Drain Water Conditions and People Mentality

The flowing water is clear, and there are hundreds of small fish swimming around. The drain water in front of my house is not polluted, thanks to the residents of the upper stream of drain, for not dumping everything into the drain. This is often related to the wealth and education of the residents. Those residents are all well-to-do tycoons owing half acre land and detached houses. Opposite the road, the houses are single storey terrace, and the drain water is grey. Some residents like to throw the rubbish everywhere.
From the drain water conditions, you can also conclude the general mentality and wealth of the residents.