The study of spatiotemporal variation in temperature is vital to assess changes in climate, espec... more The study of spatiotemporal variation in temperature is vital to assess changes in climate, especially in the Himalayan region, where the livelihoods of billions of people living downstream depend on water coming from the melting of snow and glacier ice. To this end, temperature trend analysis is carried out in the Narayani River basin, a major river basin of Nepal, characterized by three climatic regions: tropical, subtropical and alpine. Temperature data from six stations located within the basin were analyzed. The elevation of these stations ranges from 460 to 3800 m a.s.l. and the time period of available temperature data ranges from 1960–2015. Multiple regression and empirical mode decomposition (EMD) methods were applied to fill in missing data and to detect trends. Annual as well as seasonal trends were analyzed and a Mann–Kendall test was employed to test the statistical significance of detected trends. The results indicate significant cooling trends before the 1970s, and warming trends after the 1970s in the majority of the stations. The warming trends range from 0.028 to 0.035 ∘C year−1 with a mean increasing trend of 0.03 ∘C year−1 after 1971. Seasonal trends show the highest warming trends in the monsoon season, followed by winter and the premonsoon and postmonsoon season. However, the difference in warming rates between different seasons was not significant. An average temperature lapse rate of −0.006 ∘C m−1 with the steepest value (−0.0064 ∘C m−1) in the pre-monsoon season and the least negative (−0.0052 ∘C m−1) in the winter season was observed for this basin. A comparative analysis of the gap-filled data with freely available global climate dataset show reasonable correlation, thus confirming the suitability of the gap-filling methods
Several supraglacial ponds are developing and increasing in size and number in the Himalayan regi... more Several supraglacial ponds are developing and increasing in size and number in the Himalayan region. They are the precursors of large glacial lakes and may become potential for glacial lake outburst floods (GLOFs). Recently, GLOF events originating from supraglacial ponds were recorded; however, the spatial, temporal, and seasonal distributions of these ponds are not well documented. We chose 23 debris-covered glaciers in the Everest region, Nepal, to study the development of supraglacial ponds. We used historical Landsat images (30-m resolution) from 1989 to 2017, and Sentinel-2 (10-m resolution) images from 2016 to 2018 to understand the long-term development and seasonal variations of these ponds. We also used fine-resolution (0.5-2 m) WorldView and GeoEye imageries to reveal the high-resolution inventory of these features and these images were also used as references for accuracy assessments. We observed a continuous increase in the area and number of ponds from 1989-2017, with minor fluctuations. Similarly, seasonal variations were observed at the highest ponded area in the pre-and postmonsoon seasons, and lowest ponded area in the winter season. Substantial variations of the ponds were also observed among glaciers corresponding to their size, slope, width, moraine height, and elevation. The persistency and densities of the ponds with sizes >0.005 sq.km were found near the glacier terminuses. Furthermore, spillway lakes on the Ngozompa, Bhote Koshi, Khumbu, and Lumsamba glaciers were expanding at a faster rate, indicating a trajectory towards large lake development. Our analysis also found that Sentinel-2 (10-m resolution) has good potential to study the seasonal changes of supraglacial ponds, while fine-resolution (<2 m) imagery is able to map the supraglacial ponds with high accuracy and can help in understanding the surrounding morphology of the glacier.
The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an i... more The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is determined by the amount of heat conducted through debris material lying over the ice. This study presents the vertical temperature gradients, thermal properties in terms of thermal diffusivity and thermal conductivity, and positive degree-day factors for the debris-covered portion of Lirung Glacier in Langtang Valley, Nepal Himalaya using field-based measurements from three different seasons. Field measurements include debris temperatures at different debris thicknesses, air temperature, and ice melt during the monsoon (2013), winter (2013), and pre-monsoon (2014) seasons. We used a thermal equation to estimate thermal diffusivity and thermal conductivity, and degree-day factors (DDF) were calculated from cumulative positive temperature and ice melt of the measurement period. Our analysis of debris temperature profiles at different depths of debris show the daily linear gradients of ?20.81 °C/m, 4.05 °C/m, and ?7.79 °C/m in the monsoon, winter, and pre-monsoon seasons, respectively. The values of thermal diffusivity and thermal conductivity in the monsoon season were 10 times greater than in the winter season. The large difference in these values is attributed to surface temperature and moisture content within the debris. Similarly, we found higher values of DDFs at thinner debris for the pre-monsoon season than in the monsoon season although we observed less melting during the pre-monsoon season. This is attributed to higher cumulative temperature during the monsoon season than in the pre-monsoon season. Our study advances our understanding of heat conductivity through debris material in different seasons, which supports estimating ice melt and discharge from glacierized river basins with debris-covered glaciers in the Himalayan region.
The main objective of the paper is to assess the role of the biogas to mitigate the climate chang... more The main objective of the paper is to assess the role of the biogas to mitigate the climate change and adaptation. For this amount of fuel wood reduced by the use of biogas and ultimate result of forest save, time save, health improvement, agricultural production improvement and reduction of greenhouse gases are the bases for research objectives. Biogas and TCS users are separate sampling frame for this research. The total of 62.30% of the less fuel wood was used by the biogas user than the TCS user. The higher percentage of reduction of fuel wood is contributed by the reduction in cooking. The amount of the greenhouse gas emission reduction due to reduction in the fuel wood consumption was 8.02 tons per plant per year of carbon dioxide equivalent. The number of trees saved per plants per year is found to be 10.15 trees that help to mitigate the climate change through carbon sequestration and increase adaptive capacity of the user. The occurrences of the diseases were considerably lower among biogas user than the TCS user. The total time save within the family was 2 hour and 24 minutes per day from collection of fuel wood, cooking food and cleaning of utensils if the family cook food for one times per day and one person involved in collection of the fuel wood. There was positive perception of the people in quality of the fertilizer and saving of the money by not buying chemical fertilizer.
Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, ... more Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, i.e. most likely to cause death and destruction in case of a glacier lake outburst flood (GLOF). Imja Lake and the associated Imja and Lhoste-Shar glaciers have been intensively studied; Thulagi Glacier and its lake are much less studied. Collectively, we have undertaken a series of increasingly thorough bathymetric and land surveys and satellite remote sensing analyses of Imja Lake and its glacier setting. We are analyzing several expeditions' data to build a detailed assessment of the glacier and lake to better establish the dynamical evolution of the system and its future GLOF potential. Our most recent, most complete bathymetric survey of Imja Lake has revealed a much greater volume (75,200,000 cubic meters) and maximum depth (149.8 m) than found before. Our analysis suggests that not all possible Imja GLOF scenarios would result in devastation. Some moraine melt-through or down-...
Glaciers are key resources of water for hydropower, irrigation, and drinking water. The extensive... more Glaciers are key resources of water for hydropower, irrigation, and drinking water. The extensive debris cover often covers glaciers in ablation part of the Himalayan region; hence, it is essential to assess the effect of debris on glacier ice melt. In this study, the main objective is to generate the seasonal vertical temperature profile and estimate the temperature gradient from debris surface to debris/ice interface on Lirung Glacier in Langtang Valley, Rasuwa district, Nepal. Three field campaigns are carried out in monsoon (2013), winter (2013) and pre-monsoon (2014) season during which 2 set of thermistors are installed at different debris thickness. Debris temperature data are collected in different layers of debris from atmosphere/debris interface to debris/ice interface using temperature sensors during each season. Similarly, the debris temperature profile shows higher fluctuation of temperature near surface and lower fluctuation in lower layers with increasing lag time. Th...
Proceedings of the International Association of Hydrological Sciences, 2015
In the Nepalese Himalayas, the complex topography, occurrence of debris covered glaciers, and lim... more In the Nepalese Himalayas, the complex topography, occurrence of debris covered glaciers, and limited data availability creates substantial difficulties for modelling glacier melt. The proper recognition of melt processes governs the accurate estimation of melt water from glacier dominated systems, even in the presence of debris-covered glaciers. This paper presents a glacier melt model developed for the Lirung subbasin of Langtang valley, which has both a clean glacier area, 5.86 km 2 , and a debris-covered glacier area, 1.13 km 2 . We use a temperature index approach to estimate sub-daily melt water discharge for a two week period at the end of monsoon, and the melt factor is varied according to the aspect and distributed to each grid processed from the digital elevation model. The model uses easily available data and simple extrapolation techniques capable of generating melt with limited data. The result obtained from this method provides accurate estimate with an R 2 value of 0.89, bias of 0.9% and Nash-Sutcliffe efficiency of 0.86, and suitable in Himalaya where data availability is major issue.
Proceedings of International Association of Hydrological Sciences, doi:10.5194/piahs-368-57-2015, May 6, 2015
Glaciers are one of the important natural resources of freshwater and sources of water for hydrop... more Glaciers are one of the important natural resources of freshwater and sources of water for hydropower, agriculture and drinking whenever the water is scarce. This mapping and change analysis helps to understand the status and decadal changes of glaciers in Hidden Valley, Mustang district, Nepal. The investigation is carried out using Landsat images of the years 1977 (~1980s), 1990, 2000 and 2010. We mapped 10 glaciers of the Hidden Valley covering an area of 19.79 km2 based on the object-based image classification method using an automatic method and manual delineation by a Geographic Information System (GIS), separately. The glacier outlines for 2010, 2000, 1990 and 1980s in both methods are delineated from the multispectral Landsat images of the respective years. The total area losses of the glaciers from the automatic method are 1.713 and 0.625 km2 between 1990−2000 and 2000−2010 and from manual delineation are 2.021, 1.264, 1.041 km2 between ~1980s−1990, 1990−2000 and 2000−2010. The amount of average estimated glacier ice reserves lost is 0.326 km3 (26.26 %) and the total glacier area loss is 4.33 km2 (21.87 %) from the 1980s to 2010 based on manual delineation. The glaciers of Hidden Valley are shrinking and fragmented due to decrease in glacier area and ice reserves.
Proceeding of International Association of Hydrological Sciences, doi:10.5194/piahs-368-21-2015, May 6, 2015
Glaciers in the Himalayan region are often covered by extensive debris cover in ablation areas, h... more Glaciers in the Himalayan region are often covered by extensive debris cover in ablation areas, hence it is essential to assess the effect of debris on glacier ice melt. Seasonal melting of ice beneath different thicknesses of debris on Lirung Glacier in Langtang Valley, Nepal, was studied during three seasons of 2013–14. The melting rates of ice under 5 cm debris thickness are 3.52, 0.09, and 0.85 cm d-1 during the monsoon, winter and pre-monsoon season, respectively. Maximum melting is observed in dirty ice (0.3 cm debris thickness) and the rate decreases with the increase of debris thickness. The energy balance calculations on dirty ice and at 40 cm debris thickness show that the main energy source of ablation is net radiation. The major finding from this study is that the maximum melting occurs during the monsoon season than rest of the seasons.
The study of spatiotemporal variation in temperature is vital to assess changes in climate, espec... more The study of spatiotemporal variation in temperature is vital to assess changes in climate, especially in the Himalayan region, where the livelihoods of billions of people living downstream depend on water coming from the melting of snow and glacier ice. To this end, temperature trend analysis is carried out in the Narayani River basin, a major river basin of Nepal, characterized by three climatic regions: tropical, subtropical and alpine. Temperature data from six stations located within the basin were analyzed. The elevation of these stations ranges from 460 to 3800 m a.s.l. and the time period of available temperature data ranges from 1960–2015. Multiple regression and empirical mode decomposition (EMD) methods were applied to fill in missing data and to detect trends. Annual as well as seasonal trends were analyzed and a Mann–Kendall test was employed to test the statistical significance of detected trends. The results indicate significant cooling trends before the 1970s, and warming trends after the 1970s in the majority of the stations. The warming trends range from 0.028 to 0.035 ∘C year−1 with a mean increasing trend of 0.03 ∘C year−1 after 1971. Seasonal trends show the highest warming trends in the monsoon season, followed by winter and the premonsoon and postmonsoon season. However, the difference in warming rates between different seasons was not significant. An average temperature lapse rate of −0.006 ∘C m−1 with the steepest value (−0.0064 ∘C m−1) in the pre-monsoon season and the least negative (−0.0052 ∘C m−1) in the winter season was observed for this basin. A comparative analysis of the gap-filled data with freely available global climate dataset show reasonable correlation, thus confirming the suitability of the gap-filling methods
Several supraglacial ponds are developing and increasing in size and number in the Himalayan regi... more Several supraglacial ponds are developing and increasing in size and number in the Himalayan region. They are the precursors of large glacial lakes and may become potential for glacial lake outburst floods (GLOFs). Recently, GLOF events originating from supraglacial ponds were recorded; however, the spatial, temporal, and seasonal distributions of these ponds are not well documented. We chose 23 debris-covered glaciers in the Everest region, Nepal, to study the development of supraglacial ponds. We used historical Landsat images (30-m resolution) from 1989 to 2017, and Sentinel-2 (10-m resolution) images from 2016 to 2018 to understand the long-term development and seasonal variations of these ponds. We also used fine-resolution (0.5-2 m) WorldView and GeoEye imageries to reveal the high-resolution inventory of these features and these images were also used as references for accuracy assessments. We observed a continuous increase in the area and number of ponds from 1989-2017, with minor fluctuations. Similarly, seasonal variations were observed at the highest ponded area in the pre-and postmonsoon seasons, and lowest ponded area in the winter season. Substantial variations of the ponds were also observed among glaciers corresponding to their size, slope, width, moraine height, and elevation. The persistency and densities of the ponds with sizes >0.005 sq.km were found near the glacier terminuses. Furthermore, spillway lakes on the Ngozompa, Bhote Koshi, Khumbu, and Lumsamba glaciers were expanding at a faster rate, indicating a trajectory towards large lake development. Our analysis also found that Sentinel-2 (10-m resolution) has good potential to study the seasonal changes of supraglacial ponds, while fine-resolution (<2 m) imagery is able to map the supraglacial ponds with high accuracy and can help in understanding the surrounding morphology of the glacier.
The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an i... more The extensive debris that covers glaciers in the ablation zone of the Himalayan region plays an important part in regulating ablation rates and water availability for the downstream region. The melt rate of ice is determined by the amount of heat conducted through debris material lying over the ice. This study presents the vertical temperature gradients, thermal properties in terms of thermal diffusivity and thermal conductivity, and positive degree-day factors for the debris-covered portion of Lirung Glacier in Langtang Valley, Nepal Himalaya using field-based measurements from three different seasons. Field measurements include debris temperatures at different debris thicknesses, air temperature, and ice melt during the monsoon (2013), winter (2013), and pre-monsoon (2014) seasons. We used a thermal equation to estimate thermal diffusivity and thermal conductivity, and degree-day factors (DDF) were calculated from cumulative positive temperature and ice melt of the measurement period. Our analysis of debris temperature profiles at different depths of debris show the daily linear gradients of ?20.81 °C/m, 4.05 °C/m, and ?7.79 °C/m in the monsoon, winter, and pre-monsoon seasons, respectively. The values of thermal diffusivity and thermal conductivity in the monsoon season were 10 times greater than in the winter season. The large difference in these values is attributed to surface temperature and moisture content within the debris. Similarly, we found higher values of DDFs at thinner debris for the pre-monsoon season than in the monsoon season although we observed less melting during the pre-monsoon season. This is attributed to higher cumulative temperature during the monsoon season than in the pre-monsoon season. Our study advances our understanding of heat conductivity through debris material in different seasons, which supports estimating ice melt and discharge from glacierized river basins with debris-covered glaciers in the Himalayan region.
The main objective of the paper is to assess the role of the biogas to mitigate the climate chang... more The main objective of the paper is to assess the role of the biogas to mitigate the climate change and adaptation. For this amount of fuel wood reduced by the use of biogas and ultimate result of forest save, time save, health improvement, agricultural production improvement and reduction of greenhouse gases are the bases for research objectives. Biogas and TCS users are separate sampling frame for this research. The total of 62.30% of the less fuel wood was used by the biogas user than the TCS user. The higher percentage of reduction of fuel wood is contributed by the reduction in cooking. The amount of the greenhouse gas emission reduction due to reduction in the fuel wood consumption was 8.02 tons per plant per year of carbon dioxide equivalent. The number of trees saved per plants per year is found to be 10.15 trees that help to mitigate the climate change through carbon sequestration and increase adaptive capacity of the user. The occurrences of the diseases were considerably lower among biogas user than the TCS user. The total time save within the family was 2 hour and 24 minutes per day from collection of fuel wood, cooking food and cleaning of utensils if the family cook food for one times per day and one person involved in collection of the fuel wood. There was positive perception of the people in quality of the fertilizer and saving of the money by not buying chemical fertilizer.
Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, ... more Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, i.e. most likely to cause death and destruction in case of a glacier lake outburst flood (GLOF). Imja Lake and the associated Imja and Lhoste-Shar glaciers have been intensively studied; Thulagi Glacier and its lake are much less studied. Collectively, we have undertaken a series of increasingly thorough bathymetric and land surveys and satellite remote sensing analyses of Imja Lake and its glacier setting. We are analyzing several expeditions' data to build a detailed assessment of the glacier and lake to better establish the dynamical evolution of the system and its future GLOF potential. Our most recent, most complete bathymetric survey of Imja Lake has revealed a much greater volume (75,200,000 cubic meters) and maximum depth (149.8 m) than found before. Our analysis suggests that not all possible Imja GLOF scenarios would result in devastation. Some moraine melt-through or down-...
Glaciers are key resources of water for hydropower, irrigation, and drinking water. The extensive... more Glaciers are key resources of water for hydropower, irrigation, and drinking water. The extensive debris cover often covers glaciers in ablation part of the Himalayan region; hence, it is essential to assess the effect of debris on glacier ice melt. In this study, the main objective is to generate the seasonal vertical temperature profile and estimate the temperature gradient from debris surface to debris/ice interface on Lirung Glacier in Langtang Valley, Rasuwa district, Nepal. Three field campaigns are carried out in monsoon (2013), winter (2013) and pre-monsoon (2014) season during which 2 set of thermistors are installed at different debris thickness. Debris temperature data are collected in different layers of debris from atmosphere/debris interface to debris/ice interface using temperature sensors during each season. Similarly, the debris temperature profile shows higher fluctuation of temperature near surface and lower fluctuation in lower layers with increasing lag time. Th...
Proceedings of the International Association of Hydrological Sciences, 2015
In the Nepalese Himalayas, the complex topography, occurrence of debris covered glaciers, and lim... more In the Nepalese Himalayas, the complex topography, occurrence of debris covered glaciers, and limited data availability creates substantial difficulties for modelling glacier melt. The proper recognition of melt processes governs the accurate estimation of melt water from glacier dominated systems, even in the presence of debris-covered glaciers. This paper presents a glacier melt model developed for the Lirung subbasin of Langtang valley, which has both a clean glacier area, 5.86 km 2 , and a debris-covered glacier area, 1.13 km 2 . We use a temperature index approach to estimate sub-daily melt water discharge for a two week period at the end of monsoon, and the melt factor is varied according to the aspect and distributed to each grid processed from the digital elevation model. The model uses easily available data and simple extrapolation techniques capable of generating melt with limited data. The result obtained from this method provides accurate estimate with an R 2 value of 0.89, bias of 0.9% and Nash-Sutcliffe efficiency of 0.86, and suitable in Himalaya where data availability is major issue.
Proceedings of International Association of Hydrological Sciences, doi:10.5194/piahs-368-57-2015, May 6, 2015
Glaciers are one of the important natural resources of freshwater and sources of water for hydrop... more Glaciers are one of the important natural resources of freshwater and sources of water for hydropower, agriculture and drinking whenever the water is scarce. This mapping and change analysis helps to understand the status and decadal changes of glaciers in Hidden Valley, Mustang district, Nepal. The investigation is carried out using Landsat images of the years 1977 (~1980s), 1990, 2000 and 2010. We mapped 10 glaciers of the Hidden Valley covering an area of 19.79 km2 based on the object-based image classification method using an automatic method and manual delineation by a Geographic Information System (GIS), separately. The glacier outlines for 2010, 2000, 1990 and 1980s in both methods are delineated from the multispectral Landsat images of the respective years. The total area losses of the glaciers from the automatic method are 1.713 and 0.625 km2 between 1990−2000 and 2000−2010 and from manual delineation are 2.021, 1.264, 1.041 km2 between ~1980s−1990, 1990−2000 and 2000−2010. The amount of average estimated glacier ice reserves lost is 0.326 km3 (26.26 %) and the total glacier area loss is 4.33 km2 (21.87 %) from the 1980s to 2010 based on manual delineation. The glaciers of Hidden Valley are shrinking and fragmented due to decrease in glacier area and ice reserves.
Proceeding of International Association of Hydrological Sciences, doi:10.5194/piahs-368-21-2015, May 6, 2015
Glaciers in the Himalayan region are often covered by extensive debris cover in ablation areas, h... more Glaciers in the Himalayan region are often covered by extensive debris cover in ablation areas, hence it is essential to assess the effect of debris on glacier ice melt. Seasonal melting of ice beneath different thicknesses of debris on Lirung Glacier in Langtang Valley, Nepal, was studied during three seasons of 2013–14. The melting rates of ice under 5 cm debris thickness are 3.52, 0.09, and 0.85 cm d-1 during the monsoon, winter and pre-monsoon season, respectively. Maximum melting is observed in dirty ice (0.3 cm debris thickness) and the rate decreases with the increase of debris thickness. The energy balance calculations on dirty ice and at 40 cm debris thickness show that the main energy source of ablation is net radiation. The major finding from this study is that the maximum melting occurs during the monsoon season than rest of the seasons.
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Papers by Mohan Chand