Question

How does the agricultural sector cause water pollution?

Answer 1

1. Fertiliser runoff (nitrate and phosphate): stimulates excessive algae and plant growth (algal blooms) that decompose and deplete dissolved oxygen, killing fish and reducing water quality (eutrophication).
2. Pesticides and insecticides: wash or leach into surface and groundwater, poisoning aquatic organisms, entering food chains, and posing risks to human health.
3. Livestock manure and animal waste: introduce large loads of nutrients (N, P), organic matter, and pathogens (bacteria, viruses) that cause oxygen depletion, disease risk, and contamination of drinking water sources.
4. Soil erosion and sedimentation: runoff carries soil into waterways, smothering habitats, reducing light penetration, transporting bound pesticides/metal contaminants, and increasing treatment costs.
5. Leaching to groundwater: soluble fertilisers, pesticides, and salts percolate through soil to contaminate aquifers used for drinking water (e.g., nitrate contamination linked to infant health risks).
6. Irrigation return flow and salinization: poorly managed irrigation can concentrate salts and agrochemicals in drainage water that pollute downstream waters and soils.