Continuous modeling of intermittent stormflows on a semi-arid agriculturalcatchment

The major barriers to modeling hydrological processes in semi-arid and arid areas are a lack of understanding and model representations of the distinc tive features and processes associated with runoff generation in those regi ons and a paucity of field data. In this study, TOPOG, developed by CSIRO i n Australia, was modified by adding model representations of some of the pr edominant features and processes identified through field and experimental investigations on a semi-arid agricultural catchment with complex-terrain a nd mixed land use in the Loess Plateau of China. The modified models were t hen used to continuously simulate both slowly changing hydrologic states du ring interstorm periods and fast-responding overland and tunnel flows durin g stormflow periods. Finally, the effectiveness of model simulation under a wide range of rainfall and spatiotemporally varied land cover conditions w as tested by comparison of simulated and observed stormflow discharges from both catchment outlet and internal plots. Considerable variability in simu lation accuracy was found among storm events and within the catchment. The simulation results highlight the critical importance of crusting and some l and management practices on stormflow generation and its spatial variation in this area. Overall, the simulations showed that the model represents rea sonably well stormflows generated by rainfall events with recurrence interv als >2 years, which account for more than 60% of runoff and 70% of sediment leaving this area. (C) 1999 Elsevier Science B.V. All rights reserved.