Using a lumped conceptual hydrological model for five different catchments in Sweden

Abstract: Hydrological models offer powerful tools for understanding and predicting. In this thesis we havereviewed the advantages and disadvantages of physically based distributed hydrological models andconceptually lumped hydrological models. Based on that review, we went into depth and developed aMATLAB code to test if a simple conceptual lumped hydrological model, namely GR2M, wouldperform satisfactory for five different catchments in different parts of Sweden. The model had ratherunsatisfactory results and underestimated runoff systematically throughout all the five catchments.Additions to the model structure, such as a buffer allowing an approximation for snowmelt delay, wereintroduced with varying degrees of success. Based on analytical exploration of the model theory, it canbe seen that the instability of the model is mainly caused by one of the two free parameters used inGR2M, namely the maximum soil storage capacity. The optimization method used showed lowsensitivity to changes in this parameter while the calculated soil storage had strong dependence on thisparameter. Based on these results, it is fair to say that a simple lumped model likely does not have theability to represent the full range of hydrological conditions found along the gradient of Sweden.