Abstract: Systems and methods include a method for oil-in-water content. A water injection hydraulic simulation model is calibrated using water disposal pressures and rates of a water disposal system of a gas oil separation plant, including generating baseline disposal pressures and disposal rates. The model is updated based on lab results estimating emulsion viscosity at different oil-in-water content levels. A sensitivity analysis is performed to evaluate changes in disposal pressures relative to the baseline in response to changes in water quality based on an oil-in-water emulsion content. Curves of disposal pressures versus disposal rates at different oil-in-water concentrations are generated using the changes in the disposal pressures. Changes in disposal pressures and disposal rates of the water disposal system are recorded, and the changes are compared against the generated curves.