In Greece the hydrological analysis of ephemeral streams has been especially difficult due to the lack of precipitation and discharge gauges. This study focuses on the investigation of possible relationship between mo...In Greece the hydrological analysis of ephemeral streams has been especially difficult due to the lack of precipitation and discharge gauges. This study focuses on the investigation of possible relationship between morphometric characteristics of small to medium drainage basins and hydrological indices in order to discover morphometric parameters “predictors” of flash flood potential of ungauged catchments. Twenty-two morphometric parameters of twenty-seven drainage basins (ranging in area between 3.6 km2 and 330.5 km2) located in the northern part of the Peloponnese in southern Greece were calculated utilizing GIS software ArcGIS10. Hydrological modeling was performed using a simplified Matlab implementation of TOPMODEL, a conceptual model based on the principle of variable contributing area to runoff production through saturated overland flow, and LISEM, a physically based hydrologic and soil erosion model. Rainfall-runoff simulations were performed for an extreme precipitation event. The simulations outcomes, which include the peak discharge, time to peak and the percentage runoff, were correlated with the morphometric parameters of the catchments. Results were not consistent between the two models, probably due to their different structure, with the LISEM results being closer to what is anticipated. The results demonstrate that area, length of the basin, perimeter and compactness factor appear better correlated with the peak discharge (Qpeak) of the catchment. The same parameters as well as Melton’s number correlate with percentage runoff (C), while “celerity” of the flood wave (length of the basin/time to peak) is better correlated with relief, indicating that as the relief becomes greater, the response of the basin becomes fastest.展开更多
Ecological and hydrological impacts are expected when watersheds are under commercial eucalyptus.In this study we evaluated event-based hydrology and sedimentation in paired watersheds under commercial eucalyptus and ...Ecological and hydrological impacts are expected when watersheds are under commercial eucalyptus.In this study we evaluated event-based hydrology and sedimentation in paired watersheds under commercial eucalyptus and grasslands cover.Flow,suspended sediment concentration,and sediment production were measured and simulated with the Limburg Soil Erosion Model(LISEM)in paired hydrographic watersheds located in southern Brazil;one occupied with 7-years old Eucalyptus saligna plantation(forest watershed-FW;0.83 km^(2))and another Pampa biome with native and exotic grasses used for beef cattle production(grassland watershed-GW;1.10 km^(2)).The effect of rainfall on hydrological and sedimentological variables was more evident in GW compared with FW.The shape of the hydrograph was steepest in GW,with rapid,marked increase and decrease in flow during rainfall.The parameters changed for model calibration in FW and GW were soil saturated hydraulic conductivity,initial soil moisture,and Manning roughness coefficient,whereby the statistical performance was classified as good(NSE>0.75).Fourteen events different from those used in the calibration process were validated for FW and GW,with NSE index classified as“good”and“very good”for hydrology.Our study shows limitations of LISEM in calibrating and validating the sediment yield for individual events due to the spatial variability of factors controlling soil erosion.The validated modeling results of this study may be applied in simulating soil and crop scenarios in watersheds cultivated with commercial forest and grassland for grazing.展开更多
文摘In Greece the hydrological analysis of ephemeral streams has been especially difficult due to the lack of precipitation and discharge gauges. This study focuses on the investigation of possible relationship between morphometric characteristics of small to medium drainage basins and hydrological indices in order to discover morphometric parameters “predictors” of flash flood potential of ungauged catchments. Twenty-two morphometric parameters of twenty-seven drainage basins (ranging in area between 3.6 km2 and 330.5 km2) located in the northern part of the Peloponnese in southern Greece were calculated utilizing GIS software ArcGIS10. Hydrological modeling was performed using a simplified Matlab implementation of TOPMODEL, a conceptual model based on the principle of variable contributing area to runoff production through saturated overland flow, and LISEM, a physically based hydrologic and soil erosion model. Rainfall-runoff simulations were performed for an extreme precipitation event. The simulations outcomes, which include the peak discharge, time to peak and the percentage runoff, were correlated with the morphometric parameters of the catchments. Results were not consistent between the two models, probably due to their different structure, with the LISEM results being closer to what is anticipated. The results demonstrate that area, length of the basin, perimeter and compactness factor appear better correlated with the peak discharge (Qpeak) of the catchment. The same parameters as well as Melton’s number correlate with percentage runoff (C), while “celerity” of the flood wave (length of the basin/time to peak) is better correlated with relief, indicating that as the relief becomes greater, the response of the basin becomes fastest.
基金This study was financed in part by the“Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior”(CAPES)-Finance Code 001Fapergs(“Fundacao de Amparoa Pesquisa do Estado do Rio Grande do Sul”)CMPC Celulose Riograndense.JMR thanks CNPq(Brazilian Council for Scientific and Technological Development)for the research fellowship.
文摘Ecological and hydrological impacts are expected when watersheds are under commercial eucalyptus.In this study we evaluated event-based hydrology and sedimentation in paired watersheds under commercial eucalyptus and grasslands cover.Flow,suspended sediment concentration,and sediment production were measured and simulated with the Limburg Soil Erosion Model(LISEM)in paired hydrographic watersheds located in southern Brazil;one occupied with 7-years old Eucalyptus saligna plantation(forest watershed-FW;0.83 km^(2))and another Pampa biome with native and exotic grasses used for beef cattle production(grassland watershed-GW;1.10 km^(2)).The effect of rainfall on hydrological and sedimentological variables was more evident in GW compared with FW.The shape of the hydrograph was steepest in GW,with rapid,marked increase and decrease in flow during rainfall.The parameters changed for model calibration in FW and GW were soil saturated hydraulic conductivity,initial soil moisture,and Manning roughness coefficient,whereby the statistical performance was classified as good(NSE>0.75).Fourteen events different from those used in the calibration process were validated for FW and GW,with NSE index classified as“good”and“very good”for hydrology.Our study shows limitations of LISEM in calibrating and validating the sediment yield for individual events due to the spatial variability of factors controlling soil erosion.The validated modeling results of this study may be applied in simulating soil and crop scenarios in watersheds cultivated with commercial forest and grassland for grazing.
