AGRHYMET DHC_CPDHC_CP Diagnostic Hydrique des Cultures CIRAD Champs Pluviométriques Crop Water...

AGRHYMETAGRHYMET

DHC_CPDHC_CPDiagnostic Hydrique des CulturesDiagnostic Hydrique des Cultures

CIRADCIRAD

Champs PluviométriquesChamps Pluviométriques

Crop Water Balance CalculationCrop Water Balance Calculation Using Satellite based Rainfall EstimatesUsing Satellite based Rainfall Estimates

PresentedPresented by : by :Abdallah SAMBA, AgrometeorologistAbdallah SAMBA, Agrometeorologist

AGRHYMET Regional Centre at Niamey, NIGERAGRHYMET Regional Centre at Niamey, NIGERTrieste, June 2001Trieste, June 2001

IntroductionIntroduction Brief presentation of the geoclimatic contextBrief presentation of the geoclimatic context

Simulated water balance componentsSimulated water balance components

Evolution of the modelEvolution of the model

DHC_CP functionalitiesDHC_CP functionalities

Simulated resultsSimulated results

IntroductionIntroduction Brief presentation of the geoclimatic contextBrief presentation of the geoclimatic context

Simulated water balance componentsSimulated water balance components

Evolution of the modelEvolution of the model

DHC_CP functionalitiesDHC_CP functionalities

Simulated resultsSimulated results

OverviewOverviewOverviewOverview

AGRHYMETAGRHYMET CIRADCIRAD

Need to forecast the yields of food crops in Need to forecast the yields of food crops in order to :order to :

• best manage the cereal stocks, best manage the cereal stocks, • control the fluxes and control the fluxes and • start in time the food aids.start in time the food aids.

Heaviness of the techniques based on the Heaviness of the techniques based on the statistical investigations and pollsstatistical investigations and polls

Using the water balance simulation to obtain Using the water balance simulation to obtain parameters allowing to estimate the yields.parameters allowing to estimate the yields.

IntroductionIntroductionIntroductionIntroduction

The geoclimatic ContextThe geoclimatic ContextThe geoclimatic ContextThe geoclimatic Context

– The sudano-sahelian beltThe sudano-sahelian belt• CILSS member countriesCILSS member countries• Main cropsMain crops• Average annual rainfallAverage annual rainfall

– Local constraints Local constraints • Rainfall and its interannual variabilityRainfall and its interannual variability• Drought spells during the crop cycleDrought spells during the crop cycle• The « Water management » approachThe « Water management » approach

Apr

il

Sep

tem

ber

0

500

Seasonal Rainfall from April to November 1995

Dakar-yoff (Senegal) Bamako ville (Mali)

Niamey ville (Niger)

Monthly Rainfall (mm)


Water fluxes and their effects Water fluxes and their effects

on agricultural hydrosystemon agricultural hydrosystem

Agricultural Agricultural productionproduction


Crop Crop transpirationtranspiration


Soil Soil evaporationevaporation


DrainageDrainageDrainageDrainage

PrecipitationsPrecipitationsPrecipitationsPrecipitations

Capilary riseCapilary riseCapilary riseCapilary rise

LixiviationLixiviationGround water Ground water

RunoffRunoff

ErosionErosionErosionErosion

( )( )

( ( ))



DrainageDrainageDrainageDrainage

PrecipitationPrecipitationPrecipitationPrecipitation

Ground water Ground water

Simplification for Water Balance simulation Simplification for Water Balance simulation

(The DHC4 model )(The DHC4 model )





The Evolution of the modelThe Evolution of the modelThe Evolution of the modelThe Evolution of the model

–Recent historyRecent history• 19861986 : the first surveys ;: the first surveys ;• 1987-19891987-1989 : the ESPACE project: the ESPACE project (Evaluating and Monitoring Agricultural Production as related to (Evaluating and Monitoring Agricultural Production as related to

Climate and EnvironnementClimate and Environnement) )

–DHC4, a first approach DHC4, a first approach • Diagnosis tool Diagnosis tool • Water balance simulation Water balance simulation • Current limitations Current limitations


DHC4DHC4a first approacha first approach

DHC4DHC4a first approacha first approach

WATER BALANCE WATER BALANCE SIMULATIONSIMULATION

WATER BALANCE WATER BALANCE SIMULATIONSIMULATION

FileFile ScreenScreen GISGIS SpreadsheetSpreadsheet PrinterPrinter

DATA BASES DATA BASES PET (ATLAS)PET (ATLAS) Daily rainfall data (SUIVI)Daily rainfall data (SUIVI) Daily historical rainfall data (CLIMBASE)Daily historical rainfall data (CLIMBASE)

n n yearsyears x stationsx stations

n stationsn stations

RESULTSRESULTSRESULTSRESULTS

Agrometeorological Agrometeorological StationsStations

Available soil water Available soil water CropCrop Cycle durationCycle duration Sowing dateSowing date Daily rainfall dataDaily rainfall data

Modem/FaxModem/Fax


FileFile ScreenScreen GISGIS Spreadsheet Spreadsheet PrinterPrinter

METEOSATMETEOSATSatelliteSatellite

DATA BASESDATA BASES PETPET Historical rainfall dataHistorical rainfall data

Stochastic Rainfall Generation Stochastic Rainfall Generation Parameter CalibrationParameter Calibration

n yearsn yearsx stationsx stations

n stationsn stations

AGRHYMETAGRHYMET

RESULTSRESULTSRESULTSRESULTS

Agrometeorological Agrometeorological StationsStations

WATER BALANCEWATER BALANCESIMULATIONSIMULATION

WATER BALANCEWATER BALANCESIMULATIONSIMULATION

Rainfall dataRainfall data

CIRADCIRAD

The model functionnalitiesThe model functionnalitiesThe model functionnalitiesThe model functionnalities

– Input dataInput data• Climatic dataClimatic data

– Rainfall (satellite estimates)

– PET ( ATLASETP, 1951-1980 period)

• Agronomic ParametersAgronomic Parameters– Available soil water (spatialised data)

– Crop (species and cycle duration, crop coefficients)

– Sowing dates (estimated from METEOSATimages , meteorological and field data)

– Simulation resultsSimulation results• Dates of the beginning of the agricultural seasonDates of the beginning of the agricultural season• Actual evapotranspiration Actual evapotranspiration • Water requirement satisfaction indices Water requirement satisfaction indices • Potential yields estimated 2 months before harvestPotential yields estimated 2 months before harvest

– Optional TreatmentsOptional Treatments• Image processing Image processing • Raster to Vector conversionRaster to Vector conversion


Calcul de l’ETR par l’algorithme d’EaglemanCalcul de l’ETR par l’algorithme d’EaglemanCalcul de l’ETR par l’algorithme d’EaglemanCalcul de l’ETR par l’algorithme d’Eagleman

0

12

34

5

67

89

10

0 2 4 6 8 10

Demande évaporative ETM (mm)

ET

R (

mm

)

HR = 0.5

HR = 0.8HR = 0.9

HR = 0.7 situation favorable

Modeling water dynamics in the soil and root growthModeling water dynamics in the soil and root growth

SowingSowing

Rooting frontRooting front

Wetting front Wetting front

Maximum Maximum availableavailable waterwater

Root Root availableavailable waterwater

Time

mm of watermm of water

First rainFirst rain

Les coefficients culturaux (KCs)Les coefficients culturaux (KCs)Les coefficients culturaux (KCs)Les coefficients culturaux (KCs)

Kcmin Kcmax KcfinInterpolationInterpolation

végétation maturation floraison

Coefficientcultural

Cycle de la plante

Intervalles des coefficients culturauxStades phénologiques de la plante

The Simulated Water Balance Components (1)The Simulated Water Balance Components (1)The Simulated Water Balance Components (1)The Simulated Water Balance Components (1)

Probability of a rain event :Probability of a rain event :Let Aj be the event of rain on day j and Äj the opposite event:

p(Aj / Aj-1) = a11

p(Aj / Äj-1) = a01

Ajustment of rainfall amounts :justment of rainfall amounts :for random rainfall generation, the repartition for random rainfall generation, the repartition function is function is :

F(x) = 1 - eF(x) = 1 - e-((x- x-((x- x00

)/a) )/a)

its reciprocal is :

FF-1-1(y) = x(y) = x00 - a.ln (1-y) - a.ln (1-y)

Synthesis : we know theSynthesis : we know the three parameters that caracterise a given site for a given month (a01, a11, a). We are therefore able to generate as much likely rainfall sequences as we want.

Probability of a rain event :Probability of a rain event :Let Aj be the event of rain on day j and Äj the opposite event:

p(Aj / Aj-1) = a11

p(Aj / Äj-1) = a01

Ajustment of rainfall amounts :justment of rainfall amounts :for random rainfall generation, the repartition for random rainfall generation, the repartition function is function is :

F(x) = 1 - eF(x) = 1 - e-((x- x-((x- x00

)/a) )/a)

its reciprocal is :

FF-1-1(y) = x(y) = x00 - a.ln (1-y) - a.ln (1-y)

Synthesis : we know theSynthesis : we know the three parameters that caracterise a given site for a given month (a01, a11, a). We are therefore able to generate as much likely rainfall sequences as we want.


The Rainfall generator : The Rainfall generator : theoretical basistheoretical basis– Semi-random Generation Semi-random Generation

• probabilistic daily rainfall on a probabilistic daily rainfall on a given site given site

• Ajustement of daily rainfall to a Ajustement of daily rainfall to a probabilistic lawprobabilistic law

– Data spatialisation Data spatialisation using interpolation (logistic regression between stations) at a 25 km 25 km scale.

The Simulated Water Balance Components (2)The Simulated Water Balance Components (2)The Simulated Water Balance Components (2)The Simulated Water Balance Components (2)

The Eagleman relationshipThe Eagleman relationshipETR = 0.732 - 0.05 ETM + (4.97 ETM - 0.661

ETM2) HR- (8.57 ETM - 1.560 ETM2) HR2 + (4.35 ETM - 0.880 ETM2) HR3

with with

HR : fraction of currently available soil water relative to HR : fraction of currently available soil water relative to potentialpotential

ETMp : crop maximum evapotranspirationETMp : crop maximum evapotranspiration

= Kc= Kc ETPp ETPp

IRESP index IRESP index IRESP % = ETR / ETM cycle ETR / ETM sensible

the sensible phase corresponds to the flowerins-fruit set the sensible phase corresponds to the flowerins-fruit set periodperiod

Yield estimationYield estimationRDT (kg/ha) = 11.3 IRESP -128

r

The Eagleman relationshipThe Eagleman relationshipETR = 0.732 - 0.05 ETM + (4.97 ETM - 0.661

ETM2) HR- (8.57 ETM - 1.560 ETM2) HR2 + (4.35 ETM - 0.880 ETM2) HR3

with with

HR : fraction of currently available soil water relative to HR : fraction of currently available soil water relative to potentialpotential

ETMp : crop maximum evapotranspirationETMp : crop maximum evapotranspiration

= Kc= Kc ETPp ETPp

IRESP index IRESP index IRESP % = ETR / ETM cycle ETR / ETM sensible

the sensible phase corresponds to the flowerins-fruit set the sensible phase corresponds to the flowerins-fruit set periodperiod

Yield estimationYield estimationRDT (kg/ha) = 11.3 IRESP -128

r


Principles of DHC_CP Principles of DHC_CP algorithmsalgorithms

• Calculation of daily crop water Calculation of daily crop water consomption using the consomption using the Eagleman relationship Eagleman relationship

• Water satisfaction index Water satisfaction index IRESPIRESP

• Yield estimationYield estimation

DHC_CP: An Early Warning SystemDHC_CP: An Early Warning SystemDHC_CP: An Early Warning SystemDHC_CP: An Early Warning System

AET: Actual EvapoTranspirationAET: Actual EvapoTranspirationAET: Actual EvapoTranspirationAET: Actual EvapoTranspiration

Actual evapotranspiration Actual evapotranspiration estimated one month beforeestimated one month before harvestharvest

AGRHYMETAGRHYMETCIRADCIRAD

Potential Yield in 1994Potential Yield in 1994

Potential Yield EstimationPotential Yield EstimationPotential Yield EstimationPotential Yield Estimation

Suivi de la campagne agricoleSuivi de la campagne agricoleSuivi de la campagne agricoleSuivi de la campagne agricole

Suivi de la campagne agricoleSuivi de la campagne agricoleSuivi de la campagne agricoleSuivi de la campagne agricole

Satisfaction des besoins en eau du mil Satisfaction des besoins en eau du mil

pendant la 3ème décade d ’août 2000pendant la 3ème décade d ’août 2000

Prévision des rendementsPrévision des rendementsPrévision des rendementsPrévision des rendements

Rendements du mil estimés au 30 Septembre 2000Rendements du mil estimés au 30 Septembre 2000

dans les pays du CILSSdans les pays du CILSS

Prévision des rendementsPrévision des rendementsPrévision des rendementsPrévision des rendements

AGRHYMET DHC_CPDHC_CP Diagnostic Hydrique des Cultures CIRAD Champs Pluviométriques Crop Water...

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