Rivers of Sikkim & Its Impact on Physiography
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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. Volume XII, Issue XII, DECEMBER 2019 Page No: 1429 JAC : A Journal Of Composition Theory ISSN : 0731-6755 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 Volume XII, Issue XII, DECEMBER 2019 Page No: 1430 JAC : A Journal Of Composition Theory ISSN : 0731-6755 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 Volume XII, Issue XII, DECEMBER 2019 Page No: 1431 JAC : A Journal Of Composition Theory ISSN : 0731-6755 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 Volume XII, Issue XII, DECEMBER 2019 Page No: 1432 JAC : A Journal Of Composition Theory ISSN : 0731-6755 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.