Helensburgh No. 2 Reservoir
Argyll and Bute, United Kingdom
The reservoir was of the non-impounding variety. It is no longer part of the local water supply system and, as with reservoir No. 3, is drained and no longer holds water. The earthen dam is 9 metres high and records show it was constructed before 1875.
Reservoir data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).