Mid Calder weir, in it’s original form, was constructed in the early 19th Century although there is evidence of a similar structure on this site dating as far back as the 16th Century. The main function of this weir is difficult to see today as there has been development of the site over the last 30 years. A mill once stood on the site of the water treatment works and would have processed the grain from the surrounding farms. Power for the mill would have come from the lade, now blocked, which ran along the river bank almost exactly where the path runs today.

Although this weir has a fish pass already, it has proved itself inadequate since it’s construction almost 40 years ago. Construction of a new fish pass is currently underway, which will ensure clear passage for fish migrating upstream. It is due for completion in summer 2022.