A Socio‐Hydrological Model for Adaptive Water Allocation in the Heihe River Basin

Abstract Sustainable management of river basins requires an understanding of how water allocation responds to the human decisions driving it, along with the subsequent economic and ecological consequences. Current models often consider water allocation decisions as single and discontinuous events, overlooking the continuous and adaptive nature of human decision‐making processes. This limitation can lead to unintended economic and ecological consequences or even system collapse. We developed a socio‐hydrological model of water allocation that endogenizes the human decision‐making subsystem, which consists of Societal Value, Technology/Practice, and Government Regulation, and couples it with hydrological, economic, and ecological subsystems. Using a 70‐year data set (1949–2019) from the Heihe River Basin, we successfully reproduced the historical trajectory of water allocation. Our results reveal that while the economic subsystem (population and agricultural output) exhibited rapid, self‐propagating growth due to accumulation effects, the ecological subsystem (NPP of the natural vegetation and environmental flow) was characterized by significant hysteresis manifested as two distinct time lags: a delay in decision‐making recognition of ecosystem deterioration and delayed biophysical recovery following remedial interventions. These dual lags explain the transition phase (1990s–2000s) and the persistent trade‐off between economic expansion and ecological restoration. By formalizing the adaptive water allocation dynamics, our model provides a tool for anticipating response delays, thus more predictable water allocation strategies for sustainable basin management.