In which types of areas might there be no downstream effect from pesticides?

The selection of areas deeper than 12 feet as having no downstream effect from pesticides is rooted in the physical and chemical dynamics of how pesticides interact with water bodies. In deeper waters, the dilution effect is much greater due to the increased volume of water. This means that any pesticide introduced into such areas may become dispersed over a larger body of water, significantly reducing its concentration and potential for harmful downstream effects.

Additionally, deeper water bodies often have slower movement of sediments and organic materials, which may lead to less resuspension of pesticides compared to shallow areas. The stratification that can occur in deeper bodies of water can also help to sequester pesticides and minimize their movement into downstream areas.

Conversely, fast-moving torrents can quickly transport pesticides downstream, overwhelming natural dilution processes. Wetlands, while sometimes capable of filtering contaminants, can also facilitate movement into other water systems. Overhead irrigation fields can lead to direct contact with water sources as runoff occurs. Thus, the characteristics of deeper water effectively support the assertion of minimal downstream effects from pesticide application compared to other scenarios.