The researchers used a model called SWMM to study pollution in a black and stinking river in Chengdu City. They looked at pollutants like CODCr, NH3-N, and TP during different rainfall conditions. The model accurately predicted pollution levels, showing that pollutants peaked early in the rain and decreased later. CODCr and NH3-N levels dropped with rainfall, while TP levels initially stayed steady but then decreased as phosphorus compounds washed into the river. Overall, more rain led to more pollution in the river, but the pollutants decreased as the rain continued.