What is the initial stage of self-purification of water where visible pollution is present called?

The initial stage of self-purification of water where visible pollution is present is known as the Zone of Degradation. During this phase, the water body experiences significant pollution with visible indicators such as reduced clarity and unpleasant odors. This is characterized by high levels of organic matter and other pollutants that can lead to adverse environmental effects.

In this stage, microorganisms begin to break down the pollutants, but the water quality remains poor, and the ecosystem is under stress. This phase is crucial because it sets the stage for subsequent stages of purification, where the conditions may improve as pollutants are broken down and consumed by microorganisms, leading to recovery. However, in the Zone of Degradation, the focus is specifically on the presence of severe pollution and its immediate impact on the water environment.