AGRHYMET AGRHYMET DHC_CP DHC_CP Diagnostic Hydrique des Diagnostic Hydrique des Cultures Cultures CIRAD CIRAD Champs Pluviométriques Champs Pluviométriques Crop Water Balance Calculation Crop Water Balance Calculation Using Satellite based Rainfall Using Satellite based Rainfall Estimates Estimates Presented Presented by : by : Abdallah SAMBA, Agrometeorologist Abdallah SAMBA, Agrometeorologist AGRHYMET Regional Centre at Niamey, NIGER AGRHYMET Regional Centre at Niamey, NIGER Trieste, June 2001 Trieste, June 2001
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AGRHYMET DHC_CPDHC_CP Diagnostic Hydrique des Cultures CIRAD Champs Pluviométriques Crop Water Balance Calculation Using Satellite based Rainfall Estimates.
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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)
AGRHYMETAGRHYMET CIRADCIRAD
Water fluxes and their effects Water fluxes and their effects
on agricultural hydrosystemon agricultural hydrosystem
Simplification for Water Balance simulation Simplification for Water Balance simulation
(The DHC4 model )(The DHC4 model )
Crop Crop transpirationtranspiration
Crop Crop transpirationtranspiration
Soil Soil evaporationevaporation
Soil Soil evaporationevaporation
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
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)
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
AGRHYMETAGRHYMET CIRADCIRAD
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
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.
AGRHYMETAGRHYMET CIRADCIRAD
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)
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