Glacier retreat and its impact on summertime run‐off in a high‐altitude ungauged catchment

Wang, Rui; Yao, Zhijun; Wu, Shanshan; Liu, Zhaofei

doi:10.1002/hyp.11287

Cited by 14 publications

(24 citation statements)

References 56 publications

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“…While these glaciers are undeniably significant in sustaining the populations of South and East Asia, they also provide some of the best gauges for understanding regional and global climate change, since temperatures in high altitudes are increasing faster than in lower elevations (Wang et al, 2017;Kraaijenbrink et al, 2017). Mass loss on both debriscovered and clean-ice glaciers has been observed throughout the Himalayas, and glacial lake formation has been increasing since the 1960s (Bolch et al, 2008;Nie et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Modeling the glacial lake outburst flood process chain in the Nepal Himalaya: reassessing Imja Tsho's hazard

Lala

Rounce

McKinney

2018

Hydrol. Earth Syst. Sci.

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Abstract. The Himalayas of South Asia are home to many glaciers that are retreating due to climate change and causing the formation of large glacial lakes in their absence. These lakes are held in place by naturally deposited moraine dams that are potentially unstable. Specifically, an impulse wave generated by an avalanche or landslide entering the lake can destabilize the moraine dam, thereby causing a catastrophic failure of the moraine and a glacial lake outburst flood (GLOF). Imja-Lhotse Shar Glacier is amongst the glaciers experiencing the highest rate of mass loss in the Mount Everest region, in part due to the expansion of Imja Tsho. A GLOF from this lake may have the potential to cause catastrophic damage to downstream villages, threatening both property and human life, which prompted the Nepali government to construct outlet works to lower the lake level. Therefore, it is essential to understand the processes that could trigger a flood and quantify the potential downstream impacts. The avalanche-induced GLOF process chain was modeled using the output of one component of the chain as input to the next. First, the volume and momentum of various avalanches entering the lake were calculated using Rapid Mass Movement Simulation (RAMMS). Next, the avalanche-induced waves were simulated using the Basic Simulation Environment for Computation of Environmental Flow and Natural Hazard Simulation (BASEMENT) model and validated with empirical equations to ensure the proper transfer of momentum from the avalanche to the lake. With BASEMENT, the ensuing moraine erosion and downstream flooding was modeled, which was used to generate hazard maps downstream. Moraine erosion was calculated for two geomorphologic models: one site-specific using field data and another worst-case based on past literature that is applicable to lakes in the greater region. Neither case resulted in flooding outside the river channel at downstream villages. The worst-case model resulted in some moraine erosion and increased channelization of the lake outlet, which yielded greater discharge downstream but no catastrophic collapse. The site-specific model generated similar results, but with very little erosion and a smaller downstream discharge. These results indicated that Imja Tsho is unlikely to produce a catastrophic GLOF due to an avalanche in the near future, although some hazard exists within the downstream river channel, necessitating continued monitoring of the lake. Furthermore, these models were designed for ease and flexibility such that local or national agency staff with reasonable training can apply them to model the GLOF process chain for other lakes in the region.

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Section: Introductionmentioning

confidence: 99%

Modeling the glacial lake outburst flood process chain in the Nepal Himalaya: reassessing Imja Tsho's hazard

Lala

Rounce

McKinney

2018

Hydrol. Earth Syst. Sci.

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show abstract

“…While these glaciers are undeniably significant in sustaining the populations of South and East Asia, they also provide some of the best gauges for understanding regional and global climate change, since temperatures in high altitudes are increasing faster than in lower 5 elevations (Wang et al, 2017;Kraaijenbrink et al, 2017). Mass loss on both debris-covered and clean-ice glaciers has been observed throughout the Himalayas, and glacial lake formation has been increasing since the 1960s (Bolch et al, 2008;Nie et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Modeling the Glacial Lake Outburst Flood Process Chain in the Nepal Himalaya: Reassessing Imja Tsho's Hazard

Lala¹,

Rounce²,

McKinney³

2017

Preprint

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Abstract. The Himalayas of South Asia are home to many glaciers that are retreating due to climate change and causing the formation of large glacial lakes in their absence. These lakes are held in place by naturally deposited moraine dams that are potentially unstable. Specifically, an impulse wave generated by an avalanche or landslide entering the lake can destabilize 10 the moraine dam, thereby causing a catastrophic failure of the moraine and a glacial lake outburst flood (GLOF). ImjaLhotse Shar glacier is amongst the glaciers experiencing the highest rate of mass loss in the Mount Everest region, which has contributed to the expansion of Imja Tsho. A GLOF from this lake may have the potential to cause catastrophic damage to downstream villages, threatening both property and human life. Therefore, it is essential to understand the processes that could trigger a flood and quantify the potential downstream impacts. The avalanche-induced GLOF process chain was 15 modeled using the output of one component of the chain as input to the next. First, the volume and momentum of various avalanches entering the lake were calculated using RAMMS. Next, the avalanche-induced waves were simulated using BASEMENT and validated with empirical equations to ensure the proper transfer of momentum from the avalanche to the lake. With BASEMENT, the ensuing moraine erosion and downstream flooding was modeled, which was used to generate hazard maps downstream. Moraine erosion was calculated for two geomorphologic models: one site-specific using field 20 data and another worst-case based on past literature that is applicable to lakes in the greater region. Neither case resulted in flooding outside the river channel at downstream villages. The worst-case model resulted in some moraine erosion and increased channelization of the lake outlet, which yielded greater discharge downstream but no catastrophic collapse. The site-specific model generated similar results, but with very little erosion and a smaller downstream discharge. These results indicated that Imja Tsho is unlikely to produce a catastrophic GLOF due to an avalanche in the near future, although some 25 hazard exists within the downstream river channel, necessitating continued monitoring of the lake. Furthermore, these models were designed for ease and flexibility so that they can be adopted by a wide range of stakeholders and appropriated for other lakes in the region.Hydrol. Earth Syst. Sci. Discuss., https://doi

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“…According to the Glacier Inventory of China (Guo et al, 2015), the glaciers had a total area and volume of approximately 382 km 2 and 40 km 3 , respectively, in the 1960s. However, due to climate warming, the total glacier area decreased by ~45 km 2 (11.8%) from 1969 to 2009 (Wang et al, 2017). Most of the region is covered by continuous permafrost, which has extensively degraded in recent decades.…”

Section: Resultsmentioning

confidence: 99%

“…In the TTH, the area of glaciers is 382 km 2 (glacier coverage is ~2%). From 1969 to 2009, the glaciers in the TTH region decreased by 45 km 2 , equivalent to a reduction of 11.8% (Wang et al, 2017). Glaciers mainly melt in summer (July–August).…”

Section: Methodsmentioning

confidence: 99%

Substantial Increases in the Water and Sediment Fluxes in the Headwater Region of the Tibetan Plateau in Response to Global Warming

Zhou³

et al. 2020

Geophysical Research Letters

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The long‐term effects of increased temperatures on sediment fluxes in cold regions remain poorly investigated. Here, we examined the multidecadal changes in runoff and sediment fluxes in the Tuotuohe River, a headwater river of the Yangtze River on the Tibetan Plateau (TP). The sediment fluxes and runoff increased at rates of 0.03 ± 0.01 Mt/yr (5.9 ± 1.9%/yr) and 0.025 ± 0.007 × km3/yr (3.5 ± 1.0%/yr) from 1985 to 2016, with net increases of 135% and 78% from 1985–1997 to 1998–2016, respectively. The increases are primarily due to warming temperature (+1.44°C) and intensified glacier‐snow‐permafrost melting, with enhanced precipitation (+30%) as a secondary cause. Sediment fluxes are much more susceptible to climate warming than runoff in this undisturbed cold environment. The substantially increased sediment fluxes from the headwater region could threaten the numerous constructed reservoirs and influence the aquatic ecosystems of the TP and its marginal areas.

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Glacier retreat and its impact on summertime run‐off in a high‐altitude ungauged catchment

Cited by 14 publications

References 56 publications

Modeling the glacial lake outburst flood process chain in the Nepal Himalaya: reassessing Imja Tsho's hazard

Modeling the glacial lake outburst flood process chain in the Nepal Himalaya: reassessing Imja Tsho's hazard

Modeling the Glacial Lake Outburst Flood Process Chain in the Nepal Himalaya: Reassessing Imja Tsho's Hazard

Substantial Increases in the Water and Sediment Fluxes in the Headwater Region of the Tibetan Plateau in Response to Global Warming

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