A high-volume pump has been used to draw water from Loch Morlich to support firefighting efforts.
The Cairngorms National Park Authority (CNPA) said on Sunday there was “growing optimism that the heroic efforts of people on the ground to tackle the wildfire are working”.
However, they added the incident remained live and roadblocks would remain in place until the firefighting operation was completed.
The public has been asked to avoid Glenmore, Abernethy, Loch Morlich and the surrounding areas.
Homes and businesses, including campsites and a ski resort in the Glenmore Forest Park area, were previously evacuated as a safety precaution.
The SFRS said six appliances and specialist resources, including all-terrain vehicles, remained on the scene.
Videos from the response on Saturday showed helicopters water-bombing affected areas.