The best way to "forecast" is to build a predictive geochemical model. This includes, but is not limited to: an appropriate conceptual model, a reasonable accurate water balance, an associated mass balance. Then you need loading rates (kinetic testing) paired with static test results to assess the rate of NP consumption to make reasonably accurate pH predictions. Then you need to find some way to factor in solubility constraints.

KCB has won awards for this type of modeling work and we're continuing to make significant innovations leading to more robust predictions.

We use phreeqc code in GoldSim to provide dynamic solubility constraints for changing conditions within the construct of GoldSim that handles all the water balance and mass balance aspects. We use several geochemical observations to allow system progression to be tied to NP mineral abundance i.e. dolomite vs. calcite, which is paired to pH, alkalinity and activity, from there the pH recursively affects source term loading rates, which affect source term mineral depletion; activity and pH affect OH, alkalinity as carbonate and bicarbonate which directly affect metal solubility such as Cu (Malachite), Mn (Rhodochrosite), Zn (Smithsonite), Fe (Ferrihydrite/Goethite in some cases Siderite), as well as Ca/SO4 (gypsum), Al (gibbsite), and others. Precipitated solute is removed from solution resulting in your near equilibrium solution containing dissolved metals.