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1 U Mekong River Commission Regional Flood Management and Mitigation Centre Weekly Flood Situation Report for the Mekong River Basin Prepared at: //, covering the week from the rd August to the th August Weather Patterns, General Behaviour of the Mekong River and Flood Situation General weather patterns During the week of rd August to th August five weather bulletins were issued by the Departmentt of Meteorology (DOM) of Cambodia. The weather maps of the th August and 9 th August are presented in the Figures & below: Figure : Weather map for th August Figure : Weather map for 9 th August Moderate South-West (SW) Monsoon The moderate Southwest monsoonn prevailed over Andamann Sea, the Gulf of Thailand, Thailand and Indochina Peninsular at the surface (Figure ). Tropical depressions (TD), tropical stormss (TS) or typhoons (TY) No TD, TS or TY was presented in LMB during last week. Other weather phenomena thatt affect the discharge The Inter Tropical Convergence Zone (ITCZ) laid across the middle of Myanmar, the North of Thailand, the South of Lao PDR and the middle of Viet Nam. The trough laid across Myanmar, Thailand and Indochina Peninsular at the height of.km ( hpa). Over weather situation During the last week, the weather was influenced by ITCZ, trough of low pressure and moderate Southwestt monsoon. Therefore, scattered moderate and heavy rain occurred in some stations of upper and middle reaches of the Mekong River Basin during last week; see Figure and Table A MRC Weekly Flood Situation Report Week rd - th August Page

2 Monday, th August Figure : Weekly Rainfall Distribution over the LMB from rd - th August MRC Weekly Flood Situation Report Week rd - th August Page

3 Monday, th August General behaviour of the Mekong River During the last week, the water levels at all stations in the upper and middle reaches of LMB were rising above the Long Term Average (LTA) and below the LTA in the lower reach of LMB. For stations from Chiang Saen and Luang Prabang Compared to the long term average (LTA), during last week the water levels at these stations were rising above the LTA. For stations from Chiang Khan, Vientiane and Nong Khai and Paksane Compared to the long term average (LTA), during last week the water levels at these stations were rising above the LTA. For stations from Thakhet/Nakon Phanom to Pakse Compared to the long term average (LTA), during last week the water levels at these stations were rising above the LTA. For stations from Stung Treng to Kompong Cham Compared to the long term average (LTA), during last week the water levels at these stations were rising just about the LTA, except Kampong Cham was rising below the LTA. For stations from Phnom Penh to Koh Khel/Neak Luong Compared to the long term average (LTA), during last week the water levels at these stations were rising below the LTA. Tan Chau and Chau Doc Compared to the long term average (LTA), during last week the water levels at these stations were rising below the LTA. Note: For areas between forecast stations, please refer to the nearest forecast station. Flood Situation Flood stage or alarm stage: No alarm stage (where the forecast is expected to reach flood level within three days) was reported anywhere on the mainstream of the Mekong River during the last week. Water levels were still significantly below flood levels (as defined by the national agency) at all forecast stations. Damage or victims: No damage or loss of life due to river flooding was recorded anywhere along the Mekong River during the last week. For more details see the following annexes: - 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 MRC Weekly Flood Situation Report Week rd - th August Page

4 Monday, th August Annex A: Graphs and Tables Table A: observed water levels Unit in m Jinghong 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 Table A: observed rainfall Unit in mm Jinghong Chiang Saen Luang Prabang Chiang Khan Vientiane Nongkhai Paksane Nakhon Phanom Thakhek Mukdahan Savannakhet / nr..9 - nr.... / nr nr / nr 9... nr /.... nr nr 7... nr - nr. nr. - 7/.... nr... nr nr nr.. nr - nr - nr nr - / nr nr /.... nr. nr. nr. nr. nr.. 7. nr -.. nr nr - / nr. nr..7.9 nr. nr... nr nr.. 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 rd - th August Page

5 Monday, th August Figure A: Observed water level and rainfall for Jinghong, Chiang Saen, and Luang Prabang MRC Weekly Flood Situation Report Week rd - th August Page

6 Monday, th August Figure A: Observed water level and rainfall for Chiang Khan, Vientiane, Nongkhai, and Paksane Vientiane Nongkhai / / / / 7/ / 9/ / / / / / 7/ / 9/ / / / / / 7/ Vientiane / / / / 7/ / 9/ / / / / / 7/ hour rainfall at 7am (mm) / 9/ / Nongkhai MRC Weekly Flood Situation Report Week rd - th August Page Paksane hour rainfall at 7am (mm) / 9/ / / / / / 7/ / 9/ /.... Paksane hour rainfall at 7am (mm) / / / / 7/ / 9/ / Chiang Khan Chiang Khan..... / / / / 7/ / 9/ / hour rainfall at 7am (mm)

7 Monday, th August Figure A: Observed water level and rainfall for Nakhon Phanom, Thakhek, Mukdahan and Savannakhet Thakhek Mukdahan / / / / 7/ / 9/ / / / / / 7/ / 9/ / / / / / 7/ Thakhek / / / / 7/ / 9/ / hour rainfall at 7am (mm).... / / / / 7/ / 9/ / hour rainfall at 7am (mm) / 9/ / Mukdahan.... MRC Weekly Flood Situation Report Week rd - th August Page 7 Savannakhet / / / / 7/ / 9/ / / / / / 7/ / 9/ / Savannakhet hour rainfall at 7am (mm) / / / / 7/ / 9/ / Nakhon Phanom Nakhon Phanom.... hour rainfall at 7am (mm)

8 Monday, th August Figure A: Observed water level and rainfall for Khong Chiam, Pakse, Stung Treng, and Kratie Khong Chiam Pakse Stung Treng / / / / 7/ / 9/ / / / / / 7/ / 9/ / / / / / 7/ Pakse / / / / 7/ / 9/ / hour rainfall at 7am (mm) / 9/ / Stung Treng MRC Weekly Flood Situation Report Week rd - th August Page Kratie / / / / 7/ hour rainfall at 7am (mm) / 9/ / / / / / 7/ / 9/ / Kratie hour rainfall at 7am (mm) / / / / 7/ / 9/ / Khong Chiam..... / / / / 7/ / 9/ / hour rainfall at 7am (mm)

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

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

11 Monday, th August 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. In general, the overall accuracy is quite good for -day to -day forecast lead time at stations in the upper and middle parts of the LMB. However, the accuracies at upper reach of the LMB stations as Chiang Saen to Savannakhet for -day forecast were less than expected. The above differences due to two main factors: () internal model functionality in forecasting; for which the parameter adjustment in the model is not possible especially at stations in the upper part and in the Mekong delta where are affected by tidal; () the adjustment by utilizing the practical knowledge and experience of flood forecaster-in-charge. Flood Forecasted Performance Chiang Saen Luang Prabang Chiang Khan Vientiane Nong Khai Paksane Nakhon Phanom Thakhek Mukdahan Savannakhet Khong Chiam Pakse Stung Treng Kratie Kompong Cham Bassac Chaktomuk Phnom Penh Port Koh Khel Neak Luong Prek Kdam Tan Chau Chau Doc Mean Absolute Differences (cm) -Day -Day -Day -Day -Day Figure B: Average flood forecast accuracy along the Mekong mainstream MRC Weekly Flood Situation Report Week rd - th August Page

12 Monday, th August 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 B). Table B: 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 B: 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 Khong Chiam -day -day -day -day 7 7 -day 7 7 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 B 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 ( A new set of performance indicators that is established by combining international standards and the specific circumstances in the Mekong River Basin, is applied officially for the flood season of onward. MRC Weekly Flood Situation Report Week rd - th August Page

13 Monday, th August Performance Performance is assessed by evaluating a number of performance indicators, see table and graphs below: Table B: Overview of performance indicators for the past days including the current report date FF completed and sent (time) stations without forecast FF completed and sent (time) Weather informaition available (number) NOAA data China Cambodia - DHRW Cambodia - DOM week : - :7 7: 7:7 7:7 : 7: 7: month :9 - : 7: 7: 7:7 : 7: 7: 9 season : - : 7: 7: 7:9 : 7: 7:9 9 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 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 / / / / 7/ / 9/ / Date Figure B: Data delivery times for the past days including the current report date NOAA China CAM DHRW CAM DOM LAO DMH THAI DWR VN NCHMF MRC Weekly Flood Situation Report Week rd - th August Page

14 Monday, th August Numbe r Data Delive ry - Missing Data / / / / 7/ / 9/ / Date NOAA China CAM DHRW CAM DOM LAO DMH THAI DWR VN NCHMF Figure B: Missing data for the past days including the current report date Time Flood Forecast - Completion Time Flood Forecast - Stations without Forecast Time Flood Forecast - Second Forecast Needed : : : : : : : : 9: 9: Date / / / / 7/ / 9/ / Date / / / / 7/ / 9/ / Date / / / / 7/ / 9/ / Figure B: Flood forecast completion time Figure B: Flood forecast stations without forecast Figure B: Second forecast needed MRC Weekly Flood Situation Report Week rd - th August Page

15 Monday, th August 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 FLOOD SEASON FROM JUNE TO OCTOBER Water Level at 7am of Mekong at Jing Hong -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Av9-99 Time in days Water Level at 7am of Mekong at Chiang Saen -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99 Time in days 99 Water Level at 7am of Mekong at Luang Prabang -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99 Time in days 99 MRC Weekly Flood Situation Report Week rd - th August Page

16 Monday, th August Water Level at 7am of Mekong at Chiang Khan Gaugeheight in metres -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov 99 Time in days99 Alarm Flood Av- Water Level at 7am of Mekong at Vientiane -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov 99Time in days 99 Alarm Flood Av- Water Level at 7am of Mekong at Nong Khai Gaugeheight in metres -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov 99 Time in days99 Alarm Flood Av- Water Level at 7am of Mekong at Paksane Gaugeheight in metres -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov 99Time in days 99 Alarm Flood Av- MRC Weekly Flood Situation Report Week rd - th August Page

17 Monday, th August Water Level at 7am of Mekong at Nakhon Phanom -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99Time in days 99 Water Level at 7am of Mekong at Thakhek -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99Time in days 99 Water Level at 7am of Mekong at Savannakhet -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99Time in days 99 Water Level at 7am of Mekong at Mukdahan -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99 Time in days 99 MRC Weekly Flood Situation Report Week rd - th August Page 7

18 Monday, th August Water Level at 7am of Mekong at Khong Chiam -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99Time in days 99 Water Level at 7am of Mekong at Pakse -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99Time in days 99 Water Level at 7am of Mekong at Stung Treng -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99Time in days 99 Water Level at 7am of Mekong at Kratie -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov 99Time in days 99 Alarm Flood Av- MRC Weekly Flood Situation Report Week rd - th August Page

19 Monday, th August Water Level at 7am of Mekong at Kampong Cham -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99Time in days 99 Water Level at 7am of Mekong at Phnom Penh Chaktomuk -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99 Time in days 99 Water Level at 7am of Tonle Sap at Phnom Penh Port -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99Time in days 99 9 Water Level at 7am of Bassac at Koh Khel 7 -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99 Time in days99 MRC Weekly Flood Situation Report Week rd - th August Page 9

20 Monday, th August 9 Water Level at 7am of Mekong at Neak Luong 7 -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99 Time in days99 Water Level at 7am of Tonle Sap at Prek Kdam -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99 Time in days 99 Water Level at 7am of Mekong at Tan Chau - -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99 Time in days99 Water Level at 7am of Bassac at Chau Doc - -Jun -Jun -Jul -Jul -Jul -Aug -Aug -Sep 9-Sep -Oct 9-Oct -Nov Alarm Flood Av- 99 Time in days99 MRC Weekly Flood Situation Report Week rd - th August Page