MEKONG RIVER INUNDATIONSIMULATIONUSING K-SUPER COMPUTER

Research Center for Urban Safety andSecurity/Civil Engineering Dept.
Associate Professor, Ken KOBAYASHI

Advantage of home

82944 CPUs
663552 cores

Specification of the K super computer
82944 CPUs
663552 coresLiterature survey

for Osaka

We tried up to8192 CPUs.

A Shallow water equationh M N raint x yM uM vM
Hu v
2  gh
 gn utxyx
h1 3222N uN vN
Huv
  gh gn 2 v
1 3txyyh2

Mekong River simulation
 Mekong RiverRiver length: 4,200km, Area:795,000km2
Largest river in South East Asia

 Flooding occurs in rainy season: Hugedamages in 2000 and 2011

Computationalarea
Cell size

Cambodia, Vietnam,
Mekong Delta
200 m（Dem：JAXA ALOS
World 3D - 30m）

Computational UTC 2000/5/1～UTCduration
2000/10/31

Mekong River simulation
Upper B.C. at Kratie (Observed water level)
Approx. 350km × 350km area

184 day simulation became possible within 24 hours by K
supercomputer (1,891×1,900=3,592,900 node, 200m resol.)
8 times larger
than theTonegawa riverbasin, the largest
basin in Japan
With 960CPU

Checked that thetime step could
be doubled
though theaccuracy was notchecked.

Comparison with MODIS＜max. inundation depth＞＜MODIS image＞

Volta river basin, West Africa
SATREPS 1st Phase (2012-2017): Main theme was agriculture andmeteorology. It could not establish enough relationship with Water
Authorities such as Water Resources Commission.
FrenchFrenchFrenchFrenchFrenchFrenchEnglishCECAR Ghana Project – Thank you very much for the opportunity

12Issues needs to be solved• We can obtain the hydrological data only within Ghana.
• Burkinafaso recently started to inform Ghana about thedam water release from Bagre dam but they do not tellGhana how much it is.

• Language problem when developing the flood warning
system (English or French?)• The information from Burkinafaso is French.

Dam water release hypothesis
3745 m /s as of 18 Aug. 2016 isreleased for 5 days.

Mesh size: 2219×4439(100m)＝
221.9 km×443.9 km
98501.41 km2
Approx. 5.8times larger
than the Tone riverbasin82944 CPUs663552 coresWith K supercomputer 960 CPUs (32×30 domain
decompositions),
SPARC64VIIIx (2.0 GHz), 8 cores/CPU/node),
Approx. 6.3 hour（25 day simulation）[Open MP only]
Lab. WS, 16core、Xeon CPU E5-2670 (2.6GHz)
probably approx. 46 hours (1 day simulation）?
 The information of the dam water release came on Aug. 19.
 If the simulation finishes within Aug. 19, then the prediction
becomes possible until Sep. 13 2016.
 It takes 3 days until the released water reaches to the border between
Ghana and Burukinafaso.
 Supercomputer K was crowded so that we waited for one day.

A Combined disasters in TokyoApprox.
14 mil. Node
10 m resolution

Typhoon downscaling experiment
JMA GCM 2093 August Typhoon

Kanogawa Typhoon best track was moved by 50km
eastward, the central pressure was lowered by 40 hPa.
The initial depth was plus 83cm due to a climate change
and plus 99 cm by high tide, thus totaly 1.82 m plus

Concluding remarks
The flood inundation simulation becomes very fast
using K super-computer.
If we could show an upper limit of the simulation
speed using the super computer, someone will realize
it by much cheaper way as people knows the limit tobreak.
Parallel efficiency is not good enough yet whichneeds to be improved.

Thank you very muchfor your attention.