<p>Flow routing in rivers is essential for effective surface water management and the strategic design of flood control systems. This study explores the role of considering/ignoring the flow routing component in a daily rainfall-runoff simulation. Hydrological modeling for the basin of interest was conducted using a daily water balance model with two scenarios: one incorporating flow routing and the other omitting it. The results of this model were compared with those of the Exp-Hydro model, which this Python-coded model shares a simple structure and requires minimal input data (daily precipitation, temperature, runoff, and potential evapotranspiration). The study period spanned from 2000 to 2020, with two-thirds of the data allocated for calibration and one-third for validation. Performance assessment of the daily water balance models revealed that the developed model, boasting Nash–Sutcliffe and Kling Gupta coefficients of 0.71 and 0.75, respectively, surpassed the Exp-Hydro model, which yielded values of 0.37 and 0.69, during the calibration period. Notably, the incorporation of flow routing significantly enhanced the performance of the developed model in flow simulation. This study provides valuable insights for rainfall-runoff simulation in data-scarce large-scale basins, favoring the adoption of lumped models over data-intensive distribution models. While integrated models, often criticized for neglecting spatial parameter variations, have exhibited promising results in various studies, their performance can vary between basins due to differing influential factors. Daily flow routing emerged as a pivotal factor, as demonstrated by this study, emphasizing its significance for improving discharge simulations, particularly in large basins.</p>