Aeration of the water basically allows the CO2 in the water to outgas, causing the water to lose some of its acidity, therefore raising the pH. Splashing kids, fountains, returns rippling the surface, they all have that same effect.

Directing the returns upward is part of the process for lowering alk. If you want the whole process, log out of the forum, go to the forum home page under the section called "dealing with alkalinity and calcium" and then read the sticky there about alkalinity How-to and FAQ.

Janet