INTERCOMPARISON OF THE LUMPED VERSUS SEMI-DISTRIBUTED HEC - HMS HYDROLOGICAL MODEL IN THE KALAMAS RIVER BASIN

This paper compares the lumped and semi-distributed structure of the HEC-HMS model, using daily data of the 1449.3 km(2) Kalamas river basin, Greece. The hydrologic analysis of the study area is attempted for four storm events in two ways: a) with division of the area in two sub-basins (lumped model) and b) with division of the area in eight sub-basins (semi-distributed model). The model calibration procedure was conducted on two out of four flood events, and the model parameters were optimised by trial and error technique. Results show that all applied individual mathematical models provide a reliable representation of the corresponding components of hydrological circle; however, they provide better results when they are applied in small catchments. The results arising from both the lumped and the semi-distributed application of HEC-HMS lead to the conclusion that the semi-distributed form of the model has an advantage against the lumped form in the case of simulating complex flood hydrographs and when spatially detailed rainfall is available. With regard to the calibration of HEC-HMS, for both lumped and semi-distributed application scenarios, the resulting conclusion is that, for a more objective calibration of the model, which will support more reliable forecasts, a global multi-objective optimisation algorithm should be applied.