controls the flow of the Gan- ges, diverting some of the water into a feeder canal linking the Hooghly to keep it relatively silt-free. The Farakka barrage project consists of a barrage across the Ganga at Farakka and another across the Bhagirathi at Jangipur.

After entering Bangladesh, the main branch of the Ganges is known as the Padma River until it is joined by the largest distributary of the Brahmaputra- the Jamuna River at Goalundo. Further downstream, it is fed by the Meghna River, the second largest tributary of the Brahmaputra, and flows as Meghna to enter the Meghna Estuary near Sagar island.

The total length of Ganga is 2525 km, of which 310 km is in Uttarakhand, 1140 km in Uttar Pradesh, 445 km in Bihar, and 520 km in west Bengal. The remaining 110 km stretch of the Ganga forms the boundary between Bihar and Uttar Pradesh. The Yamuna and the Son are its major right bank trib- utaries. The important left bank tributaries are the Ramganga, the Gomati, the Ghaghara, the Gandak, the Kosi and the Mahananda in the order from west to east.

The Yamuna, the western most and the longest tributary of the Ganga, has its source in the Yamnotri glacier on the western slopes of Banderpunch range (6,330 m). Small streams like Rishiganga, Uma, and Hanuman Ganga join it in the mountains. Tons joins it near Kalsi. It enters plains at Tajewala. It is joined by the Chambal, the Sind, the Betwa and the Ken on its right bank which originates from the Peninsular plateau while the Hindon, the Rind, the Sengar, the Varuna, join it on its left bank. It joins the Ganga at Prayag (Allahabad). The total length of Yamuna from its origin to Prayag is 1,376 km. Much of its water feeds the western and eastern Yamuna and the Agra canals for irrigation purposes.

The Chambal rises from Janapao hills near Mhow in the Malwa plateau of Madhya Pradesh and flows northwards through a gorge upwards of Kota in Rajasthan, where the Gandhisagar dam has been constructed. From Kota, it traverses down to Bundi, Sawai Madhopur and Dholpur, and finally joins the Yamuna in Etawah district of U.P. The Chambal is famous for its badland topography called the Chambal ravines. The total length of the river is 1,050 km. The Banas joins it at Sawai Madhopur.

The Sind originates in Vidisha plateau of Madhya Pradesh. It flows for a distance of 415 km before joining Yamuna.

The Betwa rises in the Bhopal district and joins Yamuna near Hamirpur after traversing a distance of 590 km. The Dhasan is its important tributary.

The Ken is 360 km long river rising from the Barner Range of Madhya Pradesh. It joins Yamuna near Chila.

The Son is a large south bank tributary of the Ganga, originating in the Amarkantak plateau. After forming a series of waterfalls at the edge of the pla- teau, it turns northeastward. It reaches Arrah, west of Patna, to join the Ganga. The important tributaries of the Son are the Johilla, the Gopat, the Rihand, the Kanhar and the North Koel.

The Damodar occupies the eastern margins of the Chotanagpur Plateau where it flows through a rift valley and finally joins the Hooghly. The Barakar is its main tributary. Once known as the ‘sorrow of Bengal’ for its devastating floods, the Damodar has been now tamed by the Damodar Valley Corpora- tion, a multipurpose river project.

The Ramganga is a small river rising in the Garhwal hills near Kalagarh.

It changes its course to the southwest direction after crossing the Shiwalik and enters into the plains of Uttar Pradesh near Najibabad. Finally, it joins the Ganga near Kannauj. Its main tributaries are the Khoh, the Gangan, the Aril, the Kosi, and the Deoha (Gorra).

The Ghaghara originates in the glaciers of Mapchachungo near Gurla Mandhata peak south of Mansarovar. It is known as Karnali in western Nepal. After collecting the waters of its tributaries – Tila,

Seti and Beri, it comes out of the mountain, cutting a deep gorge at Shishapani. The river Sarda (Kali or Kali Ganga) joins it in the plain before it finally meets the Ganga at Chhapra. Its other tributaries are the Sarju and the Rapti. Its average annual flow is 94,000 million cubic meter.

The Sarda or Saryu river rises in the Milan glacier in the Nepal Himalayas where it is known as the Goriganga. Along the Indo-Nepal border, it is called Kali. After reaching the plain near Tanakpur, it is called as Chauka. Then it takes southeasterly course to join the Ghaghara.

The Gandak comprises two streams, namely Kaligandak and Trishul Ganga. It rises in the Nepal Himalayas between the Dhaulagiri and Mount Ever- est and drains the central part of Nepal. Gandak is known as narayani in Nepal. It enters the Ganga plain in Champaran district of Bihar and joins the Ganga at Sonpur near Patna. The average annual flow is 52,200 million cubic meters. Its main tributaries are the Mayangadi and the Bari. The Burhi Gandak orig- inates from the western slopes of Sumesar hills near Indo-Nepal border and flows in south-east direction. It joins Ganga opposite Monghyr. Its length is 610 km.

The Kosi is an antecedent river with its source to the north of Mount Everest in Tibet, where its main stream Arun rises. After crossing the Central Himalayas in Nepal, it is joined by the Sun Kosi from the West and the Tamur Kosi from the east. It forms Sapt Kosi after uniting with the river Arun at Triveni. Soon after debouching onto the plain the river becomes sluggish due to heavy load. The river channel is braided and it shifts its course frequently. This causes devastating floods. Thus the Kosi is known as ‘the Sorrow of Bihar’. Hanuman Nagar barrage has been constructed in 1965 to tame the river. The Kosi joins Ganga near Kursala.

THE BRAHMAPUTRA RIVER SYSTEM #

The Brahmaputra, one of the largest rivers of the world, has its origin in the Chemayungdung glacier of the Kailash range. Mariam La separates its source from the Mansarovar lake. From here, it traverses eastward longitudinally for a distance of nearly 1,200 km in a dry and flat region of southern Tibet, where it is known as the Tsangpo, which means ‘the

purifier.’ The Rango Tsangpo is the major tributary of this river from the north in Tibet. It emerges as a turbulent and dynamic river after carving out a deep gorge in the Central Himalayas near Namcha Barwa (7,756 m). The river emerges from the foothills under the name of Siang or Dihang. It enters India west of Sadiya town in Arunachal Pradesh. Flowing southwest, it receives its main left bank tributaries, viz., Dibang or Sikang and Lohit; thereafter, it is known as the Brahmaputra.

The Brahmaputra receives numerous tributaries in its 750 km long journey through the Assam valley. Its major left bank tributaries are the Burhi Dihing, Noa Dihing, Dhansiri (South), Dibru, Dikhu, and Kalang whereas the important right bank tributaries are the Subansiri, Kameng, Dhansiri (north), Manas, and Sankosh. The Subansiri, which has its origin in Tibet, is an antecedent river. The Brahmaputra enters Bangladesh near Dhubri and flows southward. In Bangladesh, the Tista joins it on its right bank from where the river is known as the Jamuna. It finally merges with the river Padma, which falls in the Bay of Bengal.

The Brahmaputra is well-known for floods, channel shifting and bank erosion. This is due to the fact that most of its tributaries are large, and bring large quantity of sediments owing to heavy rainfall in its catchment area. It has a braided channel for most of its course in Assam and forms the worlds largest river island ‘Majuli’.

THE PENINSULAR DRAINAGE SYS- TEM #

The Peninsular drainage system is older than the Himalayan one. This is evident from the broad, largely-graded shallow valleys and the maturity of the rivers. The Western Ghats running close to the western coast act as the water divide between the major Peninsular rivers, discharging their water in the Bay of Bengal and small rivulets joining the Arabian Sea. Most of the major Peninsular Rivers except Narmada and Tapi flow from west to east. The major river systems of the peninsular drainage are – the Mahanadi the Godavari, the Krishna and the Cauvery. Peninsular rivers are characterized by fixed course, absence of meanders and non perennial flow of water. The Narmada and the Tapi which flow through the rift valley are, however, exceptions.

Evolution of the peninsular drainage #

Three major geological events in the distant past have shaped the present drainage systems of Peninsular India :

• Subsidence of the western flank of the Penin- sula leading to its submergence below the sea during the early tertiary period. Generally, it has disturbed the symmetrical plan of the riv- er on either side of the original watershed.
• Upheaval of the Himalayas when the north- ern flank of the peninsular block was subject- ed to subsidence and the consequent trough faulting. The Narmada and the Tapi flow in trough faults and fill the original cracks with their detritus materials. Hence there is a lack of alluvial and deltaic deposits in these rivers.
• Slight tilting of the Peninsular block from northwest to the southeastern direction gave orientation to the entire drainage system to- wards the Bay of Bengal during the same pe- riod.

The Peninsular River Systems Important features of the Peninsular River system:

• The peninsular rivers originates at lower alti- tudes and drain areas which are geologically more stable and, therefore, are devoid of meanders.
• The river Channels have reached the base levels and have low gradients.
• Larger deltas are formed by larger rivers at their mouth (except those flowing towards west).
• The broad, largely graded and shallow valleys of the peninsular rivers indicate that they have existed for a much longer period than the Himalayan rivers.
• Most of the peninsular river flow towards the east because the main watershed lies in Western Ghats in close proximity to the west coast. Notable exceptions are Narmada and Tapi, which flows in a direction opposed to this general trend.
• There are a large number of river systems in the peninsular drainage. There are three main directions of flow of peninsular rivers-

• The Mahanadi, the Godavari, the Krish- na, the Cauvery and several small rivers draining south-east into the Bay of Bengal.
  • The Narmada and the Tapi flowing west as well as several small streams originat- ing from the Western Ghats flow west- ward into the Arabian sea.
  • The tributaries of Ganga and Yamuna such as Chambal, Sind, Betwa, Ken, Son and Damodar flow in north-easterly di- rection.

THE EAST FLOWING RIVERS OF THE PENINSULA #

The Mahanadi rises near Sihawa in Raipur district of Chhattisgarh and runs through Orissa to discharge its water into the Bay of Bengal. It is 851 km long and its catchment area spreads over

1.42 lakh sq. km. Some navigation is carried on in the lower course of this river. 53 per cent of the drainage basin of this river lies in Madhya Pradesh and Chhattisgarh, while 47 per cent lies in Orissa. The main tributaries are the the Mand, the Hasdo and the Sheonath on the left bank and the Ong, the Jonk, and the Tel on the right bank. World’s longest dam Hirakud is situated on this river.

The Godavari is the largest peninsular river. It is also called the Vridha Ganga or the Dakshin Ganga. It rises from the Triambak plateau in the Nasik dis- trict of Maharashtra and discharges its water into the Bay of Bengal. Its tributaries run through the states of Maharashtra, Madhya Pradesh, Chhattisgarh, Orissa and Andhra Pradesh. It is 1,465 km long with a catchment area spreading over 3.13 lakh sq. km, 49 per cent of which lies in Maharashtra, 21 per cent in Madhya Pradesh and Chhattisgarh, 24 percent in Andhra Pradesh and the rest in Orissa. The Manjra is the only important right bank tributary which passes through Nizam Sagar dam. The Penganga, the Wardha, the Wainganga, the Indravati, the Pranhita, and the Sabari are its principal left bank tributaries. The Penganga joins the Wardha which in turn joins the Wainganga to become short-span Pranhita which merges with the Godavari. The Indravati rises from Kondhan hills of Eastern Ghats. The Godavari is subjected to heavy floods in its lower reaches to the south of Polavaram, where it forms a picturesque

gorge. It is navigable for only 300 km in the deltaic stretch. After Rajamundri, the river splits into Gau- tami Godavari in the east and Vashishtha Godavari in the west forming a large Lobate type delta.

The Krishna is the second largest eastflowing peninsular river which rises near Mahabaleshwar in the Sahyadris. Its total length is 1,400 km. The Koyna, the Muneru, the Ghatprabha, the Malprabha, the Tungbhadra, the Musi, and the Bhima are its major tributaries. Of the total catchment area of the Krishna, 27 per cent lies in Maharashtra, 44 per cent in Karnataka and 29 per cent in Andhra Pradesh.

The Kaveri rises from Taal Kaveri in Brahmagiri hills in Karnataka. Its length is 800 km and it drains an area of 81,155 sq. km. Since the upper catchment area receives rainfall during the southwest monsoon season (summer) and the lower part during the northeast monsoon season (winter), the river carries water throughout the year with comparatively less fluctuation than the other peninsular rivers. The river descends from the South Karnataka Plateau to the Tamilnadu Plains through the Sivasamudram Falls. The river island Srirangam is in its middle course. About 3 per cent of the Kaveri basin falls in Kerala, 41 per cent in Karnataka and 56 per cent in Tamil Nadu. Its important tributaries are the Herangi, the Hemavati, the Lokpavani, the Shimsha and the Arkavati from the north and the Lakshamantirtha, the Kabini, the Suvarnavati, the Bhavani and the Amravati from south.The other east flowing rivers of the peninsular India are, from north to south, the Subarnarekha, the Brahmani, the Penneru, the Ponnaiyar, and the Vaigai. The Brahmani forms after the confluence of the Koel and the Sankh near Rourkela. Its tributaries are the Kura, the Sankhad and the Tikra. The tributaries of the Penneru are the Jayamangli, the Kunderu, the Saigileru, the Chitra- vati, the Papagni and the Cheyyeru. The Baitarni, the Vamsadhara and the Palar are other important rivers.

THE WEST FLOWING RIVERS OF THE PENINSULA #

The Narmada, the largest west flowing river of the peninsula, originates on the western flank of the Amarkantak plateau at a height of about 1,057 m. Flowing in a rift valley between the Satpura in the south and the Vindhyan range in the north, it forms

a picturesque gorge in Marble Rocks and Dhuandhar waterfall near Jabalpur. It makes other waterfalls at Mandhar, Dardi and Maheshwar (Sahasradhara Falls). After flowing a distance of about 1,310 km, it meets the Arabian sea south of Bharuch, forming a broad 27 km long estuary in the Gulf of Khambhat. Its catchment area is about 98,796 sq. km. The Sardar Sarovar Project has been constructed on this river. The Hiran, the Orsang, the Barna and the Kolar are its major right bank tributaries. The major left bank tributaries are the Burhner, the Banjar, the Shar, the Shakkar, the Kundi and the Tawa.

The Tapi or the Tapti is the second largest westward flowing river. It is also known as ‘The Twin’ and ‘The Handmaid’ of the Narmada. It orig- inates from Multai in the Betul district of Madhya Pradesh. It is 730 km long and drains an area of 65,145 sq. km. Nearly 79 per cent of its basin lies in Maharashtra, 15 per cent in Madhya Pradesh and the remaining 6 per cent in Gujarat. Its main tributary is the Purna joining it near Bhusawal. Other tributaries are the Betul, the Patki, the Aner, and Gomai on the right bank and the Khursi, the Girna, the Bori and the Panjhara on the left bank.

The Luni is the largest river system of Rajast- han, west of Aravali. It originates near Pushkar in two branches, i.e. the Saraswati and the Sagarmati, which join with each other at Govindgarh. From here, the river comes out of Aravali and is known as Luni. It flows towards the west till Telwara and then takes a southwest direction to join the Rann of Kuchchh. The entire river system is ephemeral.

The Sabarmati is the name given to the com- bined streams of the Sabar and the Hathmati. It rises from Mewar in Aravali range and falls into the Gulf of Khambhat. Its tributaries are the Sedhi, the Meshwa, etc.

The Mahi rises in the Vindhyas and falls into the Gulf of Khambhat. Its drainage area is shared by Madhya Pradesh (19%), Rajasthan (47%), and Gujarat (34%). Its tributaries are the Som, the Anas and the Panam.

THE WEST FLOWING RIVERS OF THE SAHYADRIS #

The rivers flowing towards the Arabian sea have short courses. These drain 3% of India’s land

area but carry 18% of country’s water resources. In Karnataka, the Kalinadi rises from Belgaum district and falls in the Karwar Bay. The source of Bedti river lies in Hubli Dharwar and traverses a course of 161 km. The Sharavati is another important river in Karnataka flowing towards the west. It originates in Shimoga district and drains a catchment area of 2,209 sq. km. The famous Jog or Gersoppa Falls made by the Sharavati is the highest in India. The Bhadra originates near Aniali village in Rajkot dis- trict in Gujrat. The Vaitarna rises from the Triambak in Nasik district at an elevation of 670 m.

Goa has a few rivers which can be mentioned here. They are Mandovi, Rachol and Juari.

Kerala has a narrow coastline. The longest river of Kerala, Bharathapuzha rises near Annamalai hills. It is also known as Ponnani. It drains an area of 5,397 sq. km. The Periyar is the second largest river of Kerala. Its catchment area is 5,243 sq. km. Other rivers of Kerala worth mentioning are the Pamba river which falls in the Vembanad lake after traversing a course of 177 km, the Beypore and the Pannam.

DRAINAGE PATTERNS #

A drainage system is the pattern formed by the streams, rivers, and lakes in a particular drainage basin. They are governed by the topography of the land, whether a particular region is dominated by hard or soft rocks, and the gradient of the land.

Types of drainage system #

1. Dendritic drainage system: Dendritic drain- age systems are the most common form of drainage system. In a dendritic system, there are many contributing streams (analogous to the twigs of a tree), which are then joined together into the tributaries of the main riv- er (the branches and the trunk of the tree, respectively). They develop where the river channel follows the slope of the terrain. Den- dritic systems form in V-shaped valleys; as a result, the rock types must be impervious and non-porous.
2. Parallel drainage system: A parallel drain- age system is a pattern of rivers caused by steep slopes with some relief. Because of

the steep slopes, the streams are swift and straight, with very few tributaries, and all flow in the same direction. This system forms on uniformly sloping surfaces, for example, rivers flowing southeast from the Aberdare Mountains in Kenya.

• Trellis drainage system: The geometry of a trellis drainage system is similar to that of a common garden trellis used to grow vines. As the river flows along a strike valley, smaller tributaries feed into it from the steep slopes on the sides of mountains. These tributaries enter the main river at approximately 90 de- gree angles, causing a trellis-like appearance of the drainage system. Trellis drainage is characteristic of folded mountains, such as the Appalachian Mountains in North Ameri- ca.
• Rectangular drainage system: Rectangular drainage develops on rocks that are of ap- proximately uniform resistance to erosion, but which have two directions of jointing at approximately right angles. The joints are usually less resistant to erosion than the bulk rock so erosion tends to preferentially open the joints and streams eventually develop along the joints. The result is a stream system in which streams consist mainly of straight line segments with right angle bends, and tributaries join larger streams at right angles.
• Radial drainage system: In a radial drainage system the streams radiate outwards from a central high point. Volcanos usually display excellent radial drainage. Other geological features on which radial drainage commonly develops are domes and laccoliths. On these features the drainage may exhibit a combina- tion of radial and annular patterns.
• Deranged drainage system: A deranged drainage system is a drainage system in drain- age basins where there is no coherent pattern to the rivers and lakes. It happens in areas where there has been much geological dis- ruption. The classic example is the Canadi- an Shield. During the last ice age, the topsoil was scraped off, leaving mostly bare rock. The melting of the glaciers left land with many irregularities of elevation, and a great

deal of water to collect in the low points, ex- plaining the large number of lakes which are found in Canada. The watersheds are young and are still sorting themselves out. Eventual- ly the system will stabilize.

• Annular drainage pattern: In an annular drainage pattern streams follow a roughly circular or concentric path along a belt of

weak rock, resembling in plan a ring like pat- tern. It is best displayed by streams draining a maturely dissected structural dome or ba- sin where erosion has exposed rimming sed- imentary strata of greatly varying degrees of hardness, as in the Red Valley, which near- ly encircles the domal structure of the Black Hills of South Dakota.