How can agricultural practices impact water quality?

Agricultural practices can significantly impact water quality, primarily through the phenomenon of agricultural runoff. This occurs when rainfall or irrigation causes excess water to flow over the land, picking up and carrying with it various substances that may be present in the fields. This runoff can introduce pesticides, fertilizers, and other chemicals into nearby waterways, leading to pollution and detrimental effects on aquatic ecosystems.

When fertilizers are applied to crops, nutrients like nitrogen and phosphorus can wash away and enter streams, rivers, and lakes. This nutrient enrichment can result in phenomena such as algal blooms, which deplete oxygen levels in the water and harm fish and other aquatic organisms. Similarly, pesticides used to control pests may also find their way into water sources, posing risks to both human health and wildlife.

The other options do not accurately reflect the reality of how agricultural practices interact with water quality. While practices like filtering pollutants may occur in certain cases, they do not represent the broader impact of agricultural runoff. Similarly, asserting that agricultural practices have no impact on water quality overlooks the well-documented evidence of water pollution stemming from farming activities. Finally, while some natural filtration may occur, it is often overwhelmed by the volume of pollutants introduced through agricultural practices.