Keywords
conceptual model, hydrological response units, process identification, ungauged basins
Start Date
1-7-2006 12:00 AM
Abstract
Widely available geological and topographical maps contain a high level of potential information on the runoff behaviour on meso-scale (10-1000 km2). They can be used to identify major storage volumes or to estimate the reactivity of rainfall-runoff processes. Within this case study on the Alzette river basin in the Grand-Duchy of Luxembourg, basic characteristics like the location of sources, the spatial distribution of soils and a qualitative interpretation of the permeability of geological formations were used to roughly estimate the extension of hydrological similarly reacting areas (so-called Hydrological Response Units, HRU’s). With discharge data of basins within or surrounding the area of interest, the runoff behaviour of the individual HRU’s was verified and additionally identified runoff processes were added to eventually form parsimonious, conceptual model structures for each HRU. These model structures were evaluated through a Monte Carlo procedure on hourly discharge data of 8 representative basins, after which the parameters were calibrated and fixed. The resulting combined semi-distributed model was validated on discharge data of 10 other basins, with an average efficiency (Reff) loss of 0.04, compared to an optimized reference model, and an acceptable mean Reff of 0.79. This modelling approach only reproduces the general runoff behaviour of ungauged meso-scale basins within the region of interest and to less detail the specific behaviour of ungauged basins individually. In this respect, model uncertainty in the prediction can only been judged from the validation results, since model and parameter uncertainties are not easily transferable to ungauged basins. Application conditions for this approach are the availability of a number of discharge data sets and reasonable physio-geographical homogeneity in the study area.
Conceptual modelling of individual HRU’s as a trade-off between bottom-up and top-down modelling, a case study.
Widely available geological and topographical maps contain a high level of potential information on the runoff behaviour on meso-scale (10-1000 km2). They can be used to identify major storage volumes or to estimate the reactivity of rainfall-runoff processes. Within this case study on the Alzette river basin in the Grand-Duchy of Luxembourg, basic characteristics like the location of sources, the spatial distribution of soils and a qualitative interpretation of the permeability of geological formations were used to roughly estimate the extension of hydrological similarly reacting areas (so-called Hydrological Response Units, HRU’s). With discharge data of basins within or surrounding the area of interest, the runoff behaviour of the individual HRU’s was verified and additionally identified runoff processes were added to eventually form parsimonious, conceptual model structures for each HRU. These model structures were evaluated through a Monte Carlo procedure on hourly discharge data of 8 representative basins, after which the parameters were calibrated and fixed. The resulting combined semi-distributed model was validated on discharge data of 10 other basins, with an average efficiency (Reff) loss of 0.04, compared to an optimized reference model, and an acceptable mean Reff of 0.79. This modelling approach only reproduces the general runoff behaviour of ungauged meso-scale basins within the region of interest and to less detail the specific behaviour of ungauged basins individually. In this respect, model uncertainty in the prediction can only been judged from the validation results, since model and parameter uncertainties are not easily transferable to ungauged basins. Application conditions for this approach are the availability of a number of discharge data sets and reasonable physio-geographical homogeneity in the study area.
