Mekong River Commissionffw.mrcmekong.org/weekly_report/2011/Seasonal Flood Situation... · Northern...

U

Mekong River Commission Flood Management and Mitigation Programme

Final

Seasonal Flood Situation Report for the Lower Mekong River Basin

Covering period from 1st June to 13rd November 2011

Prepared by Regional Flood Management and Mitigation Centre

December 2011

Certification of Approval of Internal FMMP Technical Document

Seasonal Flood Situation Report for the Lower Mekong River Basin Covering period from 1st June to 31st December 2011

MRC Seasonal Flood Situation Report for the Lower Mekong River Basin, 1 June – 13 November 2011

Page i

Table of Contents

Table of Contents ....................................................................................................................... i

List of Figures ............................................................................................................................. i

List of Tables ............................................................................................................................. ii

1. Flood season 2011 .......................................................................................................... 3 1.1 Rainfall situation .......................................................................................................... 3 1.2 General Behaviour of the Mekong River and Seasonal Flood Situation ........................ 9

2 Flood Forecast in 2011..................................................................................................15 2.1 Data collection for models and flood forecast bulletin dissemination ........................ 15 2.2 Accuracy and limitations in forecasting ...................................................................... 15 2.3 Lesson learned and actions to be taken ..................................................................... 17

Annex A Graphics and Tables ..................................................................................................... 21 Annex B Accuracy and performance .......................................................................................... 45 Annex C Season Water Level Graphs .......................................................................................... 53

List of Figures

Figure 1‐1 Total depth of rainfall in the flood season of the years 2000, 2002, 2008, 2009, 2010, 2011 and the long‐term average flood seasonal rainfall. ...................................... 3

Figure 1‐2 Weather map for Southwest Monsoon in the mid of July (17th July 2011). ................... 4 Figure 1‐3 Weather maps for ITCZ in the beginning of August and in the end of September. ......... 5 Figure 1‐4 HAIMA Storm Track. ....................................................................................................... 5 Figure 1‐5 Weather map for HAIMA Tropical Storm on 24th June 2011, before landing. ................ 6 Figure 1‐6 Weather map for HAIMA Tropical Storm on 25th June 2011, after landing. .................... 6 Figure 1‐7 NOKTEN Storm Track. .................................................................................................... 6 Figure 1‐8 Weather map for NOKTEN Tropical Storm at 13h on 30th July 2011, before

landing. .......................................................................................................................... 7 Figure 1‐9 Weather map for NOKTEN Tropical Storm at 19h on 30th July 2011, after

landing. .......................................................................................................................... 7 Figure 1‐10 NESAT Storm Track ........................................................................................................ 8 Figure 1‐11 Weather map for NESAT Tropical Storm on 26th September 2011, before

landing. .......................................................................................................................... 8 Figure 1‐12 Weather map for NESAT Tropical Storm on 2nd October 2011, after landing. ................. 8 Figure 1‐13 Rapidly rising of water levels at stations: Luang Prabang, Chiang Khan and Pak

Beng during 19th – 27th June. ..................................................................................... 11 Figure 1‐14 Rapidly rising of water levels at stations: Paksane, Nakon Phanon and Thakhet

during 19th – 27th June. ................................................................................................. 12 Figure 2‐1 Forecast performance based on original results by URBS and Regression. ................... 17 Figure 2‐2 Forecast performance based on original results by URBS and ISIS. .............................. 17


Page ii

Figure A1 Monthly rainfall distribution for Jinghong, Chiang Saen, Luang Prabang and Chiang Khan. ................................................................................................................ 22

Figure A2 Monthly rainfall distribution for Chiang Khan, Vientiane, Nongkhai, Paksane and Nakon Phanom. ........................................................................................................... 23

Figure A3 Monthly rainfall distribution for Thakhek, Mukdahan, Savannakhet and Khong Chiam. ......................................................................................................................... 24

Figure A4 Monthly rainfall distribution for, Pakse, Stung Treng , Kratie and Kompong Chiam. ......................................................................................................................... 25

Figure A5 Monthly rainfall distribution for Phnom Penh (Bassac and Port), Koh Khel and Neak Luong. ................................................................................................................. 26

Figure A6 Monthly rainfall distribution for Prek Kdam, Tan Chau and Chau Doc. ........................ 27 Figure A7 Monthly rainfall in June for main stations along the Mekong River. ............................ 28 Figure A8 Monthly rainfall in July for main stations along the Mekong River. ............................. 30 Figure A9 Monthly rainfall in August for main stations along the Mekong River. ........................ 32 Figure A10 Monthly rainfall in September for main stations along the Mekong River. .................. 34 Figure A11 Monthly rainfall in October for main stations along the Mekong River. ...................... 36 Figure B1 Average flood forecast accuracy along the Mekong mainstream................................. 45 Figure B2 Data delivery times for flood season 2011 from June to October. ............................... 49 Figure B3 Missing data for flood season 2011 from June to October. ......................................... 50 Figure B4 Flood forecast completion time. .................................................................................. 51 Figure B5 Flood forecast stations without forecast. .................................................................... 51 Figure B6 Second forecast needed. ............................................................................................. 51

List of Tables Table 1‐1 The flood peaks of main locations along the Mekong mainstream during 2011

flood season. ............................................................................................................... 10 Table A1 Monthly observed rainfall in flood season 2011. ......................................................... 21 Table A2 The characteristics of flood events for station from Chiang Saen to

Vientiane/Nong Khai. .................................................................................................. 38 Table A3 The characteristics of flood events for stations from Paksane to Pakse. ...................... 39 Table A4 The characteristics of flood events for stations from Strung Treng to Kompong

Cham. .......................................................................................................................... 40 Table A5 The characteristics of flood events for stations from Phnom Penh Bassac/Phnom

Penh Port, Koh Khel/Neak Luong to Prek Kdam. .......................................................... 42 Table A6 The characteristics of flood events for stations from Tan Chau and Chau Doc

(**). ............................................................................................................................. 43 Table B1 Achievement of daily forecast against benchmarks. .................................................... 46 Table B2 Benchmarks of success (Indicator of accuracy in mean absolute error). ...................... 47 Table B3 Overview of performance indicators for flood season 2011 from June to

October. ...................................................................................................................... 48


Page 3

1. Flood season 2011

1.1 Rainfall situation

During the five months flood season 2011, the critical rainfall situation in the Lower Mekong Basin was concentrated in end of June to beginning of July and August, a period of Southwest Monsoon activity, low pressure troughs, storm and typhoon’s appearances in the South China Sea. In terms of total seasonal rainfall, the general picture was higher than the average years (see Figure 1‐1). It can be seen that the total rainfall in the flood season 2011 at stations in the upper and lower reaches of the LMB was higher than the long‐term average and higher than in the previous flood season 2010.

The spatial variation of rainfall was high indicating that the intensity of heavy rain situations along the Lower Mekong Basin from upstream to downstream took place as a function of time (Annex A: 1. Graphs and Tables for monthly observed rainfall distribution during flood season):

• The wet season started in early June; the heavy rain mostly occurred in upper and middle reaches of the LMB.

• During July ‐ August, the intensive and continued rain covered the entire LMB and appeared more frequently during this period.

• Usually, from September to October was the time of intensive rainfall in lower reach, but this year it covered the entire LMB.

0

500

1000

1500

2000

2500

3000

3500

4000

Chieng

Saen

Luon

gPraB

ang

Chieng

Khan

Vientia

ne

NongK

hai

Paksa

ne

Thakh

ek

Nakon

Phano

m

Mukda

han

Savan

nakh

et

Khong

Chiam

Pakse

STrungT

reng

Kratie

KongP

ongC

ham

Phnom

PenhB

assa

c

NeakL

uong

Tan C

hau

Chau D

oc Stations

Tota

l dep

th o

f rai

nfal

l in

2011

floo

d se

ason

(mm

)

200020022008200920102011Mean

Figure 1‐1 Total depth of rainfall in the flood season of the years 2000, 2002, 2008, 2009, 2010, 2011 and the long‐term average flood seasonal rainfall.


Page 4

In 2011, three main weather patterns caused heavy rains, which are presented below:

• Southwest monsoon: influenced the Mekong River basin from early June to mid‐October; the critical activity mostly occurred in July. Typically, heavy rain event from 11th ‐ 18th July in the upper and middle reaches of LMB, which caused rapid rise in water level. From mid‐September, there was moderate to weak SW monsoon, which prevailed over Indochina Peninsula as a common phenomenon.

Figure 1‐2 Weather map for Southwest Monsoon in the mid of July (17th July 2011).

• Tropical Low Pressure (TLP) and Inter Tropical Convergence Zone (ITCZ): these periodically appeared from early June to the mid of October with on average 3 to 7 days duration. In the flood season 2011, the frequent appearances of TLP and ITCZ during almost the entire flood season were one of the main phenomena which caused continuous heavy rain and rising water along the Mekong River. In August, TLP and ITCZ were observed and had significant influence on the upper and middle reaches of the LMB while the influence on the lower reach took place mostly in September. Figure 1-3 shows an illustration of the appearances and influences of TLP and ITCZ to the LMB in August and September.


Page 5

Figure 1‐3 Weather maps for ITCZ in the beginning of August and in the end of September.

• Tropical depressions (TD), tropical storms (TS) or typhoons (TY): there were about 8 tropical depressions, storms and typhoons which came to South China Sea and affected the Mekong River basin with different levels. Of these, the four storms HAIMA, NOKTEN, HAITANG and NESAT were the most noticeable.

1. HAIMA was formed as a tropical storm on the 21st June when travelling through South China Sea. After moving across Leizhou Peninsular of China on 23rd June, the TS HAIMA landed over the North of Viet Nam on 24th June and then downgraded into low pressure and disappeared when it hit to the Northern part of Lao PDR on 26th June. HAIMA Storm Track was shown in Figure 1‐4. Weather maps for HAIMA before and after landing were shown in Figure 1‐5 and Figure 1‐6, respectively.

Figure 1‐4 HAIMA Storm Track.


Page 6

Figure 1‐5 Weather map for HAIMA Tropical

Storm on 24th June 2011, before landing.

Figure 1‐6 Weather map for HAIMA Tropical Storm on 25th June 2011, after landing.

2. Tropical storm NOKTEN was formed in the East Philippines on the 26th July 2011, cased intensive damages in the Luzon Island of the Philippines and moved into South China Sea on 29th July 2011. After travelling though Hainan Island of China, the TS landed over Northern part of Central of Viet Nam on the 30th July and arrived at middle part of Lao PDR. It downgraded into low pressure on the 31st July when moving into Thailand territory. NOKTEN Storm Track was shown in Figure 1‐7 and its weather maps before and after landing were shown in Figure 1‐8 and Figure 1‐9, respectively.

Figure 1‐7 NOKTEN Storm Track.


Page 7

Figure 1‐8 Weather map for NOKTEN Tropical

Storm at 13h on 30th July 2011, before landing.

Figure 1‐9 Weather map for NOKTEN Tropical Storm at 19h on 30th July 2011, after landing.

3. Tropical storm HAITANG was formed on 25th September in the East Sea of Viet Nam, landed over Quang Ngai, Da Nang provinces in the Central of Viet Nam on 26th September. On 27th September afternoon, it downgraded in to a Tropical Depression and disappeared in the Thailand territory after moving deep in to the mainland.

4. Typhoon NESAT was formed on 24th September in the East Sea of the Philippines, caused extensive damage when landing over Luzon Island of the Philippines on 27th September, 2011. After travelling through South China Sea, the TY‐NESAT hit to the Hainan Island, China and kept moving West‐Northwest ward and finally made landfall in the North of Viet Nam on 30th September, 2011. It downgraded in to low pressure and disappeared when moving deep into mainland. Figure 1‐10 presents the track of TY NESAT when it travelled through South China Sea and Hainan Island before landing over Viet Nam coastline. NESAT’s weather maps before and after landing were shown in Figure 1‐11 and Figure 1‐12, respectively.


Page 8

Figure 1‐10 NESAT Storm Track

Figure 1‐11 Weather map for NESAT Tropical

Storm on 26th September 2011, before landing.

Figure 1‐12 Weather map for NESAT Tropical Storm on 2nd October 2011, after landing.


Page 9

1.2 General Behaviour of the Mekong River and Seasonal Flood Situation

The terms “flood” and “flooding” may world‐wide have different meanings. Therefore the definitions as used in this report are basically adopted from the Mekong Annual Mekong Flood Forums:

• Flood: natural abundance of water in response to storm, rainfall, snowmelt, etc ... ergo the flood season on the Mekong ...... however, this does not necessarily lead to flooding;

• Flooding: the inundation of areas, which usually are not submerged. The 2011 flood season started earlier than in previous flood years. The first flood event occurred at end of June and July with the appearances and influences of low pressures and two tropical storms: HAIMA and NOK‐TEN.

In general terms, the water levels at most stations in LMB started about or above the long‐term average (LTA) at the beginning of flood season, then rose up rapidly above the LTA in July till September in which water level at Nong Khai was twice above alarm level of 11.4m (as defined by the national agencies) on 23rd August and during 21st – 26th September, Thakhek was twice above alarm level of 13.0m (as defined by the national agencies) during 4th – 13th August and 20th – 21st September, Mukdahan was above alarm level of 12.5m on 8th August and then above flood level of 12.6m during 9th – 14th August, Pakse was twice above flood level of 12.0m during 8th – 19th August and 19th – 24th September, Stung Treng was twice above alarm level of 10.7m during 11th – 13th August and 22nd – 25th September, Kratie was above alarm level of 22.0m during 22nd – 27th September, Kompong Cham was twice above alarm level of 15.2m during 14th – 16th August and 20th September – 1st October, Phnom Penh Bassac was above alarm level of 10.5m during 24th September – 24th October, Phnom Penh Port was above alarm level of 9.5m during 23rd September – 25th October, Koh Khel was twice above alarm level of 7.4m during 15th – 19th August and 12th September – 31st October, Neak Luong was above flood level of 8.0m during 27th – 30th September, Prek Dam was above flood level of 10.0m during 2nd – 26th October, Tan Chau was above flood level of 4.2m during 21st September – 1st November, Chau Doc was above flood level of 3.5m during 19th September – 5th November (Annex C presents the hydrographs of 22 main hydrological stations along the Mekong River).

In 2011, flood season has distinct characteristics compared to previous year:

- The rapid rise of the flood peak of the year was observed in early July at many stations in the upper, middle and upper‐lower reaches of LMB.

- By the tropical storm HAIMA and NOKTEN influences, a flood event with large amplitude of 3 to 6 meters occurred on the mainstream from Luang Prabang to Kompong Cham from beginning to mid of July. The situation on the tributaries was more extreme.

Table 1‐1 shows the flood peaks of main locations along the Mekong mainstream during 2011 flood season.


Page 10

Table 1‐1 The flood peaks of main locations along the Mekong mainstream during 2011 flood season.

Hmax

(m)

10501 Chiang Saen 11.5 11.8 27-Aug 6.49 Below alarm level

11201 Luang Prabang 17.5 18 22-Sep 14.06 Below alarm level

11903 Chiang Khan 17.32 17.4 23-Sep 13.14 Below alarm level

11901 Vientiane 11.5 12.5 23-Sep 10.62 Below alarm level

12001 Nong Khai 11.4 12.2 23-Sep 11.88 Above alarm level

12703 Paksane 13.5 14.5 22-Sep 13.42 Below alarm level

13101 Nakhon Phanom 12.6 12.7 05-Aug 12.25 Below alarm level

13102 Thakhek 13 14 05-Aug 13.30 Above alarm level

13402 Mukdahan 12.5 12.6 11-Aug 13.00 Above Flood level

13401 Savanakhet 12 13 12-Aug 11.89 Below alarm level

13801 Khong Chiam 16 16.2 11-Aug 15.72 Below alarm level

13901 Pakse 11 12 11-Aug 13.11 Above Flood level

14501 Stung Treng 10.7 12 23-Sep 11.25 Above alarm level

14901 Kratie 22 23 24-Sep 22.88 Above alarm level

19803 Kompong Cham 15.2 16.2 25-Sep 16.02 Above alarm level

33401 Phnom Penh Bassac 10.5 12 11-Oct 10.86 Above alarm level

20111 Phnom Penh Port 9.5 11 10-Oct 10.00 Above alarm level

33402 Koh Khel 7.4 7.9 28-Sep 7.89 Above alarm level

19806 Neak Luong 7.5 8 28-Sep 8.06 Above Flood level

20112 Prek Dam 9.5 10 20-Oct 10.19 Above Flood level

19803 Tan Chau 3 4.2 10-Oct 4.78 Above Flood level

39801 Chau Doc 2.5 3.5 08-Oct 4.24 Above Flood level

Day/Month of Peak CommentID Station Alarm level Flood Level

(Alarm levels and flood levels are defined by the national Line Agency)

The main hydrological situations along the Mekong River are presented in more detail below:

For stations from Chiang Saen to Vientiane/Nong Khai

During the 2011 flood season, water level of all stations started about or above the long‐term average (LTA) then quickly rose up above LTA in end of June and beginning of July by influences of Tropical Storm‐HAIMA and NOKTEN, then continue rising above LTA till October by influence of South west monsoons and ITCZs. Only Chiang Sean station had less effect from tropical storms, SW and ITCZ as compared to the rest. There were two flood events with amplitudes over 3 meters which occurred at those stations, except Luang Prabang with three flood events (see more detail in Annex A, Part 3, Table A2).


Page 11

During June to July there were two tropical storms (HAIMA and NOKTEN), moderate to heavy rainfall occurred in this region. All recorded rainfalls in July were over 200mm, such as at Chiang Sean (244.3mm), at Luang Prabang (245.6mm), at Chiang Khan (248.3mm), at Vientiane (367.7mm) and at Nong Khai (639.7mm). Therefore, the water level rising occurred at all stations from Chiang Saen to Vientiane/ Nong Khai. It should be noted that flood amplitudes for the stations Luang Prabang, Chiang Khan, Vientiane and Nong Khai were over 3.5m (Annex A, Part 3, Table A2). Figure 1‐13 shows rapidly rising of water levels at stations Luang Prabang, Chiang Khan and Pak Beng during 19th – 27th June.

6

8

10

12

14

16

19-Jun 20-Jun 21-Jun 22-Jun 23-Jun 24-Jun 25-Jun 26-Jun 27-Jun

Time (day)

H (m

)

0

50

100

150

200

250

300

350

400

R (m

m)

R_Luang PrabangR_Pak BengR_Chiang KhanH_Luang PrabangH_Pak BengH_Chiang Khan

Δ HPak Beng = 4.6 m

Δ HLuang Prabang = 2.84 m

Δ HChiang khan = 3.75 m

Figure 1‐13 Rapidly rising of water levels at stations: Luang Prabang, Chiang Khan and Pak Beng

during 19th – 27th June. Continuous occurrences of south west monsoons as well as ITCZ across upper Lao PDR, Northern Thailand, Viet Nam and Myanmar from mid‐July to September resulted in intensive rainfalls in Eastern part of Thailand, upper part of Lao PDR, middle part of Viet Nam and the middle of the LMB. The amount of rainfall in this region was recorded from the 15th to the 30th September at Chiang Saen (218mm), at Luang Prabang (161.5mm),; at Chiang Khan (105.7mm), at Vientiane (211.7mm) and at Nong Khai (311.3mm). A flood event occurred at those stations with flood amplitudes over 2 meters (Annex A, Part 3, Table A2). It was to note that from the 23rd August, 21st to 25th September, water level at Nong Khai was recorded above the respective alarm level of 11.4m.

For stations from Paksane to Pakse

During the 2011 flood season, water level of all stations started above the long‐term average (LTA) then quickly rose up above LTA in end of June and beginning of July by influences of Tropical Storm‐HAIMA and NOKTEN, then continue rising above LTA till October by influence of South west monsoons and ITCZs. There were two flood events with amplitudes over 4 meters which occurred at those stations (see more detail in Annex A, Part 3, Table A3).

During June to July there were two tropical storms (HAIMA and NOKTEN), moderate to heavy rainfall occurred in this region. All recorded rainfalls in July were about or over 300mm, such as at Paksane (791.9mm), at Nakhon Phnom (747.4mm), at Thakhek (772mm), at Mukdahan (445.5mm), at Savannakhet (422.6mm), at Khong Chiam (364.2mm)


Page 12

and at Pakse (277.8mm). It should be noted that flood amplitudes for all stations were over 4.5m (Annex A, Part 3, Table A3). Figure 1‐14 shows rapidly rising of water levels at stations Paksane, Nakon Phanon and Thakhet during 19th – 27th June.

4

6

8

10

12

19-Jun 20-Jun 21-Jun 22-Jun 23-Jun 24-Jun 25-Jun 26-Jun 27-Jun

Time (day)

H (m

)

0

50

100

150

200

250

300

350

400

R (m

m)

R_PaksaneR_ThakhetR_Nakon PhanonH_PaksaneH_ThakhetH_Nakon Phanon

Δ HPaksane= 3.87 m

Δ HNakon Phanon = 3.34 m

Δ HThakhet = 3.48 m

Figure 1‐14 Rapidly rising of water levels at stations: Paksane, Nakon Phanon and Thakhet

during 19th – 27th June.

Continuous occurrences of south west monsoons as well as ITCZ across upper Lao PDR, Northern Thailand, Viet Nam and Myanmar from mid‐July to September resulted in intensive rainfalls in Eastern part of Thailand, upper part of Lao PDR, middle part of Viet Nam and the middle of the LMB. The amount of rainfall in this region was recorded from the 15th to the 30th September at Paksane (282.5mm), at Nakhon Phnom (258.1mm), at Thakhek (241.3mm), at Mukdahan (50mm), at Savannakhet (72.1mm), at Khong Chiam (281.5mm) and Pakse (288.9mm). A flood event occurred at those stations with flood amplitudes about or over 2 meters (Annex A, Part 3, Table A3).

It was to note that water levels at Thakhet was above alarm level of 13m during 4th to 7th August, 10th to 13th August and 20th to 21st September; Mukdahan was above flood level of 12.6m during 20th to 21st September and 9th to 14th August; and Pakse was above flood level of 12m during 19th to 24th September and 8th to 19th August.

For stations from Stung Treng to Kompong Cham

During the 2011 flood season, water level of all stations started above the long‐term average (LTA) then quickly rose up above LTA in end of June and beginning of July by influences of Tropical Storm‐HAIMA and NOKTEN, then continue rising above LTA till October by influence of South west monsoons and ITCZs. There was one flood event with amplitudes over 2 meters at Stung Treng, and over 3.5 meters at Kratie and Kompong Cham (see more detail in Annex A, Part 3, Table A4).

During June to July there were two tropical storms (HAIMA and NOKTEN), moderate to heavy rainfall occurred in this region. All recorded rainfalls in July were over 200mm, such as at Stung Treng (260.1mm), at Kratie (271.7mm) and at Kompong Cham (245.7mm). It


Page 13

should be noted that flood amplitudes for all stations were over 2m (Annex A, Part 3, Table A4).

Continuous occurrences of south west monsoons as well as ITCZ across upper Lao PDR, Northern Thailand, Viet Nam and Myanmar from mid‐July to September resulted in intensive rainfalls in Eastern part of Thailand, upper part of Lao PDR, middle part of Viet Nam and the middle of the LMB. The amount of rainfall in this region was recorded from the 15th to the 30th September at Stung Treng (285.5mm), at Kratie (235.4mm) and at Kompong Cham (139.6mm). A flood event occurred at Stung Treng and Kratie with flood amplitudes over 1.5 meters (Annex A, Part 3, Table A4).

It was to note that water levels at Stung Treng, Kratie and Kompong Cham were above alarm level during 22nd to 25th September, 22nd to 27th September and 20th September to 1st October, respectively (see Table 1‐1 for more details on Day/Month of Peak).

For stations from Phnom Penh to Koh Khel/Neak Luong

During the 2011 flood season, water level of all stations started above the long‐term average (LTA) then quickly rose up above LTA in end of June and beginning of July by influences of Tropical Storm‐HAIMA and NOKTEN, then continue rising above LTA till October by influence of South west monsoons and ITCZs. There was one flood event with amplitudes over 2 meters at Bassac Chaktomuk, Phnom Penh Port and Prek Kdam (see more detail in Annex A, Part 3, Table A5).

During June to July there were two tropical storms (HAIMA and NOKTEN) that had less affected in this region. All recorded rainfalls in July were less than 200mm, such as at Bassac Chaktomuk (152mm), at Koh Khel (160.5mm), at Neak Luong (107.5mm) and at Prek Kdam (152.6mm). As a result of flood water from the upper and middle reaches of the LMB, water levels of stations at downstream rose steadily with average intensity of 0.10 ‐ 0.20m/day except at Bassac Chaktomuk, Phnom Penh Port and Prek Kdam where flood amplitudes for were over 2 meter had occurred (Annex A, Part 3, Table A5).

Continuous occurrences of south west monsoons as well as ITCZ across upper Lao PDR, Northern Thailand, Viet Nam and Myanmar from mid‐July to September resulted in small rainfall in this region which were recorded from the 15th to the 30th September at Bassac Chaktomuk (94.2mm), at Koh Khel (104.4mm), at Neak Luong (126mm) and at Prek Kdam (179.1mm). A flood event occurred at Neak Luong and at Prek Kdam stations with flood amplitudes over 1 meter (Annex A, Part 3, Table A5).

It was to note that water levels at Bassac Chaktomuk, Phnom Penh Port and Koh Khel were above alarm level during 24th September to 24th October, 23rd September to 25th October and 12th September to 30th October, respectively; while water levels at Neak Luong and Prek Kdam were above flood level during 27th to 30th September and 2nd to 26th October, respectively (see Table 1‐1 for more details on Day/Month of the flood peak).

Tan Chau and Chau Doc

During the flood season 2011, the two stations recorded water levels that remained about the LTA, even though water levels at these stations are affected by tidal regime. This was one of the main reasons why during the beginning of June to the end of July water levels at these two stations showed rising and falling trends with high fluctuation amplitudes. From


Page 14

August to September, as a result of flood water from the upper and middle reaches of the LMB, water levels of these stations rose steadily with average intensity of 0.10 ‐ 0.15m/day levels (see more detail in Annex A, Part 3, Table A6).

It was to note that from the 21st September to 1st November 2011 and 19th September to 1st November 2011 water levels at Tan Chau and Chau Doc were recorded above the flood levels of 4.2 and 3.5 meters, respectively.


Page 15

2 Flood Forecast in 2011

2.1 Data collection for models and flood forecast bulletin dissemination

Daily data collection consisted of hydrological and meteorological data (observed water level and rainfall) by HydMet from Line Agencies, Satellite Rainfall Estimate (SRE) and Numerical Weather Prediction (NWP) obtained from NOAA which served as inputs for the Mekong Flood Forecasting System (FFS). The performance indicators are shown in the Tables and graphs of the forecast achievement, Annex B (Table B3, Figure B2 to Figure B4).

The results of the evaluation show that the data from most of LAs normally arrived before 9 AM (Annex B, Table B3 and Figure B2). The manual data collected by HydMet was checked by LAs; hence, the quality of data is in general terms fairly good. However, there are a number of unavoidable problems in data transmission such as the late transfer of data, errors and especially missing data during five months of this flood season (see more detail in Table B3 and graphs in Performance, Annex B).

Satellite Rainfall Estimation and Numerical Weather Prediction inputs for the URBS/FEWS, were the most important factors to determine forecast results. Following the investigations and comments of the forecaster‐in‐charge in the weekly reports throughout the 2011 flood season, it is found that the high variability in both SRE and NWP was one of the main reasons which lead to large errors of forecast results, especially when the weather patterns caused heavy rain as tropical storms, south west monsoon and ITCZ.

Performance indicators of bulletin delivery (Annex B, Table B3 and Figure B4) shows that the flood bulletins containing flood situation information were disseminated timely to the registered national Line Agencies, MRC website, and other interested users around 10h30 AM, which is a prescribed time in the Operational Manual. It can be seen that the time of flood forecasting bulletin delivery in July to October of the flood season was a bit later than 10h30. This was due to two main factors:

• The late transfer and incomplete of data from LA’s usually occurred during flood season.

• The low water level together with significant tidal effect in the downstream of the LMB, which resulted in difficulties for forecaster‐in‐charge in analysing and adjusting forecast results and which consequently lead to the late bulletin dissemination.

During the 2011 flood season, the data of several stations was sometimes not updated by national Line Agency for 2 to 3 continuing days, and in case data were missing over 2‐3 days it was not possible to provide a forecast at those stations. Figure B5 in Annex B shows that during the 2011 flood season (in June) there was one station without forecasts.

2.2 Accuracy and limitations in forecasting

During the 2011 flood season, the degree of accuracy varies from station to station. The shorter the lead time, the more accurate of the forecast (see Annex B, Figure B1). The evaluation of forecast achievement is presented in Figure B1 by indicating the % of days


Page 16

“successful” against a respective benchmark presented in Figure B2 (which were narrower than those of the year 2010). In general, the forecast errors for all lead time at all stations along the Mekong River did not show large differences, except for Luang Prabang, Paksane to Pakse and Kratie which were strongly affected by tropical storms (HAIMA and NOKTEN) where accuracies for 3‐5 day forecast lead times were less than expect, if following the benchmarks of success. Based on the weekly flood situation reports, the large errors on 3‐5 day forecasts at these stations mainly occur during mid‐June to mid‐July when flood amplitudes of mentioned stations were greater than 4.0 meters (see Annex A, Table A2 to A4).

Forecast errors for 3‐5 day lead time were less than 0.90 meter for all stations in LMB, although the worse was at Luang Prabang times (Figure B1: Average flood forecast accuracy along the Mekong mainstream, Annex B). T

For the lower reach of Mekong River, it can be seen that the use of a regression model is quite promising. Stations downstream from Phnom Penh Bassac, show average errors for 1‐day and 2‐day forecasts smaller than 0.05m and 0.10m respectively, while average errors for 4‐day to 5‐day forecasts were smaller than 0.25m.

Based on investigations and forecasting experiences of the RFMMC, the main factors that influenced forecast accuracy can be summarized as below:

1. Internal model functionality in forecasting at tidal affected stations in downstream: The limitations in developing URBS models were mentioned and analysed by Terry Malone in the report “Sensitivity Analysis and Evaluation of the MRC Mekong Flood Forecasting Systems”, April 2009, in which the main factors, which influenced the results of model calibration can be found as rating curves, inventory of dams, reservoirs and operational regulations, future development of dams. At the same time the sparse gauge network was another reason leading to poor results for forecast at stations in the upstream of LMB. The forecast results at Luang Prabang were a specific illustration of this. The forecast performances by mean absolute error in using original forecast results from both regression and ISIS models were presented in Figure 2‐1 and Figure 2‐2 respectively. It was easily realized that the average error for 3‐day to 5‐day forecasts at Koh Khel, Neak Luong, Prek Kdam and Tan Chau were under 0.1 meter for Regression model as compared to ISIS model.

2. The high variability of satellite rainfall estimate (SRE) and Numerical Weather Prediction (MWP): SRE rainfall was used instead of observed rainfall, and the NWP model provided a 7‐day GFS rainfall forecast. Throughout the 2011 flood season, the output for the URBS model, as could be seen from the results of daily forecast, was really sensitive to both SRE and NWP. SRE could be either under‐ or overestimated if compared with the observed rainfall. NWP could provide high variable rainfall forecast leading to high variation of forecast results, especially at stations in the upper and middle reaches when critical weather patterns such as tropical storms occurred. Based on weekly investigation of the forecasting team, the original forecast results calculated from the model caused relatively large errors as compared to observations. This was a practical difficulty for forecaster‐in‐charge in forecast adjustment.


Page 17

Figure 2‐1 Forecast performance based on original results by URBS and Regression.

Figure 2‐2 Forecast performance based on original results by URBS and ISIS.

3. The quality and accuracy of forecast is also determined by the quality of forecast adjustment, which was usually performed by forecaster‐in‐charge so their knowledge, expertise and experiences were also the prominent determinant of the final forecast result.

2.3 Lesson learned and actions to be taken

The following lessons have been drawn from the 2011 flood season, which can serve as the main factors that need to be taken into account by the flood forecasting team of the RFMMC in improving the forecast results:


Page 18

1. The availability and quality of both hydrological and meteorological (rainfall) data as inputs for models are always the highest priority because these are the deciding factors for forecast results and accuracy. A Senior International Satellite Precipitation Expert was engaged by the RFMMC in 2010 to develop a tool of bias correction of SRE to produce corrected SRE‐rainfall. The product depends very much on observed rainfalls provided from LAs which contained lot of missing data (see Annex B, Table B3 and Figure B3). Correct SRE can provide better results if less missing data.

2. The data from stations in the upstream of the Mekong River system in China is very important for analysing and forecasting in the LMB, not only during the flood season but also during the dry season. Hydrological and meteorological data from stations belonging to China need as much and as often as possible to be shared during dry season of 2011‐2012.

3. Strengthening the relationship and cooperation with Line Agencies in exchanging and collecting observed water level and rainfall data at stations on the Mekong mainstream in order to collect daily data on time and to minimize the missing and incorrect data.

4. Improving model calibration by updating the rating curves and other parameters at stations in the MRC’s member countries to be supported by LAs.

5. The forecaster‐in‐charge needs to have more understanding of sub‐basin characteristics, flow regime of left bank tributaries in the middle part of the LMB where frequently intensive rainfall and flooding occurs as well as more understanding of influences of tidal regime to the downstream of the LMB.

Aside from above‐mentioned lessons in order to improve the accuracy of flood forecasting for next flood season 2012, a number of additional actions need to be undertaken as follows:

6. Performance of the ISIS model in the Cambodian Floodplain and the Mekong Delta should be compared with that of the Regression Model during the 2011 flood season. It is found that the discharges generated in ISIS are not consistent with the observed water levels. It is recommended to replace the old version in the MRC Mekong Flood Forecast System with the latest version of ISIS.

7. Continue to efficiently use water level and rainfall of the existing two stations: Jinhong and Manan of China. Analyse the impact of water release from dams to the water levels at Jinhong and to water level changes at stations in the upper part, such as at Chiang Saen and Luang Prabang, especially during transitional period between dry and wet season.

8. Watch closely situations of the sudden increasing water levels of left bank tributaries in the middle part of the LMB, such as Ban Mixay and Muong Ngoy, Moung Mai, Moung Kao, Ban Phone Si, Se Kong River at Vuen Khen, Se Bang Fai River at Mahaxai, when the weather patterns would inflict intensive rainfall such as Typhoon or Tropical Depression occurrences in South China Sea, the creations of low pressure trough line and Inter Tropical Convergence Zone (ITCZ) and sometimes the critical activity of South West monsoon.

9. Through the 2011 flood season, forecast results of water levels at stations in downstream of the LMB by using Regression model were evaluated as fairly good, however the error for 3‐day and 4‐day forecasts at hydrological stations affected by tidal at Tan Chau and Chau Doc were high although forecaster had referred to the


Page 19

reference of tidal regime forecast documentation in 2011 provided by National Centre for Hydro‐meteorology of Viet Nam. Therefore, availability of such a document in 2012 will be useful in improving the accuracy at those stations.

10. Learn more about the weather products of rainfall forecast published on the websites of the World Meteorological Organization and their practical applications.

11. Study the possibility of having 2nd run of daily flood forecast and medium‐term forecast (6‐10 days) – data availability and other requirements of the system by having further evaluation of the system’s performance by using historically similar rainfall patterns.

For more details see the following Annex:

Annex A;

- Graphs and Tables for monthly observed rainfall distribution during flood season 2011

- Graphs for monthly rainfall in flood season from 2000 to 2011 and long‐term average along the Mekong River

- Tables of flood event characteristics along the Mekong River during flood season 2011

Annex B:

- Graph for flood forecast accuracy along the Mekong mainstream

- Table of forecast achievement

- Tables and graphs for performance

Annex C:

- Seasonal Water Level Graphs


Page 21

Annex A Graphics and Tables 1. Graphs and Tables for monthly observed rainfall distribution during flood season

2011

Table A1 Monthly observed rainfall in flood season 2011.

Unit in m

m (*

) Observed d

ata for Jin

hong

from

15th Ju

ne to

15th Octo

ber

2011

Jinghong

Chiang Saen

Luang Prabang

Chiang Khan

Vientiane

Nong Khai

Paksane

Thakhek

Nakhon Phanom

Mukdahan

Savannakhet

Khong Chiam

Pakse

Stung Treng

Kratie

Kompong Cham

Phnom Penh Port

Bassac Chaktomuk

Neak Luong

Tan Chau

Chau Doc

June

46.0

111.5

215.3

223.7

123.5

151.3

203.8

173.8

139.2

135.2

92.9

139.8

110.7

135.6

335.7

185.5

106.4

68.8

21.8

18.4

July

158.7

148.8

320.8

313.8

218.9

255.7

326.7

313.8

280.6

276.4

251.2

301.5

246.9

228.4

515.7

337.6

199.8

134.9

55.3

41.0

Augu

st22

0.916

8.436

2.735

2.027

1.831

3.838

8.938

8.535

5.936

5.632

9.942

7.935

5.529

9.463

6.644

5.027

8.519

8.910

1.478

.3

Sept

ebe r

187.0

160.9

363.8

351.3

275.5

314.8

372.5

351.1

321.1

318.9

284.8

399.9

333.4

296.4

634.3

447.5

299.3

218.8

122.8

104.8

Octo

ber

0.011

7.126

7.127

2.118

5.721

7.728

5.027

7.824

3.224

2.522

0.132

6.526

8.625

9.059

7.543

8.032

8.324

0.914

4.612

9.5

Seas

on61

2.670

6.71,5

29.6

1,513

.01,0

75.4

1,253

.21,5

76.9

1,504

.91,3

39.9

1,338

.51,1

78.9

1,595

.51,3

15.0

1,218

.82,7

19.8

1,853

.61,2

12.3

862.3

446.0

372.0

No Data


Page 22

Figure A1 Monthly rainfall distribution for Jinghong, Chiang Saen, Luang Prabang and Chiang

Khan.

Jin

ghon

g

58.0

360.

0

182.

8

124.

0

23.0

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.

Monthly Rainfall (mm)Ch

iang

Saen

243.

8

311.

4

449.

7

293.

1

78.5

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.

Monthly Rainfall (mm)

Luan

g Pr

aban

g

154.

4

278.

4

401.

6

145.

6

55.0

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.


Chian

g Kh

an

97.2

289.

5

455.

043

0.7

213.

9

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.



Page 23

Figure A2 Monthly rainfall distribution for Chiang Khan, Vientiane, Nongkhai, Paksane and Nakon Phanom.

Vi

entia

ne

262.

519

8.2

669.

7

199.

9

71.6

0

200

400

600

800

1000

June

July

Aug.

Sep.

Oct.


Nong

khai

201.

421

3.5

659.

0

302.

1

45.4

0

200

400

600

800

1000

June

July

Aug.

Sep.

Oct.


Paks

ane

573.

561

9.2

736.

8

613.

9

125.

7

0

200

400

600

800

1000

June

July

Aug.

Sep.

Oct.


Nakh

on P

hano

m

175.

1

411.

2

513.

0

219.

518

9.7

0

200

400

600

800

1000

June

July

Aug.

Sep.

Oct.



Page 24

Figure A3 Monthly rainfall distribution for Thakhek, Mukdahan, Savannakhet and Khong Chiam.

`Th

akhe

k

167.5

386.3

524.0

230.2

202.9

0

200

400

600

800

1000

June

July

Aug.

Sep.

Oct.


Mukd

ahan

197.9

113.5

641.9

209.8

215.7

0

200

400

600

800

1000

June

July

Aug.

Sep.

Oct.


Sava

nnak

het

215.6

158.0

507.9

166.7

194.6

0

200

400

600

800

1000

June

July

Aug.

Sep.

Oct.


Khon

g Ch

iam

211.6

229.6

380.2

222.6

179.6

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.



Page 25

Figure A4 Monthly rainfall distribution for, Pakse, Stung Treng , Kratie and Kompong Chiam.

Pa

kse

164.

718

2.8

458.

2

209.

7

167.

4

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.


Stun

g Tr

eng

99.2

173.

4

233.

4

121.

8

250.

4

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.


Krat

ie

167.

418

5.2

323.

9

214.

023

0.2

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.


Kom

pong

Cha

m

316.

2

159.

3

236.

5

137.

5

288.

5

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.



Page 26

Figure A5 Monthly rainfall distribution for Phnom Penh (Bassac and Port), Koh Khel and Neak Luong.

Ph

nom

Pen

h (B

assa

c)

172.

1

246.

327

8.7

165.

6

443.

8

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.

Monthly Rainfall (mm)Ph

nom

Pen

h Po

rt

0

500

June

July

Aug.

Sep.

Oct.


No m

easu

rem

ent

Koh

Khel

191.

110

9.1

135.

518

3.9

552.

5

0

200

400

600

800

1000

June

July

Aug.

Sep.

Oct.


Neak

Luo

ng

98.2

163.

9

230.

122

9.0

357.

8

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.



Page 27

Figure A6 Monthly rainfall distribution for Prek Kdam, Tan Chau and Chau Doc.

Prek

Kda

m

176.

7

73.1

173.

7

122.

5

425.

6

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.


Tan

Cha

u

174.

7

113.

2

178.

0

269.

8

332.

8

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.


Cha

u D

oc

103.

012

5.9

88.6

150.

616

3.5

0

100

200

300

400

500

June

July

Aug.

Sep.

Oct.



Page 28

2. Graphs for monthly rainfall in flood season from 2000 to 2011 and long‐term average along the Mekong River

Chia

ng S

aen

318.

2

100.

213

9.3

128.

718

9.9

262.

4

118.

022

6.7 2

07.0

110.

5

243.

8

111.

517

8.1

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(mm

)Lu

angP

raba

ng

269.

1 155.

815

5.6

315.

420

8.423

7.6

78.1

185.

018

8.0

73.3

154.

421

5.3

182.

6

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(mm

)Ch

iang

kha

n

210.

5

62.5

73.8

275.

419

8.6

263.

5

29.0

186.

089

.013

3.4

97.2

223.

716

8.1

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(mm

)

Vien

tiane

346.

6

177.

528

8.338

4.8

286.

9338.

0

151.

3

297.

0459.

0

110.

3

262.

5

123.

5

269.

5

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(mm

)

Thak

het

482.

5672.

9

887.

8 336.

231

9.2

556.

3 258.

6522.

0698.

0

238.

216

7.5

173.

8

432.

9

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(mm

)Na

kon

Phan

om

373.

0409.

0

754.

0

180.

722

6.133

5.0

303.

0638.

0

134.

017

5.1

139.

2

333.

4

No

Dat

a0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(mm

)M

ukda

han

227.

7387.

830

1.8

152.

211

9.9

204.

111

4.0

117.

0

272.

020

6.0

197.

913

5.2

213.

1

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(mm

)

Nong

Kha

i

287.

319

4.5

265.

737

4.1 26

8.8

361.

8

92.3

268.

9307.

426

6.7

201.

415

1.3

255.

2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(mm

)Pa

kSan

e

1075

.7

714.

582

1.4

699.

9 288.

61086

.6

514.

858

4.711

99.3

367.

4573.

5 203.

8

683.

7

0

500

1000

1500

2000

2500

3000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(mm

)

Figure A7 Monthly rainfall in June for main stations along the Mekong River.


Page 29

Sava

nnak

het

200.

1447.

5 270.

215

8.1

128.

118

0.2

121.

7

292.

0323.

0

158.

321

5.6

92.9

224.

5

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Paks

e

286.

9475.

8

605.

3 240.

2443.

7

212.

1 205

.690

.319

7.0

348.

1 164.

711

0.7

269.

9

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Stru

ng T

reng

449.

1 251.

826

9.8

43.0

305.

821

8.6

90.0

33.2

125.

047

.899

.213

5.6

172.

4

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Krat

ie

225.

8

356.

2 348

.4

77.0

112.

372

.696

.015

0.2

167.

4

335.

7

194.

2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

D

ata

No

D

ata

Khon

g Ch

iam

339.

831

3.0

289.

729

4.236

2.5

333.

123

5.1 19

6.9

211.

613

9.8

262.

2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No D

ata

Phno

mPe

nh B

assa

c

125.

010

3.0

37.4

174.

0

28.0

80.0

279.

6

74.0

129.

917

2.1

106.

411

9.0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

D

ata

Neak

Luo

ng

187.

011

9.7

55.0

128.

719

3.0

122.

015

8.0

209.

8

82.9

98.2

68.8

129.

4

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

D

ata

Tan

Chau

99.1

39.5

45.3

110.

213

7.0

133.

226

.312

0.7

6.4

174.

7

21.8

83.1

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

D

ata

Chau

Doc

68.2

91.9

92.4

117.

618

9.3

117.

111

2.7

24.9

14.4

103.

018

.494

.1

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

D

ata

Figure A7 (cont.)


Page 30

Chia

ng S

aen

242.

9305.

636

8.9 30

9.8

183.

7

364.

031

1.0

161.

9

308.

030

8.8

311.

4

148.

8

299.

5

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Luan

gPra

bang

274.

4

393.

1 384

.4

195.

528

6.9

196.

330

6.9

140.

220

0.2

241.

427

8.4

320.

826

1.4

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Chia

ng k

han

110.

312

3.4

95.0

215.

223

4.8

103.

311

6.0

58.2

84.0

93.6

289.

531

3.8

146.

3

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Vien

tiane

211.

331

4.2

276.

6

130.

1350.

423

7.143

9.9

108.

1366.

0 230.

319

8.2

218.

926

0.4

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Thak

het

570.

0 549

.0

729.

4

319.

429

1.0

736.

4747

.6

417.

3

583.

050

9.4 38

6.3

313.

8

490.

0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Nako

n Ph

anom

542.

0 482.

0

766.

0 242.

0 235

.0

506.

0

233.

7585.

056

9.2

411.

2

280.

6

467.

4

756.

0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Muk

daha

n

225.

932

5.143

9.2 20

8.858

3.7

519.

340

5.0

128.

722

3.0

159.

811

3.5

276.

428

3.8

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Nong

Kha

i

214.

630

1.8

244.

624

4.6

198.

224

0.12

53.5

150.

225

0.12

57.6

213.

525

5.7 22

9.8

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

PakS

ane

633.

471

8.2

780.

271

5.8

677.

973

7.811

02.4

691.

7

1112

.310

26.4

619.

232

6.7

711.

8

0

500

1000

1500

2000

2500

3000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Figure A8 Monthly rainfall in July for main stations along the Mekong River.


Page 31

Sava

nnak

het

204.

627

1.5

481.

9

155.

6

491.

359

5.4 37

2.9

219.

121

1.0

156.

115

8.0

251.

228

1.3

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Paks

e

728.

7 352.

4623.

8 222.

7398.

7408

.4

846.

3

399.

9

113.

0

468.

8

182.

824

6.939

6.2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Stru

ng T

reng

269.

0304.

827

3.72

94.0

175.

323

6.5

517.

9

68.1

111.

014

9.1

173.

422

8.4

233.

4

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(m

m)

Krat

ie

200.

010

3.6

208.

314

7.5

375.

0

54.4

182.

514

2.0

371.

6

185.

2

515.

7

226.

0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

D

ata

Khon

g Ch

iam

336.

430

1.8

558.

9

185.

6

454.

1 358.

628

3.350

4.2

229.

630

1.5

341.

1

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No D

ata

Phno

mPe

nh B

assa

c

125.

013

.032

.0

244.

014

2.0

251.

020

7.0

231.

312

6.0

71.0

246.

319

9.8

157.

4

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Neak

Luo

ng

96.0

97.0

240.

022

1.3

178.

212

6.0

158.

177

.588

.816

3.9

134.

914

3.8

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(m

m)

No

D

ata

Tan

Chau

46.4

71.1

366.

9

27.0

215.

173

.541

.210

.6

180.

0 113.

255

.310

9.1

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

D

ata

Chau

Doc

109.

398

.167

.0

239.

1

61.0

240.

2

112.

735

.076

.715

5.5

125.

941

.012

7.2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Figure A8 (cont.)


Page 32

Chia

ng S

aen

268.

5

416.

545

5.3

217.

0

374.

9

226.

7580.

0

310.

334

0.0

383.

8449.

7

168.

4

362.

9

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Luan

gPra

bang

233.

9395.

7

258.

931

3.6

233.

032

2.4 26

6.333

7.5 22

5.0

414.

040

1.6

362.

731

0.0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Chia

ng k

han

145.

7

521.

1 343.

8

119.

416

6.4

77.6

284.

021

5.4

113.

013

0.5

455.

0 352.

0 239.

6

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Vien

tiane

245.

8340.

541

1.2

235.

828

8.141

7.4

300.

937

2.23

68.0

309.

7

669.

7

271.

835

5.7

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Thak

het

492.

461

3.8

481.

6

720.

481

6.4

931.

1 757.

6 623.

651

0.0

374.

1524.

0 388.

5

572.

8

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Nako

n Ph

anom

518.

047

2.0

523.

0

156.

0

759.

0

601.

0

377.

8558.

062

9.0

513.

0

355.

9

511.

2

672.

0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Muk

daha

n

205.

8

414.

941

8.7

279.

6309.

330

5.239

3.0 27

4.7

153.

015

0.2

641.

9

365.

631

7.5

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Nong

Kha

i

314.

1

476.

3484

.5

158.

725

3.130

8.9

192.

128

3.92

94.3

267.

7659.

0

313.

832

8.7

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

PakS

ane

669.

2695

.4

826.

977

1.8

671.

3

856.

1 666.

0 507.

0 367.

526

8.673

6.8 38

8.9

605.

9

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Figure A9 Monthly rainfall in August for main stations along the Mekong River.


Page 33

Sava

nnak

het

284.

3389.

3447.

7 333.

732

3.5 28

5.92

89.8

341.

3

129.

010

2.3

507.

9 329.

9 306

.5

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Paks

e

507.

8

665.

1 384.

8480.

258

3.7 40

4.0

250.

6 240

.6

704.

0

291.

6

458.

2 355.

544

2.5

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Stru

ng T

reng

360.

9454.

6

219.

822

4.043

7.0

336.

0 283.

9389.

2 328.

0

120.

523

3.429

9.4

307.

2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Krat

ie

328.

0 262.

826

6.2

229.

118

0.0

253.

5407.

932

6.0

189.

5

323.

9636.

6

309.

4

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Khon

g Ch

iam

389.

5843.

0 303.

8

512.

945

7.6 42

2.0

383.

1 317.

338

0.242

7.94

36.2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Phno

mPe

nh B

assa

c

84.0

134.

016

3.0

167.

021

1.0

206.

0239.

0278.

8

125.

069

.8

278.

7278

.518

6.2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Neak

Luo

ng

310.

0 134.

0 114

.010

2.8

69.0

143.

7198.

8208

.194

.823

0.1 1

98.9

164.

0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Tan

Chau

203.

012

6.7

131.

610

3.6

93.2

155.

375

.414

2.9

162.

217

8.0

101.

413

3.9

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Chau

Doc

307.

421

0.3

126.

118

1.1

86.4

121.

823

4.7

56.7

251.

216

3.3

88.6

78.3

159.

7

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Figure A9 (cont.)


Page 34

Chia

ng S

aen

177.

027

2.1 20

6.62

23.6

269.

1321.

831

4.0

496.

3 275.

017

7.4

293.

1 160.

927

1.0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Luan

gPra

bang

234.

4246

.216

1.4

222.

615

2.2

183.

316

4.1

179.

094

.012

2.8

145.

6

363.

8

182.

2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Chia

ng k

han

106.

622

0.9

507.

5 308.

6 277.

329

0.8

132.

017

3.0

233.

032

2.043

0.7

351.

327

2.5

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Vien

tiane

247.

9277.

027

9.22

97.2

237.

6372.

0

137.

025

7.028

5.0

169.

919

9.9

275.

524

7.8

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Thak

het

451.

7

207.

228

9.847

4.6 4

57.0

406.

1

70.2

214.

0

480.

0

221.

323

0.2

351.

132

4.3

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Nako

n Ph

anom

495.

0

256.

1 209.

0233

.0

390.

0 324.

6

109.

0

348.

0

214.

521

9.5

321.

126

3.9

47.0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Muk

daha

n

265.

2329.

228

9.0

341.

4

208.

532

3.2

68.0

234.

0265.

0

97.7

209.

831

8.9

244.

1

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Nong

Kha

i

263.

2299.

338

2.552

8.7

187.

6

491.

4

82.6

260.

5270

.624

3.3

302.

1314

.829

0.7

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

PakS

ane

688.

3 295.

2

457.

5573.

6 569

.2

376.

4

221.

1533.

6 284.

630

7.9

613.

9

372.

542

8.9

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Figure A10 Monthly rainfall in September for main stations along the Mekong River.


Page 35

Sava

nnak

het

267.

031

5.2

225.

1272.

9 207.

0332.

5

130.

819

1.0

246.

013

2.1

166.

728

4.8 22

9.5

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Paks

e

232.

5

374.

1 235.

2498.

7 245.

425

0.6 2

40.6

168.

028

3.0

388.

4 209.

7333.

429

7.6

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Stru

ng T

reng

281.

524

7.12

57.5

334.

5

204.

4320.

9327

.923

2.028

4.03

08.8

121.

8

296.

426

8.1

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Krat

ie

182.

0 160

.2

402.

0 270.

931

9.0 14

0.624

1.032

6.044

2.6 21

4.063

4.3 30

3.0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Khon

g Ch

iam

203.

5556.

5

410.

9

611.

3

262.

0

419.

641

3.4

491.

6

222.

6

399.

9 394

.7

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Phno

mPe

nh B

assa

c

73.0

230.

617

0.0

86.7

256.

3 244

.029

8.033

9.0

367.

4

165.

6

299.

323

0.0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Neak

Luo

ng

185.

015

7.0

145.

023

8.8

236.

516

2.0

113.

0

240.

214

0.3

229.

021

8.8

187.

8

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Tan

Chau

136.

317

5.7

132.

321

7.0

203.

4304.

5

90.8

294.

0

128.

8

269.

8

122.

818

8.7

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Chau

Doc

156.

313

1.6

86.7

93.9

236.

320

9.2

144.

874

.2

364.

3

97.0

150.

610

4.8

149.

1

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Figure A10 (cont.)


Page 36

Chia

ng S

aen

60.1

198.

110

6.0

10.8

114.

312

7.4

139.

015

0.0

205.

0

80.5

78.5

117.

111

9.5

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Luan

gPra

bang

116.

019

2.3

71.0

35.0

165.

5

18.6

122.

510

7.0

83.0

49.8

55.0

267.

1

102.

3

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Chia

ng k

han

61.0

155.

4

30.6

4.5

2.2

10.8

237.

020

6.0

129.

077

.9

213.

927

2.1

116.

2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Vien

tiane

59.0

80.9

133.

641

.628

.9

312.

2

138.

012

2.0

84.4

71.6

185.

710

8.6

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Thak

het

59.7

27.9

10.0

13.8

5.0

52.8

232.

5328.

0

82.0

55.4

202.

9277.

8

111.

7

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Nako

n Ph

anom

83.0

4.0

17.7

202.

0

71.0

54.0

189.

724

3.2

121.

322

7.0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Muk

daha

n

40.4

70.5

61.9

14.0

29.5

168.

027

2.0

102.

094

.1

215.

724

2.5

111.

5

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Nong

Kha

i

63.2

98.2

74.4

36.0

0.0

49.5

157.

114

5.6

146.

491

.945

.4

217.

7

88.0

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

PakS

ane

71.9

127.

155

.016

.80.

07.

812

2.3

191.

915

5.4

48.9

125.

7

285.

0

103.

3

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Figure A11 Monthly rainfall in October for main stations along the Mekong River.


Page 37

Sava

nnak

het

28.5

85.9

27.4

5.2

20.2

157.

5

336.

0

97.0

78.2

194.

622

0.1

105.

9

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Ye

ar

X(m

m)

Paks

e

165.

815

7.6

176.

751

.20.

318

.2

257.

528

9.0

85.0

77.3

167.

426

8.6

135.

8

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Stru

ng T

reng

150.

015

3.2

57.9

130.

364

.8

194.

418

0.8

198.

014

0.8

250.

425

9.0

161.

8

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Krat

ie

309.

0432.

4

133.

369

.937

.691

.0

420.

6 236.

015

3.0

155.

222

5.659

7.5

238.

4

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Khon

g Ch

iam

139.

815

2.7

79.2

17.3

0.5

17.6

207.

0

33.1

179.

6

326.

5

110.

6

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Phno

mPe

nh B

assa

c

164.

0

354.

0 272.

038

5.1 18

3.0

151.

6

443.

6 328.

3 285.

2

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Neak

Luo

ng

345.

0

140.

015

8.0

177.

5

317.

0

172.

0

349.

9 309.

932

3.735

7.8 24

0.9

262.

9

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Tan

Chau

424.

0 292.

726

9.930

4.4

452.

3 233.

411

9.1

267.

021

4.7

332.

8

144.

6

277.

7

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

No

Dat

a

Chau

Doc

249.

9

457.

1

88.5

251.

6

375.

0 340.

9 239.

2

101.

7

295.

9

80.8

163.

512

9.5

231.

3

0

200

400

600

800

1000

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Mean Y

ear

X(m

m)

Figure A11 (cont.)


Page 38

3. Tables of flood event characteristics along the Mekong River during flood season 2011

Table A2 The characteristics of flood events for station from Chiang Saen to Vientiane/Nong

Khai.


Page 39

Table A3 The characteristics of flood events for stations from Paksane to Pakse.

Risin

gFl

ood

IDSt

atio

nTi

me

Ampl

itude

Inte

rval

of Im

axIm

axIav

erag

eCo

mm

ent

Date

Hb (m

)Da

teHp

(m)

Tp (d

ay)

(m)

(Dat

e) (m

/day

) (m

/day

)

0105

01Ch

iang

Saen

25-J

un3.4

529

-Jun

4.56

41.1

122

-Jun

- 23

-Jun

0.57

0.28

TS-H

AIM

A

15-J

ul4.0

622

-Jul

5.83

71.7

717

-Jul

- 18

-Jul

0.52

0.25

SW

0112

01Lu

ang

Prab

ang

24-J

un6.4

803

-Jul

11.28

94.8

025

-Jun

- 26

-Jun

1.72

0.53

TS-H

AIM

A

15-J

ul8.7

225

-Jul

13.62

104.9

024

-Jul

- 25

-Jul

0.76

0.49

SW

15-S

ep10

.6622

-Sep

15.25

74.5

916

-Sep

- 17

-Sep

1.26

0.66

SW, IT

CZ

0119

03Ch

iang

Khan

26-J

un6.9

928

-Jun

10.76

23.7

726

-Jun

- 27

-Jun

3.70

1.89

TS-H

AIM

A

15-J

ul8.8

226

-Jul

12.14

113.3

225

-Jul

- 26

-Jul

0.57

0.30

SW

17-S

ep11

.0423

-Sep

13.14

62.1

018

-Sep

- 19

-Sep

0.65

0.35

SW, IT

CZ

0119

01Vi

entia

ne26

-Jun

3.85

28-J

un7.5

92

3.74

27-J

un -

28-J

un3.2

71.8

7TS

-HAI

MA

15-J

ul5.6

326

-Jul

9.14

113.5

125

-Jul

- 26

-Jul

0.74

0.32

SW

17-S

ep8.7

223

-Sep

10.62

61.9

018

-Sep

- 19

-Sep

0.54

0.32

SW, IT

CZ

0120

01No

ng K

hai

24-J

un4.4

729

-Jun

8.88

54.4

127

-Jun

- 28

-Jun

3.40

0.88

TS-H

AIM

A

15-J

ul6.8

427

-Jul

10.30

123.4

625

-Jul

- 26

-Jul

0.54

0.29

SW

18-S

ep10

.2523

-Sep

11.88

51.6

319

-Sep

- 20

-Sep

0.53

0.33

SW, IT

CZ

Begi

nnin

g of

Flo

od E

ven

Peak

of f

lood

even

tIn

tens

ity o

f Flo

od R

ising


Page 40

Table A4 The characteristics of flood events for stations from Strung Treng to Kompong Cham.

Ris

ing

Flo

od

IDS

tati

on

Tim

eA

mp

litu

de

Inte

rval

of

Imax

Imax

Iave

rag

eC

om

men

t

Dat

eH

b (

m)

Dat

eH

p (

m)

Tp

(d

ay)

(m)

(Dat

e) (

m/d

ay)

(m

/day

)

0127

03P

aksa

ne

24-J

un

6.26

03-J

ul

12.0

09

5.74

25-J

un

- 2

6-Ju

n2.

670.

64T

S-H

AIM

A

15-J

ul

9.14

27-J

ul

11.4

412

2.30

16-J

ul -

17-

Jul

0.72

0.19

SW

30-J

ul

10.8

104

-Au

g13

.24

52.

4331

-Ju

l - 0

1-A

ug

1.24

0.49

TS

-NO

KT

EN

12-S

ep11

.52

22-S

ep13

.42

101.

9012

-Sep

- 1

3-S

ep0.

540.

19S

W, I

TC

Z

0131

01N

akh

on

Ph

ano

m20

-Ju

n4.

1204

-Ju

l10

.06

145.

9426

-Ju

n -

27-

Jun

1.76

0.42

TS

-HA

IMA

13-J

ul

7.29

18-J

ul

9.23

51.

9416

-Ju

l - 1

7-Ju

l0.

810.

39S

W

30-J

ul

9.32

04-A

ug

12.2

45

2.92

31-J

ul -

01-

Au

g1.

050.

58T

S-N

OK

TE

N

12-S

ep9.

7820

-Sep

11.9

58

2.17

13-S

ep -

14-

Sep

0.47

0.27

SW

, IT

CZ

0131

02T

hak

hek

20-J

un

5.23

04-J

ul

11.1

314

5.90

26-J

un

- 2

7-Ju

n1.

680.

42T

S-H

AIM

A

13-J

ul

8.43

18-J

ul

10.3

35

1.90

16-J

ul -

17-

Jul

0.84

0.38

SW

30-J

ul

10.3

904

-Au

g13

.29

52.

9031

-Ju

l - 0

1-A

ug

1.11

0.58

TS

-NO

KT

EN

13-S

ep10

.70

20-S

ep13

.00

72.

3013

-Sep

- 1

4-S

ep0.

680.

33S

W, I

TC

Z

0134

02M

ukd

ahan

21-J

un

4.07

04-J

ul

10.0

313

5.96

26-J

un

- 2

7-Ju

n1.

660.

46T

S-H

AIM

A

14-J

ul

7.06

18-J

ul

9.20

42.

1416

-Ju

l - 1

7-Ju

l0.

730.

54S

W

30-J

ul

9.15

05-A

ug

12.3

76

3.22

31-J

ul -

01-

Au

g1.

080.

54T

S-N

OK

TE

N

12-S

ep9.

7820

-Sep

11.9

58

2.17

15-S

ep -

16-

Sep

0.49

0.27

SW

, IT

CZ

0134

01S

avan

nak

het

21-J

un

2.40

04-J

ul

8.80

136.

4026

-Ju

n -

27-

Jun

1.80

0.49

TS

-HA

IMA

14-J

ul

6.24

18-J

ul

8.41

42.

1716

-Ju

l - 1

7-Ju

l0.

720.

54S

W

30-J

ul

8.38

05-A

ug

11.2

16

2.83

01-A

ug

- 0

2-A

ug

0.72

0.47

TS

-NO

KT

EN

11-S

ep8.

6621

-Sep

11.0

510

2.39

15-S

ep -

16-

Sep

0.61

0.24

SW

, IT

CZ

0138

01K

ho

ng

Ch

iam

21-J

un

4.57

04-J

ul

10.7

213

6.15

29-J

un

- 3

0-Ju

n1.

540.

47T

S-H

AIM

A

14-J

ul

7.55

20-J

ul

10.0

46

2.49

17-J

ul -

18-

Jul

0.76

0.42

SW

31-J

ul

10.4

111

-Au

g15

.72

115.

3101

-Au

g -

02-

Au

g0.

960.

48T

S-N

OK

TE

N

13-S

ep12

.31

21-S

ep15

.34

83.

0315

-Sep

- 1

6-S

ep0.

900.

38S

W, I

TC

Z

0139

01P

akse

24-J

un

3.91

04-J

ul

8.75

104.

8428

-Ju

n -

29-

Jun

1.70

0.48

TS

-HA

IMA

15-J

ul

6.13

19-J

ul

8.16

42.

0317

-Ju

l - 1

8-Ju

l0.

600.

51S

W

31-J

ul

8.74

11-A

ug

13.1

111

4.37

07-A

ug

- 0

8-A

ug

0.77

0.40

TS

-NO

KT

EN

14-S

ep10

.22

22-S

ep12

.72

82.

5015

-Sep

- 1

6-S

ep0.

710.

31S

W, I

TC

Z

Beg

inn

ing

of

Flo

od

Ev

enP

eak

of

flo

od

eve

nt

Inte

nsi

ty o

f F

loo

d R

isin

g


Page 41

Risin

gFl

ood

IDSt

atio

nTi

me

Ampl

itude

Inte

rval

of Im

axIm

axIav

erag

eCo

mm

ent

Date

Hb (m

)Da

teHp

(m)

Tp (d

ay)

(m)

(Dat

e) (m

/day

) (m

/day

)

0145

01St

ung

Tren

g18

-Jun

4.30

22-J

un5.6

74

1.37

19-J

un -

20-J

un0.5

50.3

4TS

-HAI

MA

29-J

un5.3

003

-Jul

7.40

42.1

030

-Jun

- 01

-Jul

0.88

0.53

SW

07-A

ug9.3

612

-Aug

10.87

51.5

107

-Aug

- 08

-Aug

0.64

0.30

TS-N

OKTE

N

07-S

ep8.6

111

-Sep

10.55

41.9

409

-Sep

- 10

-Sep

0.52

0.49

SW, IT

CZ

0149

01Kr

atie

19-J

un11

.1023

-Jun

13.64

42.5

419

-Jun

- 20

-Jun

0.85

0.64

TS-H

AIMA

29-J

un12

.4007

-Jul

17.00

84.6

030

-Jun

- 01

-Jul

1.42

0.58

SW

07-A

ug19

.6613

-Aug

21.79

62.1

308

-Aug

- 09

-Aug

0.63

0.36

TS-N

OKTE

N

08-S

ep19

.6312

-Sep

21.80

42.1

710

-Sep

- 11

-Sep

0.65

0.54

SW, IT

CZ

0198

02Ko

mpo

ng C

ham

19-J

un6.0

024

-Jun

8.32

52.3

220

-Jun

- 21

-Jun

0.80

0.46

TS-H

AIMA

30-J

un7.4

607

-Jul

11.26

73.8

001

-Jul

- 02

-Jul

1.28

0.54

SW

08-S

ep13

.8413

-Sep

15.19

51.3

510

-Sep

- 11

-Sep

0.37

0.27

SW, IT

CZ

Begi

nnin

g of

Flo

od E

ven

Peak

of f

lood

even

tIn

tens

ity o

f Flo

od R

ising


Page 42

Table A5 The characteristics of flood events for stations from Phnom Penh Bassac/Phnom Penh Port, Koh Khel/Neak Luong to Prek Kdam.

Risin

gFlo

od

IDSt

ation

Time

Ampli

tude

Inter

val o

f Imax

Imax

Iaver

age

Comm

ent

Date

Hb (m

)Da

teHp

(m)

Tp (d

ay)

(m)

(Date

) (m

/day)

(m/da

y)

0334

01Ba

ssac

Cha

ktomu

k20

-Jun

3.57

24-Ju

n4.6

94

1.12

21-Ju

n - 22

-Jun

0.34

0.28

TS-H

AIMA

30-Ju

n4.2

708

-Jul

6.59

82.3

202

-Jul -

03-Ju

l0.6

70.2

9SW

08-S

ep9.3

715

-Sep

9.95

70.5

812

-Sep

- 13-S

ep0.1

20.0

8SW

, ITCZ

0201

01Ph

nom

Penh

Por

t19

-Jun

2.63

24-Ju

n3.8

15

1.18

22-Ju

n - 23

-Jun

0.44

0.24

TS-H

AIMA

30-Ju

n3.3

008

-Jul

5.71

82.4

102

-Jul -

03-Ju

l0.6

80.3

0SW

09-S

ep8.5

916

-Sep

9.14

70.5

513

-Sep

- 14-S

ep0.1

10.0

8SW

, ITCZ

0334

02Ko

h Khe

l20

-Jun

3.29

24-Ju

n4.2

24

0.93

21-Ju

n - 22

-Jun

0.30

0.23

TS-H

AIMA

30-Ju

n3.8

808

-Jul

5.80

81.9

202

-Jul -

03-Ju

l0.5

80.2

4SW

09-S

ep7.2

517

-Sep

7.56

80.3

110

-Sep

- 11-S

ep0.0

50.0

4SW

, ITCZ

0198

06Ne

ak Lu

ong

20-Ju

n2.2

624

-Jun

3.02

40.7

621

-Jun -

22-Ju

n0.2

40.1

9TS

-HAI

MA

30-Ju

n2.6

608

-Jul

4.48

81.8

202

-Jul -

03-Ju

l0.5

30.2

3SW

09-S

ep6.7

928

-Sep

8.06

191.2

725

-Sep

- 26-S

ep0.1

30.0

7TS

-HAI

TANG

, TS-

NALG

AE

0201

02Pr

ek K

dam

19-Ju

n2.5

524

-Jun

3.67

51.1

221

-Jun -

22-Ju

n0.3

10.2

2TS

-HAI

MA

30-Ju

n3.3

308

-Jul

5.38

82.0

502

-Jul -

03-Ju

l0.5

80.2

6SW

09-S

ep8.5

129

-Sep

9.98

201.4

713

-Sep

- 14-S

ep0.1

30.0

7SW

, ITCZ

Begin

ning o

f Floo

d Eve

nPe

ak of

flood

even

tInt

ensit

y of F

lood R

ising


Page 43

Table A6 The characteristics of flood events for stations from Tan Chau and Chau Doc (**).

(**

) Wate

r leve

ls at

Tan C

hau a

nd C

hau D

oc ar

e infl

uenc

ed by

tidal

effec

t; the

WL i

n the

Table

A6 w

ere re

corde

d at 7

AM du

ring 2

011 f

lood s

easo

n.

Rising

Flood

IDSta

tion

Time

Ampli

tude

Interv

al of

Imax

Imax

Iavera

geCo

mmen

t

Date

Hb (m

)Da

teHp

(m)

Tp (d

ay)

(m)

(Date

) (m

/day)

(m/da

y)

0198

03Ta

n Cha

u08

-Jun

0.38

14-Ju

n1.0

86

0.70

12-Ju

n - 13

-Jun

0.24

0.12

Tidal

Influe

nce

01-Ju

l1.0

808

-Jul

1.82

70.7

402

-Jul -

03-Ju

l0.2

00.1

1SW

10-Se

p3.7

528

-Sep

4.75

181.0

024

-Sep -

25-Se

p0.1

10.0

6TS

-HAIT

ANG,

TS-N

ALGA

E

0398

01Ch

au Do

c08

-Jun

0.21

14-Ju

n1.1

06

0.89

12-Ju

n - 13

-Jun

0.34

0.15

Tidal

Influe

nce

02-Ju

l0.9

008

-Jul

1.30

60.4

004

-Jul -

05-Ju

l0.2

00.0

7SW

10-Ju

l3.2

229

-Sep

4.13

812

0.91

24-Se

p - 25

-Sep

0.11

0.00

TS-H

AITAN

G, TS

-NAL

GAE

Begin

ning o

f Floo

d Eve

nPe

ak of

flood

even

tInt

ensit

y of F

lood R

ising


Page 45

Annex B Accuracy and performance

Accuracy

“Accuracy” describes the accuracy of the adjusted and published forecast, based on the results of the MRC Mekong Flood Forecasting System, which are then adjusted by the Flood Forecaster in Charge taking into consideration known biases in input data and his/her knowledge of the response of the model system and the hydrology of the Mekong River Basin.

The information is presented as a graph below, showing the average flood forecasting accuracy along the Mekong mainstream.

The graph of average difference between forecast and actual water levels for the whole flood season from the 1st June to the 31st October shows the normal pattern.

In general terms, the accuracy is good for all forecasts lead time at most stations along Mekong River, however the accuracy for 3‐day forecast at Vientiane, Nakhon Phanom, Mukdahan to Kratie. The detail analysis is presented in paragraph 2.2.

Figure B1 Average flood forecast accuracy along the Mekong mainstream.


Page 46

Forecast Achievement

The forecast achievement indicates the % of days that the forecast at a particular station for a lead‐time is successful against a respective benchmark (Table B2).

Table B1 Achievement of daily forecast against benchmarks.

unit in %

Chiang Saen

Luang Prabang

Chiang Khan

Vientiane

Nongkhai

Paksane

Nakhon Phanom

Thakhek

Mukdahan

Savannakhet

Khong Chiam

Pakse

Stung Treng

Kratie

Kompong Cham

Phnom Penh (Bassac)

Phnom Penh Port

Koh Khel

Neak Luong

Prek Kdam

Tan Chau

Chau Doc

Average

1-da

y70

.173

.180

.854

.559

.950

.953

.956

.354

.553

.950

.354

.555

.162

.982

.694

.686

.897

.095

.295

.290

.483

.870

.7

2-da

y76

.576

.584

.959

.665

.159

.660

.262

.057

.256

.655

.461

.457

.857

.881

.977

.769

.388

.689

.888

.681

.975

.370

.2

3-da

y66

.758

.277

.048

.557

.652

.142

.450

.938

.841

.838

.846

.744

.237

.060

.061

.262

.476

.471

.572

.774

.569

.156

.7

4-da

y77

.461

.064

.064

.669

.568

.956

.160

.456

.761

.050

.660

.462

.853

.775

.047

.079

.967

.188

.484

.865

.257

.965

.1

5-da

y68

.752

.157

.752

.159

.560

.142

.946

.044

.252

.839

.957

.156

.444

.862

.668

.768

.782

.283

.480

.485

.976

.761

.0


Page 47

Table B2 Benchmarks of success (Indicator of accuracy in mean absolute error).

Unit in cm

Note: A

n ind

icatio

n of the

accuracy given in t

he Ta

ble B2

is ba

sed o

n the

perfo

rman

ce of

the f

orecast m

ade in 2

008 f

rom th

e new

flood

forecasting

syste

m an

d the

configu

ratio

n for

the 2

009 f

lood s

eason a

nd is pu

blished

on th

e website o

f MRC

(http

://ffw

.mrcm

ekon

g.org/accuracy.h

tm).

A new set o

f perform

ance indic

ators tha

t is e

stablished

by co

mbin

ing internation

al sta

ndards an

d the

specific

circu

msta

nces in th

e Mekon

g Rive

r Basin,

is ap

plied

officially for the

flo

od se

ason

of 20

11 on

ward.

Chiang Saen

Luang Prabang

Chiang Khan

Vientiane

Nongkhai

Paksane

Nakhon Phanom

Thakhek

Mukdahan

Savannakhet

Khong Chiam

Pakse

Stung Treng

Kratie

Kompong Cham

Phnom Penh (Bassac)

Phnom Penh Port

Koh Khel

Neak Luong

Prek Kdam

Tan Chau

Chau Doc

1-d

ay

25

25

25

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

2-d

ay

50

50

50

25

25

25

25

25

25

25

25

25

25

25

25

10

10

10

10

10

10

10

3-d

ay

50

50

50

25

25

25

25

25

25

25

25

25

25

25

25

10

10

10

10

10

10

10

4-d

ay

75

75

50

50

50

50

50

50

50

50

50

50

50

50

50

10

25

10

25

25

10

10

5-d

ay

75

75

50

50

50

50

50

50

50

50

50

50

50

50

50

25

25

25

25

25

25

25


Page 48

Performance

Performance is assessed by evaluating a number of performance indicators, see Table and graphs below:

Table B3 Overview of performance indicators for flood season 2011 from June to October.

2011

FF completed and sent (time)

stations without forecast

FF2 completed and sent (time)

Weather informaition available (number)

NOAA data

China

Cambodia - DHRW

Cambodia - DOM

Lao PDR - DMH

Thailand - DWR

Viet Nam - NCHMF

NOAA data

China

Cambodia - DHRW

Cambodia - DOM

Lao PDR - DMH

Thailand - DWR

Viet Nam - NCHMF

June

10:12

1-

2708

:1209

:5107

:3105

:5309

:0608

:0007

:140

432

398

621

1218

9Ju

ly10

:360

-13

08:12

07:38

07:31

06:24

09:02

07:41

07:13

112

327

851

55

162

Augu

st10

:360

-14

08:11

08:14

07:36

05:52

09:01

07:42

07:06

00

215

948

14

176

Septe

mber

10:34

0-

1908

:0608

:1407

:2306

:2709

:1407

:3906

:590

028

311

532

1013

1Oc

tober

10:34

0-

2008

:1108

:0907

:2805

:5709

:1007

:3607

:171

060

712

490

1331

4se

ason

10:31

1-

9308

:1008

:1807

:3006

:0709

:0607

:4307

:102

1612

518

5826

3944

972

Flood

Forec

ast: t

ime s

ent

Arriv

al tim

e of in

put d

ata (a

verag

e)Mi

ssing

data

(numb

er)


Page 49

Figure B2 Data delivery times for flood season 2011 from June to October.

Data

Deliv

ery -

Deliv

ery T

imes

07:00

08:00

09:00

10:00

June

July

Augu

stSe

ptem

ber

Octob

erse

ason

Date

Time

NOAA

China

CAM

DHR

W

CAM

DOM

LAO

DMH

THAI

DWR

VN N

CHM

F


Page 50

Figure B3 Missing data for flood season 2011 from June to October.

Data

Deliv

ery -

Miss

ing Da

ta

0

1000

2000

3000

June

July

Augu

stSe

ptemb

erOc

tober

seas

onDa

te

Num

ber

NOAA

China

CAM

DHRW

CAM

DOM

LAO D

MH

THAI

DWR

VN NC

HMF


Page 51

Flood Forecast - Completion Time

09:00

10:00

11:00

June August OctoberDate

Time

Figure B4 Flood forecast completion time.

Flood Forecast - Stations w ithout Forecast

0

2

4

6

8

10


Figure B5 Flood forecast stations without forecast.

Flood Forecast - Second Forecast Needed

09:00

10:00

11:00

12:00

13:00

14:00

15:00


Time

Figure B6 Second forecast needed.


Page 53

Annex C Season Water Level Graphs

This Annex has the water level and rainfall graphs of the report date. These graphs are distributed daily by email together with the Flood Bulletins.

HYDROGRAPHS OF THE MEKONG AT MAINSTREAM STATIONS

IN FLOOD SEASON FROM 1 JUNE TO 3 OCTOBER

Water level at 7am of Mekong at Chiang Saen

0

2

4

6

8

10

12

14

01-Jun 16-Jun 01-Jul 16-Jul 31-Jul 15-Aug 30-Aug 14-Sep 29-Sep 14-Oct 29-Oct 13-Nov

Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Mekong at Jing Hong

534

536

538

540

542

544

546

548

15-Jun

15-Jul

15-Aug

15-Sep

15-Oct

15-Nov

Time in days

Gau

ge h

eigh

t in

met

res

Av98-10 1998 2000 2010 2011


Page 54

Water level at 7am of Mekong at Luang Prabang

0

2

4

6

8

10

12

14

16

18

20


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Mekong at Chiang Khan

0

2

4

6

8

10

12

14

16

18

20


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Mekong at Vientiane Km4

0

2

4

6

8

10

12

14


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011


Page 55

Water level at 7am of Mekong at Nong Khai

0

2

4

6

8

10

12

14


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Mekong at Paksane

0

2

4

6

8

10

12

14

16


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Mekong at Nakhon Phanom

0

2

4

6

8

10

12

14


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011


Page 56

Water level at 7am of Mekong at Thakhek

0

2

4

6

8

10

12

14

16


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Mekong at Savannakhet

0

2

4

6

8

10

12

14


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Mekong at Mukdahan

0

2

4

6

8

10

12

14


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011


Page 57

Water level at 7am of Mekong at Paksé

0

2

4

6

8

10

12

14


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Mekong at Stung Treng

0

2

4

6

8

10

12

14


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Mekong at Kratie

0

2

46

8

10

1214

16

18

2022

24

26


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011


Page 58

Water level at 7am of Mekong at Kompong Cham

0

2

4

6

8

10

12

14

16

18


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am at Phnom Penh Chaktomuk

0

2

4

6

8

10

12

14

16


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Tonle Sap at Phnom Penh Port

0

2

4

6

8

10

12

14

16


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011


Page 59

Water level at 7am of Bassac at Koh Khel

0

1

2

3

4

5

6

7

8

9


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Mekong at Neak Luong

0

1

2

3

4

5

6

7

8

9


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Tonle Sap at Prek Kdam

0

2

4

6

8

10

12


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011


Page 60

Water level at 7am of Mekong at Tan Chau

-1

0

1

2

3

4

5

6


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Water level at 7am of Bassac at Chau Doc

-1

0

1

2

3

4

5

6


Time in days

Gau

ge h

eigh

t in

met

res

A larm Flood Av80-10 1992 1998 2000 2010 2011

Date post:	06-May-2018
Category:	Documents
Upload:	trinhnhu
View:	217 times
Download:	1 times

Mekong River Commissionffw.mrcmekong.org/weekly_report/2011/Seasonal Flood Situation... · Northern...

Documents