RESEARCH REPORT Inventory of glacial lakes and identification of potentially dangerous glacial lakes in the Koshi, Gandaki, and Karnali river basins of Nepal, the Tibet Autonomous Region of China, and India INVENTORY OF GLACIAL LAKES AND IDENTIFICATION OF POTENTIALLY DANGEROUS LAKES 1 Published by International Centre for Integrated Mountain Development GPO Box 3226, Kathmandu, Nepal and United Nations Development Programme (UNDP) GPO Box 107, Kathmandu, Nepal ISBN 978 92 9115 699 3 (print) 978 92 9115 691 7 (electronic) LCCN 2020-325703 Production team Nagraj Adve (Consultant editor) Samuel Thomas (Senior editor) Copyright © 2020 Rachana Chettri (Editor) International Centre for Integrated Mountain Development Dharma R Maharjan (Graphic designer) United Nations Development Programme (UNDP) Nepal This work is licensed under a Creative Commons Attribution Non-Commercial, No Derivatives 4.0 Photos International License (https://creativecommons.org/licenses/by-nc-nd/4.0/) Sudan Bikash Maharjan: Cover Deepak K.C.: pp 8–9, 19, 20–21, 24, 32–33, 44–45, 46 Note Jitendra Bajracharya: pp ix, 29 This publication may be reproduced in whole or in part and in any form for educational or nonprofit purposes Nabin Baral: pp v, 4–5 without special permission from the copyright holders, Nakul Chettri: pp 2–3 provided acknowledgement of the source is made. ICIMOD Rakesh Kayastha: pp vi–vii and UNDP Nepal would appreciate receiving a copy of any Sudan Bikash Maharjan: pp iii, viii, x–1, 7, 31, 47, 48–49 publication that uses this publication as a source. No use of this publication may be made for resale or for any other Udayan Mishra: pp ix, 43 commercial purpose whatsoever without prior permission in writing from the copyright holders. The contents of this publication do not necessarily reflect the views or policies Citation of ICIMOD or UNDP and do not imply the expression of any opinion concerning the legal status of any country, Bajracharya, S.R., Maharjan, S.B., Shrestha, F., territory, city or area of its authorities, or concerning the Sherpa, T.C., Wagle, N., Shrestha, A.B. (2020). Inventory of glacial delimitation of its frontiers. lakes and identification of potentially dangerous glacial lakes in the Koshi, Gandaki, and Karnali River Basins of Nepal, the This publication is available in electronic form at www.icimod.org/himaldoc and Tibet Autonomous Region of China, and India. Research Report. www.np.undp.org/library ICIMOD and UNDP. For further information, please contact: Sudan Bikash Maharjan (corresponding author) [email protected] Deepak KC [email protected] 2 RESEARCH REPORT RESEARCH REPORT Inventory of glacial lakes and identification of potentially dangerous glacial lakes in the Koshi, Gandaki, and Karnali river basins of Nepal, the Tibet Autonomous Region of China, and India Authors Samjwal Ratna Bajracharya, Sudan Bikash Maharjan, Finu Shrestha, Tenzing Chogyal Sherpa, Nisha Wagle, and Arun Bhakta Shrestha INVENTORY OF GLACIAL LAKES AND IDENTIFICATION OF POTENTIALLY DANGEROUS LAKES i Contents PAGE iii SECTION III | PAGES 8–19 Abbreviations and acronyms Approach and methodology PAGE iv The glacial lakes presented in this study consist of Foreword water bodies that are proximal to present glaciers as well as those located in lowland areas that were PAGES vi–vii covered by glaciers in the past. This section covers Key findings detailed methods on mapping and monitoring of glacial lakes, identification of potentially dangerous PAGE viii glacial lakes, and ranking of these lakes using remote Acknowledgements sensing and geospatial techniques. SECTION I | PAGES ix–3 SECTION IV | PAGES 20–31 Introduction Status of glacial lakes Most Himalayan glaciers are rapidly melting and Glacial lakes in the Koshi, Gandaki, and Karnali river shrinking, concurrent with the warming climate. The basins are found on the upper reaches at altitudes rapid shrinking and retreating of glaciers not only above 3000 metres. This section provide detailed impacts water resources and hydrological processes, information on glacial lakes in the Koshi, Gandaki, but also influences the formation and expansion of and Karnali basins including spatial distribution, size, glacial lakes, increasing the risk of GLOFs. Therefore, type, altitudinal distribution, and linkages to glaciers. systematic and regular assessment of glaciers and glacial lakes, and identification of potentially SECTION V | PAGES 32–43 dangerous glacial lakes, and ranking of their hazard Potentially dangerous glacial lakes in the levels are useful in designing GLOF risk management Koshi, Gandaki, and Karnali basins and reduction strategies. The stability of a lake depends on its physical SECTION I I | PAGES 4–7 characteristics, the damming materials, and the Study area characteristics of surrounding features. This section provides detailed information on lake stability and the Nepal consists of three major river basins – Koshi, processes applied in identifying potentially dangerous Gandaki, and Karnali (including Mahakali), all of glacial lakes, in the Koshi, Gandaki, and Karnali river which are major tributaries of the Ganges. These basins. river basins are transboundary, straddling the Tibet Autonomous Region (TAR) of China (upper section), SECTION VI | PAGES 44–47 Nepal (upper and middle sections), and India (largely Conclusions the lower section, barring the western middle section GLOFs are a crucial problem for people living in of the Kali River). the mountains, which develop at high altitudes and can extend for long distances, gravely damaging downstream infrastructure. The identification of potentially dangerous glacial lakes will help design GLOF risk management and reduction strategies. PAGES 48–53 References ii RESEARCH REPORT Na, a village near Tsho Rolpa glacial lake in Rolwaling Valley, Nepal. Abbreviations and acronyms ALOS Advanced Land Observing Satellite I (v) Lakes dammed by tributary valley glaciers ASTER Advanced Space-borne Thermal Emission and LIGG Lanzhou Institute of Glaciology and Geocryology Reflection Radiometer M Moraine-dammed lake B (c) Cirque lake M (e) End moraine-dammed lake B (o) Other bedrock-dammed lake M (l) Lateral moraine-dammed lake co Compressed and old dam M (o) Other moraine-dammed lake DEM Digital elevation model NAP National Adaptation Plan, Nepal dl Dam length NASA National Aeronautics and Space Administration dm Distance to source glacier nc No crest DMS Degree minute second NCVST Nepal Climate Vulnerability Study Team ds Dam slope NDC Nationally Determined Contributions ETM+ Enhanced Thematic Mapper Plus NDWI Normalized Difference Water Index GCF Green Climate Fund NEA Nepal Electricity Authority GCM Global climate model NIR Near infrared GIS Geographic information system NSIDC National Snow and Ice Data Center GL Glacial lakes O Other glacial lakes GLIMS Global Land Ice Measurements from Space OLI Operational Land Imager GLOBE Global Land One km-Base Elevation Project PDGL Potentially dangerous glacial lake GLOF Glacial lake outburst flood RCM Regional Climate Model GloVis USGS Global Visualization Viewer RS Remote sensing HKH Hindu Kush Himalaya sm Slope of source glacier I Ice-dammed lake Spot Satellite Pour l’Observation de la Terre ICIMOD International Centre for Integrated Mountain SRTM Shuttle Radar Topography Mission Development TAR Tibet Autonomous Region IPCC Intergovernmental Panel on Climate Change UNDP United Nations Development Programme I (s) Supraglacial lake WECS Water and Energy Commission Secretariat INVENTORY OF GLACIAL LAKES AND IDENTIFICATION OF POTENTIALLY DANGEROUS LAKES iii Foreword Glaciers and glacial lakes are major sources of region. These research initiatives have helped freshwater in the Himalaya. They play a significant identify the most critical glacial lakes in the region role in local and regional hydrology, and in for the implementation of mitigation measures and maintaining ecosystem services in the high mountain installation of early warning systems. Such measures areas and downstream. Himalayan glaciers are have enabled the Nepal government to lower water vulnerable to global climate change, and have been levels in two of its largest and most critical glacial melting at an unprecedented rate since the mid-20th lakes, both considered high-risk. More recently, century, impacting flow regimes in major associated ICIMOD and the United Nations Development river basins. The shrinking, thinning, and retreating Programme (UNDP) Nepal have worked together of glaciers not only impacts water resources and river to prepare an updated comprehensive glacial lake flows, but also leads to the formation of new lakes inventory of three major transboundary basins – the as well as the expansion of existing glacial lakes, Koshi, Gandaki, and Karnali (including Mahakali) – increasing the risk of glacial lake outburst floods which cover parts of China and Nepal, and a small (GLOFs). portion of India. GLOFs, which are caused by a sudden release of water The present report provides an update on the status from glacial lakes that have breached their moraine and changes in the number and area of glacial lakes in dams, are a prominent water-induced hazard in the three basins along with a detailed methodology for Nepal and other mountainous countries. Historically, the identification of critical glacial lakes in remote and GLOFs have had catastrophic consequences in Nepal, inaccessible mountain terrain using remote sensing leading to a loss of lives and livestock, and damages tools and technologies. It also identifies a number