Homo Juridicus , Homo Heuristicus , and Homo Anticipans : A Sociohydrological Study of Operator Behavior and Flood‐Drought Tradeoffs in Reservoirs

Reservoir operators make decisions in complex environments where formal rule curves intersect with human discretionary judgment to shape actual operations. Although operators may rely on past experiences in their discretions, little is known about how such discretions, when continuously applied to a reservoir, influence long‐term drought and flood trends. Understanding these discretionary judgments is crucial for assessing their effects on actual storage trajectories, risk tradeoffs, and interactions with forecast‐based decisions. To explore this, we focused on three generic traits of human behavior: homo juridicus (operators strictly follow formal rules), homo heuristicus (operators use heuristics driven by past experiences), and homo anticipans (operators anticipate and adapt using forecast information). We conducted model experiments to assess the effects of these traits and their combinations on long‐term flood and drought trends. This led to the development of a novel sociohydrological model of a coupled human‐reservoir system, inspired by Lake Mendocino Reservoir in California, a region experiencing alternating droughts and floods due to periodic dry spells and sudden extreme rainfall from atmospheric rivers. Results indicate that the salience bias heuristic—prioritizing the recurrence of severe past events—closely mirrors real‐world operator behavior in our study system. Even with rule curves, reservoirs following this heuristic may adapt to the dominant hydrological extreme (drought in Lake Mendocino), increasing vulnerability to the opposite extreme (flood) over time. Introducing an anticipatory strategy like Forecast‐Informed Reservoir Operations (FIRO) may mitigate this trade‐off. The counteracting effect of FIRO on the salience bias heuristic offers insights for enhancing reservoir management.