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Comparison  of  recently  formed  glacial  lakes  in  the  Bolivian  Andes  and  the  Southern  Alps  of  New  Zealand  -­‐  Differences  and  similarities  

Dirk Hoffman

Bolivian Mountain Institute – BMI Email: dirk.hoffmann@bolivian-mountains.org

Abstract  

As  mountain  glaciers   recede,   there   is   the  potential   for   the   formation  of  glacial   lakes,  depending   on   the   conditions   of   the   terrain   as   well   as   the   characteristics   of   the  moraines.   These   newly   formed   glacial   lakes   have   been   recognized   in   high  mountain  regions  around  the  world  as  posing  a  considerable  risk.  

In  the  Bolivian  Andes  glacial  lakes  have  not  yet  received  much  attention,  neither  by  the  local  population  nor  by  researchers.  A   first  documented  case  of  a  GLOF  (Glacial  Lake  Outburst   Flood),   which   in   November   2009   destroyed   numerous   fields,   various  kilometers  of  a  rural  road  and  killed  some  farm  animals  has  made  it  clear  that  Bolivian  glacial  lakes  –  even  though  relatively  small  in  size  -­‐  are  potentially  dangerous.  

In  New  Zealand’s  Southern  Alps,  glacial   lakes  are  not  as  numerous,  but   larger   in  size.  They  can  be  found  most  prominently  on  the  lower  parts  of  the  tongues  of  the  12  long  valley  glaciers.  There  is,  however,  no  known  case  of  a  glacial   lake  outburst  flood,  and  lakes  are  widely  considered  as  not  being  dangerous.  

This  paper  explores  the  differences  and  similarities  of  recently  formed  glacial   lakes  in  the  Bolivian  Andes  and  those  in  the  Southern  Alps  of  New  Zealand,  focussing  especially  on  the  risks  associated,  and  management  options  resulting  thereof.  

Key  words  

Glacial   lakes,   climate   change,   glacial   retreat,   Bolivia,   New   Zealand,   Andes,   Southern  Alps  

Glacial Flooding & Disaster Risk ManagementKnowledge Exchange and Field Training

July 11-24, 2013 in Huaraz, PeruHighMountains.org/workshop/peru-2013

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Introduction  

Wherever  mountain  glaciers  recede,  there  is  the  potential  for  the  formation  of  glacial  lakes,  depending  on  the  conditions  of  the  terrain  as  well  as  the  characteristics  of  the  moraines.   These   newly   formed   lakes   often   pose   a   considerable   risk   to   human  settlements   and   infrastructure   downstream,   which   is   not   always   recognized   and  managed  adequately.    

In  January  and  February  of  this  year,  I  undertook  a  climate  change  study  tour  to  New  Zealand,  organized  with  the  Bolivian  Mountain  Institute  –  BMI.  One  objective  had  been  to  investigate  how  climate  change  impacted  the  Southern  Alps  of  New  Zealand,  and  to  gain  insides  into  how  potentially  dangerous  glacial  lakes  were  managed.  –  I  was  in  for  a  surprise.  

 

Glacier  retreat  and  glacial  lakes  in  Bolivia  

Climate   change   is   a   reality   in   the   Bolivian   Andes.   Temperature,   precipitation   and  humidity  have  changed  considerably  over  the  last  50  years.  Temperature  increase  has  been  about  0.3°  C  per  decade  at  the  end  of  the  20th  century.  

Bolivia  is  home  to  around  20%  of  the  world’s  tropical  glaciers,  with  Peru  holding  about  70%,  Ecuador  and  Columbia  combined  4%,  and  the  rest  of  the  world  less  than  1%.  As  in  most  regions  of  the  world,  accelerated  melting  of  glaciers  set   in  around  1980.  At  this  time   Bolivia   held   566   km²   of   glacier   area   in   its   cordilleras.   Due   to   global   warming,  Bolivia’s  tropical  glaciers  are  retreating  at  an  unprecedented  rate.  

Recent   investigations   of   glacial   recession   indicate   that   glacier   surface   and   area   have  been  reduced  by  about  50%  during  the  last  35  years  (Soruco  et  al.  2009).  Hundreds  of  glacial  lakes  have  subsequently  formed  at  the  tip  of  the  tongue  of  the  glaciers,  which  might   grow   to   considerable   size   depending   on   local   terrain   conditions.   These   glacial  lakes  are  often  dammed  by  moraines  made  up  of  loose  material  that  might  yield  to  the  pressure  of  the  water  and  break,  releasing  enormous  amounts  of  water  downstream.  

In  the  Bolivian  Andes  glacial  lakes  have  not  yet  received  much  attention,  neither  by  the  local  population  nor  by  researchers.  The  recent  glacial   lake  inventory  and  preliminary  risk   assessment   realized   in   2011   by   Daniel   Weggenmann   for   the   Apolobamba  mountain   range   is   the   first   work   of   its   kind   (an   inventory   for   the   Cordillera   Real   is  presently  being  prepared  by  other  researchers).  The  results  of  the  Apolobamba  glacier  lake  inventory  show  that  the  total  number  of  contemporary  glacial  lakes  went  up  from  174  to  216  in  the  period  from  1986-­‐2008,  while  total  lake  area  grew  by  approximately  2.5  km²  (Weggenmann,  2011).    

 

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     Graphic  1:  The  ice-­‐dammed  glacial  lake  above  Keara  before  its  outbreak  (left;  Google  Earth  image,  2005)  and  as  seen  today  (right;  photo  by  author,  May  2013).  

 

The   first   and   only   documented  GLOF   incident   in   Bolivia   took   place   on  November   3,  2009  in  the  village  of  Keara  in  the  Northern  part  of  the  Apolobamba  mountain  range,  causing   damage   to   the   local   road,   a   bridge,   killing   farm   animals,   invading   fields   and  eroding  the  river  banks;  fortunately  not  causing  any  human  casualties.  

This   incident,   together   with   the   glacial   lake   inventory   and   the   efforts   of   individuals  from  NGOs  and  UMSA  state  university,  helped  to  include  glaciers  and  glacial  lakes  into  the  Social  Monitoring  Program  adopted  by  Apolobamba  Protected  Area  in  2012.  

 

Glacier  retreat  and  glacial  lakes  in  New  Zealand  

New  Zealand’s  glaciers  are  almost  exclusively  located  in  the  Southern  Alps  of  its  South  Island,  covering  an  area  of  approximately  1,160  km².  One  of  the  particularities  of  the  Southern   Alps   consists   in   the   extremely   high   rate   of   mountain   uplift   of   around   10  mm/yr,  due  to  plate  movements.  This  figure  is  more  than  double  than  for  other  major  mountain  ranges.  

Because   of   the   moderating   effect   of   the   huge   water   mass   of   the   Pacific   Ocean  surrounding  New  Zealand,  global  warming  is  less  pronounced  than  in  other  mountain  ranges  within   large   continental  masses.   Temperature   rise   for   the   Southern   Alps   has  been  calculated  to  be  around  1°  C  (by  1979),  largely  after  the  1950s,  which  at  present  should  stand  between  1.5  –  2  °C.  This  has  led  to  the  retreat  of  New  Zealand  glaciers,  even  though  not  always  in  synchrony  with  the  retreat  patterns  predominating  globally.    

“Wholesale  retreat  of  New  Zealand  glaciers  over  most  of  the  20th  century  is  generally  attributed   to   regional   warming   (...).   However,   there   have   been   reversals   within   this  overall  recession  from  glacier  retreat  to  glacier  advance.  These  have  sometimes  been  related   to   regional   precipitation   increases”,   writes   Trevor   Chinn,   New   Zealand’s  foremost  glacier  expert  (Chinn  et  al.  2012).  

Total  ice  loss  volume  has  been  calculated  from  54.53  km³  in  1976  to  46.12  km³  in  2008,  which  equals   about  15%.  Up   to  now,   glacial   lakes  have  only   formed  on   the  12   large  valley   glaciers,   characterized   by   low-­‐gradients   and   extensive   debris   cover.   Those  remained   their   areal   extent   until   the   70s,   even   though   notable   down-­‐wasting   took  place.   Because   of   their   slow   response   time,   these   long   glaciers   filter   out   more   of  

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regional   climate  as   compared   to   the  overall  warming  of   the  atmosphere  across  New  Zealand.  

 

     Hooker  and  Mueller  lakes  (left);  alluvial  gravel  fan  below  Mueller  glacier  (right);  photos  by  author.  

 

Mainly   during   the   1980s   the   formation   of   small   supra-­‐glacial   ponds   set   in,   which  quickly  lead  to  the  formation  of  glacial  lakes.  What  followed  during  the  1990s  was  the  rapid   expansion   of   these   lakes,   which   for   the   respective   glaciers   marked   “a   tipping  point   once   rapid   frontal   retreat   is   initiated  by   lake   growth”   (Chinn  et   al.   2012).   This  feedback  mechanism   has   started   a   new   dynamic   of   accelerated   lake   expansion   and  accelerated  melting  of  the  glacier  tongue,  which  is  now  under  way.  

It   is   important   to   notice,   however,   that   these   glacial   lakes   are   dammed   by   alluvial  outwash   gravel   plains,   and   not   by   brittle   moraines,   which  makes   them  much  more  stable.  It  is  for  this  reason,  that  existing  glacial  lakes  are  not  considered  dangerous,  but  as   a   tourist   attraction.   Research   is   mainly   directed   to   understand   lake   building   and  expansion  processes,  as  well  as  calculating  the  impact  glacial  lakes  have  on  the  rate  of  glacial  recession  at  the  tongues  that  are  in  contact  with  lake  water.  

 

Similarities  

The   similarities   between   glacial   lakes   in   Bolivian   and   New   Zealand   high   mountain  regions  can  be  resumed  the  following  way:  

• There   is   a   clear   trend   of   glacial   recession   in   both   regions,   largely   in   line   with  worldwide  trends  of  glacial  retreat.  

• In  both  cases,  a  number  of  glacial   lakes  have  formed  over  the  last  decades  at  the  snouts  of  glaciers.  

• These  lakes  have  notably,  sometimes  dramatically  increased  in  size.  

• Formation  of  glacial  lakes  is  an  ongoing  phenomenon.  

 

Differences  

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Differences  between  glacial   lakes  of  the  New  Zealand  Southern  Alps  and  the  Bolivian  Andes  are  numerous;  they  can  be  summarized  as  follows:  

• Ice   loss   in   Bolivia   (45-­‐50%)   over   the   last   40   years  was   about   three   times   that   of  New  Zealand  (15%).  

• Glacial  lakes  in  Bolivia  are  more  numerous  (a  few  hundred  compared  to  12).  

• Glacial  lakes  in  New  Zealand  are  much  larger  in  size  and  water  volume.  

• Some   of   the   lakes   in   Bolivia   are   to   be   considered   dangerous;   there   was   a   first  recorded  GLOF  incident  in  2009.  

• New  Zealand’s  recently  formed  lakes  are  considered  not  to  pose  any  danger,  they  are  even  used  as  a  new  tourist  attraction.  

• Besides   traditional   settlements   in   glacierized   watersheds,   in   Bolivia   there   are  mining  and  agricultural  activities  taking  place  close  to  glaciers.  

• In  New   Zealand   there   is   no   native   population   in   high  mountain   areas;   in   certain  places  touristic  infrastructure  is  present.  

• Differences   in   mountain   geo-­‐morphology   and   topography   are   important:    -­‐   long   valley   glaciers   in   New   Zealand   (absent   in   Bolivia);  -­‐   very   high   rates   of   uplift   in   the   Southern   Alps:   10   mm/yr;  -­‐   lake   levels   in   New   Zealand   are   lowering   over   time;  -­‐  alluvial  outwash  gravel  plains  instead  of  moraine  dams  

 

 Drawing  showing  the  formation  of  large  alluvial  outwash  plains  at  the  heads  of  modern  day  glaciers  and  glacial  lakes  in  New  Zealand;  source:  Chinn  

 

 

Conclusions  

Contrary   to  my   initial   expectations,   differences   are  more   significant   than   similarities  when  comparing  glacial  lakes  in  the  Bolivian  Andes  and  New  Zealand’s  Southern  Alps.  

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They   are   based   mainly   on   the   geo-­‐morphological   characteristics   of   the   mountain  ranges  and  its  glaciers.  

In  Bolivia,  there  is  a  need  to  realize  glacial  lake  inventories  of  other  mountain  regions,  especially  Cordillera  Real,  expand  monitoring  activities,  and  to  realize  on-­‐site  technical  expert  surveys  of  those  glacial  lakes  identified  as  possibly  dangerous.  

In  New   Zealand,   in   contrast,   there   is   presently   no   need   for   management   of   glacial  lakes.   It  might  be  good,  however,   to  analyze  the  possibility  of  rock  avalanches  falling  into   glacier   lakes,   as   well   as   to   take   another   close   look   at   topography   higher   up   to  make  sure  no  dangerous  glacial  lakes  would  form  there  in  the  future.  

 

 

Acknowledgements  

I   would   like   to   thank   Daniel  Weggenmann,   Rodrigo   Tarquino,   Apolobamba   National  Park,  Stefan  Winkler,  Trevor  Chinn,  the  participants  of  the  annual  Snow  &  Ice  Research  Group   (SIRG)  meeting,   and  many   others   for   their   contribution   to   this   work   and   the  time  dedicated   to  discuss   the  situation  of  glacial   lakes   in   the  Bolivian  Andes  and   the  New   Zealand   Southern   Alps.   It   is   my   wish   that   in   the   future   some   more   intense  cooperation  might  result  from  this  first  comparative  exploration.  

 

 

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