Moraine Dam Research Articles

Rockfall hazard in the Imja Glacial Lake, eastern Nepal

In Nepal, rockfall related studies are rarely conducted and are limited to the landslide study along with few case studies on rockfall events. Rockfall problems in Nepal are more frequent in the Higher Himalayan region than Midland and Lesser Himalayan regions. In the glaciated valley and glacial lakes, rockfall and associated tsunami like huge wave are a recently initiated research. In this context, a glacial lake of the Himalaya, named as Imja Glacial Lake situated in eastern Nepal has been selected to understand the rockfall problems and their possible consequences. The lake was formed at the end part of the Imja glacier. The northern valley slope of Imja Glacier Lake, i.e. southern slope of the Island Peak has serious problem of rockfall into the lake. Rockfall simulation was performed during this research with field data. Three different Plots were defined for simulation of rockfall. Among them, Plot III seems to be the most hazardous since the detached boulders on the higher elevation can enter into the lake with the maximum velocity of 40 m/s with pre-impact energy more than 3500 kJ. This can develop a surge in the lake water that can break moraine dam. This leads to a serious threat to the downstream communities. Moreover, this research confirms that the rockfall hazard in the higher mountain region of Nepal is critical to creating flash floods due to tsunamis like surge in the lake water and breaching of the dam.

Glacial Lake Outburst Floods (GLOFs) in the Cordillera Huayhuash, Peru: Historic Events and Current Susceptibility

The aim of this paper is to create a glacial lake inventory for the Cordillera Huayhuash in Peru and to evaluate the susceptibility of lakes to the generation of glacial lake outburst floods (GLOFs). Using high-resolution satellite images, we undertook qualitative and quantitative analysis of lake type, characteristics and distribution, and placed our findings within the context of existing Peru-wide lake inventories. We also mapped and analyzed past GLOFs, revealing a total of 10 GLOFs and 4 ambiguous events, most of which have not been reported before. We found that past GLOFs usually occurred as a result of moraine dam breach during the proglacial stage of lake evolution. Further, we used our lake inventory to evaluate GLOF susceptibility of all lakes larger than 20,000 m2. Of 46 evaluated lakes, only two lakes (Lake Tsacra and Lake W014) are currently susceptible to generating a GLOF, which would most likely be through dam overtopping resulting from a flood originating in smaller lakes located upstream. The future perspectives of lake evolution and implications for GLOF hazard management are discussed in light of the post-Little Ice Age glacier ice loss as well as in the context of extensive related research undertaken in the nearby Cordillera Blanca.

Reconstructing the Chongbaxia Tsho glacial lake outburst flood in the Eastern Himalaya: Evolution, process and impacts

Glacial lake outburst floods (GLOF) are one of the most destructive natural disasters. Understanding GLOF evolution, and their impacts, plays a fundamental role in GLOF hazard assessment and risk management. Reconstructing historical GLOFs is an important exercise because detailed case studies of such glacial hazards are rare, which hinders the capacity of glacial hazard practitioners to learn from these events. In this study, we reconstruct a historical GLOF from moraine-dammed Chongbaxia Tsho (89.745°E, 28.211°N) in the Eastern Himalaya, which is a unique case study because the outburst flood cascaded into two further lakes downstream. We employ a combination of i) multi-source and multi-temporal satellite imagery, ii) field investigation (including an unmanned aerial vehicle survey), iii) numerical dam breach and hydrodynamic modelling and, iv) qualitative and quantitative cryospheric and meteorological analysis, to investigate the evolution of the GLOF hazard, simulate moraine dam failure and GLOF propagation, and explore the role that long- and short-term climate trends played in providing the conditioning factors for the outburst. Chongbaxia Tsho expanded rapidly between 1987 until 2001 in response to glacier recession most likely caused by a regional warming trend of +0.37 °C per decade. Based on satellite image analysis we refine the outburst date to be 6 August 2001, instead of 6 August 2000, as previously reported, and attribute an ice avalanche into the glacial lake originating from the receding parent glacier as the most likely trigger for moraine dam failure. Through DEM differencing and lake level decrease, we estimate that a total water volume of 27.1 ± 1.6 × 106 m3 was released from the lake during the event, and using dam breach modelling we estimate that the peak discharge at the breach was >6600 m3 s−1. The GLOF flowed through downstream Chongbamang Tsho and Chongbayong Tsho, both of which served to attenuate the GLOF and reduce downstream losses; the latter stored an estimated 96% of the flood volume. Precipitation totals in the weeks preceding the GLOF exceeded the historical mean by up to 40%, and may have contributed to instability of the parent glacier, and generation of an ice avalanche with enough impact energy to cause lake water to overtop the moraine dam and initiate breach development. A future GLOF from Chongbaxia Tsho cannot be ruled out, but more field data, including detailed lake bathymetry, and information pertaining to the sedimentological and geotechnical characteristics of the moraine dam, are required for a more robust parameterization of a predictive GLOF model and quantification of the hazard posed by a future GLOF.

Glacial advances and stability of the moraine dam on Mount Namcha Barwa since the Last Glacial Maximum, eastern Himalayan syntaxis

The Tibetan Plateau and Indian Plain exhibit the largest altitudinal difference between two geographically contiguous areas on Earth, but the eastern margin of the Plateau has not experienced headward erosion of the Yarlung Zangbo River (YZR) since ~2.5 Ma. In the past, some scientists have argued that moraine dams on Mount Namcha Barwa (in the Eastern Himalayan syntaxis) frequently blocked the YZR, thus keeping the Plateau's margin intact at this point. In this study, three sets of moraines were identified in the Pai Valley alongside Namcha Barwa, and were dated using optically stimulated luminescence (OSL) and 10Be exposure dating. The resultant ages would suggest that three glaciations occurred at ~22.2, 4.7 and 1.3 ka, respectively. Comparison of OSL and 10Be ages for glacial advances with local paleoclimatic proxies would suggest that temperature was the dominant factor controlling glacial change. Because of the paleoglacial advance frequency, coupling with rapid fluvial incision, moraine dams were cut through by the YZR. Thus, any moraine dams that lost their efficacy in impacting upon knickpoint migration. Instead, similarities between rock uplift and fluvial incision, rather than moraine dams, might have been the main control impeding headward erosion of the YZR, thereby keeping this part of the eastern Tibetan Plateau margin intact.

Geospatial analysis and simulation of glacial lake outburst flood hazard in Shyok Basin of Pakistan

The Upper Indus Basin (UIB) is prone to Glacial Lake Outburst Floods (GLOFs). Physical monitoring of such a large area on regular basis is a challenging task especially when the temporal and spatial extent of the hazard is highly variable. The study has been conducted in the Shyok sub-basin of UIB, where there are several human settlements which are endangered due to the GLOF hazard. Sudden breaches in the unstable moraine dams adjoining receding glaciers may occur because of rapid and huge accumulation of turbulent water in the glacial lakes. The purpose of this study was to map the two potentially dangerous glacial lakes and simulate the associated hazard in the downward settlements using HEC-RAS in the GIS environment using Landsat 7 remote sensing data. The ASTER Digital Elevation Model (DEM) is utilized to detect flow accumulation of glacial hazard involving slope, elevation, and orientation of the mountain glaciers. The study results have revealed that settlements of the Shyok Basin are threatened by the GLOF hazard. Keeping in view the seasonal growth of the two potentially dangerous glacial lakes of the Shyok Basin, a low discharge of 100 m3/s from both lakes can affect 20%, whereas a moderate discharge of 300 m3/s and a high discharge of 500 m3/s, respectively, can impact 30% and 40% of the Barah village habitat. The results of the study can provide a platform for the establishment of an early warning and monitoring system to minimize the impact of future GLOFs.

Climatically driven late Pleistocene – Holocene hydrological system transformation and landscape evolution in the eastern periphery of Chuya basin, SE Altai, Russia

This paper presents the results of geological, geomorphological, geochronological investigations and the analysis of the biological composition of deposits within the high-mountainous Boguty river basin. The main stages of landscape evolution during the last 14 ka have been investigated through 32 radiocarbon dates. The area is located in the most arid southeastern part of Russian Altai and constitutes the eastern periphery of the Chuya intermountain depression, and the western side of the Chikhachev range.Postglacial landscape development of the upper reaches of the Chuya River began from the degradation of its vast glaciation. By 14 ka cal BP the glaciers had either completely melted or retreated above 2500 m above sea level. As a result, numerous lakes occupied open places and five types of these basins can be seen in the modern topography. They are large moraine-dammed lakes connected with the Boguty River, while some basins have been dammed by uplifted tectonic blocks and numerous lakes are of thermokarst origin or are small cirque lakes and temporal lakes fed by seasonal meltwater from meteoric, ground water and permafrost degradation.Large moraine-dammed lakes within the Boguty basin were developed before the Holocene. The water filling these basins was controlled by the height of moraine dams and by the depth of the Boguty river incision. The moraine-dammed Low Boguty Lake formed earlier than 10 ka cal BP. Its partial draining and transformation of littoral zone into peat bog took place about 8.2-7.6 ka cal BP. As a result of the analysis of biological composition, four stages of water level fluctuations in the lacustrine-boggy system were recognized.The specific geomorphic and sedimentary features in the middle part of the Boguty basin determined the recurrence of debris flow events at about 8-7; 2.9-1; 0.65 and 0.3 ka cal BP, but the last event occurred in June 2017.The occurrence of fossil forest soils dating to about 11-8.5 ka cal BP and of charcoals (Larix sibirica Ledeb) of about 8.5-7.8 ka cal BP indicate a prolonged period of developing forest vegetation in the Boguty basin, which is currently treeless. In general, the data suggest that in SE Altai the climate in the first half of the Holocene was warmer and more humid in comparison with the modern one. The second half of the Holocene has been characterized by colder climate conditions accompanied by aridity intensification, which became especially pronounced during the last 2-1.5 ka.

Reconstruction of the 1941 GLOF process chain at Lake Palcacocha (Cordillera Blanca, Peru)

Abstract. The Cordillera Blanca in Peru has been the scene of rapid deglaciation for many decades. One of numerous lakes formed in the front of the retreating glaciers is the moraine-dammed Lake Palcacocha, which drained suddenly due to an unknown cause in 1941. The resulting Glacial Lake Outburst Flood (GLOF) led to dam failure and complete drainage of Lake Jircacocha downstream, and to major destruction and thousands of fatalities in the city of Huaráz at a distance of 23 km. We chose an integrated approach to revisit the 1941 event in terms of topographic reconstruction and numerical back-calculation with the GIS-based open-source mass flow/process chain simulation framework r.avaflow, which builds on an enhanced version of the Pudasaini (2012) two-phase flow model. Thereby we consider four scenarios: (A) and (AX) breach of the moraine dam of Lake Palcacocha due to retrogressive erosion, assuming two different fluid characteristics; (B) failure of the moraine dam caused by the impact of a landslide on the lake; and (C) geomechanical failure and collapse of the moraine dam. The simulations largely yield empirically adequate results with physically plausible parameters, taking the documentation of the 1941 event and previous calculations of future scenarios as reference. Most simulation scenarios indicate travel times between 36 and 70 min to reach Huaráz, accompanied with peak discharges above 10 000 m3 s−1. The results of the scenarios indicate that the most likely initiation mechanism would be retrogressive erosion, possibly triggered by a minor impact wave and/or facilitated by a weak stability condition of the moraine dam. However, the involvement of Lake Jircacocha disguises part of the signal of process initiation farther downstream. Predictive simulations of possible future events have to be based on a larger set of back-calculated GLOF process chains, taking into account the expected parameter uncertainties and appropriate strategies to deal with critical threshold effects.

Pleistocene fluvial catastrophes in now arid NW areas of Mongolian Inland drainage basin

Abstract The distribution of glacial landforms and deposits in the upper part of the Mogen-Buren River basin provide evidence for extended ice sheet formation along the Shapshal range in the late Pleistocene. At that time the Mongun-Taiga massif and Chikhachev range were also affected by glaciation. Advanced glaciers blocked the Khindiktig-Khol and Ak-Khol depressions and impounded significantly larger lakes. Overfilling any of the Khindiktig-Khol, Ak-Khol or probably the supraglacial lakes by melt-water caused repeated outburst floods along the Mogen-Buren River into the Achit-Nuur Lake, Mongolian Great Lakes Basin. Significant landscape transformation took place due to geological work of these processes. Specific landforms were generated, including high lake shorelines, lacustrine bars and sediments, marginal channels, indicators of fluvial activity on the floor of the basin, and fluvial transported boulders that mark the flood pathways as well as the specific vertical lithofacies profile of outwash deposits. Available absolute dates suggest some chronological bench marks of the hydrological system transformation in the region. Changing of deposition patterns in the Achit-Nuur Lake about 11,000 cal BP can be assumed from the age-depth model of the lake core ( Sun et al., 2013 ). The period of the maximal lakes filling at 2380 m a.s.l. in the upper part of the Mogen-Buren basin started no later than 14,000 cal BP, based on data from Ak-Khol Lake core ( Blyakharchuk et al., 2007 ). There are no absolute dates that identify the time of partial draining of former Ak-Khol Lake, which was dammed by glacier ice, and its prolonged preservation at 2270 m a.s.l. – the height of the moraine dam. This stage ended before 8200 cal BP. The postglacial hydrological system evolution within the studied area is characterized by formation of local lakes in the Mogen-Buren depression from about 11,600–8800 cal BP. All cataclysmic outburst floods from glacier- and moraine-dammed lakes took place before 11,600 cal BP, and significant hydrological system transformations were completed before 5100 cal BP.

Hazard assessment of glacial lake outburst floods in Southeast Tibet based on RS and GIS technologies

ABSTRACTGlacial lakes are widely distributed across glaciated mountainous regions such as Southeast Tibet (ST). As a result of climate change, glacial lakes have expanded continually in ST over recent five decades, and ST is seriously suffering from glacial lake outburst floods (GLOFs). Hence, glacial lake investigations and hazard assessments of GLOFs are very necessary to perform and are of great practical significance for this area. The region running from Ranwu to Tongmai (RTR) in ST was selected as a study area. To assess hazard degrees of GLOFs, nine factors (F1–F9) were selected from glacial characteristics: the scale of glacial lakes, meteorological conditions, moraine dam parameters and downstream gullies. Average monthly (May to September) land surface temperatures (LSTs), temperature change rates, and average annual precipitation levels were first calculated using Moderate Resolution Imaging Spectroradiometer (MODIS) LST product and Tropical Rainfall Measuring Mission (TRMM) precipitation data. Then, glacial lake areas, downstream gully slopes, distances to glacial lakes, upper glacier areas, average gradients of upper glaciers, and terminal moraine dam widths were obtained based on Thematic Mapper (TM) and Operational Land Imager (OLI) images and Digital Elevation Model (DEM) data. Finally, the fuzzy comprehensive assessment (FCA) method was used to assess hazard degrees of GLOFs in the study area. According to the results, 135 glacial lakes existed during the study periods, five new glacial lakes formed due to lake collapse and snow and ice melt, and one disappeared due to GLOFs. The number of glacial lakes in the area increased from 130 in 1986 to 134 in 2015, and the total area of glacial lakes increased from 832.77 ha in 1986 to 850.51 ha in 2015 due to lake expansion and GLOFs. Of the 134 glacial lakes present in 2015, 10 are identified as high hazardous lakes, eight are identified as medium hazardous lakes, two are considered low hazardous lakes, and 114 are considered extremely low hazardous lakes. The results illustrate hazard levels of GLOFs in ST, which can help guide future hazard prevention in the area.

Multi-Source Glacial Lake Outburst Flood Hazard Assessment and Mapping for Huaraz, Cordillera Blanca, Peru

Filiacion institucional de autor: Alejo Cochachin Rapre / Autoridad Nacional del Agua - Unidad de Glaciologia y Recursos Hidricos (ANA-UGRH), Huaraz, Peru

Glacial lake evolution and Atlantic-Pacific drainage reversals during deglaciation of the Patagonian Ice Sheet

Modelling experiments of drainage events from proglacial lakes of the Río Baker catchment (central Patagonia, 46–48 ⁰S) indicate that Atlantic-Pacific drainage reversals may have caused freshwater forcing of regional climate. However, much of the region remains unmapped in detail and available geochronological data is equivocal, leading to multiple published palaeolake evolution models. We evaluate these models through new geomorphological mapping from the Baker valley; cosmogenic dating of moraine boulders that demonstrates an Antarctic Cold Reversal ice readvance that blocked drainage through the Río Baker; an altitudinal-based review of published geochronology; and regional analysis of shoreline glacio-isostasy and palaeolake levels. We use these datasets to present a new regional palaeolake evolution model underpinned by Bayesian age modelling. We demonstrate that 103 km3 of freshwater was released to the Pacific over at least 6 drainage events from before 15.3–15.0 cal yr BP to the early Holocene. The final stages of lake drainage involved catastrophic flooding along the Baker valley, evidenced by high magnitude flood landforms such as boulder bars, likely caused by failure of large valley floor moraine dams. We place these drainage events in the context of Late Quaternary meltwater pathways associated with advance/retreat of the Patagonian Ice Sheet and early human occupation across the region. Although broad patterns of ice retreat and lake formation may be similar across Patagonia, driven by Southern Hemisphere palaeoclimate, regional topographic settings likely resulted in spatial and temporal heterogeneity of Atlantic-Pacific drainage reorganisation across southernmost South America.

Lake systems in mountain borders of the Great Lakes Basin of Mongolia: From Pleistocene catastrophes to Holocene gradual evolution (case study from southwestern Tuva)

The paper presents results of integrated geological, geomorphological, geochronological, and geoarchaeological studies in the basin of Lake Ak-Hol located in southwestern Tuva (Russia), in mountains north of the Great Lakes Basin of Mongolia. The Pleistocene-Holocene history of the basin consisted of several stages recorded in terrain and deposition patterns. The highest stand of Lake Ak-Hol (180 m above the present level and 16 times greater area) was due to an ice dam and was coeval to the appearance of organic matter (remnants of higher aquatic plants and algae) in lake sediments about 14 ka cal BP. At the next stage, the lake was impounded by a moraine dam. 14C ages of buried soils indicate that the level of the ice- and moraine-dammed lake fell to below 222 m asl long before 8.5 ka cal BP. Erosion of the moraine dam may correspond to the event of lake drying about 12 ka cal BP evident from a deposition gap in sedimentary cores. That event of sudden drainage may have been the last catastrophic flood into the Great Lakes Basin traceable in the catchment of the Mogen-Buren River. Judging from the obtained 14C ages of sediments from the Mogen-Buren Valley, ice- and moraine-dammed lakes in the Ak-Hol system underwent cataclysmic outburst floods only before 11.6 ka cal BP. In the Holocene, after the moraine dam failure, the lake level changes were controlled solely by climate. The general decreasing trend was repeatedly interrupted by high stand excursions (up to 15 m of relative level rise). Nomad peoples settled on the floor of the highland Ak-Hol basin since the Late Bronze Age. All archaeological sites (from that time to the time of Turkic cultures) mapped in the basin are located above 2220 m asl and lack signatures of water erosion, indicating that the lake never rose above that altitude for the past 3 ka years.

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

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.

Moraine dam breach and glacial lake outburst flood generation by physical and numerical models

Summary The areas of glacial lakes in the Himalayas continue to increase alarmingly due to global warming with consequent risk of glacial lake outburst flood (GLOF). The outburst is most common for moraine-dammed lakes as a result of a failure of the dam by overtopping and erosion or piping due to seepage. In the present context, GLOF events, especially for the moraine dam failure process needs to be predicted to assess the drastic and detrimental impacts on the downstream river valley. This study focuses on validating an integrated model for simulating the failure of moraine dam by overtopping and erosion using a coupled numerical simulation model. The proposed numerical methodology is validated with the data from experiments in laboratory scale physical models. The results of the model are compared for both the erosional profiles during collapse of the dam and the resulting outflowing flood hydrograph. The primary finding is that the moraine dam height and the volume of the lake upstream of the dam are the most sensitive parameters influencing the GLOF peak. The model is also applied to the field problem of the Tangjiashan lake outburst and dam failure and shows reasonably good agreement with observations. The validated model is also run for the South Lhonak glacial lake in the Sikkim Himalayas, India to obtain the probable flood hydrograph in case of failure of the moraine dam.

Geophysical study on moraine dam of Imja Glacial Lake in Eastern Nepal using Electrical Resistivity Tomography Method

Glacial Lake Outburst Flood (GLOF) is one of the potential disaster of Nepal. The Imja glacial lake is considered as one of the fastest growing glacial lake with high risk of GLOF. The internal structure of moraine dams, especially the distribution of buried ice blocks and permafrost materials is key factors in assessing GLOF risk. This study covers exploration and assessment of subsurface conditions of the moraine material such as quantification of buried ice, seepage channel and permafrost material distribution. The geophysical study of dam was carried out by using Dipole–dipole array of Electrical Resistivity Tomography (ERT) method. This study presents the results regarding use of electrical resistivity survey for assessment of the subsurface buried glacier ice and permafrost zones within the dam of the Imja glacial lake. The interpretation of resistivity data at end moraine of Imja glacial lake is based not only on specific resistivity values, but also with field observations and correlation with previous studies. The maximum depth of information obtained from the modeling is about 25 m and; highest and lowest values of resistivity ranges from 117 Wm to 2682240 Wm. The distribution of major subsurface materials from lowest resistivity value to highest resistivity values are classified as saturated moraine (<5000 Wm), frozen moraine (5000 Wm to 20000 Wm) and dead ice (>20000 Wm). The distribution of dead buried ice in moraine dam is found to be heterogeneous. The minimum and maximum depth of dead ice from surface is about 0 m to 20 m at various locations. Based on the information of this study, an open channel was cut through the lake to lower its level and the result is found to be successful.

Recuperación de Servicios Ecosistémicos de Áreas Afectadas por el Aluvión de 2012 en la Microcuenca Santa Cruz, Huaylas, Ancash

Los ecosistemas de montaña son espacios de gran importancia para la humanidad por los servicios ecosistémicos que proveen y, a la vez, son vulnerables y frágiles frente al cambio climático. La Cordillera Blanca, ubicada en el departamento de Ancash, es representativa de este contexto. En 2012, la microcuenca Santa Cruz, ubicada en esta cordillera, fue afectada por un aluvión debido a la sobresaturación del dique morrénico de la laguna Artizón Bajo. Este aluvión afectó los medios de vida de la población aguas abajo. Los servicios principales, como agua para consumo humano y actividades económicas, fueron rehabilitados inmediatamente. Sin embargo, se perdieron 236 ha de ecosistemas importantes de la microcuenca. Esta pérdida ha influido en la calidad de servicios ecosistémicos de regulación hídrica debido a la alteración de la calidad de agua, en los servicios ecosistémicos culturales debido a la reducción de la calidad paisajística de la microcuenca, y en el servicio de provisión de alimento para ganado. Estas áreas necesitan ser recuperadas y, para ello, el INAIGEM, con participación de la población local, ha desarrollado acciones para generar procesos sociales y técnicos hacia la recuperación de los servicios afectados. En esta fase inicial, se han instalado dos parcelas representativas de 15 y 20 ha para investigar procesos ambientales y sociales de recuperación y conservación de los ecosistemas y contribuir con la sostenibilidad de los servicios ecosistémicos.

Evolution and Controls of Large Glacial Lakes in the Nepal Himalaya

Glacier recession driven by climate change produces glacial lakes, some of which are hazardous. Our study assesses the evolution of three of the most hazardous moraine-dammed proglacial lakes in the Nepal Himalaya—Imja, Lower Barun, and Thulagi. Imja Lake (up to 150 m deep; 78.4 × 106 m3 volume; surveyed in October 2014) and Lower Barun Lake (205 m maximum observed depth; 112.3 × 106 m3 volume; surveyed in October 2015) are much deeper than previously measured, and their readily drainable volumes are slowly growing. Their surface areas have been increasing at an accelerating pace from a few small supraglacial lakes in the 1950s/1960s to 1.33 km2 and 1.79 km2 in 2017, respectively. In contrast, the surface area (0.89 km2) and volume of Thulagi lake (76 m maximum observed depth; 36.1 × 106 m3; surveyed in October 2017) has remained almost stable for about two decades. Analyses of changes in the moraine dams of the three lakes using digital elevation models (DEMs) quantifies the degradation of the dams due to the melting of their ice cores and hence their natural lowering rates as well as the potential for glacial lake outburst floods (GLOFs). We examined the likely future evolution of lake growth and hazard processes associated with lake instability, which suggests faster growth and increased hazard potential at Lower Barun lake.

Monitoring and simulation of hydrothermal conditions indicating the deteriorating stability of a perennially frozen moraine dam in the Himalayas

ABSTRACTThermal and hydrological dynamics and their impacts on the stability of a moraine dam were analyzed and simulated for the Longbasaba Lake in the Himalaya, based on soil temperature, moisture and heat flux data observed at different depths in the dam from 2012 to 2016. Annual average heat income is greater than heat expenditure on the dam surface. The mean annual temperature at observed the depths of 0–150 cm is >0°C, although the average annual air temperature was −3.6°C over the dam, indicating a relatively larger temperature difference between moraine dam and air. The volumetric soil moisture content is relatively low with an annual average of 5%, peaking after the snow cover melting and active layer thawing. Simulation results indicate that the average yearly maximum thawing depth has been ~0.3 m deeper than the average yearly maximum freezing depth during the observation period. In the past 55 years, the yearly maximum thawing depth has increased, while yearly maximum freezing depth has decreased, implying that the permafrost in the dam has been deteriorating. The annual surplus heat and increasing permafrost thawing depth will result in further deterioration of permafrost and melting of buried ice in the dam, thereby decreasing its stability.

Climate change and the global pattern of moraine-dammed glacial lake outburst floods

Abstract. Despite recent research identifying a clear anthropogenic impact on glacier recession, the effect of recent climate change on glacier-related hazards is at present unclear. Here we present the first global spatio-temporal assessment of glacial lake outburst floods (GLOFs) focusing explicitly on lake drainage following moraine dam failure. These floods occur as mountain glaciers recede and downwaste. GLOFs can have an enormous impact on downstream communities and infrastructure. Our assessment of GLOFs associated with the rapid drainage of moraine-dammed lakes provides insights into the historical trends of GLOFs and their distributions under current and future global climate change. We observe a clear global increase in GLOF frequency and their regularity around 1930, which likely represents a lagged response to post-Little Ice Age warming. Notably, we also show that GLOF frequency and regularity – rather unexpectedly – have declined in recent decades even during a time of rapid glacier recession. Although previous studies have suggested that GLOFs will increase in response to climate warming and glacier recession, our global results demonstrate that this has not yet clearly happened. From an assessment of the timing of climate forcing, lag times in glacier recession, lake formation and moraine-dam failure, we predict increased GLOF frequencies during the next decades and into the 22nd century.

Reconstruction of postglacial landscape evolution within the eastern periphery of Chuya depression on the basis of multidisciplinary analysis of peats in Boguty river basin, SE Altai, Russia

This paper presents the results of multidisciplinary investigations of the peat-bed under hummocky permafrosted boggy meadow within the Boguty basin. For the last 7600 years 4 evolutionary phases of peatbog formation within the drained part of Low Boguty Lake bottom were established and corresponding 4 pollen complexes were described. 18 radiocarbon dates suggest some chronological bench marks of postglacial landscape evolution in the region. After degradation of Sartan glaciation about 14000 BP, trees grew in now forestless areas at 11000 BP and 8500-7800 BP. The climate in the first half of the Holocene was warmer and more humid. Accumulation of lacustrine loams within the studied peatbog occurred before 7600 BP with predominated algae Pediastrum, Zygnemataceae and Botryococcus. After the lake level lowered in the result of destructing moraine dam, two lower peat horizons were developed about 7600 – 7200 BP. An episode of significant lake desiccation (later than 7200 BP) was recorded in all proxy archives. Further rise of water supply led to increasing the number of water-bog plants, diatomaceous, euglenic and green algae. At the same time, the pollen of xerophytes began to predominate in the pollen complexes, indicating aridization. The final stage reflects stable peatbog drying and its transformation into boggy meadow, decomposition and mineralization of peat.