Evidence of recent pollution (Foam)

White, cream, or brown bubbles collecting on the water surface or edges, forming patches or clumps that persist for some time. Small amounts of foam can occur naturally, especially after rain or in fast-flowing water.

Limited impact

Small natural foam patches in eddies (has an ‘off-white’ tinge.

Noticeable impact

Noticeable foam lines or accumulations – may be pure white indicating chemical origin.

Significant impact

Thick persistent foam covering large areas – especially if accompanied by chemical odour.