Subansiri River Research Articles

The Promotion of Cultural Tourism in Lower Subansiri District of Arunachal Pradesh: An Evolution of Accommodation Facilities and Tourists Arrivals

The Lower Subansiri district is one of the oldest district of Arunachal Pradesh with an area of about 3460 sq.km andabout 83,030 population (2011) spreading in 536 villages. Geographically, it is an undulating terrain, altitude variesfrom place to place. The greater part of it falls within the higher mountain zone consisting of tangled peaks andenthralling valleys. The district is lying approximately between 26°55’ to 28°21’ N of latitudes, and 92° 40’ to 94°21’ E of longitudes. The name of the district derived from the Subansiri River, a tributary of mighty Brahmaputra.The district is rich in natural as well as cultural aspects. Nature has nurtured and groomed the district in the form ofsuperb scenery of majestic mountainous landscape, inter-montane plateau and wonderful sights of colourful tribalcultures which attracts the tourists from within and outside the country. Thus, there lie possibilities for promotingcultural tourism. Cultural tourism is one dimension of such development which can provide benefit to local peopleboth financially and socially. But certain regulatory constraints, lack of basic infrastructure as well as trainedmanpower hindering the development of the tourism in the distict. Through this paper an attempt has been made toexamine the trend of tourist flow and changes in accommodation facilities as a result of promoting cultural tourismbased on field investigation and documentation.

Length-weight relationships of Badis dibruensis Geetakumari and Vishwanath, 2010 (Badidae) and Lepidocephalichthys arunachalensis (Datta and Barman, 1984) (Cobitidae) from Subansiri River (Brahmaputra basin), Northeast India

Length–weight relationships (LWRs) for Badis dibruensis and Lepidocephalichthys arunachalensis, collected from the lower Subansiri River (Brahmaputra basin) in Assam, India from March 2016 to April 2017 using fishing gears namely cast nets (2.5 m, 1 m; 10–15 mm mesh size) and gillnets (30 × 0.9 m; 5–10 mm mesh size), are presented based on seasonal collections. The b values in the LWRs were determined as 2.56 for B. dibruensis and 3.28 for L. arunachalensis.

Assessment of River Bank Erosion and Vulnerability of Embankment to Breaching: A RS and GIS Based Study in Subansiri River in Assam, India

Temporal Satellite Remote Sensing data of a river system of highly unstable bank can be analyzed in GIS environment for identification of river bank erosion as well as patches of embankment vulnerable to breaching. A case study was carried out in the Subansiri River, a tributary of river Brahmaputra of Assam, in India to identify locations of bank erosion and corresponding patches of embankment vulnerable to breaching. Temporal dataset of cartosat-1 imagery for the year 2007 and 2009 were used for mapping the flow channel of river Subansiri. Embankments present in the river were mapped from the cartosat-1 data with the help of embankment index map collected from Assam State Water Resource Department. Based on the degree of convergence and narrowness between the flow channel and embankment, some patches of embankment identified as vulnerable to breaching and classified as very high, high and moderate vulnerable to breaching. Three patches of embankment were identified as very high vulnerable to breaching which came to be true in successive flood season of 2010. The method may be a good tool for predicting embankment vulnerability to breaching due to bank erosion and can be implemented for planning of river bank protection work and preparedness for flood season for a flood prone state like Assam.

Structural controls on topography and river morphodynamics in Upper Assam Valley, India

The basement in Upper Assam foreland basin exhibits a typical flexure pattern. An elongated continuous subsurface basement high has developed between Himalaya and Naga-Patkai ranges. A few prominent basement lows have developed adjacent to the foothill regions. It is noticed that the general topographic slope near the foothill regions is not only controlled by aggradation process, but also influenced by the flexured basement of the region. The basement lows have influenced the overlying topography significantly. Rivers flowing over those regions have shown unidirectional lateral migration. North bank tributaries like Subansiri, Jiadhal and Dikrang have been affected by the Subansiri basement low. Coseismic subsidence of sediments over Subansiri basement low had resulted subsidence of the North Lakhimpur-Ranga Nadi region in 1950 Assam earthquake. Some south bank tributaries like Disang and Dikhow have been affected by Nazira basement low. Topographic elevation along the Subansiri river is lower than that part of the Brahmaputra located south of Majuli. This typical topographic setting of the region makes the mouth of the Subansiri river and Majuli region highly susceptible to erosion.

Morphometric Analysis of Kakoi River Watershed for Study of Neotectonic Activity Using Geospatial Technology

Morphometric analysis is defined as the quantitative measurement of landscape shape. Morphometric studies of a watershed helps the researcher to compare different landform and calculate the geomorphic indices that may be useful for identifying a particular characteristic such as the level of neotectonic activity in a watershed. The present study has been carried out in Kakoi River Watershed which is a part of Lower Subansiri River Basin in Assam. The study area is geo-dynamically unstable region characterized by active faults, continuing crustal movements and complicated structural region which fall under the seismic zone V of India. In recent century, the Lower Suabsiri River Basin has gone tremendous morphological changes due to active tectonics activities. After the Assam Earthquake of 1950, some of the rivers like Subansiri and its tributaries Dirgha, Kadam and Kakoi suddenly changed their channels giving birth to new channels. The present study is to examine the neotectonic domains and the changes of river course. The geomorphic indices such as Hypsometric Integral (HI), Elongation ratio (Re), Asymmetry Factor (AF), Stream-length Gradient Index (SI), Mountain Front Sinuosity (Mfs), Basin shape index (Bs), Ratio of Valley floor width to Valley Height (Vf) and Channel sinuosity (S) etc. have been studied from remote sensing data. The results shows that the study area is under active tectonic area based on Vf (0.301), Rl (0.461), Bs (3.6), Sl (165.73) and other parameters such as S (1.38) and Mfs (2.02) indicated as moderate active tectonic region. Utilization of geospatial technology and remote sensing data in the present study becomes more reliable and helpful in analyzing, monitoring and understanding the landform changes in a watershed.

Analysis of the change in temperature trends in Subansiri River basin for RCP scenarios using CMIP5 datasets

This study focuses on changes in the maximum and minimum temperature over the Subansiri River basin for different climate change scenarios. For the study, dataset from Intergovernmental Panel on Climate Change (IPCC) fifth assessment report (AR5) (i.e., coupled model intercomparison project phase five (CMIP5) dataset with representative concentration pathway (RCP) scenarios) were utilized. Long-term (2011–2100) maximum temperature (Tmax) and minimum temperature (Tmin) time series were generated using the statistical downscaling technique for low emission scenario (RCP2.6), moderate emission scenario (RCP6.0), and extreme emission scenario (RCP8.5). Trends and change of magnitude in Tmax, Tmin, and diurnal temperature range (DTR) were analyzed for different interdecadal time scales (2011–2100, 2011–2040, 2041–2070, 2070–2100) using Mann-Kendall non-parametric test and Sen’s slope estimator, respectively. The temperature data series for the observed duration (1981–2000) has been found to show increasing trends in Tmax and Tmin at both annual and monthly scale. Trend analysis of downscaled temperature for the period 2011–2100 shows increase in annual maximum temperature and annual minimum temperature for all the selected RCP scenarios; however, on the monthly scale, Tmax and Tmin have been seen to have decreasing trends in some months.

First geomorphological and sedimentological evidence for the combined tectonic and climate control on Quaternary Yarlung river diversion in the eastern Himalaya

This study investigates the combined effects of Quaternary climate change and tectonically induced topography on the Yarlung River drainage-system evolution in the eastern Himalaya. Our work integrates field mapping, geomorphological analysis, stratigraphy, sedimentology, optically stimulated luminescence dating, radiocarbon dating, and detrital-zircon dating of a Holocene valley-fill sequence in a Yarlung River tributary. This holistic approach reveals an aggradational event, which started at or soon after 24–20 k.y. B.P. and continued to or after 9.2–8.0 k.y. B.P. across the Himalayan drainage divide between the east-flowing Yarlung River in the north and the south-flowing Subansiri River in the south. The aggradational event was associated with a major phase of glacier advance during a period of warm and wet climate conditions in the eastern Himalaya; it was expressed by the deposition of a valley-fill sequence across the modern Yarlung-Subansiri drainage divide. South-flowing fluvial sediments across the divide and the elevation distribution of the fluvial terraces require the existence of a major glacier dam that either blocked a tributary or the main trunk of the Yarlung River. Although we are unable to differentiate the two competing scenarios, our work reveals that combined Holocene climate change and tectonically induced topography have played a major role in controlling rapid shifts in drainage geometry at a time scale of <10 k.y. across the Himalaya.

A Comparative Analysis of Selected Environmental Parameters of Water Quality of the Subansiri River in Eastern Himalayas and the Alaknanda River in Western Himalayas

The paper attempts to analyze, interpret, compare and contrast water quality of selected environmental parameters of the Subansiri river in the eastern Himalayas and the Alaknanda river in the western Himalayas. Standard methodologies (APHA, 1995) are adopted to analyze the data and obtain the values for the samples of both the rivers in summer season. The results of the analysis are compared with the drinking water quality standards such as WHO and BIS. It is found from the study that the water quality parameters show a similar trend in case of the pH and electrical conductivity, but most of the parameters show dissimilarities in the eastern and western Himalayan basins.

Assessment of Water Quality in Relation to Fishery Perspective in Flood Plain Wetlands of Subansiri River Basin Assam, India

Assessment of Water Quality in Relation to Fishery Perspective in Flood Plain Wetlands of Subansiri River Basin Assam, India

Estimation of heavy metals contamination and silicate mineral distributions in suspended sediments of Subansiri River

Suspended sediments samples were collected from ten different locations through the Subansiri River to assess heavy metals contamination such as Fe, Al, Ti, Pb, Zn, Cu, Ni, Co, Mn and Cr. The enrichment factor (EF), contamination factor (CF), geo-accumulation index (Igeo) and pollution load index (PLI) were investigated for evaluate metal contamination in the sediments. The relative distribution of major minerals such as quartz, feldspar (orthoclase and microcline) and kaolinite are determined by calculating extinction co-efficient. The mean concentration exhibits positive correlations among Fe, Al, Ti, Mn, Zn, Pb, Ni, and Co. The relative distributions of the contamination are: Al > Ti > Fe > Mn > Cu > Cr > Zn > Pb > Ni > Co. The investigating factors suggest the significant contamination for Subansiri river sediments are Cu and Pb. The mean concentrations of heavy metals in the sediments were found to be below the geochemical background level of world surface rock average. The elemental correlation is indicative to the metamorphosed pyrophanite (MnTiO3) deposition. The infrared analysis indicates presence of micro-crystalline quartz particles and weathered metamorphous silicate minerals. Key words: Heavy metals, suspended sediments, pollution.

Vegetation history and monsoonal fluctuations during the last 12,500 years BP inferred from pollen record at Lower Subansiri Basin, Assam, Northeast India

A 120 cm sediment profile from 4.5 m deep exposed section of Lower Subansiri River Basin has been pollen analyzed to trace palaeovegetation and climate in relation to monsoonal activity since 12,500 years BP. The study has depicted the existence of tropical mixed tree–savannah type to tropical mixed deciduous type forest under four climatic regimes, viz. cold and dry to warm and relatively dry since 12,500 years BP followed by a palynologically barren zone indicating strong fluvial activity. Four sets of monsoon fluctuations, i.e. relatively low to considerably decline in monsoonal activities have been estimated by using pollen marker taxa during the period. The marker taxa signifying high monsoonal activity are – Dipterocarpaceae, Syzygium cumunii, Arecaceae and Moraceae. Melastoma malabathricum, the only taxa which is marked as low monsoonal activity and dry depositional environment. The consistent occurrences of high land taxa are suggestive of long distance pollen transport from higher elevation via strong wind and water source.

A grave danger for the Ganges dolphin (Platanista gangetica Roxburgh) in the Subansiri River due to a large hydroelectric project

The Ganges River dolphin (Platanista gangetica Roxburgh) of Subansiri River may be in great danger of extinction due to the construction of the 2,000-MW Lower Subansiri Hydroelectric Project, which started in 2006. A recent survey indicates that there are now 29 Ganges dolphins, up from 21 in 2006. It is feared that drastic changes would occur in the downstream hydrology and ecology of the Subansiri River after the installation of the project, scheduled for 2012. The water discharge during a major part of the day in dry months would come down to a meager 6 cumecs from the present average of 450 cumecs (1 cumec is shorthand for cubic meter per second; also cms, or m3/s (m3s–1). Riverine mega fauna like the dolphin would be worst hit by this extremely low discharge. Dumping of an extra amount of sediment from different construction phases has already increased sediment load in the Subansiri downstream and degraded some earlier pockets of dolphin up to 20 km below the dam site. There is reason to believe that high sediment influx might have silted up some of the deeper pools downstream, a preferred habitat of dolphins, forcing them to congregate close to the confluence of the Subansiri.

Minimizing diurnal variation of downstream flow in hydroelectric projects to reduce environmental impact

Hydroelectric projects are generally operated as peaking power plant, particularly during lean period; consequently, diurnal variation of flow in the downstream of the dam is induced even in a run-of-the-river scheme. Although such deviation from the natural flow may have significant impact downstream, it generally goes unnoticed. Lower Subansiri Hydroelectric project, located on the Subansiri River of Assam, India, is one of the major hydroelectric projects proposed in the Northeastern part of India. Reservoir Simulation Model has been developed with the objective of assessing the extent of flow variation in the downstream due to operation of the Lower Subansiri Reservoir. Simulation has been carried out using a Standard Operating Policy proposed for the project. The study has revealed that during the peaking hour, the discharge downstream increases about eight times of the normal flow in the lean period and becomes almost zero during the non-operating period. While the high discharge poses erosion and flood threats, the low discharge may lead to adverse environmental impacts such as increase in pollutant concentrations. The possibility of adopting structural and non-structural measures for minimizing the deviation of flow from its normal condition is investigated and performance of these measures is compared based on seven performance criteria. The comparisons have revealed that the structural measure provide the best solution. As an alternative, the non-structural measure also promises notable improvement over the baseline standard operation scenario.

Gangdese arc detritus within the eastern Himalayan Neogene foreland basin: Implications for the Neogene evolution of the Yalu–Brahmaputra River system

In order to assess the spatial and temporal extent of sediment transport from the Gangdese batholith of Tibet to the eastern Himalayan Neogene foreland basin, we performed U–Pb and Lu–Hf analyses on eleven sandstone samples from three locations within the Arunachal and Sikkim Himalaya. We also analyzed detrital zircons from eight modern river sand samples of the Yalu–Brahmaputra River system and its major tributaries in the eastern Himalaya. Results from the river sands are used to contrast the provenance characteristics of the Gangdese arc in southern Tibet with nominally equivalent arc rocks east of the Himalaya in the northernmost Indo-Burma Ranges. Our results indicate that the deposition of Gangdese batholith-derived sediment within the eastern Himalayan foreland: (1) occurred throughout Late Miocene and Pliocene time (~ 10–3 Ma), (2) was limited to the Arunachal Himalaya, and (3) was sourced north of the Himalaya. This detritus may have been deposited by a transverse Himalayan river, such as the Subansiri River, as suggested by high percentages of the Gangdese-derived zircons within the Neogene samples (15–31%) and S- to SW-oriented paleocurrent directions from two of the Neogene sample localities. At this time, our preferred model to explain the data invokes capture of an originally westward-flowing Yalu River by the Subansiri River at ~ 10 Ma, followed by capture of the Yalu River by the Siang River at ~ 3–4 Ma.

Origin and some geomorphological changes of Majuli Island of the Brahmaputra River in Assam, India

The present study on Majuli, the largest river island of the Brahmaputra, aims at exploring its origin and geomorphological evolution during the last century. According to the earlier official data, in 1901 the island covered an area of 1255 km 2. The databases of the study comprised historical reports, SOI topographic maps of 1917, 1966–1972 and satellite images of 1996 and 2001. The Brahmaputra and one of its major tributaries, the Dihing, once flowed parallel and close to each other. An extreme flood, which occurred around 1750, appears to have diverted part of the flow of the Brahmaputra through the channel of the Dihing about 190 km upstream of its confluence. When the two rivers joined, the intervening land area formed the Majuli Island. According to the first geographical report, Majuli was a cluster of 15 large and numerous small islands in 1792. The description of the island during the 19th century has been given based on various written reports. Whereas the changes in the island during 20th century have been assessed in detail at different parts of the island by superimposing the bank lines of 1917, 1966–1972, 1996 and 2001 and subdividing the island into an array of twenty-six 5′ latitude×5′ longitude blocks. The rate of bank line shift has not been uniform throughout the island in time and space; migration leading to erosion along the Brahmaputra is dominant at the south bank, the maximum rate of retreat being 0.480 km/year. Bank line migration leading to silting is confined chiefly to the north bank due to the Subansiri River, the maximum rate of advance being 0.146 km/year. In 1917, the island had an area of 751.31 km 2, which gradually shrank to 564.01 km 2 in 1966–1972, 453.76 km 2 in 1996 and 421.65 km 2 in 2001. Similar changes were noticed in the length and width of the island. The average annual rate of erosion was 1.77 km 2 from 1917 to 1972, 1.84 km 2 from 1972 to 1996 and 6.42 km 2 from 1996 to 2001, indicating a gradual increase in the rate of erosion in later periods. In 1917, the number of named streams draining Majuli was 49, which decreased to only 7 in 1966–1972. Drainage density was 0.963 km/km 2 in 1917, which decreased to 0.442 km/km 2 in 1966–1972. Similarly, stream frequency also decreased from 0.346/km 2 in 1917 to 0.144/km 2 in 1966–1972. Majuli has a fairly large number of swamps and wetlands. The larger swamps owe their origin to pre-existing rivers. The total number of swamps and wetlands observed during 1917 was 112 covering total area of 20.13 km 2, which decreased to 50 occupying a composite area of 17.88 km 2 during 1966–1972.

River channel changes of the Subansiri in Assam, India

The sequential changes in the position of banklines as a result of bank erosion, as well as various changes in the channel have been studied in the Subansiri river in Assam, India. The study was carried out from available topographic maps of 1920, 1970 and satellite imagery of 1990. The types of changes taking place in the Subansiri river channel as observed from the above-mentioned maps and imagery are grouped into four categories: (1) alteration of the direction of flow due to neck cut-off, (2) widening of a channel in response to bar development, (3) development (and subsequent abandonment) of anabranches, and (4) progressive shifting of meander bends. The river channel has become substantially wider during the period of 1970–1990. There has also been a progressive increase in the number and area of mid-channel bars with a corresponding decrease in the number and area of point bars during 1920–1990. These periodic and progressive changes are responsible for a change in channel pattern of the river. A study made on nature and amount of change in the banklines of the Subansiri river by dividing the channel (84 km in 1970) into 10 equal segments reveals that the types of change are varied, and in some cases chaotic in nature. Study of the bankline shift of the Subansiri determined separately for the periods 1920–1970, 1970–1990 and 1920–1990 at 20 evenly spaced transverse sections reveals that there has been a substantial westward shift of both the banklines, up to a maximum of 6 km, in the three upstream sections during 1920–1970. However, shifting of banklines in both directions and the unequal amount of shifting in the same direction have caused a marked increase in channel width during 1970–1990. It is found that due to bankline migration, the total amount of area eroded along the entire course under study during 1920–1970 and 1970–1990 are 107.90 and 57.50 km 2, respectively. The overall sinuosity which was 1.51 in 1920 has decreased to 1.30 in 1970, while the corresponding braiding intensity has increased from 0.79 to 1.32. The river channel seems to make a remarkable change from a meandering pattern in 1920 towards a braided pattern by 1990 as seen from gradual increase in overall braiding intensity.

Status of Tibet red deer

Reports of the Tibet red deer, a subspecies of Cervus elaphus, have been so few in recent years that there were fears that the animal was extinct. A survey in a mountainous region of south-east Tibet in October 1995 found evidence that a few deer survive in one small area and possibly two others in high-altitude valleys of the tributaries of the Subansiri River. The most exciting finding of the survey, however, was an estimated 200-strong population of this deer in high rolling hills near the village of Zhenqi, north of the Yarlung Tsangpo River. This is the only known viable population of the deer and, although some hunting occurs, including by professional poachers from outside Tibet, the fact that it survives is an indication of the tolerance of the local people. The Tibet Forest Bureau has agreed to fund guards and to establish a reserve for the deer in co-operation with local people.

Myths of the Tagins

TAGINS are a tribe of the Subansiri District of the North-East Frontier Agency (NEFA) of India. They inhabit the upper valley of the Subansiri river and the valleys of its tributaries such as Sipi and Mengya. Broadly speaking, the tribe comprises such tribal groups as 'Tagin-Moya', 'Mayu', 'Mara' and 'Na'. The last two groups of people inhabit the Limeking and Taksing Circles which lie close to Tibet. The tribal groups called Soreng-Lingpu inhabiting the upper valley of the Kamla river are also often referred to as Tagin. There are wide cultural differences amongst these groups, e.g. Na and Mara Tagins have been, to some extent, influenced by the Tibetan culture and mode of life. The myths reproduced here, however, were recorded among the Tagins of the Subansiri valley, living in the Taliha circle. These Tagins, sometimes referred to as Tagin-Moya, live by 'Slash-and-burn' agriculture, growing dry paddy and millets. They hunt, fish, rear mithans, pigs and fowls like other Subansiri tribes. They live in large bamboo houses built on stilts and thatched with dried banana leaves. In a house usually live three or four families, each occupying the place around its hearth. Formerly Tagin men went about naked or wore bamboo penis covers, wrapping a piece of blanket or cloth above the waist, and a cane helmet on the head; nowadays, most of them wear loin-cloths. They carry a sword and a knife on their persons. The Tagins regard themselves as children of Abo Teni, the epynomous ancestor of such tribes of Subansiri region as the Apa Tanis, Daflas and Hill Miris. A large number of myths surround this great ancestor. They are divided into several clans and each clan is exogamous. Marriages are patrilocal and a Tagin is required to pay bride-price to obtain a wife. Polygyny is the privilege of the rich few. A Tagin may inherit (with the exception of his mother) all

Botanical and Geographical Exploration in the Assam Himalaya

GEOGRAPHICALLY Assam is the valley of the Brahmaputra between its exit from the hills and its right-angled turn to the south, in Bengal: a triangular or funnel-shaped plain lying on its side, with its mouth gaping open to the west, corked at its apex by a knotted mass of mountains. A trident of rivers enter the apex and unite to form the Brahmaputra. North and south the Assam valley is bounded by converging ranges of mountains : those to the south are the Naga Hills, separating Assam from Burma; those to the north are the Assam Himalaya, forming the ramparts of Tibet. In the first decade of the present century the Assam Himalaya were still an almost mythical region; geographers did not know what became of the Great Himalayan range east of Bhutan, or even whether it continued as a well-knit range. It was unlikely that it ended abruptly in Bhutan, but precise knowledge was lacking. Looking northwards from Kohima in the Naga Hills in winter, one can see across the plain of Assam and the Brahmaputra a distant line of snow peaks, over 21,000 feet high. These are the Assam Himalaya, seen obliquely, so that they quickly fade out of the picture; they do not stretch squarely across the horizon. Opposite the Bay of Bengal the Himalaya reach their southernmost limit, and from a general north-west-south-east alignment gradually turn northeast, and trend clear away from the plains. If we try to pass along the foot of the mountains, we shall find it a more exacting task going east than it is going west. The reason is that owing to the funnel shape of the valley the monsoon rushes up it like a tidal bore in a narrowing estuary, and the rainfall increases rapidly eastwards, till at the foot of the Abor and Mishmi Hills beyond Sadiya it exceeds 200 inches. The deep screen of lesser ranges between the edge of the plain and the main crest-line, drained by the Subansiri river and its tributaries, also adds to the difficulties of eastern Himalayan exploration; as a climax, these foothills are inhabited by quite unreliable tribes. Hence