Rivers of Sikkim & Its Impact on Physiography

JAC : A Journal Of Composition Theory ISSN : 0731-6755

Rivers of Sikkim & its Impact on Physiography

Amrita SardarPramanick Research Scholar, Dept. of. Geography, C.M.J. University, Jorabat, Meghalaya, India.

Dr.Harsha Kumar Das Gupta Research Guide, Dept. of. Geography, C.M.J. University, Jorabat, Meghalaya, India.

Abstract: Sikkim Himalaya is the eastern part of Himalaya. Physiographic formation & locational altitude is the source of formation of rivers. Sikkim may have a small size, but this is amply compensated by formidable physical features. It is the physical features like the rivers and mountains that define the boundaries of the state with its neighbors. The edge of the Tibetan plateau more or less demarcates the northern border of Sikkim with Tibet. The eastern boundary with Tibet is represented by the Chola range whereas the border of Bhutan is constituted by the Pangolia Range. In the west of the Singalila range forms the watershed as well as the border between Nepal and Sikkim. Parts of the river Rangit, Tista, Rangpo-chu combine to define the border of Sikkim with West Bengal. The terrain of Sikkim is so rugged that from the air it looks as though a giant plough had been carelessly run through it. Keywords: Importance of Rivers, Sikkim, Impact on Physiography,Impact on Physiography Introduction According to Wadia the Archaeans are here represented by Daling& Darjeeling Series. Daling is a schistose group; it grades by transition zone into the dominated as Gneissic Darjeeling series. But in the localized zones Dalings are typically slate &phyllites in upper zones. Dalings of Sikkim contain in lower parts in pockets of copper ore in places like Rangpo, Jorthang etc. In the transition zone phyllites carry porphyroblasts of chlorite and biotite with occasional zones containing tiny garnets, it is known as garnet-biotite-schist. The composition based on staurolite, kynite, and sillimanite. Composition called as granite-gneiss. In nor then Sikkim & adjoining part of Nepal it is predominant. Auden classified the types of metamorphism as thrust zone. The extension projected towards north, there are also presence of marble, calcphyres, quartzite & pyroxene-granulates amidst to gneisses. The basic composition consists of Gondwana thrust slice. Presence of limestone also the main source of hot water springs'. In placesess, the hot springs are not very frequent in Sikkim. But in Southern & eastern part of Sikkim occasional presence are recorded like in between Namchi&Ravangla.

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Climate Small though it may look, one would be surprised to learn that Sikkim possesses all the climates right from the tropical to the tundra’s. So much so, it is possible to drop from the arctic heights to the tropical lowlands within a matter of a couple of hours. On most parts of the northern, eastern, and western borders the earth blanketed with snow almost throughout the year because of high altitudes. Elevations of 6000mts (19900 ft) and above remain snowbound throughout the year whereas places as low as 3000mts (9840 ft) come within the snow line during the winters. Moving to the southern border we can find altitudes plummeting down to as low as sea level full of rich tropical forests. Even the climate on two opposite sides of a hill can vary considerably.

Rainfall Sikkim is one of the rainiest regions in India. Because of the proximity of Sikkim to the Bay of Bengal and the fact that the mountains of the state come directly in the path of the monsoon clouds, most part of the Sikkim experience torrential rain during summer. So much so that even a small depression over the Bay of Bengal triggers off a downpour in Sikkim. Even during spring and autumn moisture laden clouds are formed due to local evaporation

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and it continues to be a greater part of Sikkim. It is only during October to March that there is hardly any rain and the weather remains more or less clear.

Rainfall, however, varies considerably from place to place because of the hill features. The northern border of Sikkim experiences comparatively low rainfall because of the monsoon clouds dry out by the time they hit the northern barrier. For the sake of comparison, Gangtok registers an average of 325 cm rainfall per annum whereas Muguthang, in the extreme north, experiences an average rainfall of only 60 cm per annum. Most of Sikkim does not experience high intensity winds. However, at many hill tops and passes, winds and blizzards having high speed, blow.

Rivers of Sikkim Himalaya The river that flows right across the length of Sikkim is the Tista snaking through the deep gorges taking tributaries as it goes. Its major tributary is the Rangit which originates from the Rathong glacier and meets it at the border between Sikkim and West Bengal. The river Ramam, a tributary of Rangit, and Rangpochu, a tributary of Tista define the southern border between Sikkim and West Bengal. Tista originates from the Lake Cholamu where it is The Himalayas continue from River Kali to the Singalila Ridge on the east for more than 880 Kilometer through Nepal in its most stupendous form. The highest point of mountain Mount Everest 8840 meter.

Revising the Singalila Ridge on the west the most critical River Rangit a glass shaped small geographic domain of Darjeeling Hill. On which the typical formations of metamorphosed equivalent spread of the higher ranges of Sikkim Himalayas are thrust. The reasons of geological ages changed the shape and slopes for the tectonics movements.

The river Tista in its descent form the Sikkim Himalaya cuts the Darjeeling ridge form 2135- 2440 meter in a narrow gage running west of Kalimpong at Sevok Bridge to spill on to the plain in a vast alluvial fan in other way called as paradelta.

It is difficult to explain the rivers and mountain of Sikkim and Darjeeling as the formation is co-related.The Doors in view of many on out wash plain of the glacies. Terrain is low elevation of land.

From the age of Pre-Cambrian crystalline upon alluvial fan of the Tista at many locations suggested also that the Siwaliks in this part of the Eastern Himalaya. The steep thrust of Gondwana rocks is present along the foothills at the Nepal Himalaya. Darjeeling and Sikkim

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are the frontal thrust of Arunachal Himalaya. Sikkim and the region itself is in effect all but an enclosed basin between Singalila and Donkhya Range. This sector of Darjeeling Himalaya in Sikkim is occupied by River Lachen. In view Lachen and Lachung are the source of the flow of Tista along the axis of an overturned anticline. The central Sikkim is basically by open folding like in other sense homo cling folding.

Among the main rivers are as follows:-

Teasta- 315 Lachung River- River Rangeet- 80 km Lhonak River- Rangpochu- Jaldhaka- 186 km Lachen River- Roro River- Ranikhola- Relli River- Rangpo Chu- Reley Chu- Rammam River- The main River Teesta runs down through gorge and rapids in high reach of Sikkim. At the bottom of Tibet, India from Khangsa glacier it has been originated. Altitude 7000 mts.

Rangit- is the main tributary of Teesta. It originated at Sikkim Himalaya. Rangit and Rathong Chu. In other name it is known as AfonRangeet.

Lachen River is the tributary of Teesta, Lanchung is another tributary of Teesta.

Rangpo is another imported originated at Jelep La pass at east Sikkim district. In the language of Tibatianchu means little river. This river feeds the high altitude Lake Menmecho. All the above noted rivers play a role on the formation of topography.

In view of the terrain character and seasonal positions, in winter at high altitude the rivers are frozen in north Sikkim, in South and West due to altitude modern could in winter. The entire area of Sikkim collect rain water and some rivers are having glacial water through ant the year. The drainage basin or catchment areas are in many situations large, like Teesta, Rangit, Rangpo Rivers. But in high altitude drainage network is remerged.

The shape and size of the steers are affecting stream discharge. According to R.E. Horton drainage networks design the drainage basin morphology. The litho logical character in study area Namchi modified by different cultural activity. Folds & rivers and common drainage pattern in Sikkim creating their movements along sedimentary & schist river valleys creating par delta at down landscape

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In the perspective of mostly formed by sedimentary rocks and gneisses individual streams according to their relationship with the basic slope trend developed. In the Sikkim common dendrite systems are wide spread as the folds are almost same type in nature. Occasional thrust interrupted the trend of nature. In much situation construction of roads, buildings cutting of forest, destroying the supers, ridges changed the natural sequence of consequent, subsequent, inciquent flow of the streams. For urbanization, diversities of sprig waters supplied to the urban areas, the out late change flow in new direction changing its normal flow in a new course. Thus the forest is destroyed by landslides. It creates a new irregular complex drainage. It damaged the normal system of geomorphic formation. The under laying rocks for the reason misplaced and landslide occurs. In situation anti dip stream flow becomes the common feature. For the reason high degree of conformity between streams networks according to the geological structure in evident in the change of surface morphology. This type of irregular complex drainage system destroys the morphology of the region. In mountainous region all over India it is a common incident. In Darjeeling and Sikkim Himalaya. It is the common feature. In many locations the change of natural slope destroyed. These morphological changes are affection the biodiversity and ecology of the Sikkim hilly regions.

Hardly a stream. No one can imagine that this innocuous looking stream would transform into a thundering mighty river less than a hundred kilometers downstream. From Chungthang onwards till the border with West Bengal the Tista descends just another 900 mts (3000 ft) over a course of about a hundred kms. The others smaller tributaries of the Tista River are Zemuchu, Lonakchu, Lachungchu, Talungchu, Bakchachu. While the river Tista flows in the north -south direction it tributaries tend to flow in the south- west or in south-east direction.

The rivers are fed by snow melting on the mountains as well as rain that accumulates in the catchment areas during the monsoons. The rivers of Sikkim are perennial and do not dry out even during the winters. Because of their natural steep gradient, these rivers have a potential of generating thousands of mega watts of electricity. Only a part of this energy has been tapped through a few mini hydro power generation stations, for the reason new hazards cropped in placeless’.

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Lakes

On the face of it, one would not expect to find lakes on such a rugged terrain. But surprisingly, Sikkim does have lakes though not very large in size. These lakes are both spring fed as well as river fed. They also form the source of many rivers.

On the highway between Gangtok and Nathu la, 34 kilometres from Gangtok lies the serene Changu (Tsomgo) Lake at the altitude of about 3693 metres (2310 ft.). Two other lakes nearby are the Bidangcho and the Menmecho. Kechopari Lake is another well-known lake that lies on a bifurcation of the route between Gyalshing and Yoksum. The highest concentration of lakes is on the Western border north of Chiwabhanjangtowardsthe Base Camp. Laksmipokhari, Lampokhari, Majurpokhari, twin lakes of Ram-Laxman are a few of the lakes in the area. Gurudongmar, which is the largest and probably the highest in Sikkim and Cholamu are some other beautiful lakes and both of them are in north Sikkim. Another spectacular lake located in north Sikkim towards the eastern border is SimaChoka. acesess of Sikkim, By the analysis of GIS software the stream order vide Stellar assessed the stream flows at up streams . Many lakes are the obstructed flow of small streams, like Tsamgo Lake the place of famous tourist attraction.

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Due to the folds & thrusts in various forms the pattern of river setups are dendrite, In locations around domes are annular, In placesess due to the presence of hard rock layers rectangular forms of drainage patters are in existence, However various constructions the rivers are forced to change the directions.

The main incidence in Sikkim Himalayas are mainly monitored by rivers. Many of the sources originated in China, Tibet, and a few originated in India. The main flows are creating many forms of depositions of alluvium. Small faults are the source of water falls.

Construction of roads creating many physical problems on the flow directions of streams. The location known as 0 point is the origin of Lachan River. Carrying water throughout the year

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for Teesta, Lachun is another stream originated from opposite of 0 point. Many small & big culverts are constricted for link.

Teesta is the main river of Sikkim. Carrying alluvium from the mountain, formed the Para delta attached to Siliguri, Boikunthapur forest is the last zone of forest of Sikkim, shared with west Bengal.

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Conclusion

As the population concentration was not very high the rivers had free flowing movements, even at high altitude. The temperatures that a particular place experiences varies considerably with altitude. At places of low altitude, like Singtam, Rangpo,andJorethang, Namchi, the temperatures vary between 4 degree to 35 degree centigrade. Places like Gangtok with moderate altitude of about 1800 mts (6000 ft) experience temperatures between 1 degree and 25 degree centigrade, whereas at altitude above 4000 mts (13100 ft), the temperature never rises above 15 degree centigrade and remains much below the freezing point during the winters and great part of the spring and autumn .The noted matter is now become the concentration of refugees from Tibet & Nepal creating concentrations at upper hills. Destroying forests for agriculture. Thus deposition of silt increasing in rivers. Gradually the natural characteristics loosing. More over solid wastes increasing rapidly. Most of the cases those are thrown in rivers. Thus the load capacity gradually changing.

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12) Fluvial system 1977 John Wiley & sons New York. ---- Pattern of alluvial river, Annual review of earth science Vol 133 PP 5-27 13) Wadia, D.N. 1967, The role of Himalayan mountain in the physiography of Asia, Bose research institute Vol 30. Calcutta India. 14) Singh, R.L. (ed) 1977. India –A Regional Geography. National Geographical society, Varanasi, PP 230- 305, etc. 15) Spate O.H.K. &Learmonth A.T.A. (3 rd revised edition)1967 , India &Pakisthan, A general Regional Geography , Methuen & Co. London, PP 23-67 , 83- 149 , 200- 356, 370- 384, Etc. 16) Park, C.C. 1980Ecology & environment management, Butterworth. London. PP 25- 71. 17) Sing Savindar&Dubay 1989 Fluvial erosion & sediment load character of Ganga System in environmental management. (Edited by Savindra Singh & R.C. Tewary. Allahabad Geographical society, Allahabad University, PP 153 170. 18) Tansely A.G. 1935- The use & abuse of Vegetational concept & terms, Ecology Vol 16, PP 284-307. 19) Spate O.H.K. &Learmonth A.T.A. (3 rd revised edition)1967 , India &Pakisthan, A general Regional Geography , Methuen & Co. London, PP 23-67 , 83- 149 , 200- 356, 370- 384, Etc. 20) H.L. 1963, Vegetation & hydrology in Technical communication Vol 53,

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