Mekong River Commission

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U P August UPU U August P August P and P Mekong River Commission Regional Flood Management and Mitigation Centre Weekly Flood Situation Report for the Mekong River Basin th th Prepared on: Monday,

7UPU 9U, seven weather bulletins were issued by th th the Department of Meteorology of Cambodia DOM. The weather charts of the August P 7P bulletins are presented in the figures below.

1 U P August UPU U August P August P and P Mekong River Commission Regional Flood Management and Mitigation Centre Weekly Flood Situation Report for the Mekong River Basin th th Prepared on: Monday, /9, covering the week from P P August to 7P P August 9 Weather Patterns, General Behavior of the Mekong River and Flood Situation General weather patterns th th During the week of UMonday UPU Monday 7UPU 9U, seven weather bulletins were issued by th th the Department of Meteorology of Cambodia DOM. The weather charts of the August P 7P bulletins are presented in the figures below. Figure : Weather map for P th 9 Figure : Weather map for 7P th 9 UWeakening South-West (SW) Monsoon An active SW monsoon prevailed over the Indochina Peninsula at the beginning of the week and began gradually weakening by the 7 th. (Figure and Figure ). Inter Tropical Convergence Zone (UITCZ) An ITCZ laid across Myanmar, Thailand, Northern Lao PDR, Northern Viet Nam and Hainan Island. UTropical depressions, tropical storms or typhoons The Tropical Depression (TD) MORAKOT passed over Eastern China and was moving NNE at a speed of 9 km/h. The maximum wind speed at the centre of the depression was 5 km/h. This downgraded in velocity over the week. And another Tropical Storm (TS) ETAU occurred over the Japanese Sea and was moving NE at the start of the week at a speed of 9 km/h. The maximum wind speed at the centre of the TS was 7 km/h A low pressure trough laid across Thailand, Lao PDR and Cambodia, with a ridge pressure system across Southern Viet Nam. UOther weather phenomena that affect the discharge of the Mekong River No other weather phenomena affecting the discharge were observed. MRC Weekly Flood Situation Report Week rt August to 7 th August 9 Page

2 U U P and Monday, 7 th August 9 UOverall weather situation of the Mekong Basin th th A normal weather situation prevailed between the P 7P P August 9. There were scattered Cumulus (Cu) and Cumulonimbus (Cb) clouds were observed over Cambodia and Southern Viet Nam in the afternoon and evening during the week. Scattered thunderstorms and moderate rain occurred in Thailand, Lao PDR and Viet Nam and light rain occurred in Cambodia, mostly at night. General behavior of the Mekong River There was some variation of water levels along the Mekong River in the time period monitored. While water levels in the upper reaches of the Lower Mekong River are below the long-term average, water levels in the middle reaches are at about the long-term average and in the lower part of the river water levels are above the long-term average. Water levels reached alarm levels at Tan Chau and Chau Doc monitoring stations during the week. This is normal for this time of the year for both stations. For stations from Chiang Saen to Chieng Khan Water levels dropped in the first half of the week and then rose up towards the end of the week. Most are somewhat below the long-term average for this time of the year. For stations from Vientiane to Pakse Water levels increased till mid-week and then reduced until the end of the week. Most stations are showing levels that are around the long-term average for this time of the year. For stations from Stung Treng to Phnom Penh Water levels were more-or-less stable, with an increasing trend towards the end of the week. Most stations are showing river levels that are somewhat above the long-term average for this time of the year. Downstream of Phnom Penh Water levels were rising and continued to do so throughout the week. Most stations are showing river water levels that are somewhat above the long-term average for this time of the year except at Tan Chau and Chau Doc where the water levels are about average for this time of the year. At Tan Chau, the water level is rising over the alarm level as defined by the national agency. Note: for areas between forecast stations, please refer to the nearest forecast station. Flood Situation Flood stage or alarm stage: Alarm stage (where the forecast is expected to reach flood level within three days) was reported for Tan Chau in the mainstream Mekong River during the past week. While the water level is getting close to the alarm level at Chau Doc, and is expected to reach alarm level in the following weeks. Water in the river is still below the flood levels at all forecast stations. Damage or victims: No damage or loss of life due to river flooding was recorded anywhere in the Mekong River Basin during the past week For more details see the following annex: - tables and graphs for water level and rainfall for the last week in Annex A - a graph for accuracy in Annex B - a table of forecast achievement in Annex B - tables and graphs for performance in Annex B - the water level graphs showing the observed water level for the season in Annex C Page MRC Weekly Flood Situation Report Week td August to 7 th August 9

3 Monday, 7 th August 9 Annex A: Graphs and Tables Table F: observed water levels unit in m Jinghong Chiang Saen Luang Prabang Chiang Khan Vientiane Nongkhai Paksane Nakhon Phanom Thakhek Mukdahan Savannakhet 9 / / / Flood level Khong Chiam Pakse Stung Treng Kratie Kompong Cham Phnom Penh (Bassac) Phnom Penh Port Koh Khel Neak Luong Prek Kdam Tan Chau Chau Doc Table F: observed rainfall. Unit in mm Jinghong Chiang Saen Luang Prabang Chiang Khan Vientiane Nongkhai Paksane Nakhon Phanom Thakhek Mukdahan Savannakhet 9 / / / Khong Chiam Pakse Stung Treng Kratie Kompong Cham Phnom Penh (Bassac) Phnom Penh Port Koh Khel Neak Luong Prek Kdam Tan Chau Chau Doc MRC Weekly Flood Situation Report Week td August to 7 th August 9 Page 3

4 Monday, 7 th August 9 Figure A: Water level and rainfall for Jinghong, Chiang Saen, and Luang Prabang Jinghong Chiang Saen Luang Prabang Jinghong / / / / / / / / / hour rainfall at 7am (mm) / / / / / / / / / Chiang Saen hour rainfall at 7am (mm) Luang Prabang hour rainfall at 7am (mm) Page MRC Weekly Flood Situation Report Week td August to 7 th August 9

5 Monday, 7 th August 9 Figure A: Water level and rainfall for Chiang Khan, Vientiane, Nongkhai, and Paksane Chiang Khan Vientiane Nongkhai Paksane / / / / / / / / / / / / Chiang Khan Vientiane Nongkhai Paksane / / / / / / / / / / / / / hour rainfall at 7am (mm) hour rainfall at 7am (mm) MRC Weekly Flood Situation Report Week td August to 7 th August 9 Page 5 hour rainfall at 7am (mm) 3 hour rainfall at 7am (mm)

6 Monday, 7 th August 9 Figure A3: Water level and rainfall for Nakhon Phanom, Thakhek, Mukdahan and Savannakhet Nakhon Phanom Thakhek Mukdahan Savannakhet / / / / / / / / / / / / Nakhon Phanom Thakhek Mukdahan Savannakhet 3 / / / / / / / / / / / / hour rainfall at 7am (mm) hour rainfall at 7am (mm) 3 Page MRC Weekly Flood Situation Report Week td August to 7 th August 9 hour rainfall at 7am (mm) 5 3 hour rainfall at 7am (mm)

7 Monday, 7 th August 9 Figure A: Water level and rainfall for Khong Chiam, Pakse, Stung Treng, and Kratie Khong Chiam Pakse Stung Treng Kratie / / / / / / / / / / / / Khong Chiam Pakse Stung Treng Kratie 5 3 / / / / / / / / / / / / hour rainfall at 7am (mm) hour rainfall at 7am (mm) hour rainfall at 7am (mm) MRC Weekly Flood Situation Report Week td August to 7 th August 9 Page 7 3 hour rainfall at 7am (mm)

8 Monday, 7 th August 9 Figure A5: Water level and rainfall for Kompong Cham, Phnom Penh (Bassac and Port), and Koh Khel Kompong Cham Phnom Penh (Bassac) Phnom Penh Port Koh Khel 9 / / / / / / / / / / / / Kompong Cham Phnom Penh (Bassac) Phnom Penh Port Koh Khel 5 / / / / / / / / / / / / hour rainfall at 7am (mm) hour rainfall at 7am (mm) hour rainfall at 7am (mm) hour rainfall at 7am (mm) Page MRC Weekly Flood Situation Report Week td August to 7 th August

9 Monday, 7 th August 9 Figure A: Water level and rainfall for Neak Luong, Prek Kdam, Tan Chau and Chau Doc Neak Luong Prek Kdam Tan Chau Chau Doc / / / / / / / / / / / / Neak Luong Prek Kdam Tan Chau Chau Doc / / / / / / / / / / / / hour rainfall at 7am (mm) hour rainfall at 7am (mm) 3 3 hour rainfall at 7am (mm) MRC Weekly Flood Situation Report Week td August to 7 th August 9 Page hour rainfall at 7am (mm)

10 Monday, 7 th August 9 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 forecasting differences for the past week generally shows the normal pattern. In general the accuracy is fairly good for -day to 3-day forecasts; however, the differences for -day and 5-day forecasts between Savanakhet and Kratie were less accurate than expected. The above significant differences due to mainly two factors: () modeling results is normally less accurate than expected due to quality of model calibration (lack of historical data) for that portion and () forecast adjustment made by forecaster-in-charge due to the fact that the satellite rainfall estimation is normally higher than the observed records for the lower part of the Mekong Basin. Figure A: Average flood forecast accuracy along the Mekong mainstream. Page MRC Weekly Flood Situation Report Week td August to 7 th August 9

11 Monday, 7 th August 9 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 A). Table A: Achievement of daily forecast against benchmarks unit in % Chiang Saen Luang Prabang Chiang Khan Vientiane Nongkhai Paksane Nakhon Phanom Thakhek Mukdahan Savannakhet Khong Chiam -day day day day day Pakse Stung Treng Kratie Kompong Cham Phnom Penh (Bassac) Phnom Penh Port Koh Khel Neak Luong Prek Kdam Tan Chau Chau Doc Average Table A: Benchmarks of success (Indicator of accuracy in mean absolute error) Unit in cm Chiang Saen Luang Prabang Chiang Khan Vientiane Nongkhai Paksane Nakhon Phanom Thakhek Mukdahan Savannakhet -day day day day day Khong Chiam Pakse Stung Treng Kratie Kompong Cham Phnom Penh (Bassac) Phnom Penh Port Koh Khel Neak Luong Prek Kdam Tan Chau Chau Doc Note: An indication of the accuracy given in the Table is based on the performance of the forecast made in from the new flood forecasting system and the configuration for the 9 flood season and is published on the website of MRC ( In the future these indicators will be adjusted against a set of performance indicators that is established by combining international standards and the specific circumstances in the Mekong River Basin. An expert mission to establish these performance indicators is planned for the fourth quarter of 9. MRC Weekly Flood Situation Report Week td August to 7 th August 9 Page

12 Monday, 7 th August 9 Performance Performance is assessed by evaluating a number of performance indicators, see table and graphs below: Table P: Overview of performance indicators for the past days including the current report date. Flood Forecast: time sent Arrival time of input data (average) Missing data (number) FF completed and sent (time) stations without forecast FF completed and sent (time) Weather informaition available (number) NOAA data China Cambodia - DHRW Cambodia - DOM 9 week :3 - :9 : 7:5 : : :3 7: month : :3 :5 :7 : :33 :3 : : season : :39 :3 :5 :9 : : :5 7: Lao PDR - DMH Thailand - DWR Viet Nam - NCHMF NOAA data China Cambodia - DHRW Cambodia - DOM Lao PDR - DMH Thailand - DWR Viet Nam - NCHMF Week is the week for which this report is made; Month is actually the last 3 days (or less if the flood season has just begun); Season is the current flood season up to the date of this report. Time : : : 9: : 7: Data Delivery - Delivery Times / / / Date NOAA China CAM DHRW CAM DOM LAO DMH THAI DWR VN NCHMF Figure P: Data delivery times for the past days including the current report date. Page MRC Weekly Flood Situation Report Week td August to 7 th August 9

13 Monday, 7 th August 9 Number Data Delivery - Missing Data / / / Date NOAA China CAM DHRW CAM DOM LAO DMH THAI DWR VN NCHMF Figure P: Missing data for the past days including the current report date. Time : Flood Forecast - Completion Time Flood Forecast - Stations without Forecast Time 5: Flood Forecast - Second Forecast Needed : : : 3: : : : 9: Date / / / Date / / / 9: Date / / / Figure P3: Flood forecast completion time Figure P: Flood forecast stations without forecast Figure P5: Second forecast needed MRC Weekly Flood Situation Report Week td August to 7 th August 9 Page 3

14 Monday, 7 th August 9 Annex C: Season Water Level Graphs This Annex has the water level graphs of the report date. These graphs are distributed daily by together with the Flood Bulletins. HYDROGRAPHS OF THE MEKONG AT MAINSTREAM STATIONS IN WET SEASON FROM JUNE TO 3 OCTOBER 59. Water level at 7am of Mekong at Jinghong /Jun 3/Jun 5/Jul 3/Jul /Aug 9/Aug 3/Sep /Sep 3/Oct 3 Av- 9. Water level at 7am of Mekong at Chiang Saen /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9 Page MRC Weekly Flood Situation Report Week td August to 7 th August 9

15 Monday, 7 th August 9 Water level at 7am of Mekong at Luang Prabang /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Mekong at Chiang Khan /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Mekong at Vientiane /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9 MRC Weekly Flood Situation Report Week td August to 7 th August 9

16 Monday, 7 th August 9. Water level at 7am of Mekong at Nong Khai /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Mekong at Paksane /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Mekong at Nakhon Phanom /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9 Page MRC Weekly Flood Situation Report Week td August to 7 th August 9

17 Monday, 7 th August 9. Water level at 7am of Mekong at Thakhek /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Mekong at Savannakhet /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Mekong at Mukdahan /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9 MRC Weekly Flood Situation Report Week td August to 7 th August 9

18 Monday, 7 th August 9. Water level at 7am of Mekong at Paksé /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Mekong at Stung Treng /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9 Water level at 7am of Mekong at Kratie /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9 Page MRC Weekly Flood Situation Report Week td August to 7 th August 9

19 Monday, 7 th August 9. Water level at 7am of Mekong at Kompong Cham /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Bassac at Phnom Penh /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Tonle Sap at Phnom Penh Port /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9 MRC Weekly Flood Situation Report Week td August to 7 th August 9

20 Monday, 7 th August 9 9. Water level at 7am of Bassac at Koh Khel /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av Water level at 7am of Mekong at Neak Luong /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Tonle Sap at Prek Kdam /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9 Page MRC Weekly Flood Situation Report Week td August to 7 th August 9

21 Monday, 7 th August 9. Water level at 7am of Mekong at Tan Chau /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9. Water level at 7am of Bassac at Chau Doc /Jun /Jun /Jul /Jul 3/Jul 5/Aug 3/Aug /Sep 9/Sep /Oct 9/Oct Alarm Flood Av- 9 MRC Weekly Flood Situation Report Week td August to 7 th August 9

Mekong River Commission

U Mekong River Commission Regional Flood Management and Mitigation Centre Weekly Flood Situation Report for the Mekong River Basin Prepared on: //9, covering the week from 19 to October 9 Weather Patterns,