The water environmental capacity (WEC) is an effective tool to solve the water pollution problem and achieve optimal water quality management. However, in a seasonal river, some important input data such as discharge and pollution concentration from river tributaries and lateral inflows are rarely available. This makes WEC calculating more challenging. In this study, the water environment system model that integrates hydrological process in the watershed and hydrodynamic water quality process in the river is proposed to compensate for the lack of data. Taking the Guishui River basin as an example, the SWAT and HEC‐RAS models were selected. The discharge and pollution concentration of ungauged tributary output from SWAT are used as the inputs of the water quality model HEC‐RAS. In addition, static and dynamic design hydrological conditions were used to calculate WEC. The model results basically agree with the observed data, and it was verified that the integrated water environment system model can be used to calculate WEC. The pollutant reduction targets of the tributaries under the monthly line‐fitting method are less than that under static hydrological condition. The obtained results could be used to support water pollution control and water quality management in the Guishui River basin.

中文翻译：

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用分水岭—水质联合模型模拟季节性河流的水环境容量

水环境容量（WEC）是解决水污染问题并实现最佳水质管理的有效工具。但是，在季节性河流中，很少获得一些重要的输入数据，例如河流支流的排放量和污染浓度以及侧向流入量。这使WEC计算更具挑战性。在这项研究中，提出了将流域水文过程和河流水动力水质过程相结合的水环境系统模型，以弥补数据的不足。以桂水流域为例，选择了SWAT和HEC-RAS模型。来自SWAT的未排放支流的排放和污染浓度被用作水质模型HEC-RAS的输入。此外，静态和动态设计水文条件用于计算WEC。模型结果与实测数据基本吻合，验证了该综合水环境系统模型可用于计算WEC。采用月线拟合法的支流污染物减排目标要小于静态水文条件下的目标。所得结果可用于支持贵水河流域水污染控制和水质管理。