Killington Gauge Weir River Lune

Killington gauge weir is about 2ft high. It doesn't have a fish pass and the fish will not be able to get past this weir especially at low water so the fish won't be able to reach their natural spawning grounds up stream.
The purpose of the weir is to tell how deep the water is. Surely there must be a better way of doing this in the 21st century, lol?
There is an eel pass at the end of the video.