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Seasonal Surface Velocities of a Himalayan Glacier Derived by Automated Correlation of Unmanned Aerial Vehicle Imagery
Kraaijenbrink, P.; Meijer, S. W.; Shea, J. M.; Pellicciotti, F.; De Jong, S. M.; Immerzeel, W. W.
Debris-covered glaciers play an important role in the high-altitude water cycle in the Himalaya, yet their dynamics are poorly understood, partly because of the difficult fieldwork conditions . In this study we therefore deploy an unmanned aerial vehicle (UAV) three times (May 2013, October 2013 and May 2014) over the debris-covered Lirung Glacier in Nepal. The acquired data are processed into orthomosaics and elevation models by a Structure from Motion workflow, and seasonal surface velocity is derived using frequency cross-correlation. In order to obtain optimal surface velocity products, the effects of different input data and correlator configurations are evaluated, which reveals that the orthomosaic as input paired with moderate correlator settings provides the best results. The glacier has considerable spatial and seasonal differences in surface velocity, with maximum summer and winter velocities 6 and 2.5 m a–1, respectively, in the upper part of the tongue, while the lower part is nearly stagnant. It is hypothesized that the higher velocities during summer are caused by basal sliding due to increased lubrication of the bed. We conclude that UAVs have great potential to quantify seasonal and annual variations in flow and can help to further our understanding of debris-covered glaciers
Debris-covered glaciers play an important role in the high-altitude water cycle in the Himalaya, yet their dynamics are poorly understood, partly because of the difficult fieldwork conditions . In this study we therefore deploy an unmanned aerial vehicle (UAV) three times (May 2013, October 2013 and May 2014) over the debris-covered Lirung Glacier in Nepal. The acquired data are processed into orthomosaics and elevation models by a Structure from Motion workflow, and seasonal surface velocity is derived using frequency cross-correlation. In order to obtain optimal surface velocity products, the effects of different input data and correlator configurations are evaluated, which reveals that the orthomosaic as input paired with moderate correlator settings provides the best results. The glacier has considerable spatial and seasonal differences in surface velocity, with maximum summer and winter velocities 6 and 2.5ma-1, respectively, in the upper part of the tongue, while the lower part is nearly stagnant. It is hypothesized that the higher velocities during summer are caused by basal sliding due to increased lubrication of the bed. We conclude that UAVs have great potential to quantify seasonal and annual variations in flow and can help to further our understanding of debris-covered glaciers
Understanding Dynamics of Himalayan Glaciers: Scope and Challenges of Remote Sensing
Bajracharya, S. R.; Maharjan, S. B.; Shrestha, F.
A remote-sensing based consistent semi-automated glacier mapping methodology with minimum manual intervention has been developed at ICIMOD . Using this methodology the glaciers of Hindu Kush Himalayan region were mapped in 2011 and continuously used for glacier mapping and monitoring in the region. These data were freely available to download from ICIMOD portal and GLIMS database. These comprehensive glacier information are the only data which is being used for research and development projects for countries like Bhutan, Nepal and Pakistan. Recently decadal glacier change from 1980 to 2010 of Nepal and Bhutan were published to understand the glacier change in the Himalaya. The decadal change assessment will be continued in other basins of HKH region to understand the glacier change. Due to rugged terrain, remote access, and logistic hindrance field verification is a challenging task and can be limited only in selected glaciers. Geodetic mass balance study in the selected glaciers like in Yala of Langtang basin and Rikha Samba of Hidden valley are on progress complement to field validation. High resolution images, lack of hydro-meteorological stations near to the glacier and limited competent manpower are another hindrance in the study of glacier change of the HKH region
Modelling Glacier Change in the Everest Region, Nepal Himalaya
Shea, J. M.; Immerzeel, W. W.; Wagnon, P.; Vincent, C.; Bajracharya, S.
In this study, we apply a glacier mass balance and ice redistribution model to simulate historical and future glacier change in the Everest region of Nepal . High-resolution temperature and precipitation fields derived from gridded APHRODITE data, and validated against independent station observations from the EVK2CNR network, are used to drive the historical model from 1961 to 2007. The model is calibrated against geodetically derived estimates of net glacier mass change from 1992 to 2008, termini position of four large glaciers at the end of the calibration period, average velocities observed on selected debris-covered glaciers, and total glacierized area. We integrate field-based observations of glacier mass balance and ice thickness with remotely-sensed observations of decadal glacier change to validate the model. Between 1961 and 2007, the mean modelled volume change over the Dudh Kosi basin is −6.4 ± 1.5 km3, a decrease of 15.6% from the original estimated ice volume in 1961. Modelled glacier area change between 1961 and 2007 is −101.0 ± 11.4 km2, a decrease of approximately 20% from the initial extent. Scenarios of future climate change, based on CMIP5 RCP4.5 and RCP8.5 end members, suggest that glaciers in the Everest region will continue to lose mass through the 21st century. Glaciers in the basin are concentrated between 5000 and 6000 m of elevation, and are thus expected to be sensitive to changes in temperature and equilibrium line altitude (ELA). Glacier volume reductions between −35 to −62% are possible by 2050, and sustained temperature increases to 2100 may result in total glacier volume losses of between −73 and −96%
Measurement of Changes in Glacier Extent in the Rimo Glacier, a Sub-Range of the Karakoram Range, Determined from Landsat Imagery
Kumar, P.; Bhondekar, A. P.; Kapur, P.
Accurate estimation of the spatiotemporal surface dynamics is very important for natural resource planning . This paper discusses a novel approach for the study of the surface patterns of a particular glacier Rimo located at 35°21′21″N77°22′05″E, about 20 km northeast of the snout of Siachen. Change detection in multiple images of the same location taken at different time intervals are of widely circulated use due to a large number of applications in various disciplines such as climate change, remote sensing and so on. The proposed technique uses image processing to derive regression models of selected glacier segments, these models are then used to measure area under the curve to estimate the surface area changes of the glacier. The surface area changes thus obtained have also been validated by standard method of pixel counting. With the rise in the global warming, the net change in the surface area of the concerned glacier is estimated using statistical analysis from 1998 to 2011. The results obtained show a fair degree of accuracy as compared to the standard method of pixel counting. We also discuss important pre-processing methods used in extracting the final concerned region of interest from a large satellite imagery of fairly average resolution
The 2012 Seti River Flood Disaster and Alpine Cryospheric Hazards Facing
Kargel, J.; Leonard, G.; Paudel, L.; Regmi, D.; Bajracharya, S.; Fort, M.; Joshi, S.; Poudel, K.; Thapa, B.; Watanabe, T.
We have identified the likeliest cause of the Seti River disaster of May 5, 2012, in which a flash flood killed or left missing 72 people . A cascade of deadly physical Earth processes combined with imprudent habitation on the lowest flood terraces and floodplain. The process cascade started with rockfalls into the Seti River gorge (observed via repeat ASTER imaging). The last rockfall—one to several weeks prior to the disaster-affected a knickpoint in the Seti River gorge and impounded glacial meltwater and spring snowmelt. The trigger was a large rock/ice avalanche originating from cornice ice on Annapurna IV, where part of the mass was channeled into the impoundment reservoir. That violent ground-surge event, plus possibly an air blast caused by a violent gravity flow of airborne debris—then burst the rockfall dam. This was not a glacier lake outburst flood. Glaciers were involved in the disaster by supplying meltwater, which was impounded by the rockfall dam, by triggering the disaster with collapse of cornice ice, and by contributing ice to the landslide and outburst flood. Debuttressing of moraine debris and ancient glacial lake sediment by retreat and thinning of glaciers also may have played a role—this is the only possible indirect link of the disaster to climate change. The rockfall and avalanche mass movements occurred independently of climate change. The narrow and easily blocked Seti River gorge was a key factor in the 2012 disaster, and it remains a unique component of this physiographic setting. A similar flood in this area may happen by a different cascade of Earth surface processes. An enormous mass of ancient unconsolidated glaciolacustrine and moraine sediment—many cubic kilometers—was discovered and is vulnerable to production of debris flows and hyperconcentrated slurry flows. Some aggravating processes occurring in the Sabche Cirque are related to climate change. Glaciers in that area are melting, and small lakes are forming. Although the lakes were not implicated in the 2012 disaster, the possibility exists for a small glacial lake outburst flood to trigger a larger mass movement. Such a debris flow could reach Pokhara directly. More likely, a debris flow in the Sabche Cirque could form another temporary and potentially dangerous impoundment dam in the gorge. Furthermore, the type of rockfall blockage that produced 2012's natural impoundment reservoir is likely to happen repeatedly. Hence, there is a high capacity of the Earth system in this area to produce comparable or even bigger flash floods or mass flows. The likelihood of a further disaster is magnified by imprudent habitation of the river channel and lower floodplain. Of all the changes to the Pokhara Valley, human encroachment on the flood plain is the factor most related to increasing vulnerability, but it is also the one factor that could be remedied by a complete ban on construction on lower terraces, if that is politically feasible. Warning systems could help, but fairly relocating people in jeopardy would be more effectiv
Climate Change and Challenges of Water and Food Security
Misra, A. K.
Water and food security are the key challenges under climate change as both are highly vulnerable to continuously changing climatic patterns . Studies have predicted that the average global temperature may increase by 1.4–5.8 °C and there would be substantial reduction in fresh water resources and agricultural yield by the end of the 21st century. Approximately 75% of the Himalayan glaciers are on retreat and will disappear by 2035. Moreover in Africa (Sub-Saharan Africa) by 2050 the rainfall could drop by 10%, which would reduce drainage by 17%. Majority of the fresh water resources has already been depleted and there is reduction in agricultural production globally with escalation in population and food demand. Some of the prominent climate change impacts are, growing deserts, and increase in the magnitude of floods and droughts. An extreme decline in crop yields in arid and semi arid areas globally has caused food shortages and a manifold increase in food inflation. Countries of Africa, Middle East, Arab and Asia have close economic ties with natural resource and climate-dependent sectors such as forestry, agriculture, water, and fisheries. This manuscript highlights groundwater recharge by utilization of wastewater using the Soil Aquifer Treatment (SAT) method in irrigation and the significance and methods of artificial recharge of groundwater. This paper also presents easily and economically feasible options to ensure water and food security under climate change and recommend formation of effective adaptation and mitigation polices and strategies to minimizing the impact of climate change on water resources and irrigation
Remote Sensing Data Application to Monitor Snow Cover Variation and Hydrological Regime in a Poorly Gauged River Catchment—Northern Pakistan
Hakeem, S; Bilal, M.; Pervez, A.; Tahir, A.
Snow- and glacier-nourished river basins located in the Himalaya-Karakoram-Hindukush (HKH) ranges supply a significant amount of discharge in River Indus upstream Tarbela Dam . It is, hence, important to comprehend the cryosphere variation and its relationship to the stream flow in these high-altitude river catchments. The MODIS remotely sensed database of snow products was chosen to examine the average annual snow and glacier cover (cryosphere) variations in the Shigar River basin (poorly gauged mountainous sub-catchment of the Indus River). Hydrological regime in the area was investigated through monthly database of observed stream fluxes and climate variables (precipitation and mean temperature) for the Shigar River catchment. Analysis indicated the usefulness of remote sensing techniques for estimation of the snow cover variation in the poorly or un-gauged high-elevation catchments of the HKH zone. Results also showed that Shigar River discharge was influenced mainly by the seasonal and annual snow cover area (SCA) variation and the temperature seasonality. Moreover, it is important to uncover such inter-relationship of stream flow, climate variables and snow cover in the poorly gauged high-altitude catchments of Karakoram region for better water resource management and accurate flood hazards predictions at Tarbela.
Rising River Flows and Glacial Mass Balance in Central Karakoram
B;, M.; A, K.
Field observations and geodetic measurements suggest that in the central part of the Karakoram Mountains, glaciers are either stable or expanding since 1990, in sharp contrast to glacier retreats that are prevalent in the Himalayas and adjoining high-altitude terrains of central Asia . Decreased discharge in the rivers originating from Karakoram is cited as a supporting evidence of this somewhat anomalous phenomenon. Here, in contrary to those citations, we show that, river discharge during the melting season of the glaciers in central Karakoram has increased from 1985 to 2010. We have implemented a sophisticated statistical procedure involving non-parametric tests combined with a benchmark smoothing technique that has proven to be a powerful method for empirical trend analysis to remove the stochastic component from the trend component in a time series. Melt water from winter snows is the dominant constituent of June and July flows. Glacial melts predominantly contribute to August and partially to September flows, which are controlled by monsoonal snowfall too at elevations approximately >3500 m. For all four summer months, flows increased from 1985 to 2000. August flows, which actually reflect the states of the glaciers, have continued to rise steadily after 2000 at the same rate as those did for the period 1985-2000. However, the rising trends of June and July flows changed to slightly declining trends from 2000 to 2010. These trends most likely indicate drop in winter snowfall over Karakoram and do not provide direct indications about the states of the glaciers. The rising trend of August discharge is due to change in glacial storage at a steadily decreasing rate of approximately 0.04-0.05 mm/day/year for the period 1985-2010. This rate is nearly equal to the rate of increase in precipitation during the summer months over Karakoram Mountains in recent decades as determined from the ERA-40 and GPCP precipitation datasets. Thereby, this is most plausibly, why the glacial mass balance in central Karakoram is nearly neutral. The rising river flows accompanying non-negative glacier mass balance are consistent with predicted future river flows derived from hydrologic modeling coupled with a climate projection suggesting increasing temperature and precipitation with unchanged glacier covers. This investigation reconciles two apparently contradictory observations namely rising river flows and either zero or slightly positive mass balance of central Karakoram glaciers
Consistent Increase in High Asia's Runoff Due to Increasing Glacier Melt and Precipitation
Lutz, A. F.; Immerzeel, W. W.; Shrestha, A. B.; Bierkens, M. F. P.
Rivers originating in the high mountains of Asia are among the most meltwater-dependent river systems on Earth, yet large human populations depend on their resources downstream . Across High Asia's river basins, there is large variation in the contribution of glacier and snow melt to total runoff, which is poorly quantified. The lack of understanding of the hydrological regimes of High Asia's rivers is one of the main sources of uncertainty in assessing the regional hydrological impacts of climate change. Here we use a large-scale, high-resolution cryospheric–hydrological model to quantify the upstream hydrological regimes of the Indus, Ganges, Brahmaputra, Salween and Mekong rivers. Subsequently, we analyse the impacts of climate change on future water availability in these basins using the latest climate model ensemble. Despite large differences in runoff composition and regimes between basins and between tributaries within basins, we project an increase in runoff at least until 2050 caused primarily by an increase in precipitation in the upper Ganges, Brahmaputra, Salween and Mekong basins and from accelerated melt in the upper Indus Basin. These findings have immediate consequences for climate change policies where a transition towards coping with intra-annual shifts in water availability is desirable
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