Application of Satellite Data for Flood Forecasting and Early Warning in the Mekong River Basin in South-east Asia

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1 MEKONG RIVER COMMISSION Vientiane, Lao PDR Application of Satellite Data for Flood Forecasting and Early Warning in the Mekong River Basin in South-east Asia 4 th World Water Forum March 2006 Mexico City, Mexico 1

2 Section III : Introduction to target area, Mekong River Basin Tibetan Plateau Mekong River Basin Hydro-meteorological Conditions Lower Mekong Basin (LMB) Tropical climate with two monsoon seasons Northeast : Nov mid Mar Southwest : mid May mid Oct (causes heavy and frequent rain) Mean annual rainfall in the basin ranges mm Lower basin : 1700 mm WL rises in May and attains peak level in Aug. or Sep. at U/S, while in Sep. or Oct. at D/S Usually, flood occurs after heavy and frequent rainfalls from storms or typhoons 2

3 Understanding the Mekong River Basin Mekong Catchment Area (km2) Lower Mekong Basin (km2) 795,000 (21) 606,000 Length of mainstream (km) 4,800 (12) Volume (billion m 3 ) 475 (8) Mekong River Commission (MRC) International organization between the Governments of Cambodia, Laos, Thailand and Viet Nam Established under a 1995 Agreement with the role: To promote and undertake cooperation in all fields of sustainable development, utilization, management and conservation of the water and related resources of the Basin 3

4 Background to Mekong River Flooding Recently, in 2000, 2001, and 2002, Mekong floods have caused extensive economic damage in MRC member states: Cambodia, Lao PDR, Thailand, Vietnam Damage worth about US$ 1 billion Many lives have been lost (on the order of 2,000) Call for establishment of a basin-wide Flood Management 4 and Mitigation Programme (FMMP) for the MRC in year 2001

5 MRC Flood Management and Mitigation Programme (FMMP) Objective: People s suffering and economic losses due to floods are prevented, minimized, or mitigated, while the environmental benefits of floods are preserved. Implementation: 6 years ( ), 20 Million USD FMMP 5 Components 1. Regional FMM centre 2. Structural Measures & Flood Proofing 3. Trans-boundary mediation 4. Flood Emergency Management 5. Land Use management Capacity Building (Training Unit) Data Collection & Processing Forecasting, Warning & Dissemination Annual Flood Forum, Workshops, Communications 5

6 Flood forecasting System Being Implemented by the Mekong River Commission Data collection and analysis Provision of Forecasts Forecast Dissemination Dissemination Hydrological Stations Website, bulletin, , fax, radio, telephone etc. Rainfall Estimation/ Forecast (Satellite based) 6

7 Rain Gauge Network in the Lower Mekong River Basin Rainfall gauge stations for operational flood forecasting are available only along the Mekong mainstream and main tributaries Rain gauge station Archive Near real time WMO recommendation (MRB=795,000 km2) >1500 preferably all Actual stations (flood season) Use of satellite-based rainfall data is necessary to provide averaged rainfall over sub-basins in near real time 7

8 Satellite Data Available for Flood Forecasting System of the Mekong River Commission Estimated and forecasted 24-hourly rainfall : Data provided by the United States Geological Survey (USGS) General data NOAA (National Oceanic & Atmospheric Administration ) data provides estimates of actual rainfall based on satellite imagery, corrected with readings from gauging stations of the GTS network (WMO) MM5 (Fifth Generation Meso-scale Model operated by the US Air Force) gives three, 24-hourly forecasts of rainfall for consecutive days (MM5 +0, MM5 +1, MM5 +2) Operational data 7-day forecasted rainfall : use as input for the flood forecasting system (upstream reaches : Chiang Saen to Pakse) in Upper Mekong River Basin 8

9 Available Satellite Data USGS NOAA (observed data) 10 km X 10 km resolution MM5 (3-day forecast rainfall) 80 km X 80 km Resolution Operational data requested by MRC (7-day forecasted rainfall) 100 km X 100 km Resolution (used as input for flood forecasting) Graphic missing in this slide Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar 25 km X 25 km resolution 3-hour interval 9

10 Available Satellite Data on MRC Website ( Rainfall by grid Rainfall by sub basin 10

11 Physical Modeling of Flooding in the Mekong River Basin Ten sub-basins modeled for application of Stream flow Synthesis And Reservoir Regulation (SSARR) 19 hydrological stations on the Mekong mainstream used for model calibration 11

12 Operational Forecast Satellite Data Used for Flood Forecasting Example of 7-day forecasted rainfall from NOAA Available everyday at 8:30 AM Data on 1 st September 2005 Sub basin Averaged Rainfall (mm/d) 31-Aug-05 1-Sep-05 2-Sep-05 3-Sep-05 4-Sep-05 5-Sep-05 6-Sep-05 Changsaen Luangprabang Chiangkhan Nakorn Phanom-Thakhek Vientiane-Nongkhai Mukdahan-Savannakhet Ubon Pakse Kratie Tonle Sap-Delta rainfall day Tonle Sap-Delta Kratie Pakse Ubon Mukdahan-Savannakhet Vientiane-Nongkhai Nakorn Phanom-Thakhek Chiangkhan Luangprabang Changsaen

13 Comparison of Actual Water Level with Forecast Water Level Using Rainfall Values from NOAA 7-day Advance Satellite Rainfall Estimates Difference between SSARR model forecast water levels and observed water level from staff gauges Simulation Date : 2nd September 2005 Difference between 7-d forecasted rainfall and obs WL Difference between obs NOAA rainfall and obs WL diff in WL (m) CS LB CK NK NP MK PS diff in WL (m) CS LB CK NK NP MK PS Sep no. of days Sep no. of days Accuracy of forecast water level decreases with the number of advance forecast days A constant correlation was found in the difference between forecast water level and observed water level over time Standard NOAA cloud cover-rainfall correlations over-predict observed runoff 13 in the Mekong River Basin

14 Conclusions from Flood Modeling in the Mekong River Basin Satellite rainfall data are useful for flood forecasting Little near-real time rainfall data is available from rain gauge stations Rainfall values are the most important input for flood forecasting Different sources of rainfall should be considered NOAA standard data can be used for river stage forecasting, using correlations between cloud cover and river flow volume Calibration was found to be different for each sub-basin Accuracy of flood forecast decreases with time for advanced rainfall forecasts 14

15 Recommendations from Flood Modeling in the Mekong River Basin Application of satellite rainfall data (on a global scale) for flood forecasting (at regional scale) needs further verification through use of rain gauge data Further validation is needed for the application of satellite data for flood forecasting NOAA, MM5, TRMM Close cooperation needed with weather services in the region for further improvement of regional weather forecasts WMO, ESCAP, National Typhoon Committee, and concerned organizations in each riparian country More rain gauges are required for validation of satellite data Correlation between forecast satellite data and observed rainfall should be carried out Standard format needed to automate database operations: exchange, transmission, processing and other data collection functions (AHNIP and Mekong-HYCOS, etc.) Further investigation is required of medium term environmental change Runoff from sub basins due to global warming, deforestation, etc 15

16 Thank you for your attention 16