• saturated hydraulic transmissivity;
  • uncertainty;
  • hydrograph separation;
  • constraint values;
  • the Amazon basin


Although saturated hydraulic conductivity (K0) and saturated hydraulic transmissivity (T0) are physically based parameters, quite often, their calibrated values lie out of the physically based range, driving modellers to increased K0 values in some orders of magnitude, from field measured values, in order to fit observed discharge data. Therefore, calibration is a necessary process in hydrological modelling. Within a hydrological model, K0 or T0 plays an important role. They allow the model to represent the hydrograph separation through estimates of subsurface discharges. Simulating different flow components in hydrological modelling is an increasing need for basin management and water quality predictions. The present study has the objective to develop two criteria to constrain T0 values using a TOPMODEL multi-velocity approach in order to represent the hydrograph separation in a more realistic way. The method was (i) applied to three sub-basins in the Amazon basin (the Óbidos, the Humaita and Santo Antônio basins), (ii) evaluated by means of a combined objective function and uncertainty bounds and (iii) validated in a long-term simulation. Because the constraint criteria were applied, it has verified a significant reduction in subsurface uncertainty for all the basins. The constraint criteria reduced the number of simulations to 11%, 42% and 23% for the Óbidos basin, the Humaita basin and the Santo Antônio basin, respectively. This means that a large number of simulations were rejected in the sense they represented unrealistic hydrograph separation. Copyright © 2012 John Wiley & Sons, Ltd.