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GRM 2011: Using GIS data to characterise rice ecosystems in the Mekong region
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GRM 2011: Using GIS data to characterise rice ecosystems in the Mekong region

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  • 1. GCP 2011 General Research Meeting21-25 September,2011Hyderabad, IndiaCharacterization of drought-pronerainfed rice ecosystems ofthe Mekong RegionInthavong, T., Linwattana, G., Touch, V.,Pantuwan, G, Jongdee, B., Mitchell,J.H., and Fukai, S.(NAFRI, BRRD, CARDI, UQ)
  • 2. Objectives1. Development of Soil Water Balance Modeland use it for quantifying field wateravailability during the growing season2. Identify the spatial pattern of drought proneareas in the Mekong Region.3. Estimation of yield reduction by water stress4. Conclusions
  • 3. Rainfed lowland rice production areaLarge areas of rainfed lowland areas with drought-prone and drought- &submergence-prone environments in the Mekong region 65% of total rice land in Cambodia, 44% in Laos, 56% in Thailand% Irrigated Rainfed lowland Upland DeepwaterTotal F D DS S MDCambodia 16 75 7 22 43 0 3 1 8Indonesia 54 35 20 4 0 3 8 11 0Laos 14 65 22 22 22 0 0 21 0Malaysia 66 21 15 0 0 5 1 12 1Myanmar 30 59 24 6 0 15 14 4 7Philippines 67 30 15 5 1 3 6 3 0Thailand 20 74 6 38 18 9 3 2 4Vietnam 53 39 15 8 0 12 4 5 3F: favorable, D: drought-prone, DS: drought- and submergence-prone, S: submergence-prone, MD: medium-deepSource: Mackill et al. (1996), IRRI (2005)
  • 4.  Rainfall distribution(i) uncertainty in the onset of the rainy season that can affecttimely sowing and transplanting.(ii) late season drought affects on reproductive stage ofplant growth and development.
  • 5. • Coarse soilsCL (4.5%)LL (11.5%)SL (38.1%)LS (41.3%)SA (4.5%)Proportion of % soil texture types distributed throughoutthe Savannakhet provinceSoil characteristics
  • 6. Top paddyMiddle paddyBottom paddyGroundwatertable/headDownwardmovementLateralmovementGroundwater flowRunoff(catchment)Toposequence» A sequence ofpaddy fields onslopping land
  • 7. Development and use of a soil water balancemodel (SWB) for quantifying: weekly rice field water storagespatial variation in field water availability water stress development during rice growingperiod
  • 8. RainfallTranspirationEvaporationRunoffSeepageUnder-bundPercolationLateral movementDownward movementQuantifying water balance components
  • 9. Surface layerDSubsoil layerDPbundSurface soil water content (Wsurface)within 0 - 20cmSubsoil water content (Wsubsoil) between 20 -100cm where Dsubsoil equals to deeppercolation (DP)The total amount of water storage in twolayers (surface + subsoil)+=Development of a 2-layer soil water balance modelLateral watermovement
  • 10. Quantifyingdownward watermovement (D)GroundwatertubePerched watertubePercolator
  • 11. Percolation on different soils (clay content)Large variation in percolation across locations could beexplained by clay content of the soil.0.01.02.03.04.05.06.07.08.00 10 20 30 40 50Downwardwaterflow(mm/day)Clay content (%)D= 18.7/clay -0.16 (r=0.67) D measured fromNEThailandD predicted forthese three regionsD measured fromsouthern LaosD measured fromCARDI (Cambodia)When there is standing water in the field.When field water storage decrease from soil Saturate to FCWhen there is no standing water, there is no downwater loss.
  • 12. Generate climate inputSpatial interpolation function in GIS(Variography and kriging)Rainfall data (1985-2008)325 met and hydrological stations:33 met. and 10 hydro. Stations (Laos)169 met. (North and North-East Thailand)94 stations (Cambodia)- Rainfall- Crop Evapotranspiration (ETc)ThailandLaosCambodia
  • 13. Crop Evapotranspiration (ETc)ocsc ETKKET     2234.01273900408.0UeeUTGRETdano  airdryWFCWairdryWsurfacesSSSWK___+ Crop coefficient (Kc)(Initial stage Kc=1.05,development stage Kc=1.2,late season stage Kc=0.6-0.9) (Allen et al.,1998)+Water stress coefficient (Ks)+ Reference Evapotranspiration (ETo)
  • 14. Potential evapotranspiration (Penman-Monteith equation)Week 15 Week 25Week 35 Week 40
  • 15. Soil profile samples
  • 16. Schematic diagram for quantifying free water level and water stressdevelopment based on lowland water balance modelSoil dataClay%Downward(D)Climate dataRainfall ETcFIELD WATER BALANCE MODEL: W(t)= W(t-1)+RF(t)-ETc(t)–D(t)-L(t)-R(t)Determination of LGP, SGP, EGPDaily free water levelEstimation probability of drought occurrenceSat, FC,WP, Air(Saxton & Rawls)•Point based (daily)•Gridded surface(weekly)
  • 17. Soil water balance model for quantifying LGP
  • 18. Duration for the length of growing period (LGP)
  • 19. Start of growing period (SGP) End of growing period (EGP
  • 20. The prediction of water availability can bemade with weather forecastingWeather Forecast DivisionDepartment ofMeteorology andHydrology0501001502002503003504004505005501 2 3 4 5 6 7 8 9 10 11 12Monthsmm20002001200220032004Mean
  • 21. Results of weekly water availability predictionmade at two different times in 2010.Forecast standing water level forweek 28 (9-15 July 2010)Forecast standing water level forweek 41 (8-14 Oct 2010)
  • 22. 0102030405060708090100-40 -35 -30 -25 -20 -15 -10 -5 0Ralative water level (cm)Grainyieldreduction(%)EarlyMediumLateY = -1.68X; r2 = 0.80Linear (Y = -1.68X; r2= 0.80)Y=-1.68X; r2 =0.80 (cm)1.68WL-(%)reductionYield Rel-100.00-50.000.0050.00100.00150.00200.00250.001 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51WeeksmmRainfall Depth of standing water Field water storageSoil water at FC Soil water at WPStartLGP wk19 End LGP wk41FloweringKhanthaboury (wetseason rice, 1988)Estimation of Yield limited by water stress• Water stress aroundflowering (3 weekbefore and after)Ouk et al.,(2006)Start LGP End LGP LGP Flowering date Wlrel(mm) %yield reduction19 43 25 17-Sep -74.1 12
  • 23. Using SWB in conjunction with GIS can provide: a geographical dimension of soil hydrological patterns forvarious rice growing environments. identify the spatial pattern of drought stress that is likely tooccur from long term climate data. identify strategies for plant breeding and geographical targetingof improved varieties with particular drought tolerance ordrought avoidance characteristics.To provide guidelines for practical advice to the rice farmersand researchers for the determination of appropriate cropmanagement strategies (e.g. time of planting, selection ofvarieties) and policy makers for investment decisions.Conclusion
  • 24. THANK YOU!