According to the analysis of the possible contamination of the section and the field experiment and the analogy experiment, we could obtain the interval of the properties of the section, as listed in Table 2. Let us assume that sewage spilled into the section instantly. After a period, the downstream monitoring station detects a series of pollutant concentration data, as illustrated in Figure 2. The true fluid properties and hydraulic characteristics parameters are listed in Table 2, and the designed data of the spill, including occurrence time (Time), the total load of the sewage (Load), and the location of the event (Location) are all supposed to be known, and are 120 minutes, 1,000,000 g and 5,000 m, respectively.