ABSTRACT
The concept of non-point source (NPS) pollution was first put forward and studied in North America and was the subject of intensive research, especially from the mid-1960s to the 1980s due, in part, to the eutrophication ‘crisis’ in the Great Lakes of North America. In the 1970s, although point source pollution was reasonably well controlled, the water quality compliance in surface waters was 65 per cent for rivers, 78 per cent for seas and only 42 per cent for lakes (Liang et al, 2004). This convinced researchers that some source other than the point sources was still damaging water quality. Consequently, NPS pollution refers to polluting sources that are diffuse, that is, not discharged from an identifiable point (e.g. through a pipe). This includes agriculture, street run-off, deposition of atmospheric pollutants, mine sites, transportation corridors, etc. In the US, non-point source is defined as meaning any source of water pollution that does not meet the legal definition of point source in the Clean Water Act. NPS types, amounts and best management practices became a subject of intensive research. In terms of pollution impacts, two types of NPSs are of particular concern: agricultural NPSs and urban NPSs, although NPSs can include many other types of land uses (Ongley, 1996). To this day, agricultural NPS pollution continues to be a major concern for water quality in the US (USEPA 2003a).
