4.4.1—Water pollution sources

A pollution explanation names source, pollutant, pathway, receptor and response.

Sewage, agriculture, industry, urban runoff, solid waste and oil use different pathways. Point sources are easier to locate; diffuse runoff needs catchment controls.

In November 2015, Montreal released an estimated 5–8 billion litres of untreated sewage into the St Lawrence River during sewer work. Local evidence reports pollution returning to normal after 4–10 days. Upstream/downstream DO, BOD, coliform, turbidity and nutrient monitoring can track the impact; sewage treatment and interception target the source and pathway.

A complete pollution case links a named location and source to a pollutant pathway, measured environmental impact and management response.

A visible pipe is not the only source; diffuse agricultural and urban runoff can dominate.