This study aims to develop a global lake module to enhance the representation of surface water storage in Xanthos. Xanthos is a global hydrological model designed to interact with the Global Change Analysis Model (GCAM), which in turn explores the co-evolution of energy, water, and land systems with global coverage. Although a module for simulating artificial water storage has recently been integrated into Xanthos, the model is missing a representation of natural lakes. The study's specific objectives include representing lake-river interactions, lake-atmosphere interactions, and lake level-area-volume dynamics. We first remap the over 1.4 million natural lakes recorded in HydroLAKES globally to 0.5-degree Xanthos grid cells. We represent two types of lakes per grid: main-lake and tributary-lake. Those categorized as main-lake have a lake surface area or drainage area greater than the model's spatial resolution; all others are denoted as tributary-lake. Consequently, the ~1.4 million lakes in HydroLAKES were remapped to Xanthos spatial resolution, and similar lake categories within each grid were merged (merged properties include storage, surface area, depth, and shore length), yielding ~ 7400 as main-lake and ~39300 as tributary-lake. These lakes are then represented by suitable volumetric shapes that preserve the actual lake's dimensions, including the volume, surface area, shore length, and average depth, enabling the simulation of seasonal dynamics of lake volume and surface area. The lake module explicitly accounts for the lateral (i.e., lake-stream interactions) and vertical (i.e., precipitation and evaporation) water fluxes. We validate lake surface area simulations against remote sensing derived time series data such as the Global Lake area, Climate, and Population (GLCP) Dataset. This new module enables Xanthos to fully account for freshwater storage (rivers, reservoirs, and lakes) under historical and future climate scenarios.