Hysteretic Dynamics of Stream Network Expansion and Contraction Revealed Through High‐Resolution Integrated Hydrological Modeling

Abstract As landscapes cycle through wetting and drying, stream networks expand and contract, driving material export and biogeochemical transformations with important implications for water quality and ecosystem function. Because it is challenging to measure the extent of the active network, streamflow () is often used as a proxy. However, the relationship remains uncertain, especially for larger catchments where direct observation is labor intensive. Using a process‐based integrated hydrological model capable of resolving inundation patterns at high spatial and temporal resolution, we study the dynamics of network extent for a 75 km 2 watershed and its subcatchments. Without catchment‐specific calibration, simulations using the ATS integrated hydrology model agree well with observed daily stream discharge and observed stream persistency regime (perennial vs. non‐perennial). Simulation results reveal that a unique, synchronous relationship between and exists only for small catchments. Specifically, the synchronous data exhibit substantial scatter due to hysteresis, which increases with increasing catchment size. However, a robust relationship free of hysteresis emerges when asynchronous event‐scale peaks of and are considered instead. The event‐scale asynchronous relationship is well approximated as power‐law over the range of peak simulated and remains consistent across nested catchments of varying size, independent of antecedent wetness, season, and storm details. In baseflow conditions, the scaling is also well approximated with a power law but with a larger exponent, suggesting different runoff generation mechanisms. These results offer a more robust framework for understanding stream expansion and contraction in larger, more complex basins.