Russ :

My post above was not as accurately written as it should have been. I think limestone rock rip rap will dissolve in water over time (esp. if acidic) and will help with the problem. I don't think it will be enough alone to correct an acidic water problem that would other wise require regular liming. It is a matter of amount and the ability of the lime to mix with the soil and water.

Wrt your question, depending on water flow it would IMO accelerate the effect of erosion on the rock and thus add to the reduction of water acidity. The question is how much. There is a lot written on pond liming but I have not looked wrt limestone rock as a source.

Btw there are other good reasons (in addition to erosion control and ph) to use limestone rock rip rap, like crawfish . It is a great place for then to live and hide and the food for them ,which grew on the limestone should have higher levels of lime (calcium carbonate) which aids in crawfish shell growth.