Which method is used to reduce nutrient inflows to water sources?

Preventing livestock from entering water sources is an effective method to reduce nutrient inflows. Livestock can contribute significantly to nutrient pollution through their manure, which is often high in nitrogen and phosphorus. When animals have access to water bodies, they can defecate directly into these systems or create runoff that carries these nutrients into the water, leading to issues such as eutrophication. By excluding livestock from water sources, you can effectively minimize the introduction of these nutrients, promoting better water quality and ecosystem health.

On the other hand, planting deep-rooted trees can enhance soil stability and reduce erosion, but it is not a direct method for controlling nutrient inflows to water sources. Using synthetic fertilizers typically increases nutrient levels in the soil and can contribute to runoff if not managed properly. Increasing urban runoff would likely lead to higher nutrient loads entering waterways rather than reducing them. Thus, the most effective method presented to curb nutrient inflows is preventing livestock access to water sources.