Glacial Lake Inventory of Bhutan

The Japan Aerospace Exploration Agency (JAXA) is cordially announcing public release of "Glacier and Glacial Lake Inventory of Bhutan using the Advanced Land Observing Satellite (ALOS, nicknamed "Daichi") Data" (Version 16.11), which is covered the entire country of Bhutan.

In the Himalayan region, there are numerous lakes in the vicinity of glaciers. These glacial lakes impose potential risks for sudden outbursts and consequent floods. This type of flooding event is referred to as a glacial lake outburst flood (GLOF), which occurs frequently enough in the Himalayan region. With a growing amount of public and scientific concern about hazards, climate change, and water management associated with GLOFs, the "Bhutan GLOF Project" (*1) aims at updating and improving glacial lake inventory for Bhutan using new and high spatial resolution data from ALOS as well as glacier inventory. The motivation for this release is to support the research community and various domestic and international projects.

The inventory is based on images taken between 2006 and 2011 from the two optical instruments, the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) and the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) onboard ALOS. The construction procedure consists of ortho-rectification, geometric correction, pan-sharpening, and digitization to extract water bodies. Glacial lakes included in the inventory are bodies of water that lay between the terminus of the mother glacier and the Little Ice Age moraine. Lakes located within 2 km of the Little Ice Age moraine down-valley are also included to take into account a possible flooding event with multiple lakes being involved. In addition, supraglacial lakes on debris-covered glaciers are included. Finally, we set 0.01 km2 as the minimum lake size considering small lakes contribute a less amount of GLOFs' risk. The parameters included in the inventory are ID, latitude, longitude, area, and some references in addition to a shape file for each lake. In total, 733 glacial lakes are extracted in the Bhutan Himalaya, and total area of the lakes is about 82.5 km2. In this latest version (v13.00), an ALOS-derived glacier inventory which contains polygons of glacier body and debris-covered area was connected with the glacial lake inventory. The glacier outlines and debris-covered outlines were also generated from the ALOS images with visual interpretation and manual delineation.
Figure 1: Pan-sharpened mosaic image by PRISM and AVNIR-2 in the Bhutan Himalayas as of July 2011 (R, G, B = Band 3, 2, 1 as true color composite)

Figure 1: Pan-sharpened mosaic image by PRISM and AVNIR-2 in the Bhutan Himalayas as of July 2011 (R, G, B = Band 3, 2, 1 as true color composite). The red lines show boundaries of river basin and the color dots show extracted glacial lakes in this study.

Figure 1 shows the pan-sharpened image covering the entire country of Bhutan overlaid the glacial lakes inventory (color polygons) and boundaries of river basin (red lines). Each color of polygons indicates an individual river basin. Figure 2 shows an enlarged image of Fig.1 around upper stream of Mangde Chu basin as example, which is overlaid the inventory (red polygons) and a Map ID.

Furthermore, an additional glacier inventory covering the Nepal Himalaya, which has beem developed in the same method, is released. This inventory records geo-spatial information of Nepalese glaciers around 2010 in a high accuracy. By coupling them and future results, comparison of glacial changes under different climate conditions (e.g. precipitation) will be possible. This will contribute greatly for glaciological studies with consideration of climatic heterogeneity.
Figure 2: Enlarged image around upper stream of Mangde Chu basin with glacial lake inventory (red polygons)

Figure 2: Enlarged image around upper stream of Mangde Chu basin with glacial lake inventory (red polygons).

*1 The project is a collaborative work of Nagoya University, Rikkyo University, Hokkaido University, National Research Institute for Earth Science and Disaster Prevention (NIED), Hiroshima Institute of Technology, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Remote Sensing Technology Center of Japan (RESTEC), Niigata University, Research Institute for Humanity and Nature (RIHN), Earth System Science Co.,Ltd. (ESS), Hirosaki University, Nihon University, Teikyo Heisei University, Gunma University, Keio University and the Department of Mineral and Geology (DGM) of the Royal Government of Bhutan supported by the Japan Science and Technology Agency (JST) and the Japan International Cooperation Agency (JICA) under the "Science and Technology Research Partnership for Sustainable Development" (SATREPS).


Figure 3: Example of delineated glaciers, debris-covered areas, and glacial lakes in a western part of Bhutan.

Papers to be referred:

【Glacial lake inventory】

Ukita, Jinro, et al. "Glacial lake inventory of Bhutan using ALOS data: methods and preliminary results." Annals of Glaciology 52.58 (2011): 65-71. Tadono, Takeo, et al. "Development and validation of new glacial lake inventory in the Bhutan Himalayas using ALOS 'DAICHI.'." Global Environmental Research 16.1 (2012): 31-40.

【Glacier inventory】

Nagai, Hiroto, et al. "Comparison of multiple glacier inventories with a new inventory derived from high-resolution ALOS imagery in the Bhutan Himalaya." The Cryosphere 10.1 (2016): 65-85.

Nagai, Hiroto, et al. “Evaluating the Scale and Potential of GLOF in the Bhutan Himalayas Using a Satellite-Based Integral Glacier–Glacial Lake Inventory.” Geosciences 7 (2017): 77.

【Glacier inventory in the Nepal Himalaya】

Ojha, Sunal, et al. Topographic controls on the debris-cover extent of glaciers in the Eastern Himalayas: Regional analysis using a novel high-resolution glacier inventory. Quaternary International 455 (2017): 82-92.

Ojha, Sunal, et al. “Glacier area shrinkage in eastern Nepal Himalaya since 1992 using high-resolution inventories from aerial photographs and ALOS satellite images.” Journal of Glaciology, 62.233 (2016): 512-524.

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