Why lakes would be solely influenced by the carbonate system

Question

Lakes in the Adirondack mountains of New York state areparticularly susceptable to acid rain. One strategy that has been suggested to overcome the acidification of these lakes is to peridocally add limestone (CaCO₃). To make this process work, it has been suggested that enough limestone be added to saturate the water column with Ca⁺ andCO₃^2-. Under these conditions and asuming that the water pH in these lakes would be solely influenced by the carbonate system, solve for the equilibrium pH. Hint(use a charge balance on the system that would have the following form):[H⁺] +2[Ca²⁺]=[HCO₃]+2[CO₃²]+[OH]