Agricultural runoff refers to water that flows over farmland, carrying with it various substances like fertilizers, pesticides, and soil. When it rains or when fields are irrigated, this water can wash these chemicals into nearby rivers, lakes, and streams, potentially harming aquatic ecosystems. This runoff can lead to problems such as water pollution and algal blooms, which can deplete oxygen levels in water bodies. Managing agricultural runoff is important for protecting both the environment and public health, as it can affect drinking water sources and the overall quality of ecosystems.