Though the aeration from your waterfall and the bubbles from the SWG are contributing to the pH rise, the higher TA of 130 ppm is making things that much worse in terms of the rate of pH rise. Read HOWTO: Lowering Your Alkalinity and see if you can get your TA down to 80 ppm. As for the saturation index, the tool you are using is resulting in an index that is slightly too low. The Pool Calculator I linked to earlier has a slightly more accurate index calculation (not a huge deal, however -- you don't have to be precisely at zero).

If you end up at 80 ppm for TA and find that reasonable, then you could somewhat raise the CH level to compensate or you could target 7.7 as your pH. Again, not a huge deal here -- 0.1 or 0.2 (+/-) on the index isn't a problem.