Calibration and multiple data set-based validation of a land surface model in a mountainous Mediterranean study area

A detailed understanding of the magnitude of the different components of the hydrologic cycle in Mediterranean mountainous catchments is important for a number of different reasons, such as reservoir management and land use planning. Since it is currently impossible to fully monitor a catchment continuously in a spatially distributed manner, the only way to obtain estimates of the different water and energy balance terms is the application of hydrologic models. These models rely on a large number of parameters, of which estimates are rarely available. The objective of this paper is to assess to which degree the overall performance of a hydrologic model can be improved through the estimation of model parameters using observed soil moisture values. In situ observations of soil moisture, surface runoff, infiltration, and soil temperature in the Ribera Salada catchment in the Southeastern Pyrenees are used for this purpose. Before calibration, the model yielded poor results for all these variables. The use of soil and TOPMODEL parameters estimated using one year of soil moisture observations improved the modeled soil moisture values throughout the study period. A strong improvement in the modeled surface runoff and infiltration was also obtained. The model has been found to adequately reproduce the observed soil temperature. As a summary, the results indicate that using one year of soil moisture observations to calibrate a hydrologic model in Mediterranean mountainous catchments may be sufficient, and that this parameter estimation can lead to a strong improvement in the overall model performance.