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Communication Dans Un Congrès Année : 2013

Evaluation of theoretical crop irrigation requirements in a climate change context. Application to the Durance catchment, France

Evaluation des besoins théoriques en irrigation dans un contexte de changement climatique. Application au bassin de la Durance, France

Résumé

Crop irrigation represents the major fresh water use in the world. In the context of global change, models able to simulate the water demand evolution are valuable. Plant water requirements are generally estimated using simple water balance models. Those models use daily rainfall, reference evapotranspiration ET0 and crop coefficients as inputs. Many uncertainties exist in terms of ET0 projection under climate change, depending on the climatic variables considered in its calculation (temperature, radiation, humidity and/or wind speed. SVAT models do not rely on the use of ET0 but solve the surface energy balance. They can be an alternative for plant water requirements assessment in a climate change context. In this study, conducted within the framework of the R2D2 2050 project (https://r2d2-2050.cemagref.fr/ ), three models of various complexity are used in order to assess the evolution of crop water irrigation needs between present (1980-2009) and near future (2035-2064) climate conditions in the Durance catchment located in the Provence-Alpes Côte d’Azur (PACA) region, south-east of France. The models include the Five-Core water balance model (Chopart et al., 200), the MODIC water balance model (Sauquet et al., 2010) and the SiSPAT (Simple Soil Vegetation Atmosphere Transfer) model (Braud et al., 1995). Five-Core and MODIC compute the soil water balance at the daily time step using as input: rainfall, temperature, ET0 and crop coefficients. Five-Core is used with a constant water available capacity in time, whereas MODIC takes into account root growth in the definition of this variable. MODIC also takes into account the bare soil fraction in the computation of the crop coefficient. SiSPAT is a model solving the surface energy balance, taking into account soil water vertical heterogeneity and computing the energy balance for bare soil and vegetation respectively. SiSPAT requires information about soil hydraulic properties which are derived from an existing data base following Manus et al. (2009). vegetation leaf area index and root depth evolutions are prescribed based on an interannual monthly cycle from derived from existing data bases. It is run using an hourly climate forcing. In terms of climate forcing, the combination of several downscaling methods, several GCMs structure, several GCMs initial conditions lead to about 1000 possible climate scenarii. Such a number of simulations is not compatible with the computing time of the various models. Therefore a resampling method, leading to 10 climate scenarios is proposed. It is based on a conditional latin hypercube resampling (e.g. Minasny and McBratney, 2006). The model results are compared for nine crops, representative of the PACA region: hard wheat, corn, sunflower, grassland, vegetables, potatoes, vineyard, cherry tree and apple tree. The study also provides an assessment of the uncertainty on the future irrigation needs.
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Dates et versions

hal-02599046 , version 1 (16-05-2020)

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Citer

Isabelle Braud, René Samie, Johan Cherel, François Tilmant, Jean-Philippe Vidal. Evaluation of theoretical crop irrigation requirements in a climate change context. Application to the Durance catchment, France. 7th HyMeX workshop, Oct 2013, Cassis, France. pp.2. ⟨hal-02599046⟩

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