Holistic study of glacial lakes and glacial lake outburst floods (GLOFs) in the strategically imp... more Holistic study of glacial lakes and glacial lake outburst floods (GLOFs) in the strategically important China-Nepal transportation corridors is imperative for regional connectivity and disaster risk reduction. This study focuses on four China-Nepal transportation corridors, namely Chentang-Kimathanka, Zhangmu-Kodari, KeyrungKathmandu and Taklakot-Hilsa from east to west in the Himalayan region. Within a remote integrated framework, we present the latest high-resolution inventory of glacial lakes, assess their decadal spatio-temporal changes (1992–2022), identify potentially dangerous glacial lakes, and apply hydrodynamic model to assess downstream impacts of possible GLOFs along the study area. The results show 2688 glacial lakes (≥0.001 km2) with a total area of 116.10 ± 8.53 km2 over the study area in 2022. Glacial lakes exhibited spatiotemporal heterogeneity in expansion, with overall expansion of 32 % during 30 years. Keyrung-Kathmandu corridor, among others, was assessed with high GLOF susceptibility. Furthermore, hydrodynamic modeling of four highly dangerous lakes in each transportation area reveals that GLOFs have cross-border effects, impacting ~103 km of China-Nepal highway, 103 bridges, two major dry ports and 3301 buildings in both countries. Based on thesefindings, we emphasize the joint efforts of both countries for integrated disaster management for smooth connectivity between two countries and saving downstream population through joint cooperation from central to local government levels by initiating artificial lake lowering, developing cross-border early warning systems and cooperation. This study is valuable for presenting a synergistic study of glacial lakes and GLOF for informing decision- and policy-makers of both China and Nepal for a joint approach to disaster mitigation
International journal of disaster risk reduction, Apr 1, 2024
Transboundary glacial lake outburst floods (GLOFs) pose severe risks to downstream communities an... more Transboundary glacial lake outburst floods (GLOFs) pose severe risks to downstream communities and infrastructure across international borders. However, previous GLOF research has largely
overlooked the transboundary aspects of national and sub-national level GLOFs, focusing instead
mostly on inventorying glacial lakes and assessing their hazards. The lack of cross-border coordination could have dire consequences for vulnerable communities and potential disaster preparedness. Assessing risk perception and vulnerability among downstream populations exposed to
GLOFs is crucial for effective disaster risk reduction and management. This study examined the
risk perception and vulnerabilities of Nepali communities in Bhotekoshi/Sunkoshi (Poiqu in Tibet) and Trishuli (Gyirong in Tibet) river basins, exposed to transboundary GLOFs originating
from Tibetan basins. Household-level data were collected from 90 respondents in the villages
along those two basins. The findings highlight high risk perception in the Bhotekoshi basin and
medium perception in the Trishuli basin, along with corresponding vulnerability levels. Key factors influencing risk perception and vulnerability are explored, emphasizing the need for public
awareness and policy formulation at national and regional levels. To reduce vulnerability to
transboundary GLOFs, extending early warning systems, enhancing cross-border cooperation,
supporting socioeconomically disadvantaged populations, and ensuring resilient infrastructure
are essential.
Understanding drought characteristics is vital for sustainable societal and ecosystem functioning... more Understanding drought characteristics is vital for sustainable societal and ecosystem functioning, especially in ongoing climate change. The study investigates the drought characteristics over the Nepal Himalaya using the standardized precipitation index (SPI) based on monthly precipitation data from 220 ground stations between 1980 and 2016 at seasonal and annual timescales. The results show that occurrences of drought are more frequent after the 2000s, intensifying their severity and duration. The cumulative probabilities of short‐term (SPI3) and long‐term (SPI12) drought during the period 1980–2016 were 17.1% and 23.5%, respectively. The short‐term drought over Nepal occurred with an average duration of 2.8 months and a severity of −4.3, whereas for long‐term drought the duration and severity were 8.6 months and −13.9, respectively. Meanwhile, the seasonal drought shows that the spring and autumn drought events were slightly higher than summer and winter drought. The wavelet power spectrum shows the variability signals of winter, spring and summer drought were 2–8 and 8–16 years; however, the autumn drought index only varied at 2–8 years. The NINO3.4 is the primary controlling mode of variability for summer and annual drought, whereas the dipole moment index (DMI) is used for the autumn drought at an interannual timescale. The decadal variability of summer and annual drought is linked with the Pacific Decadal Oscillation, whereas winter and spring drought are linked to the Arctic Oscillation. Furthermore, the study contributes to the understanding of the drought characteristics and its controlling factors of variability over Nepal.
Ongoing recession of glaciers in the Himalaya in response to global climate change has farreachin... more Ongoing recession of glaciers in the Himalaya in response to global climate change has farreaching impacts on the formation and expansion of glacial lakes. The subsequent glacial lake outburst floods (GLOFs) are a significant threat to lives and livelihoods as they can cause catastrophic damage up to hundreds of kilometres downstream. Previous studies have reported the rapid expansion of glacial lakes and several notable destructive past GLOF events in the Mahalangur Himalaya, suggesting a necessity of timely and updated GLOF susceptibility assessment. Here, an updated inventory of glacial lakes across the Mahalangur Himalaya is developed based on 10-m Sentinel-2 satellite data from 2018. Additionally, the GLOF susceptibilities of glacial lakes (≥0.045 km 2) are evaluated using a multi-criteria-based assessment framework where six key factors are selected and analyzed. Weight for each factor was assigned from the analytical hierarchy process. Glacial lakes are classified into very low, low, medium, high, and very high GLOF susceptibility classes depending upon their susceptibility index based on analysis of three historical GLOF events in the study area. The result shows the existence of 345 glacial lakes (>0.001 km 2) with a total area of 18.80 ± 1.35 km 2 across the region in 2018. Furthermore, out of the 64 glacial lakes (≥0.045 km 2) assessed, seven were identified with very high GLOF susceptibility. We underline that pronounced glacier-lake interaction will likely increase the GLOF susceptibility. Regular monitoring and more detailed fieldworks for these highly susceptible glacial lakes are necessary. This will benefit in early warning and disaster risk reduction of downstream communities.
Journal of tourism and himalayan adventures, Aug 19, 2021
In this paper, we present the current situation of the Gosainkunda and associated lakes based on ... more In this paper, we present the current situation of the Gosainkunda and associated lakes based on the preparation of an inventory of lakes using the Google Earth Engine and 2020 Sentinel 2A satellite imagery. Furthermore, we discuss the hydrology, hydrochemistry, and cultural significance of the lakes based on the systematic review of available literatures. In 2020, there are 22 lakes along with Gosaikunda (12.7±0.4 ha) in the Upper Trishuli watershed (59.2 km2), extending from 1274 to 4993 m elevation and covering a total area of 80 ha. The largest lake is Bhairabkunda, with an area of 15.5±0.5 ha. The water bodies in the region are drying, and some of the lakes have already disappeared from the region. But some lakes in the region are evolving as temporary water bodies. The high-altitude lakes are sensitive indicators of anthropogenic disturbance and changing climate. Though the lakes have better hydrochemical quality than the urban lakes located in the southern part of the country, the evidence shows increasing local and long-range transport and deposition of the pollutants in the lake water. The presence of chemical constituents of anthropogenic sources in the water of oligotrophic lakes is possibly evidence of the long-range transport of pollutants. Considering the cultural importance of the region, the number of visitors is increasing annually. Increasing human activities in and around the lake, long-range transport of pollutants, and changing environment in the area are demanding for the lake's conservation. We suggest regular monitoring of the high-altitude lakes to understand the ongoing climate change and anthropogenic impacts.
Himalayan glaciers, in general, are shrinking and glacial lakes are evolving and growing rapidly ... more Himalayan glaciers, in general, are shrinking and glacial lakes are evolving and growing rapidly in number and size as a result of climate change. This study presents the latest remote sensing-based inventory (2017) of glacial lakes (size ≥0.0036 km 2) across the Nepal Himalaya using optical satellite data. Furthermore, this study traces the decadal glacial lake dynamics from 1977 to 2017 in the Nepal Himalaya. The decadal mapping of glacial lakes (both glacial-fed and nonglacial-fed) across the Nepal Himalaya reveals an increase in the number and area of lakes
The retreat and shrinkage of glaciers due to climate change are the causes for the formation and ... more The retreat and shrinkage of glaciers due to climate change are the causes for the formation and expansion of glacial lakes in the Himalayas. This study presents the rapidly expanding glacial lakes in Nepal Himalayas between 1988 and 2018 based on the published glacial lake inventories produced from Landsat imageries (30 m). Glacier-fed end morainedammed glacial lakes whose surface area was ≥0.1 km 2 in 2018 with an expansion rate of more than 30% in 1988-2018 were regarded as rapidly expanding glacial lakes. The results show that 19 rapidly expanding glacial lakes are heterogeneously distributed in different sub-basins of Nepal. Among the sub-basins, Dudh Koshi sub-basin has a maximum (5) number of rapidly expanding glacial lakes. The total surface area of these 19 glacial lakes expanded by ~133%, from 4.12±0.61 km 2 in 1988 to 9.62±1.04 km 2 in 2018. Regular monitoring of rapidly expanding glacial lakes is required because the rapid expansion heightens the risk of Glacial Lake Outburst Flood (GLOF) by developing more potential flood volume and the expanding lakes can reach sites of possible avalanches.
The nationwide lockdown imposed to control the spread of novel coronavirus induced dramatic alter... more The nationwide lockdown imposed to control the spread of novel coronavirus induced dramatic alterations in different sectors of the Nepalese governance, including Solid Waste Management (SWM) practices. The study identifies SW collection gaps in seven major cities of Nepal and highlights the municipal and public households on SW management practices before and during the lockdown to emphasize the linkage between COVID-19 and SWM. It includes information on solid waste status, collection frequency and coverage, workers' safety practices, types of vehicles operated for collection and alternative methods adopted by households to manage SW during the lockdown. For this, 1329 households survey and key informant interviews were conducted in seven cities of Nepal during the lockdown. It was found that although the coverage of the collection service was similar during the pandemic in surveyed households, there was a drastic decrease in the collection frequency leading to a collection gap of around 570 tons/day. More than 50% of the surveyed households adopted no proper alternative measures as they claimed that they stored solid waste with proper management so that municipal authorities can take it. While other 50% adopted practices such as open burning, throwing in streets or composting. The study reveals poor occupational health and safety practices among solid waste workers due to the unavailability of safety gear and equipment despite being aware of the modes of transmission of the virus. The pandemic exacerbated the challenges of smooth SWM as it is an essential and needy service. This study highlights the need for a timely strategic management framework to be developed by the government to continue the smooth SWM practices during the lockdown.
Glaciers in the Himalaya are increasingly retreating and thinning due to climate change. This pro... more Glaciers in the Himalaya are increasingly retreating and thinning due to climate change. This process is the primary cause of glacial lakes expansion and has increased the possibilities of the glacial lake outburst floods (GLOFs) that have been responsible for heavy loss of life and damage to downstream infrastructures. This study examines the status of the existing potentially dangerous glacial lakes in the Nepalese Himalaya such as Imja Tsho, Tsho Rolpa, Thulagi, Chamlang South, Barun Tsho, and Lumding Tsho; which were more susceptible to GLOF after the devastating earthquake in 2015. We examined the evolution and decadal expansion rate of lakes from 1987 to 2016 using Landsat images. The results show significant expansion of Imja Tsho, Barun Tsho, and Lumding Tsho at the rates of 42.1, 46.8, and 32.9% respectively, during 2006-2016; while other glacial lakes (i.e., Chamlang South, Barun Tsho, and Lumding Tsho) are relatively stable. Although the current status of glacial lakes may be stable in term of burst risk, high expanding lakes must be prioritized for detail studies. Continuous model-based monitoring and risk assessment, mitigation measures and disaster management strategies are necessary for reducing the impact of GLOFs.
Applied ecology and environmental sciences, Apr 17, 2020
Understanding the spatial and temporal variation of precipitation is important to identify its dr... more Understanding the spatial and temporal variation of precipitation is important to identify its driving potential of extreme events that impact on the socio-economic conditions at national and provincial scales. This study presents the spatial and temporal variation of precipitation and the related extreme events in provincial scale using 143 rain-gauge stations across Nepal during 2001–2016. The results show the provincial differences in the precipitation distribution, with the highest precipitation in Province 4 (Bagmati) and lowest in Province 6 (Karnali). The precipitation is in decreasing trend at the national and provincial scale, expect for Province 6. The spatial distribution of precipitation shows the wettest (Lumle) and driest (Manang and Mustang) areas of the country located within the same Province 4. The seasonal cycle reveals the longer period of monsoon in Provinces 1 and 4; meanwhile, a shorter monsoon period was observed in Provinces 6 and 7 (Farwestern). Heavy (R10mm) and extreme precipitation (R25mm) events were higher in those provinces with a more extended monsoon period and vice-versa. The result further shows that the number of Consecutive Dry Day (CCD) spells in all the provinces was higher than the number of Consecutive Wet Day (CWD) spells. The time-series of extreme events (R10mm, R25mm, CDD and CWD) show an inter-annual variation in seven provinces during 2001-2016. The spatial variation of the number of wet and dry spells was reversed for the provinces lying in the eastern and western parts of the country. This study helps to update and upgrade our understanding of precipitation variability and related extremities over different provinces of Nepal, which can further assist the provincial government in disaster management.
Nepal, a Himalayan country, is often chosen by global scientists to study climate change and its ... more Nepal, a Himalayan country, is often chosen by global scientists to study climate change and its impact on the Himalayan environment. The changes in temperature, precipitation, glaciers, and glacial lakes over Nepal are comprehensively reviewed based on published literature and compared with regional studies. Furthermore, the published glacier datasets were used to calculate and analyze the changes in area, equilibrium line of altitude (ELA) and ice reserves to show the response of glaciers to climate change. We find that the warming trend (0.02 to 0.16 °C yr−1) is being more pronounced over Nepal, and heterogeneous changes in precipitation amount, pattern, and frequency are observed with no significant trend. Concurrently, the glaciers are found to be responding with heterogeneous shrinkage in area (− 1 to − 5 km2 yr−1), possessing negative mass balance (− 0.3 to − 0.8 m w.e. yr−1), decrease in ice volume (− 4.29 km3 yr−1) and upward shift of the ELA (~ 20.66 m decade−1). The total...
Due to ongoing global climate change, the glaciers in the Himalaya are shrinking and the glacial ... more Due to ongoing global climate change, the glaciers in the Himalaya are shrinking and the glacial lakes are increasing in number and area. This study investigates the glacier area change, mass balance and associated glacial lake evolution in the headwaters of Kawari basin, western Nepal using optical remote sensing images. The results indicate that eleven glaciers in the study area have shrunk by 1.64 km 2 between 1994 and 2021. In the same period, due to glacier recession glacial lake formed and expanded by 0.0103 km 2 yr-1 reaching 0.34±0.042 km 2 in 2021. Surface elevation change of glaciers revealed that the ablation zone of glacier thinned up to-8.18 m between 2000 and 2019. The specific mass balance of eleven glaciers was calculated to be-0.3 m w. e. yr-1 from 2000 to 2019. The study of glaciers is important as they are visible signals of climate change, and their changes often impact water resources and mountain hydrology.
Valuation of ecosystem services based on land use and land cover changes (LUCC) offers an incenti... more Valuation of ecosystem services based on land use and land cover changes (LUCC) offers an incentive to people for sustainable use of the natural resources and can encourage people to adjust the land use sustainably. In this study, we used "Object-based Image Analysis (OBIA)," a remote sensing technique to extract the land use and land cover (LULC) of the transboundary Karnali River Basin (KRB, China and Nepal) from 1990 to 2020, and ecosystem services value (ESV) coefficients derived for the Tibetan Plateau has been used to assess the ESV. The basin has highest percentage of forest (33.44%), followed by bare area (30.29%), shrub/grassland (18.5%), agriculture (13.12%), snow/ice (4.36%), waterbody (0.3%), and built-up (0.03%) as of 2020. Over 30 years, 4.07 km 2 of the forest has been converted to agricultural land, 3.31 km 2 of agricultural land has been encroached by built-up area, whereas 2.82 km 2 of snow/ice area has melted into the waterbody. Furthermore, 80.85 km 2 of bare area has been converted to snow/ice, and 2138.83 km 2 of snow/ice has been changed to bare area. The ESV of KRB has increased by nearly 2.7 million USD from 1990 to 2020, primarily due to the increase in ESV from the conversion of 133.09 km 2 of snow/ice to shrub/grassland. The ESV of forest, waterbody, and snow/ice has decreased, whereas it has increased for other LULC classes in the basin. Spatial distribution of LUCC and assessment of ESV can be a tool to facilitate for better provisioning and regulating the resources for the future.
Due to ongoing global climate change, the glaciers in the Himalaya are shrinking and the glacial ... more Due to ongoing global climate change, the glaciers in the Himalaya are shrinking and the glacial lakes are increasing in number and area. This study investigates the glacier area change, mass balance and associated glacial lake evolution in the headwaters of Kawari basin, western Nepal using optical remote sensing images. The results indicate that eleven glaciers in the study area have shrunk by 1.64 km2 between 1994 and 2021. In the same period, due to glacier recession glacial lake formed and expanded by 0.0103 km2 yr-1 reaching 0.34±0.042 km2 in 2021. Surface elevation change of glaciers revealed that the ablation zone of glacier thinned up to -8.18 m between 2000 and 2019. The specific mass balance of eleven glaciers was calculated to be -0.3 m w. e. yr-1 from 2000 to 2019. The study of glaciers is important as they are visible signals of climate change, and their changes often impact water resources and mountain hydrology.
Understanding the spatial and temporal variation of precipitation is important to identify its dr... more Understanding the spatial and temporal variation of precipitation is important to identify its driving potential of extreme events that impact on the socio-economic conditions at national and provincial scales. This study presents the spatial and temporal variation of precipitation and the related extreme events in provincial scale using 143 rain-gauge stations across Nepal during 2001–2016. The results show the provincial differences in the precipitation distribution, with the highest precipitation in Province 4 (Bagmati) and lowest in Province 6 (Karnali). The precipitation is in decreasing trend at the national and provincial scale, expect for Province 6. The spatial distribution of precipitation shows the wettest (Lumle) and driest (Manang and Mustang) areas of the country located within the same Province 4. The seasonal cycle reveals the longer period of monsoon in Provinces 1 and 4; meanwhile, a shorter monsoon period was observed in Provinces 6 and 7 (Farwestern). Heavy (R10m...
Holistic study of glacial lakes and glacial lake outburst floods (GLOFs) in the strategically imp... more Holistic study of glacial lakes and glacial lake outburst floods (GLOFs) in the strategically important China-Nepal transportation corridors is imperative for regional connectivity and disaster risk reduction. This study focuses on four China-Nepal transportation corridors, namely Chentang-Kimathanka, Zhangmu-Kodari, KeyrungKathmandu and Taklakot-Hilsa from east to west in the Himalayan region. Within a remote integrated framework, we present the latest high-resolution inventory of glacial lakes, assess their decadal spatio-temporal changes (1992–2022), identify potentially dangerous glacial lakes, and apply hydrodynamic model to assess downstream impacts of possible GLOFs along the study area. The results show 2688 glacial lakes (≥0.001 km2) with a total area of 116.10 ± 8.53 km2 over the study area in 2022. Glacial lakes exhibited spatiotemporal heterogeneity in expansion, with overall expansion of 32 % during 30 years. Keyrung-Kathmandu corridor, among others, was assessed with high GLOF susceptibility. Furthermore, hydrodynamic modeling of four highly dangerous lakes in each transportation area reveals that GLOFs have cross-border effects, impacting ~103 km of China-Nepal highway, 103 bridges, two major dry ports and 3301 buildings in both countries. Based on thesefindings, we emphasize the joint efforts of both countries for integrated disaster management for smooth connectivity between two countries and saving downstream population through joint cooperation from central to local government levels by initiating artificial lake lowering, developing cross-border early warning systems and cooperation. This study is valuable for presenting a synergistic study of glacial lakes and GLOF for informing decision- and policy-makers of both China and Nepal for a joint approach to disaster mitigation
International journal of disaster risk reduction, Apr 1, 2024
Transboundary glacial lake outburst floods (GLOFs) pose severe risks to downstream communities an... more Transboundary glacial lake outburst floods (GLOFs) pose severe risks to downstream communities and infrastructure across international borders. However, previous GLOF research has largely
overlooked the transboundary aspects of national and sub-national level GLOFs, focusing instead
mostly on inventorying glacial lakes and assessing their hazards. The lack of cross-border coordination could have dire consequences for vulnerable communities and potential disaster preparedness. Assessing risk perception and vulnerability among downstream populations exposed to
GLOFs is crucial for effective disaster risk reduction and management. This study examined the
risk perception and vulnerabilities of Nepali communities in Bhotekoshi/Sunkoshi (Poiqu in Tibet) and Trishuli (Gyirong in Tibet) river basins, exposed to transboundary GLOFs originating
from Tibetan basins. Household-level data were collected from 90 respondents in the villages
along those two basins. The findings highlight high risk perception in the Bhotekoshi basin and
medium perception in the Trishuli basin, along with corresponding vulnerability levels. Key factors influencing risk perception and vulnerability are explored, emphasizing the need for public
awareness and policy formulation at national and regional levels. To reduce vulnerability to
transboundary GLOFs, extending early warning systems, enhancing cross-border cooperation,
supporting socioeconomically disadvantaged populations, and ensuring resilient infrastructure
are essential.
Understanding drought characteristics is vital for sustainable societal and ecosystem functioning... more Understanding drought characteristics is vital for sustainable societal and ecosystem functioning, especially in ongoing climate change. The study investigates the drought characteristics over the Nepal Himalaya using the standardized precipitation index (SPI) based on monthly precipitation data from 220 ground stations between 1980 and 2016 at seasonal and annual timescales. The results show that occurrences of drought are more frequent after the 2000s, intensifying their severity and duration. The cumulative probabilities of short‐term (SPI3) and long‐term (SPI12) drought during the period 1980–2016 were 17.1% and 23.5%, respectively. The short‐term drought over Nepal occurred with an average duration of 2.8 months and a severity of −4.3, whereas for long‐term drought the duration and severity were 8.6 months and −13.9, respectively. Meanwhile, the seasonal drought shows that the spring and autumn drought events were slightly higher than summer and winter drought. The wavelet power spectrum shows the variability signals of winter, spring and summer drought were 2–8 and 8–16 years; however, the autumn drought index only varied at 2–8 years. The NINO3.4 is the primary controlling mode of variability for summer and annual drought, whereas the dipole moment index (DMI) is used for the autumn drought at an interannual timescale. The decadal variability of summer and annual drought is linked with the Pacific Decadal Oscillation, whereas winter and spring drought are linked to the Arctic Oscillation. Furthermore, the study contributes to the understanding of the drought characteristics and its controlling factors of variability over Nepal.
Ongoing recession of glaciers in the Himalaya in response to global climate change has farreachin... more Ongoing recession of glaciers in the Himalaya in response to global climate change has farreaching impacts on the formation and expansion of glacial lakes. The subsequent glacial lake outburst floods (GLOFs) are a significant threat to lives and livelihoods as they can cause catastrophic damage up to hundreds of kilometres downstream. Previous studies have reported the rapid expansion of glacial lakes and several notable destructive past GLOF events in the Mahalangur Himalaya, suggesting a necessity of timely and updated GLOF susceptibility assessment. Here, an updated inventory of glacial lakes across the Mahalangur Himalaya is developed based on 10-m Sentinel-2 satellite data from 2018. Additionally, the GLOF susceptibilities of glacial lakes (≥0.045 km 2) are evaluated using a multi-criteria-based assessment framework where six key factors are selected and analyzed. Weight for each factor was assigned from the analytical hierarchy process. Glacial lakes are classified into very low, low, medium, high, and very high GLOF susceptibility classes depending upon their susceptibility index based on analysis of three historical GLOF events in the study area. The result shows the existence of 345 glacial lakes (>0.001 km 2) with a total area of 18.80 ± 1.35 km 2 across the region in 2018. Furthermore, out of the 64 glacial lakes (≥0.045 km 2) assessed, seven were identified with very high GLOF susceptibility. We underline that pronounced glacier-lake interaction will likely increase the GLOF susceptibility. Regular monitoring and more detailed fieldworks for these highly susceptible glacial lakes are necessary. This will benefit in early warning and disaster risk reduction of downstream communities.
Journal of tourism and himalayan adventures, Aug 19, 2021
In this paper, we present the current situation of the Gosainkunda and associated lakes based on ... more In this paper, we present the current situation of the Gosainkunda and associated lakes based on the preparation of an inventory of lakes using the Google Earth Engine and 2020 Sentinel 2A satellite imagery. Furthermore, we discuss the hydrology, hydrochemistry, and cultural significance of the lakes based on the systematic review of available literatures. In 2020, there are 22 lakes along with Gosaikunda (12.7±0.4 ha) in the Upper Trishuli watershed (59.2 km2), extending from 1274 to 4993 m elevation and covering a total area of 80 ha. The largest lake is Bhairabkunda, with an area of 15.5±0.5 ha. The water bodies in the region are drying, and some of the lakes have already disappeared from the region. But some lakes in the region are evolving as temporary water bodies. The high-altitude lakes are sensitive indicators of anthropogenic disturbance and changing climate. Though the lakes have better hydrochemical quality than the urban lakes located in the southern part of the country, the evidence shows increasing local and long-range transport and deposition of the pollutants in the lake water. The presence of chemical constituents of anthropogenic sources in the water of oligotrophic lakes is possibly evidence of the long-range transport of pollutants. Considering the cultural importance of the region, the number of visitors is increasing annually. Increasing human activities in and around the lake, long-range transport of pollutants, and changing environment in the area are demanding for the lake's conservation. We suggest regular monitoring of the high-altitude lakes to understand the ongoing climate change and anthropogenic impacts.
Himalayan glaciers, in general, are shrinking and glacial lakes are evolving and growing rapidly ... more Himalayan glaciers, in general, are shrinking and glacial lakes are evolving and growing rapidly in number and size as a result of climate change. This study presents the latest remote sensing-based inventory (2017) of glacial lakes (size ≥0.0036 km 2) across the Nepal Himalaya using optical satellite data. Furthermore, this study traces the decadal glacial lake dynamics from 1977 to 2017 in the Nepal Himalaya. The decadal mapping of glacial lakes (both glacial-fed and nonglacial-fed) across the Nepal Himalaya reveals an increase in the number and area of lakes
The retreat and shrinkage of glaciers due to climate change are the causes for the formation and ... more The retreat and shrinkage of glaciers due to climate change are the causes for the formation and expansion of glacial lakes in the Himalayas. This study presents the rapidly expanding glacial lakes in Nepal Himalayas between 1988 and 2018 based on the published glacial lake inventories produced from Landsat imageries (30 m). Glacier-fed end morainedammed glacial lakes whose surface area was ≥0.1 km 2 in 2018 with an expansion rate of more than 30% in 1988-2018 were regarded as rapidly expanding glacial lakes. The results show that 19 rapidly expanding glacial lakes are heterogeneously distributed in different sub-basins of Nepal. Among the sub-basins, Dudh Koshi sub-basin has a maximum (5) number of rapidly expanding glacial lakes. The total surface area of these 19 glacial lakes expanded by ~133%, from 4.12±0.61 km 2 in 1988 to 9.62±1.04 km 2 in 2018. Regular monitoring of rapidly expanding glacial lakes is required because the rapid expansion heightens the risk of Glacial Lake Outburst Flood (GLOF) by developing more potential flood volume and the expanding lakes can reach sites of possible avalanches.
The nationwide lockdown imposed to control the spread of novel coronavirus induced dramatic alter... more The nationwide lockdown imposed to control the spread of novel coronavirus induced dramatic alterations in different sectors of the Nepalese governance, including Solid Waste Management (SWM) practices. The study identifies SW collection gaps in seven major cities of Nepal and highlights the municipal and public households on SW management practices before and during the lockdown to emphasize the linkage between COVID-19 and SWM. It includes information on solid waste status, collection frequency and coverage, workers' safety practices, types of vehicles operated for collection and alternative methods adopted by households to manage SW during the lockdown. For this, 1329 households survey and key informant interviews were conducted in seven cities of Nepal during the lockdown. It was found that although the coverage of the collection service was similar during the pandemic in surveyed households, there was a drastic decrease in the collection frequency leading to a collection gap of around 570 tons/day. More than 50% of the surveyed households adopted no proper alternative measures as they claimed that they stored solid waste with proper management so that municipal authorities can take it. While other 50% adopted practices such as open burning, throwing in streets or composting. The study reveals poor occupational health and safety practices among solid waste workers due to the unavailability of safety gear and equipment despite being aware of the modes of transmission of the virus. The pandemic exacerbated the challenges of smooth SWM as it is an essential and needy service. This study highlights the need for a timely strategic management framework to be developed by the government to continue the smooth SWM practices during the lockdown.
Glaciers in the Himalaya are increasingly retreating and thinning due to climate change. This pro... more Glaciers in the Himalaya are increasingly retreating and thinning due to climate change. This process is the primary cause of glacial lakes expansion and has increased the possibilities of the glacial lake outburst floods (GLOFs) that have been responsible for heavy loss of life and damage to downstream infrastructures. This study examines the status of the existing potentially dangerous glacial lakes in the Nepalese Himalaya such as Imja Tsho, Tsho Rolpa, Thulagi, Chamlang South, Barun Tsho, and Lumding Tsho; which were more susceptible to GLOF after the devastating earthquake in 2015. We examined the evolution and decadal expansion rate of lakes from 1987 to 2016 using Landsat images. The results show significant expansion of Imja Tsho, Barun Tsho, and Lumding Tsho at the rates of 42.1, 46.8, and 32.9% respectively, during 2006-2016; while other glacial lakes (i.e., Chamlang South, Barun Tsho, and Lumding Tsho) are relatively stable. Although the current status of glacial lakes may be stable in term of burst risk, high expanding lakes must be prioritized for detail studies. Continuous model-based monitoring and risk assessment, mitigation measures and disaster management strategies are necessary for reducing the impact of GLOFs.
Applied ecology and environmental sciences, Apr 17, 2020
Understanding the spatial and temporal variation of precipitation is important to identify its dr... more Understanding the spatial and temporal variation of precipitation is important to identify its driving potential of extreme events that impact on the socio-economic conditions at national and provincial scales. This study presents the spatial and temporal variation of precipitation and the related extreme events in provincial scale using 143 rain-gauge stations across Nepal during 2001–2016. The results show the provincial differences in the precipitation distribution, with the highest precipitation in Province 4 (Bagmati) and lowest in Province 6 (Karnali). The precipitation is in decreasing trend at the national and provincial scale, expect for Province 6. The spatial distribution of precipitation shows the wettest (Lumle) and driest (Manang and Mustang) areas of the country located within the same Province 4. The seasonal cycle reveals the longer period of monsoon in Provinces 1 and 4; meanwhile, a shorter monsoon period was observed in Provinces 6 and 7 (Farwestern). Heavy (R10mm) and extreme precipitation (R25mm) events were higher in those provinces with a more extended monsoon period and vice-versa. The result further shows that the number of Consecutive Dry Day (CCD) spells in all the provinces was higher than the number of Consecutive Wet Day (CWD) spells. The time-series of extreme events (R10mm, R25mm, CDD and CWD) show an inter-annual variation in seven provinces during 2001-2016. The spatial variation of the number of wet and dry spells was reversed for the provinces lying in the eastern and western parts of the country. This study helps to update and upgrade our understanding of precipitation variability and related extremities over different provinces of Nepal, which can further assist the provincial government in disaster management.
Nepal, a Himalayan country, is often chosen by global scientists to study climate change and its ... more Nepal, a Himalayan country, is often chosen by global scientists to study climate change and its impact on the Himalayan environment. The changes in temperature, precipitation, glaciers, and glacial lakes over Nepal are comprehensively reviewed based on published literature and compared with regional studies. Furthermore, the published glacier datasets were used to calculate and analyze the changes in area, equilibrium line of altitude (ELA) and ice reserves to show the response of glaciers to climate change. We find that the warming trend (0.02 to 0.16 °C yr−1) is being more pronounced over Nepal, and heterogeneous changes in precipitation amount, pattern, and frequency are observed with no significant trend. Concurrently, the glaciers are found to be responding with heterogeneous shrinkage in area (− 1 to − 5 km2 yr−1), possessing negative mass balance (− 0.3 to − 0.8 m w.e. yr−1), decrease in ice volume (− 4.29 km3 yr−1) and upward shift of the ELA (~ 20.66 m decade−1). The total...
Due to ongoing global climate change, the glaciers in the Himalaya are shrinking and the glacial ... more Due to ongoing global climate change, the glaciers in the Himalaya are shrinking and the glacial lakes are increasing in number and area. This study investigates the glacier area change, mass balance and associated glacial lake evolution in the headwaters of Kawari basin, western Nepal using optical remote sensing images. The results indicate that eleven glaciers in the study area have shrunk by 1.64 km 2 between 1994 and 2021. In the same period, due to glacier recession glacial lake formed and expanded by 0.0103 km 2 yr-1 reaching 0.34±0.042 km 2 in 2021. Surface elevation change of glaciers revealed that the ablation zone of glacier thinned up to-8.18 m between 2000 and 2019. The specific mass balance of eleven glaciers was calculated to be-0.3 m w. e. yr-1 from 2000 to 2019. The study of glaciers is important as they are visible signals of climate change, and their changes often impact water resources and mountain hydrology.
Valuation of ecosystem services based on land use and land cover changes (LUCC) offers an incenti... more Valuation of ecosystem services based on land use and land cover changes (LUCC) offers an incentive to people for sustainable use of the natural resources and can encourage people to adjust the land use sustainably. In this study, we used "Object-based Image Analysis (OBIA)," a remote sensing technique to extract the land use and land cover (LULC) of the transboundary Karnali River Basin (KRB, China and Nepal) from 1990 to 2020, and ecosystem services value (ESV) coefficients derived for the Tibetan Plateau has been used to assess the ESV. The basin has highest percentage of forest (33.44%), followed by bare area (30.29%), shrub/grassland (18.5%), agriculture (13.12%), snow/ice (4.36%), waterbody (0.3%), and built-up (0.03%) as of 2020. Over 30 years, 4.07 km 2 of the forest has been converted to agricultural land, 3.31 km 2 of agricultural land has been encroached by built-up area, whereas 2.82 km 2 of snow/ice area has melted into the waterbody. Furthermore, 80.85 km 2 of bare area has been converted to snow/ice, and 2138.83 km 2 of snow/ice has been changed to bare area. The ESV of KRB has increased by nearly 2.7 million USD from 1990 to 2020, primarily due to the increase in ESV from the conversion of 133.09 km 2 of snow/ice to shrub/grassland. The ESV of forest, waterbody, and snow/ice has decreased, whereas it has increased for other LULC classes in the basin. Spatial distribution of LUCC and assessment of ESV can be a tool to facilitate for better provisioning and regulating the resources for the future.
Due to ongoing global climate change, the glaciers in the Himalaya are shrinking and the glacial ... more Due to ongoing global climate change, the glaciers in the Himalaya are shrinking and the glacial lakes are increasing in number and area. This study investigates the glacier area change, mass balance and associated glacial lake evolution in the headwaters of Kawari basin, western Nepal using optical remote sensing images. The results indicate that eleven glaciers in the study area have shrunk by 1.64 km2 between 1994 and 2021. In the same period, due to glacier recession glacial lake formed and expanded by 0.0103 km2 yr-1 reaching 0.34±0.042 km2 in 2021. Surface elevation change of glaciers revealed that the ablation zone of glacier thinned up to -8.18 m between 2000 and 2019. The specific mass balance of eleven glaciers was calculated to be -0.3 m w. e. yr-1 from 2000 to 2019. The study of glaciers is important as they are visible signals of climate change, and their changes often impact water resources and mountain hydrology.
Understanding the spatial and temporal variation of precipitation is important to identify its dr... more Understanding the spatial and temporal variation of precipitation is important to identify its driving potential of extreme events that impact on the socio-economic conditions at national and provincial scales. This study presents the spatial and temporal variation of precipitation and the related extreme events in provincial scale using 143 rain-gauge stations across Nepal during 2001–2016. The results show the provincial differences in the precipitation distribution, with the highest precipitation in Province 4 (Bagmati) and lowest in Province 6 (Karnali). The precipitation is in decreasing trend at the national and provincial scale, expect for Province 6. The spatial distribution of precipitation shows the wettest (Lumle) and driest (Manang and Mustang) areas of the country located within the same Province 4. The seasonal cycle reveals the longer period of monsoon in Provinces 1 and 4; meanwhile, a shorter monsoon period was observed in Provinces 6 and 7 (Farwestern). Heavy (R10m...
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Papers by Nitesh Khadka
transportation corridors is imperative for regional connectivity and disaster risk reduction. This study focuses on
four China-Nepal transportation corridors, namely Chentang-Kimathanka, Zhangmu-Kodari, KeyrungKathmandu and Taklakot-Hilsa from east to west in the Himalayan region. Within a remote integrated framework, we present the latest high-resolution inventory of glacial lakes, assess their decadal spatio-temporal
changes (1992–2022), identify potentially dangerous glacial lakes, and apply hydrodynamic model to assess
downstream impacts of possible GLOFs along the study area. The results show 2688 glacial lakes (≥0.001 km2)
with a total area of 116.10 ± 8.53 km2 over the study area in 2022. Glacial lakes exhibited spatiotemporal
heterogeneity in expansion, with overall expansion of 32 % during 30 years. Keyrung-Kathmandu corridor,
among others, was assessed with high GLOF susceptibility. Furthermore, hydrodynamic modeling of four highly
dangerous lakes in each transportation area reveals that GLOFs have cross-border effects, impacting ~103 km of
China-Nepal highway, 103 bridges, two major dry ports and 3301 buildings in both countries. Based on thesefindings, we emphasize the joint efforts of both countries for integrated disaster management for smooth connectivity between two countries and saving downstream population through joint cooperation from central to
local government levels by initiating artificial lake lowering, developing cross-border early warning systems and
cooperation. This study is valuable for presenting a synergistic study of glacial lakes and GLOF for informing
decision- and policy-makers of both China and Nepal for a joint approach to disaster mitigation
overlooked the transboundary aspects of national and sub-national level GLOFs, focusing instead
mostly on inventorying glacial lakes and assessing their hazards. The lack of cross-border coordination could have dire consequences for vulnerable communities and potential disaster preparedness. Assessing risk perception and vulnerability among downstream populations exposed to
GLOFs is crucial for effective disaster risk reduction and management. This study examined the
risk perception and vulnerabilities of Nepali communities in Bhotekoshi/Sunkoshi (Poiqu in Tibet) and Trishuli (Gyirong in Tibet) river basins, exposed to transboundary GLOFs originating
from Tibetan basins. Household-level data were collected from 90 respondents in the villages
along those two basins. The findings highlight high risk perception in the Bhotekoshi basin and
medium perception in the Trishuli basin, along with corresponding vulnerability levels. Key factors influencing risk perception and vulnerability are explored, emphasizing the need for public
awareness and policy formulation at national and regional levels. To reduce vulnerability to
transboundary GLOFs, extending early warning systems, enhancing cross-border cooperation,
supporting socioeconomically disadvantaged populations, and ensuring resilient infrastructure
are essential.
transportation corridors is imperative for regional connectivity and disaster risk reduction. This study focuses on
four China-Nepal transportation corridors, namely Chentang-Kimathanka, Zhangmu-Kodari, KeyrungKathmandu and Taklakot-Hilsa from east to west in the Himalayan region. Within a remote integrated framework, we present the latest high-resolution inventory of glacial lakes, assess their decadal spatio-temporal
changes (1992–2022), identify potentially dangerous glacial lakes, and apply hydrodynamic model to assess
downstream impacts of possible GLOFs along the study area. The results show 2688 glacial lakes (≥0.001 km2)
with a total area of 116.10 ± 8.53 km2 over the study area in 2022. Glacial lakes exhibited spatiotemporal
heterogeneity in expansion, with overall expansion of 32 % during 30 years. Keyrung-Kathmandu corridor,
among others, was assessed with high GLOF susceptibility. Furthermore, hydrodynamic modeling of four highly
dangerous lakes in each transportation area reveals that GLOFs have cross-border effects, impacting ~103 km of
China-Nepal highway, 103 bridges, two major dry ports and 3301 buildings in both countries. Based on thesefindings, we emphasize the joint efforts of both countries for integrated disaster management for smooth connectivity between two countries and saving downstream population through joint cooperation from central to
local government levels by initiating artificial lake lowering, developing cross-border early warning systems and
cooperation. This study is valuable for presenting a synergistic study of glacial lakes and GLOF for informing
decision- and policy-makers of both China and Nepal for a joint approach to disaster mitigation
overlooked the transboundary aspects of national and sub-national level GLOFs, focusing instead
mostly on inventorying glacial lakes and assessing their hazards. The lack of cross-border coordination could have dire consequences for vulnerable communities and potential disaster preparedness. Assessing risk perception and vulnerability among downstream populations exposed to
GLOFs is crucial for effective disaster risk reduction and management. This study examined the
risk perception and vulnerabilities of Nepali communities in Bhotekoshi/Sunkoshi (Poiqu in Tibet) and Trishuli (Gyirong in Tibet) river basins, exposed to transboundary GLOFs originating
from Tibetan basins. Household-level data were collected from 90 respondents in the villages
along those two basins. The findings highlight high risk perception in the Bhotekoshi basin and
medium perception in the Trishuli basin, along with corresponding vulnerability levels. Key factors influencing risk perception and vulnerability are explored, emphasizing the need for public
awareness and policy formulation at national and regional levels. To reduce vulnerability to
transboundary GLOFs, extending early warning systems, enhancing cross-border cooperation,
supporting socioeconomically disadvantaged populations, and ensuring resilient infrastructure
are essential.