Pilot-point based multi-objective calibration in a surface-subsurface distributed hydrological model

In this study, a fully-coupled surface-subsurface, distributed, physics-based hydrological model was calibrated using the pilot-point method. A minimum variance field rule was included in the objective function to regularize the extensive calibration exercise that included 74 parameters (72 associated with pilot points and two spatially-invariant channel parameters). Because the overland and vadose zone systems are not in permanent hydrological connection, the information contained in the observation points may not be accessible by the pilot points at all times, rendering them insensitive to the observations and hindering the calibration process. An analysis of the spatial and temporal variability of parameter sensitivities was done to explore how the information contained in local observations spreads from the observation points to the pilot points, where parameter values are identified. The results show that the channel flow time series is valuable to identify the parameters at all pilot-point locations, indicating that the information in channel flow propagates to the entire basin. However, information in soil moisture measurements is of local extent and thus only valuable to identify the parameters at locations close to the observation point.Editor D. Koutsoyiannis; Associate editor I. NalbantisCitation Maneta, M.P. and Wallender, W.W., 2013. Pilot-point based multi-objective calibration in a surface-subsurface distributed hydrological model. Hydrological Sciences Journal, 58 (2), 390-407.