The Hydrological Simulation Program–FORTRAN (HSPF) is a widely used watershed-scale model; however, it does not comprise any functions that can be used to simulate rice paddy fields, thereby hindering its applicability in many Asian countries. To address this limitation, a paddy field simulation method was developed by considering the water detention effect and seasonal changes in the outlet height of paddy fields; this was achieved using the existing functions of HSPF. Surface FTABLE, a function of the relationship between surface water storage and outflow, was applied to represent the physical structure and inundated condition of paddy fields. Surface FTABLE was temporally changed by Special Actions, an HSPF module, to reflect the seasonal variation in drainage outlet height. By employing these methods, HSPF was applied to paddy fields for evaluating the model performance. On comparing the simulated and observed values of ponding depth and surface outflow, the model showed good performance with a coefficient of determination that ranged from 0.71 to 0.89 and an index of agreement that ranged from 0.92 to 0.97. Comparing the results of the simulation performed with or without Surface FTABLE, the simulation with Surface FTABLE exhibited a reduced surface outflow (−40.0%) due to the blocking effect of the paddy field, a decreased infiltration (−17.3%) due to the saturation of the upper soil zone, and a higher level of soil water in all subsurface layers. Based on these differences in each component, it is necessary to apply Surface FTABLE when considering the hydrological processes of paddy fields for HSPF modeling. The simulation method developed in this study only uses the existing functions of HSPF without performing any external modifications; therefore, it can be used conveniently to improve the applicability of HSPF in rice-growing regions.

水文模拟程序-FORTRAN (HSPF) 是一种广泛使用的流域尺度模型；但是，它不包含任何可用于模拟稻田的功能，从而阻碍了其在许多亚洲国家的适用性。针对这一局限，考虑水田出水口高度的滞水效应和季节变化，开发了一种水田模拟方法；这是使用 HSPF 的现有功能实现的。地表 FTABLE 是地表水蓄水量和出水量之间关系的函数，用于表示稻田的物理结构和淹没状况。表面 FTABLE 由 HSPF 模块 Special Actions 临时更改，以反映排水口高度的季节性变化。通过使用这些方法，将 HSPF 应用于稻田以评估模型性能。在比较积水深度和地表流出量的模拟值和观测值时，模型表现出良好的性能，确定系数在 0.71 到 0.89 之间，一致性指数在 0.92 到 0.97 之间。比较使用或不使用 Surface FTABLE 进行的模拟结果，使用 Surface FTABLE 的模拟由于稻田的阻塞效应而表现出减少的地表流出量 (-40.0%)，由于饱和而减少的入渗量 (-17.3%)上层土壤带，所有地下层的土壤水分含量较高。基于各组成部分的这些差异，在考虑稻田水文过程进行 HSPF 建模时，有必要应用 Surface FTABLE。本研究开发的仿真方法只使用了HSPF已有的功能，没有进行任何外部修改；因此，它可以方便地用于提高HSPF在水稻种植区的适用性。