资源环境科技发展态势分析平台

Abstract

Large‐scale models often use a single grid to represent an entire catchment assuming homogeneity; the impacts of such an assumption on simulating evapotranspiration and streamflow remains poorly understood. Here we compare hydrological dynamics at Shale Hills (PA, USA) using a complex model (spatially distributed, >500 grids) and a simple model (spatially implicit, two grids using “effective” parameters). We asked two questions: What hydrological dynamics can the simple model reproduce? What hydrological dynamics does the simple model miss by ignoring spatial details? Results show the simple model can reproduce annual runoff ratios and evapotranspiration, daily discharge peaks but not discharge minima. Neither can it reproduce different streamflow arising from the distinct land surface characteristics at the two sides of the catchment. The similar annual runoff ratios between the two models indicate spatial details are not as important as climate for annual scale evapotranspiration and discharge partitioning. Most of the calibrated parameters in the simple model are within the ranges in the complex model, except that soil porosity has to be reduced to 40% of the average porosity from the complex model. Comparison between the two models indicates that the “effective” porosity in the simple model represents the volume‐averaged porosity in the effective drainage area of the complex model that is connected to the stream; it does not represent the porosity in disconnected, uphill areas. This indicates that an additional uphill functional unit is needed in the Simple model to simulate the full spectrum of the high‐versus‐low streamflow dynamics in natural catchments.

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