In terms of water quality, what downstream effect does organic pollution have?

The choice indicating that lower water quality makes treatment for potable use more difficult is rooted in the fundamental impacts of organic pollution on water ecosystems. Organic pollution introduces a variety of contaminants, such as nutrients (like nitrogen and phosphorus) and organic materials, which can lead to the deterioration of water quality. When organic materials decay, they consume oxygen in the water, creating dead zones where aquatic life cannot survive.

This degradation makes it more challenging to treat the water for potable use because conventional treatment methods may need to be supplemented with advanced processes to remove additional contaminants. Higher levels of biological oxygen demand (BOD) and total dissolved solids (TDS) necessitate more intensive treatment operations, possibly increasing operational costs and complexity for water treatment facilities. Therefore, organic pollution directly translates to a more complicated path to achieving safe drinking water quality standards.

Assessing the other options: Increased flow rates typically relate to hydrological changes rather than direct effects of organic pollution, reduction in sedimentation doesn't directly connect with organic pollution's impacts, and enhanced fish population is generally contrary to the reality of organic pollution, as it typically leads to lower oxygen levels, which can harm aquatic life.