Evaluation of the Xinanjiang model structure by observed discharge and gauged soil moisture data in the HUBEX/GAME project

Abstract

Based upon the sense that the use of an inadequate model structure may be more problematic than the use of sub-optimal parameter values, the experience and progress in the HUaihe River Basin EXperiment (HUBEX) during the intensified observation period from 1998 to 1999, as a component of the GEWEX (Global Energy and Water Cycle EXperiment) Asian Monsoon Experiment (GAME) Project, is reported in this paper. It focuses on the realism of the Xinanjiang model structure evaluated not only by discharge hydrographs observed upstream (Huangnizhuang station) and downstream (Jiangji station), but also by volumetric soil moisture data gauged at three sites, Meishan, Nianyushan, and Jiangji. The Xinanjiang model was applied to subcatchments derived from the digital elevation data for runoff generation. The Muskingum method was used for the routing of discharge from the outlet of each subcatchment to the outlet of the whole studied catchment. Soil tension water storage at each time interval computed by the Xinanjiang model, in millimetres is in good agreement with soil moisture data time series gauged in the field. Their correlation coefficients range from 0.810 to 0.867. The results show that the values of soil tension water storage in the Xinanjiang model can represent temporal variability of the soil moisture state variable within the subcatchments, reflecting wet or dry situations in the real world. That, to some extent, answers the question of how far the internal model state relates to real world variables.