What is an acceptable reason for water contamination?

Runoff from agricultural fields is a well-documented source of water contamination. This occurs when rain or irrigation causes fertilizers, pesticides, and other chemicals used in farming to wash into nearby water bodies. It can introduce harmful nitrates and phosphates into the water, adversely affecting water quality and leading to issues such as algal blooms and subsequent depletion of oxygen levels, which can harm aquatic life.

Agricultural runoff is significant because it can be difficult to control, especially after heavy rainfall, and it often travels considerable distances before entering water supplies. Regulating these agricultural practices and implementing buffer zones or other mitigation strategies is crucial for protecting water sources from contamination.

In contrast, the other options are not typically considered acceptable reasons for contamination. While natural mineral deposits (option D) can affect water quality, they are generally a natural occurrence rather than a contamination issue. Excessive filtration processes (option B) might lead to other operational issues, but they do not directly cause contamination. High temperature variations (option C) can influence water chemistry and biological activity but are not sources of contamination in themselves.