Flow simulation in an ungauged basin: An alternative approach to parameterization of a conceptual model using regional data

An alternative approach to parameterization of the conceptual Soil Moisture Accounting and Routing (SMAR) model for continuous simulation of flow in an ungauged basin, using daily discharge data from neighbouring gauged catchments, is presented. The methods are suited for situations where adequate data on soil, geology, land use, etc., which are required for relating model parameters to catchment-specific hydrometeorological and physiographical characteristics, are not available. Four methods, namely: regional averaging of data, regional pooling of data, transposition of data, and averaging the parameters of the model calibrated for different gauged catchments, are applied to a group of 12 catchments in France. The concept of a pseudoungauged basin is used whereby each catchment is first considered as ungauged for the purpose of flow estimation, and only subsequently considered as gauged to evaluate the performance of the flow estimation procedures. Performance evaluation using the Nash-Sutcliffe efficiency index shows that pooling of data is the best in this approach.