The carrying capacity of a river was explored through combining use of HEC-RAS and Qual2K and the obtained results were applied to establishing the total maximum daily load (TMDL) system for water quality management, considering three water quality protection (i.e., long-, mid- and short-term) targets and two wastewater reduction strategies (i.e., individual- and group-reductions). Group-reduction control strategy was regarded as a better pollution control measure, in which more pollution reduction in high volume wastewater discharges resulted in a better improvement of river water quality. While many studies statistically investigated the conceptual framework of carrying capacity under the premises of mass balance between pollution sources and sinks, this study quantified the carrying capacity and established a TMDL system based on the respective water quality criteria using water quality modelling.