Changes in Imja Tsho in the Mount Everest Region of Nepal

Imja Tsho, located in the Sagarmatha ( Everest) National Park of Nepal, is one of the most studied and rapidly growing lakes in the Himalayan range. Compared with previous studies, the results of our sonar bathymetric survey conducted in September of 2012 suggest that its maximum depth has increased from 90.5 to 116.3 +/- 5.2 m since 2002, and that its estimated volume has grown from 35.8 +/- 0.7 to 61.7 +/- 3.7 million m(3). Most of the expansion of the lake in recent years has taken place in the glacier terminus-lake interface on the eastern end of the lake, with the glacier receding at about 52 m yr(-1) and the lake expanding in area by 0.04 km(2) yr(-1). A ground penetrating radar survey of the Imja-Lhotse Shar glacier just behind the glacier terminus shows that the ice is over 200 m thick in the center of the glacier. The volume of water that could be released from the lake in the event of a breach in the damming moraine on the western end of the lake has increased to 34.1 +/- 1.08 million m(3) from the 21 million m(3) estimated in 2002.USAID Climate Change Resilient Development (CCRD) projectFulbright FoundationNational Geographic SocietyCenter for Research in Water Resource

Neptune to the Common-wealth of England (1652): the republican Britannia and the continuity of interests

In the seventeenth century, John Kerrigan reminds us, “models of empire did not always turn on monarchy”. In this essay, I trace a vision of “Neptune’s empire” shared by royalists and republicans, binding English national interest to British overseas expansion. I take as my text a poem entitled “Neptune to the Common-wealth of England”, prefixed to Marchamont Nedham’s 1652 English translation of Mare Clausum (1635), John Selden’s response to Mare Liberum (1609) by Hugo Grotius. This minor work is read alongside some equally obscure and more familiar texts in order to point up the ways in which it speaks to persistent cultural and political interests. I trace the afterlife of this verse, its critical reception and its unique status as a fragment that exemplifies the crossover between colonial republic and imperial monarchy at a crucial moment in British history, a moment that, with Brexit, remains resonant

Bathymetric survey of Imja Lake, Nepal in 2012

Imja Lake is one of the most studied lakes in the Himalaya as well as one of the most rapidly evolving glacial lakes in Nepal. Many researchers have studied the lake and the potential of a glacier lake outburst flood from the lake. One of the important factors in assessing the outburst flood risk is the volume that could be released in the flood and good bathymetric data is necessary to estimate that value. This work reports on the 2012 bathymetric survey of Imja Lake and the rate of expansion that has been observed in the lake over the last two decades, since 1992. The survey was somewhat hampered by the extensive iceberg coverage of the lake in September 2012, but a good estimate of the bottom bathymetry and the current volume was obtained. When compared to previous surveys, it is very clear that the lake bottom has continued to deepen as the ice beneath the lake has melted. The average depth has increased by 62% since 2002 and continues to increase at a rate of 1.8 m/yr. The maximum depth has increased 28% since 2002 and is increasing currently at a rate of 5.8 m/yr. Perhaps more important in terms of glacier lake outburst flood risk is the continued rapid areal expansion of the lake which has expanded 41% since 2002 and is growing at a rate of 0.02 km2/yr. This expansion has resulted in an additional 6 million m3 of water for an outburst flood event, and increasing the maximum possible flood volume to 36.3 million m3 a 73% increase from what was calculated using 2002 data.Center for Research in Water Resource

Ground penetrating radar survey for risk reduction at Imja Lake, Nepal

This study presents observations of the structure of the terminal moraine complex at Imja Lake. Detailed ground penetrating radar (GPR) surveys were conducted at Imja Lake. The lake and the surrounding Imja glacier have been described in the previous section. This paper should contribute to the understanding of the structure of the terminal moraine and the distribution of ice in the core of the moraine. The formation of glacier lakes in the Nepal Himalaya has been increasing since the early 1960s. Accompanying this increase in the number and size of glacier lakes is an associated number of GLOF events. The Khumbu region of Nepal (which includes the Dudh Koshi basin) is regularly mentioned as an area particularly prone to GLOF events and containing important sites for possible GLOF risk reduction projects (especially in the Imja Khola). Imja lake in the Khumbu is often mentioned as a potentially dangerous glacier lake (PDGL) and its GLOF risk has been investigated for more than 20 years (Armstrong, 2010). In May and September 2012, the authors visited the lake and observed the rapid rate of change of the terminal moraine complex. They performed ground penetrating radar surveys of most of the terminal moraine complex and mapped the ice core of the moraine. Imja Lake is currently the focus of several groups in an effort to reduce the risk of a GLOF posed by the increasing lake level. The presence or absence of ice in the core of the terminal moraine complex is of critical importance in designing a risk reduction program for the lake. This work has used Ground Penetrating Radar (GPR) to investigate the internal structure of the moraine complex in order to map out the ice thickness in critical areas. The results of the GPR survey show that there is extensive ice present in the core of the terminal moraine complex at Imja Lake (see Figure 8). The thickest areas of ice are in the moraine near the western end of the lake on the northern side of the lake outlet. The ice in this region is several tens of meters thick and up to fifty meters thick in some places. Along the northern and southern sides of the lake outlet, the ice is between ten and twenty-five meters thick. In some portions of the moraine on the southern side of the outlet the ice thickness is up to forty meters. Extensive seepage of water from the terminal moraine was observed in two locations during visits to the lake in September 2011, May 2012, and September 2012. GPR transects above and below the site of seepage show the presence of ice above the seep and much less ice below the seep. Seepage of water through the terminal moraine is an indication of potential weakness in the moraine and a possible site of future moraine failure. Recent work has been initiated by the United Nations Development Programme to develop an Imja Lake Risk Reduction Program. One of the primary methods suggested for reducing risk associated with the lake is to reinforce and deepen the outlet channel so that it can lower the lake level up to 3 meters below the current level. This project involves making excavations of the outlet channel and the construction of a diversion channel on the southern side of the outlet. The results presented here indicate that there may be ice present in the moraine in the vicinity of the excavations being considered in this project. Excavation activities that encounter ice in the moraine material may cause weakening of the ice resulting in increased water seepage and erosion of the moraine. Therefore, it is recommended that additional GPR surveys be conducted in this area accompanied with Electrical Resistivity Tomography (ERT) surveys. The ER surveys will be able to more definitively indicate the presence of ice in the moraine as well as the degree of water saturation of the moraine material.Center for Research in Water Resource

Inundation Modeling of a Potential Glacial Lake Outburst Flood in Huaraz, Peru

One of the consequences of recent glacier recession is the formation and rapid growth of lakes formed at the snout of glaciers. One risk is that moraines damming these glacial lakes could fail releasing a huge volume of water and creating a glacial lake outburst flood. This happened December 13, 1941, at Lake Palcacocha, Peru, flooding the city of Huaraz and killed several thousand people. Recently Lake Palcacocha has been declared in a state of emergency state because its volume has again reached dangerous levels, threatening a flood that would quickly reach Huaraz causing major devastation and potentially loss of life. An analysis has been performed of the glacial hazards for the city of Huaraz from Lake Palcacocha. This analysis consists of physical models of each process in the chain of events that results in a glacial lake outburst flood: rock and ice avalanche; wave generation, propagation and moraine overtopping; terminal moraine breaching and draining of the lake; and downstream inundation and impacts in the city of Huaraz. Two scenarios of moraine erosion were simulated: a worst-case event of a 56 m breach and a smaller 22.5 m erosion event. These scenarios showed that flood reaches the City of Huaraz 1.06 and 1.20 hours after the avalanche for the 56 m and 22.5 m events, respectively. The inundation in the city is extensive in both breaching events with depths exceeding 1 m in many areas, especially near the channel of the Quillcay River, and the velocity of the flood exceeding 1 m/s in most of this area. Because of the inundation depth and the velocity of the flow, most of the area of the city that experiences flooding will have a very high hazard level, putting both lives and property at risk.Center for Research in Water Resource

Modeling Mitigation Strategies for Risk Reduction at Imja Lake, Nepal

A model was developed to assess the impact of a potential glacial lake outburst flood (GLOF) from Imja Lake in Nepal and its impact on downstream communities. Implications of proposed GLOF risk reduction alternatives, including one suggested by local community members, were assessed. Results provided three alternatives that offer significant risk reduction for the communities, including (1) no lowering of the lake and constructing a 60 m flood detention dam, resulting in a 43.2 percent reduction of risk, (2) lowering the lake 10 m with a 40 m dam, resulting in a 57.8 percent reduction of risk, and (3) lowering the lake 20 m with no dam, resulting in a risk reduction of 66.7 percent. An alternative to lower the lake by 3 m with no check-dam, currently under consideration by the Government of Nepal, would result in a 5.2 percent reduction of risk. This alternative does not appear to offer significant risk reduction benefits to downstream communities compared to lowering the lake by 20 m. Results suggest that either the lake must be lowered by significantly more than 3 m (20 m is recommended) or that a downstream flood detention dam be included in the project. One possible method of lowering Imja Lake is to use siphons to drain lake water by 3 m, excavate to the new water level, repeating the process until a total lowering of 20 m is achieved. This method would require the use of 13 pipes of 0.350 m diameter to lower the lake.Center for Research in Water Resource

Predicting outflow induced by moraine failure in glacial lakes: the Lake Palcacocha case from an uncertainty perspective

Moraine dam collapse is one of the causes of glacial lake outburst floods. Available models seek to predict both moraine breach formation and lake outflow. The models depend on hydraulic, erosion, and geotechnical parameters that are mostly unknown or uncertain. This paper estimates the outflow hydrograph caused by a potential erosive collapse of the moraine dam of Lake Palcacocha in Peru and quantifies the uncertainty of the results. The overall aim is to provide a simple yet hydraulically robust approach for calculating the expected outflow hydrographs that is useful for risk assessment studies. To estimate the peak outflow and failure time of the hydrograph, we assessed several available empirical equations based on lake and moraine geometries; each equation has defined confidence intervals for peak flow predictions. Complete outflow hydrographs for each peak flow condition were modeled using a hydraulic simulation model calibrated to match the peak flows estimated with the empirical equations. Failure time and peak flow differences between the simulations, and the corresponding empirical equations were used as error parameters. Along with an expected hydrograph, lower and upper bound hydrographs were calculated for Lake Palcacocha, representing the confidence interval of the results. The approach has several advantages: first, it is simple and robust. Second, it evaluates the capability of empirical equations to reproduce the conditions of the lake and moraine dam. Third, this approach accounts for uncertainty in the hydrographs estimations, which makes it appropriate for risk management studies

Assessing downstream flood impacts due to a potential GLOF from Imja Tsho in Nepal

Glacial-dominated areas pose unique challenges to downstream communities in adapting to recent and continuing global climate change, including increased threats of glacial lake outburst floods (GLOFs) that can increase risk due to flooding of downstream communities and cause substantial impacts on regional social, environmental and economic systems. The Imja glacial lake (or Imja Tsho) in Nepal, which has the potential to generate a GLOF, was studied using a two-dimensional debris-flow inundation model in order to evaluate the effectiveness of proposed measures to reduce possible flooding impacts to downstream communities by lowering the lake level. The results indicate that only minor flood impact reduction is achieved in the downstream community of Dingboche with modest (~3 m) lake lowering. Lowering the lake by 10 m shows a significant reduction in inundated area. However, lowering the lake by 20 m almost eliminates all flood impact at Dingboche. Further downstream at Phakding, the impact of the GLOF is significant and similar reductions in inundation are likely as a result of lake lowering

Brief communication: An ice-debris avalanche in the Nupchu Valley, Kanchenjunga Conservation Area, eastern Nepal

<jats:p>Abstract. Beginning in December 2020, a series of small to medium, torrent-like pulses commenced upon a historic debris cone located within the Nupchu Valley, Kanchenjunga Conservation Area (KCA), Nepal. Sometime between 16 and 21 August 2022 a comparatively large ice-debris avalanche event occurred, covering an area of 0.6 km2 with a total estimated volume of order 106 m3. The area of the debris cone left by the August 2022 event increased the historic debris cone area by 0.2 km2 (total area 0.6 km2). Although no human or livestock deaths occurred, the increase in torrent-like pulses of debris upon this historic debris cone since 2020 exemplifies a style of mass movement that may become increasingly common as air temperatures rise in the region. Although the magnitude of this event was small compared to events like the 2021 Chamoli avalanche, the widespread distribution and frequency of comparable events present a substantial, and potentially increasing, hazard across High Mountain Asia. </jats:p&gt