There are folks on this forum that are chemists and that can feed your curiosity, and I'm not one of them, but basically, yes--the operation of the SWCG releases carbon dioxide that is gassed off, which leaves the water more basic than it was. Rising pH is a normal part of SWCG operation, but adding borates as Kelemvor suggested, and keeping the TA on the low side, can help reduce the rate of the pH rise.