The primary impact of agricultural runoff on water quality is the introduction of excess nutrients, primarily nitrogen and phosphorus, into freshwater systems. This nutrient pollution leads to eutrophication, characterized by harmful algal blooms that deplete oxygen levels and create dead zones. Such conditions are detrimental to aquatic life, severely reducing biodiversity and disrupting ecosystem functions. Moreover, contaminated water poses risks to human health, affecting drinking water sources and recreational areas. Managing agricultural runoff is crucial for maintaining water quality and protecting freshwater ecosystems.