Comparison Of Two Model Approaches To Investigate Hydrological Processes In Five Selected Catchments In The Upper Blue Nile River Basin Ethiopia.

The successful application of hydrologic models depends not only on the model structure, therndifferent time and space scale associated, but also on the accuracy of the simulated discharge. Thernkey issue for operational users of hydrologic models is whether physically-based distributed modelsrnperform sufficiently better than conceptual models to justify the increased time and effort required forrntheir application. The main objective of the research was comparison of two modelling approachesrnusing on one hand quasi-semi-distributed conceptual model HBV–Light and on the other handrnspatially distributed hydrologic model ArcSWAT. These models were applied to five test catchmentsrnrepresenting wide variability in geographic location, climatic condition, areal extent andrnphysiographical characteristics located in the Upper Blue Nile River Basin. rn rnThe automatic calibration methodology, which is used in this study, applied a hierarchy of threerntechniques, namely screening, parameterization, and parameter sensitivity analysis, at the parameterrnidentification stage of model calibration. Operating in continuous river-flow simulation mode, torndemonstrate their effectiveness, a split-sample test was applied to the test catchments using a number ofrnperformance evaluation criteria. rn rnThe monthly Auto-calibration and Validation results show that with increasingly secured efficiencyrnthe two models can equivalently capture monthly and seasonal flow patterns. This finding justifies thatrnthere is no significant benefit in applying the spatially-distributed model and that the simpler conceptualrnmodels would provide acceptably better simulations for monthly and seasonal flows. From calibrationrnand validation results on daily time step, the performance of the SWAT is clearly not as good as thernHBV model. In the case of SWAT daily discharge generally, however, showed less accuraternsimulation with some major discrepancies, which is a common attribute shared by many otherrnstudies, and r² of only less than 0.6 and Nash-Sutcliffe efficiency NSE of only less than 0.5 rnautomatically were observed for all test catchments. This study confirms that simpler models forrncontinuous river-flow simulation can surpass their complex counterparts in performance. There is arnstrong justification, therefore, for the claim that increasing the model complexity, thereby increasingrnthe number of parameters, does not necessarily enhance the model performance. It is suggested that,rnin practical hydrology, the simpler models, “based largely on exercises in pattern recognition andrncurve fitting, through analysis of the available data” (O’Connor, 1998), can still play a significantrnrole as effective simulation tools, and that performance enhancement is not guaranteed by thernadoption of complex model structures. rnii

Get Full Work

Report copyright infringement or plagiarism