Water exists in a “Water Cycle” that manifests fractally at many different levels and scales – from the global climatic cycle of evaporation, cloud formation, and precipitation to more micro level versions of drawing water from a well, drinking it and disposing of it into a toilet or local stream.
When we draw water for commercial, industrial or domestic use we make it dirty. Water is cleansed of its contaminants as it passes through the Water Cycle so it can be drawn and used again.
The fact that used water is constantly recycled through the Water Cycle is both a blessing and a curse.