Incorporating lateral subsurface flow processes into Earth System Models (ESMs) is essential for accurately simulating water, energy, and biochemical cycles. These processes play a critical role in regulating the movement and distribution of water, carbon, nutrients, and energy within the Earth's subsurface environment. Lateral flow influences water storage in soil, which in turn affects water availability for ecosystems and human use. It also impacts the distribution of heat and energy within the subsurface, influencing regional climate patterns. By integrating proper simulation of subsurface water storage and water movement across landscapes into ESMs, the importance of simulating runoff and streamflow became crucial for accurately simulating and predicting for applications such as flood mapping, water resource management, and disaster risk reduction. In this research, we have integrated the WATDRN algorithm (Soulis et al., 2000) which is widely used in multiple models in Canada into the Canadian Land Surface Scheme including Biogeochemical Cycles (CLASSIC) model. We tested the implementation of the hillslope presentation in a Canadian river basin and compared the slope versus the flat version model. We performed multiple simulations including changing the model configuration, such as soil discretization structure and soil permeable depth. Moreover, to produce spatially distributed streamflow over any domain of interest, we coupled the CLASSIC model with a stand-alone routing tool, mizuRoute. To evaluate the recent integration, CLASSIC outputs were compared to streamflow observations over the domain. Results showed that recent integration improved model performance in terms of streamflow estimates compared to the flat simulation.