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Accounting for spatial variability: a way to improve lumped modelling approaches? An assessment on 3300 chimera catchments

 

M. Bourqui1, C. Loumagne1, N. Chahinian2 & M. Plantier1

 

1 CEMAGREF, Parc de Tourvoie BP 44, F-92163 Antony cedex, France

marie.bourqui@cemagref.fr

2 Institut de Recherche pour le Développement(IRD), UMR HydroSciences–Université Montpellier II, Case Courrier MSE, Place Eugène Bataillon, 34095 Montpellier cedex 5, France

 

Abstract Recent progress in collecting spatialized data with remote sensing techniques should allow the accounting for: (i) the spatial variability of rainfall and (ii) the basins’ physical characteristics in rainfall–runoff models. To benefit from this spatial information, lumped approaches can quite easily be replaced by semi-distributed approaches. However, two questions need to be investigated. Does integrating additional information into a semi-distributed approach successfully improve the performance of flow simulations at the basin outlet? Which type of heterogeneity should first be taken into account to yield the most significant improvements? This paper presents a method to account for basin heterogeneity in lumped and semi-distributed models through the use of indices. Given the requirement for a large database to produce statistically significant results, “chimera” basins (virtual aggregation of two real basins) were used. We characterized 212 French basins using approximately 50 indices of pedology, geology, morphology and land use. Lumped and semi-distributed versions of a rainfall–runoff were compared on 3300 chimera basins. Results indicate that integrating “useful” spatial data in a lumped model can improve its performance without altering its parsimon­ious structure. Some indices correlated with rainfall confirm that the semi-distributed approach is more advantageous than the lumped approach for basins with high spatial variability of precipitation. The possible relations between physical characteristics and model parameters are investigated to help regionalization attempts and hence improve modelling abilities in ungauged basins.

 

Key words  basin heterogeneities; disaggregation; rainfall–runoff modelling