Causes of water contamination：First, sea surface intrusion and backflow in coastal cities. The key reason leading to the intrusion of saltwater lake is the excessive extraction of surface water. Seawater backflow refers to the condition of sea surface intrusion into the aquifer. Second, environmental pollution. Chemical wastewater is discharged into sewer pipes, rivers and lakes in big cities or immediately into drainage ditches and large dikes, resulting in organic chemical environmental pollution of surface water. Third, environmental pollution in agriculture and animal husbandry. For example, agricultural film pollution, fertilizer pollution, improper treatment of livestock and poultry excrement, and improper feeding and management. Fourth, environmental pollution of food, clothing, housing and transportation. The treatment of domestic waste is accompanied by the cleaning of wind and sun and surface runoff, and its total mixture can gradually penetrate into the ground, polluting the surface water.
The consequences of water contamination: first, harm to human health. Second, it reduces the yield and quality of crops. Third, it affects the output and quality of fishery production. Fourth, restrict the development of industry. Fifth, accelerate the degradation and destruction of the ecological environment.
