What are common contributors to waterway pollution?

Agricultural runoff and sewage overflows are indeed common contributors to waterway pollution. Agricultural activities often involve the use of fertilizers and pesticides, which can be washed into nearby waterways during rainfall or irrigation. This runoff can lead to nutrient loading in water bodies, resulting in problems like algal blooms that deplete oxygen levels and harm aquatic life. Sewage overflows, particularly during heavy rains or system failures, can introduce harmful pathogens and pollutants directly into the water, posing serious risks to human health and the environment.

In contrast, natural sedimentation processes, while they can impact water clarity and ecosystems, do not represent pollution in the same manner as runoff and overflows. Public access areas and wildlife habitats, although they may be affected by pollution, are not direct sources of it. Structural developments for marinas can contribute to pollution through increased boat traffic and potential fuel spills, but they are not as significant as the impacts of runoff and sewage. Thus, the correct answer identifies the primary sources of pollution that significantly degrade water quality and affect aquatic ecosystems.