Oxygen transport and water drainage in the cathode side Catalyst Layer (CL) affect the performance of Polymer Electrolyte Fuel Cells (PEFC). A unique mathematical model has been developed to track local fluxes of water, both liquid in pores and lambda in the ionomer, through a fuel cell electrode. The local pressure, temperature, and heat generation is also predicted. The role of pore size distribution, ionomer to carbon (I/C) ratios, RH, and operating conditions on fuel cell performance has been studied. The results and polarization curves provide insight as to how local water balances affect electrode performance.