Arun River Research Articles

Reconsidering Himalayan river anticlines

The observation that major Himalayan rivers flow parallel to and down the axis of anticlines oriented transverse to the primary structural grain of the range has puzzled geomorphologists for decades. Although there is a general consensus that the courses of trans-Himalayan rivers predate the Himalayan orogeny, the close association of rivers and structural highs would not be expected to result from the superposition of rivers onto pre-existing structures. Moreover, in the past several decades structural studies have shown that the development of river anticlines represents the most recent phase of deformation in the range. It is proposed that Himalayan river anticlines are the consequence of focused rock uplift in response to significant differences between net erosion along major rivers and surrounding regions. This hypothesis is supported by large gradients in observed and predicted erosion rates across major Himalayan rivers and by results from an isostasy-driven model, which requires relatively low flexural rigidities to match the wavelength of Himalayan river anticlines. Whether the amplitude of these structures is due to isostasy or also reflects active crustal channeling is not well-constrained, but given the uncertainty in the flexural rigidity and in the local and far-field erosion rates, both possibilities remain viable explanations. Given the observed correlation between the Arun River anticline and local rainfall maxima, it is proposed that Himalayan river anticlines are the expression of a relatively fine-scale linkage between tectonics, erosion and climate superimposed on the broader and older canvas of the Himalayan orogeny. Finally, it is suggested that the development of river anticlines represents one example along a continuum of features arising from different degrees of erosion-structure coupling in active orogens.

Benefit-Cost Analysis of Community Forest and Its Distributional Impact on Rural Poor

This paper attempts to examine the equity impact of community forest (CF) with the help of cost-benefit analysis among the three income groups of sixteen selected community forest user groups in Arun River Valley, Eastern mid-Hill, Nepal. For the purpose of benefit analysis, eight major types of forest products from CF were incorporated considering as material values and intangible benefits of forest such as environmental service and greenery were overlooked totally. Total costs of forest use and management were classified into labor costs, transaction costs and membership fees. With the help of summary statistics of gross benefits and costs, net benefit and B-C ratios for the three income groups were calculated which showed that the net benefit and B-C ratios of poor, medium and rich households to be -3 and 0.85, 0 and 1, and 4 and 1.08 respectively. The current practices of community forest management have negative impact on rural poor that lacks the provisions for addressing equitable system of benefit distribution and cost sharing among the forest user groups and households. If community forestry is to be rural poor-friendly, poor income households should realize the full value of the share of unused forest products either from transferable rights or from marketable access. Economic Journal of Nepal Vol.29(2) 2006 pp.93-107

The Effects of Land-use and Landscape Structure on Barn Owl (Tyto alba) Breeding Success in Southern England, U.K.

To aid effective conservation and management there is a need to understand the effect of landscape on species ecology. The aim of this research was to assess the effect of landscape parameters on breeding success of barn owls throughout the Rother and Arun River catchments, Sussex, UK. We used a Geographic Information System to describe the habitat mosaic and landscape structure within an estimated home range area of 3 km2 around 85 artificial nest box sites. Results showed that land cover was less heterogeneous at successful sites, with home ranges dominated by a few habitat types of regular patch shapes. Unsuccessful nesting sites had significantly more improved grassland, suburban land and wetlands than successful sites. Cluster analysis and Principle Components Analysis was used to assess the similarity of the habitat mosaic within these areas and pellet analysis was undertaken to assess barn owl diet and prey availability. Ten prey species were recovered from pellets, field vole (Microtus agrestis), common shrews (Sorex araneus) and house mice (Mus musculus) making up nearly 90% of recoveries. However box sites varied in relative proportions of small mammal, and hence prey availability. Results indicated that land use and landscape structure can affect breeding success in barn owls. Higher levels of poor quality small mammal habitat were associated with unsuccessful sites. However, at a landscape scale, the habitat mosaic across the study area lacked variation, limiting analysis and clear correlations between habitat type and positive breeding success, suggesting that a finer scale was needed in future studies utilising this approach.

Morphometric analysis of Arun River Valley, eastern Nepal

The Arun River shows antecedent characteristics but almost all tributaries show consequent characteristics. The drainage system of the Arun River Valley (ARV) is influenced by local geological structures in number of ways. The sharp bending, sudden high gradient, narrow valleys that suddenly become wide are common. In the ARV, major tributaries are of sixth order, as the order becomes higher, total number of stream segments becomes progressively smaller, but physical dimensions of the streams increase gradually. In some areas, the divides are low and indistinct, while in others they form high mountain systems. Valley deepening is affected by various factors such as- hydraulic action, corrosion/abrasion of the valley base and weathering of the stream bed increased by subsequent removal of weathered materials. Valley deepening is very high between Pisu la and the Barun Dovan; between the Num and Yamchung as well as Leguwaghat and Barachetra. Valley widening process is predominant near Kimathanka, between Tumlingtar and Surtibari and Sattare areas. The Arun River, flowing in the state of channel equilibrium condition partially modified after local recent tectonic events. In the near future there is very low risk of vast channel shifting phenomena in the valley. The paper describes major morphometrical analysis of the Arun River Valley, eastern Nepal.

Silicate versus carbonate weathering in the Himalaya: a comparison of the Arun and Seti River watersheds

We studied the water chemistry of two large and geologically differing Himalayan watersheds in order to maximize the contrast between silicate versus carbonate weathering effects on river chemistry. Our previous research involved the Seti River of westernmost Nepal, geologically typical of many rivers in Nepal in draining mixed carbonate/silicate lithologies, including abundant carbonate rocks of the Lesser Himalayan Sequence. For comparison, the Arun River was chosen for study because south of the Himalayan front it drains almost exclusively Greater and Lesser Himalayan silicate rocks. Despite this dominance of silicate rocks, carbonate weathering—probably of metamorphic calcite in Great Himalayan paragneisses—is clearly in evidence in many Arun watersheds. Weathering of silicate rocks exposed all along the Arun south of the range front has a small impact on mainstem river chemistry. The mainstems of both the Seti and Arun systems are dominated by weathering of carbonate rocks, although the contribution of silicate weathering is more visible in Arun mainstem chemistry. The carbonate weathering source to the Arun mainstem is probably both limestone in the Tethyan Sequence widely exposed in northern headwaters of the system, and metamorphic calcite within the Greater Himalayan Sequence. A number of small watersheds along the Arun and Seti appear to be carbonate-free. They probably provide the best constraints to date on the Ca/Na and Mg/Na ratios of waters draining Himalayan silicate rocks, two critical parameters for calculation of CO 2 consumption by silicate weathering in the Himalaya. The observed Ca/Na and Mg/Na ratios would produce slightly higher estimates of silicate weathering fluxes than previous studies. The geologic contrasts between the Seti and the Arun produce large differences in the 87Sr/ 86Sr ratio of each mainstem, unlike the major element chemistry. The Seti mainstem displays much higher 87Sr/ 86Sr ratios than the Arun mainstem, the opposite of the expected relationship since radiogenic silicate rocks of the Greater and Lesser Himalaya are so widely exposed along the Arun. 87Sr/ 86Sr ratios of the Arun mainstem never exceed 0.734 and show little downstream change as the mainstem passes through silicate rocks of the Greater and Lesser Himalaya. 87Sr/ 86Sr ratios of the Seti mainstem increase sharply from 0.725 to 0.785 when the river enters the belt of metacarbonate rocks of the northern Lesser Himalayan Sequence, a pattern also displayed by other Himalayan rivers such as the Kali Gandaki and Bhotse Khola. Metacarbonate rocks, including those of the Lesser Himalaya, are a major source of radiogenic Sr in modern Himalayan Rivers and probably have been key players in elevating marine 87Sr/ 86Sr ratios since the Early Miocene.

Mountain Environmental Management in the Arun River Basin of Nepal

Mountain Environmental Management in the Arun River Basin of Nepal

Geology of the Area along the Arun River and the Dudh Kosi, East Nepal

Geology of the Area along the Arun River and the Dudh Kosi, East Nepal

New Zealand Himalayan Expedition

The Barun Valley lies on the west side of Makalu and the project of sending an expedition to it started in 1952, when Erie Shipton, Ed Hillary, George Lowe and I visited it, crossing to it for the first time from Solu Khumbu, and making a quick journey up and down it before returning to England at the end of the Cho Oyu Expedition. After that, Hillary, through the New Zealand Alpine Club, asked permission to take an expedition there in 1954. The view of Makalu from Everest led Hillary, particularly, to believe that there might be a way up Makalu from the west, and a reconnaissance of such a route was one of his ideas in launching this expedition. In the meantime, however, a Californian party had specific permission from the Nepalese to attack Makalu itself, and so our expedition was limited to making a survey of the Barun Valley and to climbing as many other mountains in the neighbourhood as we could. There were ten members of our Expedition: eight from New Zealand, namely Hillary, Harrow, Hardie, Beaven, Todd, Lowe, McFarlane, Wilkins; they very kindly asked two people from this country to join them?Michael Ball, the Expedition doctor, and myself. We are grateful to the New Zealand Alpine Club for this invitation, which kept up the association which we have had over the last four years in Himalayan exploration and climbing. Our Expedition started at Jogbani, a village of Bihar on the borders of India and Nepal, where we met towards the end of March when the ground is ankle deep in dust which rises all around you as you walk. Our first job at Jogbani was to get our loads away on coolies, most of whom were men, but we had women too and a few children. The largest loads always seemed to get on the smallest porters! When all the porters are gone and you have scoured the surrounding jungle for anyone who looks as if he might be able to carry anything, you find yourself as a rule still left with a few leaky tins of kerosene or rather uncomfortable loads of crampons, or else loads that are just heavier than all the rest, but in the end they all get away. On the first few days of our march in through the foothills we followed a wide mule track over the hills, in the general direction of the Arun river, following its left bank. We passed many Nepalese villages on the way, their houses straw-thatched and thickwalled, and remarkably cool inside. After Dhankuta we kept close to the river, only now and then climbing the ridges alongside it, from one of which we had our first view of the snows?Chamlang, a long, level mountain of about 24,000 feet. Brian Wilkins and I tried fishing on this part of the journey and concluded there were no fish in the Arun, but I am told that when Ed Hillary came down later in the season, the villagers were trying to sell lots of fish which had been left high and dry on the

The Arun River Drainage Pattern and the Rise of the Himalaya

The Arun River Drainage Pattern and the Rise of the Himalaya

A Journey into the Interior of Ashanti

them to understand what they saw, and to bring back an account of what they had done which would really add to the stock of valuable knowledge which the world possessed with regard to those mountains. Mr. Graham said the bearing of the high peaks which he saw almost due north-west, with a trifle west. When he got down he had his instruments com? pared, and they were fairly accurate. Many of the heights were well known, and the aneroid barometer might be fairly reckoned on for differential measurements. Mr. Freshfield observed that in one of the surveys published by the Indian Survey Department two peaks with an indication Yery high snowy peaks, were put down on the authority of one of the native surveyors or pundits, No. 9, to the north-west of Kabru, north of the Arun river, and north-east of Mount Everest, on the real water-parting of the Himalayas. General Walker replied that the bearing of those peaks was no doubt all right, but the native explorers had no means of estimating the altitude, which might be anything between 20,000 feet and 30,000 feet. The Presidekt, in proposing a vote of thanks to Mr. Graham, said that gentle? man had taken them to one of the most magnificent regions in the world, and considering that he went to India more for sport and ad venture than for the advancement of science, he had shown that he a discoverer of more than ordinary intelligence. If he returned to those regions he would do so still better, supplied with the lamp of science to which General Strachey had referred. It interesting to note how surveyors and discoverers had discrowned one peak after another from being the highest in the world. In his youth Dhawalagiri con? sidered to have dethroned the Andes; soon after Kangchinjanga discovered to overtop DhawTalagiri; then came a great surveyor who dethroned Kangchinjanga in favour of the mountain which now bore the name of Mount Everest; and now, if Mr. Graham right, and there appeared to be no reason to doubt it, Mount Everest must bow its cloud-capped head. No doubt others would be stirred to rival Mr. Graham, and very soon the mystery would be solved. At any rate, Mr. Graham had made a very interesting addition to the knowledge of this stupendous region, and it must be very gratifying to men like Sir Joseph Hooker, who led the way there, to find that they were followed by youthful adventurers like Mr. Graham.