It follows a routine inspection of the dam which revealed damage around a metre below the water line which needed to be repaired.
The water level in the lake has now been lowered to allow specialist engineers to assess the damage. Pumps remain in place to maintain the current water level.
The footpath remains closed on the dam bridge and at the bottom of Shipley Lake Road which used to be an overflow car park for the former American Adventure theme park.
Walkers approaching the bridge from the direction of the cricket ground or the former Shipley Hall site on Shipley hill will be diverted back around the lake.
Another diversion is in place linking Shipley Lake Road to Lodge Farm Bridleway – which links the Nutbrook Trail to Shipley View housing estate – providing access to the Nutbrook Café which will be open this weekend.
Councillor Carolyn Renwick, Derbyshire County Council’s Cabinet Member for Infrastructure and Environment, said:
“I’m pleased that with the support of Derbyshire police and Derbyshire Fire & Rescue we were able to lower the water level in the lake relatively quickly.
“Investigations are ongoing to assess the damage and determine the work needed to repair the dam and I’d urge people to take notice of the footpath closures, keep out of the areas which have been temporarily fenced off and follow the alternative routes signposted.
“I’d also like to thank local residents and park users for their patience and co-operation while this vital work takes place.”