Direct deposition to a waterway occurs when the source of the contamination occurs directly over a waterway or so close that the potential for wash-in is very high. Common causes of direct contamination include livestock defecating as they cross a stream or get access to water, and non-targeted fertiliser application. For comparison, indirect pathways include overland flow (surface runoff), subsurface drainage (deep drainage and artificial).
This distinction between direct and indirect contaminantion is important as when direct deposition occurs there no opportunity for the land to attenuate nutrients and immobilise microbes, for plants to uptake nutrients, or die-off of microbes in faecal matter to occur before reaching the waterway. The result of direct deposition is always deemed high risk.
Avoiding direct deposition comes down to how the land is managed. This section looks at some of the key land management actions that reduce the direct deposition of contaminants into a waterway.