Question to the Department for Environment, Food and Rural Affairs:

To ask Her Majesty's Government whether the primary sources of phosphates present in English watercourses are from (1) agricultural activities, (2) water industry discharges, or (3) other activities.

The overall largest source of phosphorus entering English rivers is effluent from water industry sewage treatment works, contributing about 70% of the total phosphorus loading. 25-30% of phosphorus entering rivers comes from agriculture. For lakes, agriculture tends to be the largest contributor.

Other sources of phosphate are relatively small (less than 5%) at a national scale but can sometimes be important at a local level. These include effluent from septic tanks, road/urban runoff, leaking sewers and storm overflows.