samba

DHC_CP: 

AGRHYMET DHC_CP Diagnostic Hydrique des Cultures CIRAD Champs Pluviométriques Crop Water Balance Calculation Using Satellite based Rainfall Estimates Presented by : Abdallah SAMBA, Agrometeorologist AGRHYMET Regional Centre at Niamey, NIGER Trieste, June 2001

Overview: 

Introduction Brief presentation of the geoclimatic context Simulated water balance components Evolution of the model DHC_CP functionalities Simulated results Overview AGRHYMET CIRAD

Slide3: 

Need to forecast the yields of food crops in order to : best manage the cereal stocks, control the fluxes and start in time the food aids. Heaviness of the techniques based on the statistical investigations and polls Using the water balance simulation to obtain parameters allowing to estimate the yields.

The geoclimatic Context: 

The geoclimatic Context The sudano-sahelian belt CILSS member countries Main crops Average annual rainfall Local constraints Rainfall and its interannual variability Drought spells during the crop cycle The « Water management » approach AGRHYMET CIRAD

Slide5: 

Water fluxes and their effects on agricultural hydrosystem Agricultural production Lixiviation Ground water Runoff Erosion ( ) ( )

Slide6: 

Agricultural production Ground water Simplification for Water Balance simulation (The DHC4 model )

The Evolution of the model: 

The Evolution of the model Recent history 1986 : the first surveys ; 1987-1989 : the ESPACE project (Evaluating and Monitoring Agricultural Production as related to Climate and Environnement) DHC4, a first approach Diagnosis tool Water balance simulation Current limitations AGRHYMET CIRAD

Slide8: 

File Screen GIS Spreadsheet Printer DATA BASES PET (ATLAS) Daily rainfall data (SUIVI) Daily historical rainfall data (CLIMBASE) Available soil water Crop Cycle duration Sowing date Daily rainfall data Modem/Fax AGRHYMET CIRAD

Slide9: 

File Screen GIS Spreadsheet Printer DATA BASES PET Historical rainfall data AGRHYMET Rainfall data CIRAD

The model functionnalities: 

The model functionnalities Input data Climatic data Rainfall (satellite estimates) PET ( ATLASETP, 1951-1980 period) Agronomic Parameters Available soil water (spatialised data) Crop (species and cycle duration, crop coefficients) Sowing dates (estimated from METEOSATimages , meteorological and field data) Simulation results Dates of the beginning of the agricultural season Actual evapotranspiration Water requirement satisfaction indices Potential yields estimated 2 months before harvest Optional Treatments Image processing Raster to Vector conversion AGRHYMET CIRAD

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

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

Modeling water dynamics in the soil and root growth: 

Modeling water dynamics in the soil and root growth Sowing Rooting front Wetting front Maximum available water Root available water Time mm of water First rain

Les coefficients culturaux (KCs): 

Les coefficients culturaux (KCs)

The Simulated Water Balance Components (1): 

The Simulated Water Balance Components (1) 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 : for random rainfall generation, the repartition function is : F(x) = 1 - e-((x- x0 )/a) its reciprocal is : F-1(y) = x0 - a.ln (1-y) Synthesis : 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. AGRHYMET CIRAD The Rainfall generator : theoretical basis Semi-random Generation probabilistic daily rainfall on a given site Ajustement of daily rainfall to a probabilistic law 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 Eagleman relationship ETR = 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 HR : fraction of currently available soil water relative to potential ETMp : crop maximum evapotranspiration = Kc´ ETPp IRESP index IRESP % = ETR / ETM cycle ´ETR / ETM F sensible the sensible phase corresponds to the flowerins-fruit set period Yield estimation RDT (kg/ha) = 11.3 ´ IRESP -128 r2 = 0.66 AGRHYMET CIRAD Principles of DHC_CP algorithms Calculation of daily crop water consomption using the Eagleman relationship Water satisfaction index IRESP Yield estimation

Slide16: 

Actual evapotranspiration estimated one month before harvest AGRHYMET CIRAD Potential Yield in 1994

Suivi de la campagne agricole: 

Suivi de la campagne agricole

Suivi de la campagne agricole: 

Suivi de la campagne agricole

Suivi de la campagne agricole: 

Suivi de la campagne agricole Satisfaction des besoins en eau du mil pendant la 3ème décade d ’août 2000

Prévision des rendements: 

Prévision des rendements Rendements du mil estimés au 30 Septembre 2000 dans les pays du CILSS

Prévision des rendements: 

Prévision des rendements