Entire Himalayan region is vulnerable to rain-induced （torrential rainfall） hazards in the form of flash flood, cloudburst or glacial lake outburst flood Flash floods and cloudburst are generally caused by high inte...Entire Himalayan region is vulnerable to rain-induced （torrential rainfall） hazards in the form of flash flood, cloudburst or glacial lake outburst flood Flash floods and cloudburst are generally caused by high intensity rainfall followed by debris flow or landslide often resulting into blockade of river channels. The examples of some major disasters caused by torrential rainfall events in last fifty years are the flash floods of 1968 in Teesta valley, in 1993 and 2000 in Sutlej valley, in 1978 in Bhagirathi and in 1970 in Alaknanda river valleys. The formation of landslide dams and subsequent breaching is also associated with such rainfall events. These dams may persist for years or may burst within a short span of its formation. Due to sudden surge of water level in the river valleys, havoc and panic are created in the down stream. In Maknanda valley, frequencies of such extreme rainfall events are found to be increasing in last two decades. However, the monthly trend of extreme rainfall events has partly indicated this increase. In most of the years extreme rainfall events and cloudburst disaster were reported in August during the later part of the monsoon season.展开更多
The present study is based on the field observations and geochemical analyses of flood sediments to ascertain the nature and causes of destruction in the Mandakini and Alaknanda river valleys during June 2013.The stud...The present study is based on the field observations and geochemical analyses of flood sediments to ascertain the nature and causes of destruction in the Mandakini and Alaknanda river valleys during June 2013.The study suggests that the sediments were contributed from two major sources:the moraines and alluvial fans located in the Trans and Higher Himalaya;and the landslides in the Higher and Lesser Himalaya.Although the flood was the result of a high intensity rainfall event.展开更多
Identifying the various components contributing to river discharge can be challenging.This study relies on stable isotopes and electrical conductivity(EC)of water as tracers to distinguish the different components con...Identifying the various components contributing to river discharge can be challenging.This study relies on stable isotopes and electrical conductivity(EC)of water as tracers to distinguish the different components contributing to total river discharge.Additionally,we have made an effort to comprehend the processes that may influence glacier ice melt as well as the limits of oxygen-based hydrograph separation.Two distinct geographic domains in terms of climates and topographies were examined.The first study site represents the upper Ganga catchment(central Himalaya),while the second site is located in the Chandra sub-basin in western Himalaya.Errors in estimating the proportion of glacier melt in isotope mixing model are likely if end-member isotopic compositions,are not well defined,particularly for rainfall.Hydrograph separation results indicate that snowmelt is the largest contributor to total river flow in both regions.The contribution of snowmelt to the total runoff of the upper Ganga ranged from~60%to 70%.The estimated contributions of glacier melt varied from 36%to 63%in upper Ganga headwater to 6%to 15%at Devprayag and~8%at Rishikesh.In the Hamtah River,glacier and snowmelt contributions,quantified using a two-component mixing model,ranged from 10%to 14%during the pre-and postmonsoon seasons of 2013.The significant spatial and temporal variability,coupled with overlapping isotopic signatures,suggests complex glacio-fluvial interactions in these catchments.Local slow-moving air masses with whirling motion closer to the study area irrespective of the direction,and air parcels coming through Bay of Bengal branch are characterized by depleted isotopic rainfall compared to air masses originating from the Arabian Sea.展开更多
文摘Entire Himalayan region is vulnerable to rain-induced （torrential rainfall） hazards in the form of flash flood, cloudburst or glacial lake outburst flood Flash floods and cloudburst are generally caused by high intensity rainfall followed by debris flow or landslide often resulting into blockade of river channels. The examples of some major disasters caused by torrential rainfall events in last fifty years are the flash floods of 1968 in Teesta valley, in 1993 and 2000 in Sutlej valley, in 1978 in Bhagirathi and in 1970 in Alaknanda river valleys. The formation of landslide dams and subsequent breaching is also associated with such rainfall events. These dams may persist for years or may burst within a short span of its formation. Due to sudden surge of water level in the river valleys, havoc and panic are created in the down stream. In Maknanda valley, frequencies of such extreme rainfall events are found to be increasing in last two decades. However, the monthly trend of extreme rainfall events has partly indicated this increase. In most of the years extreme rainfall events and cloudburst disaster were reported in August during the later part of the monsoon season.
文摘The present study is based on the field observations and geochemical analyses of flood sediments to ascertain the nature and causes of destruction in the Mandakini and Alaknanda river valleys during June 2013.The study suggests that the sediments were contributed from two major sources:the moraines and alluvial fans located in the Trans and Higher Himalaya;and the landslides in the Higher and Lesser Himalaya.Although the flood was the result of a high intensity rainfall event.
基金the project entitled“Finger printing of glacial melt water in the Ganga basin-implications for modelling of hydrological cycle in a Himalayan River system”grant number NO.SR/DGH-46/2012 which supported work for this paper。
文摘Identifying the various components contributing to river discharge can be challenging.This study relies on stable isotopes and electrical conductivity(EC)of water as tracers to distinguish the different components contributing to total river discharge.Additionally,we have made an effort to comprehend the processes that may influence glacier ice melt as well as the limits of oxygen-based hydrograph separation.Two distinct geographic domains in terms of climates and topographies were examined.The first study site represents the upper Ganga catchment(central Himalaya),while the second site is located in the Chandra sub-basin in western Himalaya.Errors in estimating the proportion of glacier melt in isotope mixing model are likely if end-member isotopic compositions,are not well defined,particularly for rainfall.Hydrograph separation results indicate that snowmelt is the largest contributor to total river flow in both regions.The contribution of snowmelt to the total runoff of the upper Ganga ranged from~60%to 70%.The estimated contributions of glacier melt varied from 36%to 63%in upper Ganga headwater to 6%to 15%at Devprayag and~8%at Rishikesh.In the Hamtah River,glacier and snowmelt contributions,quantified using a two-component mixing model,ranged from 10%to 14%during the pre-and postmonsoon seasons of 2013.The significant spatial and temporal variability,coupled with overlapping isotopic signatures,suggests complex glacio-fluvial interactions in these catchments.Local slow-moving air masses with whirling motion closer to the study area irrespective of the direction,and air parcels coming through Bay of Bengal branch are characterized by depleted isotopic rainfall compared to air masses originating from the Arabian Sea.
