Here the photos show it completely empty during August 1984 and a couple more showing the reservoir starting to fill up again during December 1984. (Click over the photo to enlarge)
It was always said that Brown Trout could never survive in Calf Hey because of the high acid levels and I can remember about 7 years prior to this incident (1977 ish) that some local fishing club members put a few hundred brown trout fry of approx 4" in size into Calf Hey to see how they faired. Unknown to many the fish did quite well and in later years there where odd individuals who actually did a spot of fishing now and again and where known to catch trout averaging 14 to 18" in length. I can only presume the Trout got netted prior to the reservoir becoming completely emptied in 84. I cant say as I have seen any evidence of trout in the reservoir in recent years..
Calf Hey Reservoir details extracted from the Irwell Valley Water Board Report of 1939: Earth embankments and puddle core walls, completed in 1859. The first sod cut by Thomas Aitken on 18th May 1854. Average rainfall: 52.5 inches
Top water level: 800.00ft above Ordnance Datron.Length of Embankment: 1025ft. Maximum depth: 42ft. Capacity: 133.5 million gallons.
It does seem that Calf Hey Res was also empty at sometime during the 1990's as this photo shows and kindly given by Jackie Ramsbottom.