The Kawasaki rider clinched second place behind Welshman Chaz Davies, who powered to a magnificent double on the Aruba.it Ducati.
Crucially, Rea – who finished fourth in tricky conditions in Saturday’s opening race behind his Kawasaki team-mate Tom Sykes – managed to keep his nose in front of his key title rival in race two, increasing his advantage at the top by a single point.
Yorkshire rider Sykes set a new World Superbike lap record (1m 37.864s) as he attempted to break away at the start, but he was unable to put significant distance between himself and Rea and Davies, who were in hot pursuit.
As the leading trio grouped together, Rea went for a pass on the brakes at the hairpin but ran wide, with Sykes cutting back underneath.
However, Davies capitalised on the Kawasaki riders’ loss of momentum to surge into the lead and he began to edge clear, wrapping up a brilliant brace by more than two seconds with Rea holding onto the runner-up spot from Sykes.
Ulsterman Rea hailed the importance of every point as the championship enters the final throes, with four more races to go at Jerez in Spain and Losail in Qatar in October.
“I am happy with my race because, today, second place was the best I could do and I am happy with the way I rode.
“It is a 48-point gap now and it is nice to extend the championship lead, if by one point after Lausitzring last time and by another single point here,” he added.
“Championships can be won by a point so every one of them is important. If we can just have a clean end to the season hopefully we can do the job.”
On Saturday, Davies’ tyre strategy worked perfectly as he opted to start the race on intermediates on a wet but drying course.
Rea and Sykes had chosen wets and were forced to make a pit stop, with Sykes switching to slicks while Rea went back out on intermediates.
With Davies clear out front, Honda’s Michael van der Mark came through for second place as Sykes rallied to secure the final rostrum place ahead of Rea.