Main river
Main rivers (Welsh: prif afonydd) are a statutory type of watercourse in England and Wales, usually larger streams and rivers, but also some smaller watercourses. A main river is designated by being marked as such on a main river map, and can include any structure or appliance for controlling or regulating the flow of water in, into or out of a main river. Every other open watercourse in England and Wales is determined by statute as an 'ordinary watercourse'.
How these numbers are calculated
Each number comes from the Pythagorean system applied to the title “Main river”: the Destiny number uses all letters, the Heart’s Desire uses vowels only, and the Dream number uses consonants only. Letter values are summed and reduced until a single digit or master number (11, 22, 33) is reached.