Geograph - photograph every grid square

According to a contractor involved with major upgrades to Pateshill a few years ago, the works treats 40 million litres of water every day. It would of course be interesting to know which water sources supply the untreated water, but sadly there still seems to be no easy way of gleaning this information online.
There is some information about where the drinking water goes to from here, however, although it is now ten years out of date. In 2014 West Lothian Council published a short report entitled 'Delivering infrastructure in West Lothian'. The report states that West Lothian's drinking water comes via three water treatment works: this one, which is in the SouthWest of the council area; Marchbank, which is near Balerno in SouthWest Edinburgh; and Balmore, just North of Glasgow. Pateshill supplies most of the nearby settlements (including Addiewell, Fauldhouse, Polbeth and Stoneyburn), but only delivers a portion of West Calder's water. It also supplies all of the water to some places far further away such as Torphichen and Whitburn. And as a lot of West Lothian's water is supplied by treatment works situated in other council areas it is very likely that Pateshill's water also crosses council boundary lines. Maybe one day a map will pop up on the internet that provides some answers!