Snow/Ice melt and Glacial Lake Outburst Flood in Himalayan region

Snow/Ice melt and Glacial Lake Outburst Flood in Himalayan region Dr. SANJAY K JAIN NATIONAL INSTITUTE OF HYDROLOGY ROORKEE Modelling and management flood risk in mountain areas 17-19 Feb., 2015 at Sacramento, California, USA

Himalayan Water Resources About 35% of the geographical area of India is covered by mountains and 58% of this is accounted for by the mighty Himalayas in which more than 5000 glaciers covering about 38000 km 2 area. There are 22 major river systems with about 1 million km 2 catchment area lying in the Himalayas, with snow and glacier melt runoff of more than 50%. The seasonal snow and glacier melt coming from the Himalayan Rivers is a dependable source of water for irrigation, hydroelectric power and drinking water supply. The hydropower generation contributes about 26% of total installed capacity in India in which Himalayan river systems contribute 78% of the total Indian hydropower potential. Snow melt modelling is a crucial element to predict runoff from snowcovered or glacierised areas, as well as for snow/ice melt flooding The flood due to glacial lake outburst is one of the major issue because of climate change.

Western Disturbances Nov. March/April Lesser Himalaya 3600-4600m Outer Himalaya 1500-3500m Siwalik Terai 900-1500m <300m Greater Himalaya > 4600m 4000m Tibetan Plateau SW Monsoon June Sep Glaciers 10% Winter snow cover 35-50 % Maximum monsoon precipitation at 1500 3000 m asl

INDUS, GANGA, BRAHMAPUTRA BASINS 4

The situation can become of even greater concern if the rising snowmelt runoff is compounded by runoff from heavy rainfall. SNOW/ICE MELT FLOOD It is known that the effect of global climate change on hydrologic systems, especially on mountain snow and glacier melt, can modify the timing and amount of runoff in mountainous watersheds. Streamflow simulation and forecast is of great importance to water resources management and planning, and can provide a firm basis for forecasts of water resources availability while minimizing the risk and loss from floods caused by rapid snow and glacier melt. When the ground is frozen, the water produced by the melting snow is unable to penetrate and runs off over the ground surface into streams and lakes.

Glacial Lake And Glacial Lake Outburst Flood (GLOF) Glacial dammed lakes are formed by accumulation of water from the melting of Snow and Ice cover and by blockage of end moraines. A glacial lake outburst flood (GLOF) can occur when a lake contained by a glacier or a terminal moraine dam fails. The bursting of moraine-dammed lakes is often due to the breaching of the dam by the erosion of the dam material as a result of overtopping by surging water or piping of dam material GLOF STUDIES HAVE BEEN CARRIED OUT FOR LAKES IN THE BASINS OF GHARWAL HIMALAYA, EASTERN HIMALAYA AND BHUTAN HIMALAYS

SNOW AND GLACIER MELT

STREAM FLOW MODELLING IN SATLUJ BASIN Location of the study area and meteorological stations in the Satluj basin

NOAA-AVHRR Images (2004)

MODIS SNOW Data Product (2004)

MODIS LST Data Product (2004)

Snow Cover Depletion Curve

Lapse Rate estimation from MODIS LST maps

METHODOLOGY

STREAM FLOW MODELLING Main steps in modelling are as follows: Division of Basin Into Elevation Bands Processing of Meteorological Data Temperature Distribution Precipitation Distribution Variability of Snow Covered Area Form of Precipitation Melt due to rain Degree Day Factor for Snow and Ice Routing of Surface and Sub Surface Flow

Simulation of Runoff (2000-2001)

Simulation of Runoff (2001-2002)

ASSESSMENT AND SIMULATION OF GLACIER LAKE OUTBURST FLOODS IN HIMALAYAN REGION To estimate the flood due to GLOF Valley planning and flood management To formulate emergency procedures such as warning system, evacuation plan etc. To identify and solve unexpected flood problems due to accidents To remove fear in public and make the public aware of the risk To analyze past accidents for advancement of the state of art

METHODOLOGY For estimating the Glacial Lake Outburst flood, the following approach and methodology has been adopted: Inventory of glacier and glacial lakes Finding out the potentially dangerous glacial lakes Estimation of Glacial lake volume and finalisation of Glacial lakes for GLOF simulation Estimation of breach parameter for GLOF/dam breach simulation and the consequent dam breach flood using MIKE11 model Channel routing of dam breach flood through the entire reach of river from the GLOF site to the site to get the magnitude of flood peak at site.

IDENTIFICATION OF GLACIAL LAKES Normalized Difference Water Index NDWI (GREEN (GREEN NIR ) NIR ) GREEN is a band that encompasses reflected green light and NIR represents reflected near-infrared radiation The selection of these wavelengths was done to : (1) maximize the typical reflectance of water features by using green light wavelengths (2) minimize the low reflectance of NIR by water features; and (3) take advantage of the high reflectance of NIR by terrestrial vegetation and soil features.

Yes Yes Yes Yes Yes NDWI<T 1 Slope<10% No Lake R 1 >T 2 No No Lake Glacial Lake R 2 <T 3 No No Lake R1= BGreen/BNIR R2= BNIR/BSWIR Slope<10% No No Lake Glacial Lake Algorithm to automatically classify glacial lakes on IRS Images, using a decision tree. T i represents a threshold, whose value is determined empirically on each scene by visual inspection.

CRITERIA FOR IDENTIFICATION OF DANGEROUS LAKE Rise in lake water level In general the lakes which have a volume of more than 0.01 km3 are found to have past events. A lake which has a larger volume than this is deeper, with a deeper part near the dam (lower part of lake) rather than near the glacier tongue, and has rapid increase in lake water volume is an indication that a lake is potentially dangerous. Activity of supraglacial lakes Groups of closely spaced supraglacial lakes of smaller size at glacier tongues merge as time passes and form bigger lakes. These activities of supraglacial lakes are indications that the lakes are becoming potentially dangerous.

POSITION OF LAKES The potentially dangerous lakes are generally at the lower part of the ablation area of the glacier near to the end moraine, and the mother glacier should be sufficiently large to create a potentially dangerous lake environment. The valley lakes with an area bigger than 0.1 km2 and a distance less than 0.5 km from the mother glacier of considerable size are considered to be potentially dangerous. DAM CONDITIONS The natural conditions of the moraine damming the lake determine the lake stability. Lake stability will be less if the moraine dam has a combination of the following characteristics: narrower in the crest area no drainage outflow or outlet not well defined steeper slope of the moraine walls ice cored breached and closed in the past and refilled again with water seepage flow at moraine walls

CONDITION OF ASSOCIATED MOTHER GLACIER The following general characteristics of associated mother glaciers can create danger to moraine-dammed lakes: hanging glacier in contact with the lake, bigger glacier area, fast retreating, debris cover at glacier tongue area, steep gradient at glacier tongue area, PHYSICAL CONDITIONS OF SURROUNDINGS potential rockfall/slide (mass movements) site around the lake which can fall into the lake suddenly snow avalanches of large size around the lake which can fall into the lake suddenly neo-tectonic and earthquake activities around or near the lake area climatic conditions of successive years being a relatively wet and cold year followed by a hot and wet or hot and arid year

GLOF SIMULATION: INPUT REQUIRED Glacier and Glacier lake mapping Drainage network and Length of stream d/s lake DEM of the basin Cross Section at regular interval downstream of lake Area and Volume of the lake Breach width and Depth 100 year return flood if available

MIKE11 DAM BREAK MODELLING

LAKE DEPTH The empirical relations as available by Huggel et al. (2002) is: The lake volume D = 0.104 A 0.42 where D is the depth of lake in m and A is the lake area in m 2. LAKE VOLUME The empirical relations as available by Huggel et al. (2002) is: The lake volume V = 0.104 A 1.42 where V is the lake volume in m 3 and A is the lake area in m 2.

GLOF: CASE STUDIES Chorabari Lake outburst - (June 17, 2013) Chorabari Lake

SNOW COVER DURING MAY-JUNE 2013 Satellite pictures shows that the glacial regions above Kedarnath had received fresh and excess snowfall when heavy rainfall hit the region. (Source NRSC,2013)

Elevation in meter GLOF HYDROGRAPH AT CHAMKHARCHU H.E. PROJECT BHUTAN x-section of downstream lake V=54.18 Mm 3 Chubda Lake D=40 m 118.84 km 900 m 4920 m 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 30.00 120.00 210.00 300.00 390.00 480.00 570.00 660.00 750.00 840.00 930.00 1020.00 1110.00 1200.00 1290.00 1380.00 1470.00 1560.00 1650.00 1740.00 1830.00 1920.00 2010.00 2100.00 2190.00 xsec_dam xsec_5km from dam xsec_10km from dam xsec_15km from dam xsec_20km from dam xsec_25km from dam xsec_30km from dam "xsec_35km from dam xsec_40km from dam xsec_45km from dam xsec_50km from dam xsec_55km from dam xsec_60km from dam xsec_65km from dam xsec_70km from dam xsec_75km from dam xsec_80km from dam xsec_85km from dam xsec_90km from dam xsec_95km from dam xsec_100km from dam xsec_105km from dam xsec_110km from dam xsec_115km from dam Distance from right bank to left bank in meter [m^3/s] 10500.0 Time Series Discharge 10000.0 9500.0 9000.0 8500.0 8000.0 7500.0 10251.71 cumec 7000.0 6500.0 6000.0 5500.0 5000.0 4500.0 4000.0 3500.0 3000.0 2500.0 2000.0 1500.0 1000.0 5068.59 cumec 2 hour 10 minutes 500.0 0.0 00:00:00 21-4-2006 04:00:00 08:00:00 12:00:00 16:00:00 20:00:00 00:00:00 22-4-2006 04:00:00 08:00:00 12:00:00 16:00:00 20:00:00 00:00:00 23-4-2006

Discharge (m 3 /s) KURI-GONGRI HE PROJECTS, BHUTAN Discharge (m 3 /s) Elevation (m) Kuri basin V=11.62 Mcum 4690 m D=40 m Cross-section of Kuri Basin 6000 5000 4000 xsec at dam site xsec at 1 km from dam site xsec at 3 km from dam site xsec at 4 km from dam site xsec at 5 km from dam site xsec at 6 km from dam site xsec at 7 km from dam site xsec at 8 km from dam site xsec at 9 km from dam site xsec at 10 km from dam site xsec at 11 km from dam site xsec at 12 km from dam site xsec at 13 km from dam site xsec at 14 km from dam site xsec at 15 km from dam site xsec at 16 km from dam site xsec at 17 km from dam site xsec at 18 km from dam site xsec at 19 km from dam site 3000 xsec at 20 km from dam site xsec at 21 km from dam site 194 km 2000 1000 0 1 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97 103109115121127133139145151157163169175181187 Distance (m) xsec at 22 km from dam site xsec at 23 km from dam site xsec at 24 km from dam site xsec at 26 km from dam site xsec at 27 km from dam site xsec at 28 km from dam site xsec at 29 km from dam site xsec at 30 km from dam site xsec at 31 km from dam site xsec at 32 km from dam site xsec at 33 km from dam site xsec at 34 km from dam site xsec at 35 km from dam site xsec at 36 km from dam site xsec at 37 km from dam site xsec at 38 km from dam site xsec at 39 km from dam site xsec at 40 km from dam site xsec at 41 km from dam site xsec at 42 km from dam site 14000 12000 9000 8000 8478.9 cumec 10000 8000 GLOF KURI 7000 6000 5000 GLOF KURI 6821.0 cumec 6000 4000 4000 3000 1 hour 50 minutes 2000 2000 1000 0 00:00:00 02:09:36 04:19:12 06:28:48 08:38:24 10:48:00 Time (hh:mm:ss) 0 00:00:00 02:09:36 04:19:12 06:28:48 08:38:24 10:48:00 Time (hh:mm:ss)

Discharge (m 3 /s) KURI-GONGRI HE PROJECTS, BHUTAN Discharge (m 3 /s) Elevation (m) Gongri basin 45.56 Mm 3 D=25 m 4564 m 114.3 km Cross section Of Gongri Basin 5000 4000 3000 2000 1000 0 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 113 120 127 134 141 148 155 162 169 176 183 Distance (m) xsec at lake xsec at 1km from lake xsec at 2km from lake xsec at 3km from lake xsec at 4km from lake xsec at 5km from lake xsec at 6km from lake xsec at 7km from lake xsec at 8km from lake xsec at 9km from lake xsec at 10km from lake xsec at11 km from lake xsec at 12km from lake xsec at 13km from lake xsec at 14km from lake xsec at 15km from lake xsec at 16km from lake xsec at 17km from lake xsec at 18km from lake xsec at 20km from lake xsec at 21km from lake xsec at 22km from lake xsec at 23km from lake xsec at24 km from lake xsec at 25km from lake xsec at 26km from lake xsec at 27km from lake xsec at 28km from lake xsec at 29km from lake xsec at 30km from lake xsec at 31km from lake xsec at 32km from lake xsec at 33km from lake xsec at 34km from lake xsec at 35 km from lake xsec at 36km from lake xsec at37km from lake xsec at 38km from lake xsec at 39km from lake xsec at 40km from lake xsec at 41km from lake xsec at 42km from lake xsec at 43km from lake xsec at44km from lake xsec at 45km from lake xsec at 46km from lake xsec at 47km from lake xsec at 48km from lake xsec at 49km from lake xsec at 50km from lake xsec at 51km from lake xsec at 52km from lake xsec at 53km from lake xsec at 54km from lake xsec at 55km from lake xsec at 56km from lake xsec at 57km from lake xsec at 58km from lake xsec at 59km from lake xsec at 60km from lake xsec at 61km from lake xsec at 62km from lake xsec at 64 km from lake xsec at 66km from lake xsec at 68km from lake xsec at 69km from lake xsec at70 km from lake xsec at 71km from lake xsec at 72km from lake xsec at 74km from lake xsec at 75km from lake xsec at 76km from lake xsec at 77km from lake xsec at 78km from lake xsec at 79km from lake xsec at 80km from lake xsec at 81km from lake xsec at 82km from lake xsec at 83km from lake xsec at 84km from lake 10000 9000 5000 4500 4685.3 cumec 8000 7000 6000 5000 GLOF GONGRI 4000 3500 3000 2500 GLOF GONGRI 3850.5 cuemc 4000 3000 2000 1500 1 hour 20 minutes 2000 1000 1000 500 0 00:00:00 01:26:24 02:52:48 04:19:12 05:45:36 07:12:00 08:38:24 10:04:48 11:31:12 Time (hh:mm:ss) 0 00:00:00 01:26:24 02:52:48 04:19:12 05:45:36 07:12:00 08:38:24 10:04:48 11:31:12 Time (hh:mm:ss)

Q (m 3 /s) Q (m 3 /s) elevation(m) V= 54.18 Mcum D= 16 m LACHUNG HE PROJECT, SIKKIM, INDIA 6000 5000 4000 3000 2000 1000 xsection at lake xsection at 1km from lake xsection at 2 km from lake xsection at 3 km from lake xsection at 4km from lake xsection at 5 km from lake xsection at 6 km from lake xsection at 7km from lake xsection at 8 km from lake xsection at 9 km from lake xsection at 10 km from lake xsection at 11 km from lake xsection at 12 km from lake xsection at 13 km from lake xsection at 14 km from lake xsection at 15 km from lake xsection at 16 km from lake xsection at 17 km from lake xsection at 18 km from lake xsection at 19 km from lake xsection at 20 km from lake xsection at 21 km from lake xsection at 22 km from lake xsection at 23 km from lake xsection at 24 km from lake xsection at 25 km from lake xsection at 26 km from lake xsection at 27 km from lake xsection at 28 km from lake xsection at 29 km from lake xsection at 30 km from lake xsection at 31 km from lake xsection at 32 km from lake xsection at 33 km from lake 0 1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101 106 111 116 121 126 131 136 distance(m) 4812 m Site-I 32 km Site-III 38 km Site-II 36 km 1000 900 800 700 600 500 400 300 200 100 0 919.04 cumec 1000 919.04 cumec 900 800 751.10 cumec 700 749.29 cumec Bhimkyong HEP 600 Bop HEP GLOF GLOF 500 50 minutes 0:00 1:12 2:24 3:36 4:48 6:00 7:12 8:24 9:36 TIME (HH:MM) Site-I 400 300 200 100 0 0:00 1:12 2:24 3:36 4:48 6:00 7:12 8:24 9:36 TIME (HH:MM) Site-II

TAWANG H.E. PROJECT, ARUNCHAL PRADESH Elevation(m) V= 11.62 Mcum V= 10.85 Mcum D-25 m 4564 m 36 km 1525 m 4348 m 40 km 5000 4000 3000 2000 1000 0 Cross- section of Twang Basin 1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106 113 120 127 134 141 148 155 162 169 176 183 Distance (m) xsec at lake xsec at 1km from lake xsec at 2 km from lake xsec at 3km from lake xsec at 4km from lake xsec at 5km from lake xsec at 6km from lake xsec at 7km from lake xsec at 8km from lake xsec at 9km from lake xsec at 10km from lake xsec at 12km from lake xsec at 13km from lake xsec at 14km from lake xsec at 15km from lake xsec at 16km from lake xsec at 17km from lake xsec at 18km from lake xsec at 19km from lake xsec at 20km from lake xsec at 25km from lake xsec at 26km from lake xsec at 27km from lake xsec at 28km from lake xsec at29 km from lake xsec at 30km from lake xsec at 32km from lake xsec at 33km from lake xsec at 34km from lake xsec at 38km from lake xsec at 39km from lake xsec at 40km from lake xsec at 41km from lake xsec at 42km from lake xsec at 43km from lake xsec at 44km from lake xsec at 45km from lake xsec at 46km from lake xsec at 47km from lake xsec at 48km from lake xsec at 49km from lake xsec at 50km from lake xsec at 51km from lake xsec at 52km from lake xsec at 53km from lake xsec at 54km from lake xsec at 55km from lake xsec at 56km from lake xsec at 57km from lake xsec at 58km from lake 2959.00 cumec 2791.56 cumec 3120.00 cumec 2792.05 cumec 12 minutes 12 minutes

Elevation (m) Discharge m3/s 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 Distance from right bank to left bank (m) at 5 Km from Lake at 10 km from lake at 15 Km from lake at 20 Km from Lake at 25 Km from Lake at 30 Km from Lake at 35 Km from Lake at 40 Km from Lake at 45 Km from Lake at 50 Km from Lake at 55 Km from Lake at 60 Km from Lake at 65 Km from Lake at 70 Km from Lake at 75 Km from Lake at 80 Km from Lake at 85 Km from Lake at 90 Km from Lake 3500 3000 2500 2000 1500 1000 500 0 00:57 02:09 03:21 Time (h) Dam breach flood just down stream to lake

RECENT GLOF EVENTS - BHUTAN Bhutan S.No. DATE RIVER BASIN LAKE CAUSE OF GLOF 1 1957 Pho Chu Tarina Tso Not known 2 1960 Pho Chu Unnamed Not known 3 1960 Chamkhar Chu Bachamancha Tso Not known 4 7 Oct 94 Pho Chu Luggye Tso Moraine collapse

RECENT GLOF EVENTS - NEPAL Bhutan S.No. DATE RIVER BASIN LAKE CAUSE OF GLOF 1 12 Jul 91 Tamakoshi Chubung Moraine collapse 2 3 Sep 98 Dudh Koshi Tam Pokhari Ice avalanche 3 15 Aug 03 Madi River Kabache Lake Moraine collapse 4 8 Aug 04 Madi River Kabache Lake Moraine collapse

METHODS FOR MITIGATING THE IMPACT OF GLOF REDUCING THE VOLUME OF LAKE WATER Possible peak surge discharge from a GLOF could be reduced by reducing the volume of water in the lake. In general, any one or combination of the following methods may be applied for reducing the volume of water in the lake: Controlled breaching Controlled breaching can be carried out by blasting, excavation, or even by dropping bombs from an aircraft. Construction of an outlet control structure For more permanent and precise control of lake outflows, rigid structures made out of stone, concrete, or steel can be used. Pumping or siphoning out the water from the lake, and Making a tunnel through the moraine dam Tunneling through moraines or debris barriers, although risky and difficult because of the type of material blocking the lake, has been carried out in several countries.

PREVENTATIVE MEASURES AROUND THE LAKE AREA Any existing and potential source of a larger snow and ice avalanche, slide, or rock fall around the lake area, which has a direct impact on the lake and dam has to be studied in detail. Preventative measures have to be taken such as removing masses of loose rocks to ensure there will be no avalanches into the lake. Real-time monitoring, early warning systems and preparedness education are the most beneficial ways to minimize risk. Preparedness hazard mapping, improving communication, education to create awareness

Concluding Remarks Glacier and snow-melt have major contribution to the river flows in the region. It is necessary to characterize the glaciers in different climatological regions of the basin The rate, volume and timing of snow melt are likely to change, therefore, impact of climate change on the snowmelt runoff and total streamflow of the large Himalayan rivers should be investigated using GCMs output as input to the calibrated hydrological models. Studies on the trend of changes in snow cover over the Himalayas/basins along with retreat of glaciers need immediate emphasis.

Concluding Remarks Climate warming will increase the frequency and risk of GLOFs Regular mapping and monitoring of lakes are needed Potentially dangerous glacial lakes must be provisionally identified and prioritized for further investigation Potentially dangerous lakes must be monitored on a continuous basis High resolution time series satellite image are useful for this purpose Appropriate measures to reduce the potential risks from these lakes

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