Base flows typically vary throughout the day with weekday residential peak flows occurring in the morning and in the evening. The heaviest residential use is generally seen on Saturday and Sunday. Commercial base flows typically start in the morning around 8:00 a.m., with peaks occurring around late morning/early afternoon and again around late afternoon/evening. Industrial and light industrial flows can have sporadic evening peaks, but generally have base flows during the workday with afternoon peaks. The system experiences higher weekend flows than weekday flows; therefore, the model was calibrated to the weekend flows.
Because the highest flows were governed by the residential users on Saturday and Sunday, the model was set up to mimic these high flow patterns instead of a typical weekday pattern, which was observed to be much lower in flow. The unit diurnal curve allows the InfoSWMM software to quantify the flow throughout the day for the various types of land use activities. The diurnal curve patterns that were used in the model are shown in Figure 5-1.