Glacial hazards and downstream effects of climate change on high mountain glaciers. John M. Reynolds Reynolds Geo-Sciences Ltd, Mold, UK

Transcription

1 Glacial hazards and downstream effects of climate change on high mountain glaciers John M. Reynolds Reynolds Geo-Sciences Ltd, Mold, UK

2 Glacial hazards Hazard Description Time scale Avalanche Slide or fall of large mass of snow, ice, &/or rock Minutes Aluvión Catastrophic debris flow, irrespective of its cause, generally transporting boulders (Spanish) Hours Débâcle Outburst from a proglacial lake (French) Hours Glacial Lake Outburst Flood (GLOF) Catastrophic burst from a glacial lake, typically containing many million cubic metres of water mixed with debris (Himalayan) Hours Glacier Outburst Lahar Catastrophic discharge of water from a glacier Glacier-volcanic eruption interaction Hours Hours Jökulhlaup Glacier Surge Glacier Fluctuations Glacier outburst associated with hydrostatic uplift of an ice dam and/or sub-glacial volcanic activity Rapid increase in rate of ice flow resulting in advance of glacier snout Variation in ice front position due to climatic changes Hours/days Months/ Years Years/ decades 2

3 Glacial hazards

4 Glacial hazards and climate change As climate changes: The number of glacial lakes increases The volume of water stored in lakes increases The hazard increases Rural development is increasing into the high mountains: More roads, bridges; Mining Hydropower Communities Tourist trails/lodges 4 The vulnerability increases

5 Glacial hazard assessment Regional assessment using Remote Sensing Satellite imagery Landsat, ASTER, SPOT, etc. Regional overviews Automatic classification of land surface, glacial lakes Imagery-derived information: Digital Elevation Models (from stereo images) Radar interferometry Ice flow information (feature offset tracking) Geospatial information (elevations, surface gradients) Objective data for input to Multi-Criteria Analysis Geographical Information System tools 5

6 Beding 6 Landsat 2005

7 7 Upper Indus Basin, N. Pakistan

8 Measuring glacier flow rates Kangshung Glacier in Tibet (China) Image courtesy of D. Quincey 8

9 Mapping existing lakes at risk and predicting where lakes might form Defining areas of potential lake formation following the 2 Rule: Red < 2 - new lake Orange ponds (transient) Cyan >6 - no ponds Repeat assessment after a gap of several years will reveal changes in actual and potential lake areas and indicate the rates of glacier surface deflation and increases in potential lake areas. Reynolds (2000) Existing lake 9 Image courtesy of D. Quincey

10 Hazard assessment - factor analysis ID Parameter affecting hazard\score Volume of lake N/A Low Mod. Large 2 Lake level relative to freeboard No dam Low Mod. Full 3 Seepage evident through dam None Min. Mod. Large 4 Ice-cored moraine dam +/- thermokarst features N/A Min. Partial >Mod. 5 Calving risk from ice cliff N/A Low Mod. Large 6 Ice/rock avalanche risk N/A Low Mod. Large 7 Supra- / englacial drainage None Low Mod. Large 8 Compound risk present None Slight Mod. Large Threshold parameter Trigger potential parameter Zero Medium hazard Serious High Very high >>> An outburst can occur at any time>>> 10 (Modified from Dyce and Reynolds, 1998)

11 11 (RGSL, 2007)

12 Where are the triggers? Where are the breach points? Imja Tsho, Solukhumbu, Nepal

13 Guidelines for glacial hazards & risks Integrated guidelines for holistic glacial hazard assessment and risk management Site investigation techniques Hazard assessment, vulnerability assessment Introducing objectivity into assessments Risk reduction techniques Concentrates on glacial lakes, but with broader application to other hazard types Technical sections for use by practitioners Geophysics Geotechnics Strategic risk management aspects for decision makers Available on line at: 13

14 Changing hazards as a consequence of climate change Down wasting and receding glaciers Changes in melt water run-off quantities and timing Changes in precipitation quantities and timing Thawing permafrost Rise in boundary between cold-based and temperate ice regimes Potential buoyancy of submerged ice in glacial lakes Increased lake temperatures and more rapid ablation of glacier cliffs that terminate in lakes 14

15 Increased ice avalanche activity? Sublimation dry, cold-based? Melting & sublimation water generation 15

16 Climate-induced induced change in ice loss from sublimation to sliding? 16 Change in nature of the local trigger mechanism to impact on the local glacial lake.

17 Safuna, Cordillera Blanca, Peru De-buttressing & rock avalanche

18 Potential buoyancy of submerged ice? Tsho Rolpa, Rolwaling, Nepal

19 Inundation of potato fields by 1991 GLOF

20 Additional erosion through monsoon floods

21 Degradation of trekking routes & reduced access to grazing land 21

22 22 Arhueycocha, Peru Tourist lodge

23 GLOF impact on hydropower Partial or total destruction of HEP facility Inundation and silting-up of HEP systems Long-term high suspended sediment loads (economic losses to HEP generation if >5,000 ppm) Increased abrasion of turbine blades (increased maintenance costs and loss of efficiency) Reduced stream flow and changes to hydrological gradients within rivers Losses from the above can exceed tens of $million per instance. 23

24 Namche HEP, Solukhumbu, Nepal (Courtesy of WECS)

25 1985 (Courtesy of WECS) 25

26 26 The imminent destruction of the Machupicchu HEP scheme, Peru, Net cost to the Peruvian economy ~$200 million over 3 years

27 27 Glacial hazards and mining

28 Tailings dam Airstrip Mine camp Open pit Tien Shan Mountains, Kyrgyzstan 28

29 Lake outlet Lake sediments over glacier ice 29

30 30 Davidov Glacier, Kumtor, Kyrgyzstan, Tien Shan Mountains

31 Debris-covered glaciers 31 Copper mine in Chile

32 32 Destruction of mine haul roads through ice flow and wash-out

33 Geopolitics The hazard upstream in one country, the vulnerability downstream in another How to manage this and who pays? 33

34 Glacial lakes: hazard and/or resource? Reduce hazard only: Lower lake level and decrease lake volume Reduce hazard and use water as a resource: Maintain lake volume and release water in a controlled way as required to reduce the hazard but utilise the outflow as a resource Possible benefits include: Local electrification Management of local river environment Controlled compensation of otherwise reducing river flows for hydropower generation 34

35 Hazard and/or resource? Local electrification benefits:- Reduction on use of wood and kerosene for fuel Less stress on local biodiversity Better home living conditions, healthier people Better use of time to permit cottage industries/artisanal activity More attractive for trekking lodges and tourists Increased potential for local revenue generation Management of river environment Use of water for irrigation and toilets Better control of river channel and reduced erosion of toes of hill slopes Better water quality in river including lower suspended sediment levels Improved river ecology Major power generation national GDP Improved year-round river flows through controlled discharge Less abrasion of turbine blades, improved efficiency & lower maintenance 35

36 Conclusions 1 Glacial hazards: Pose an increasing problem in response to changing climate; Are much better understood now than 10 years ago; Can be assessed using objective criteria; Can be identified remotely in a first pass assessment; Can be anticipated perhaps >2-3 decades before formation; Should be reviewed at least every five years; 36

37 Conclusions 2 Need to be managed via national strategies through local implementing agencies following international guidelines More funding should be provided for implementation of hazard assessment and management schemes; Remediation measures hazard reduction and/or water resource management, as part of rural development and climate-change adaptation programmes? Integrated not isolated solutions 37

38 Glacial hazards her future? Thank you for your attention 38 Reynolds Geo-Sciences Ltd, UK