What are the primary sources of surface water contamination?

The correct answer encompasses all the options presented because each listed source plays a significant role in contributing to surface water contamination.

Agricultural runoff occurs when rain or irrigation causes fertilizers, pesticides, and herbicides used in farming to wash into nearby streams, rivers, or lakes. This runoff can introduce high levels of nutrients, such as nitrogen and phosphorus, which can lead to algal blooms and subsequent disruptions in aquatic ecosystems.

Stormwater runoff is another critical factor, particularly in urban areas where impervious surfaces like roads and pavements increase the volume and velocity of runoff. This runoff can collect debris, oils, heavy metals, and other pollutants as it travels over the land, leading to contamination of surface water bodies.

Industrial discharges also contribute substantially to surface water contamination. Industries often release pollutants, including heavy metals, chemicals, and waste products, directly into water bodies or indirectly through stormwater systems. Such discharges can severely impact water quality and aquatic life.

By selecting all of these sources, it recognizes the multifaceted nature of surface water contamination and highlights the need for comprehensive management strategies to mitigate these impacts.