The water level at Toddbrook Reservoir in Whaley Bridge is now down by 8.4 metres, the Canal and River Trust has confirmed.
With pumping continuing throughout the night, the reservoir is currently at 25 per of its holding capacity.
An RAF Chinook helicopter remains at the scene, dropping one tonne bags filled with aggregate to further stabilise the spillway.
In an update released last night, Derbyshire police confirmed that once a level had been reached, and was able to be maintained, engineers would view the damage to the wall and a decision would then be made regarding when it is safe for evacuated residents and businesses to return to the town.
The Canal and River Trust added: "Again, our thanks go to anyone affected by the current situation for their co-operation and patience and to the many who are supporting the emergency operation."
Derbyshire Fire and Rescue Service said pontoons had been put in place on the reservoir to float high volume pumps so that pumping can continue as the water level recedes. This takes away the need to continually relocate pumps to ensure the efficient and effective removal of water. Pumping will continue until engineers and specialists deem the dam safe.
Deputy Chief Fire Officer Gavin Tomlinson said: "We hope to have the water at a safe level late this morning or by lunchtime, to allow specialist engineers to inspect the dam and feedback about its safety. This inspection will have to take place before any decision regarding the return of residents can take place.
“The priority of the incident has always been the safety of the residents of Whaley Bridge and they have been incredibly resilient throughout the evacuation. Fingers crossed for them and hopefully we can give them some good news very soon."