The adverse effects of global warming have made it critical to transition our reliance on fossil fuels to more sustainable energy sources. Renewable energy can be stored in the form of hydrogen to continuously produce clean energy using a proton exchange membrane (PEM) fuel cell. However, to accelerate commercialization, especially in heavy-duty applications, the performance and durability of the fuel cell needs to be improved. Particularly, PEM fuel cell performance is strongly dependent on the flow fields which should be designed to optimize the transport of reactants and byproducts while maintaining uniform compression of the fuel cell materials. An important flow field design parameter is the channel aspect ratio (channel width by height) which directly influences compression and the transport of reactants and products. Although novel flow field configurations have been studied previously, an investigation on the effects of channel aspect ratio on cell performance using electrochemical testing and operando X-ray imaging has yet to be performed. In this study, we compared the water saturation and electrochemical performance across varying flow field channel aspect ratios from 0.5-2.0 with a fixed active area. The ohmic and mass transport resistances were quantified using electrochemical impedance spectroscopy. Operando X-ray imaging was performed to spatially resolve water saturation under the land and channel regions of the flow fields. We observed that lower channel aspect ratios (or higher number of channels for the given active area) led to lower ohmic resistances but resulted in significant water saturation at higher current densities due to ineffective water removal from the smaller channels. Notably, from these results we elucidated that there exists an ideal channel to rib width ratio to facilitate an effective balance of enhanced water removal using the channels and contact between the porous microstructures under the lands of the flow fields.