Development and application of a water resource assessment model with threshold-directed dynamic reward-penalty weighting in arid regions: a case study of the Shule River Basin, Northwest China

The sustainability of water resource systems in arid regions plays a pivotal role in regional ecological security and socio-economic development. A scientific elucidation of their state evolution provides a critical foundation for water resources management decision-making. To address the assessment bias inherent in traditional static fuzzy comprehensive evaluation, which arises from the difficulty of fixed weights in effectively characterizing interannual variations in indicators and the impacts of extreme climate events, this study proposes an innovative fuzzy comprehensive evaluation model based on threshold-directed dynamic reward-penalty weighting. Using the Shule River Basin in northwestern China (2005–2023) as a case study, a threshold-based indicator system comprising five subsystems and 30 indicators was established. Initial indicator weights were determined via the entropy weight method, and a dynamic reward-penalty weighting function was constructed to enable real-time weight adaptation to system states. This dynamically adjusted framework was integrated with the fuzzy comprehensive evaluation method for system scoring, followed by a comparative analysis against conventional static fuzzy comprehensive evaluation results. Key results demonstrate that: (1) The threshold-directed dynamic reward-penalty mechanism significantly enhanced weight adaptability. For instance, a sharp 71.1 percent decline in precipitation in 2020 triggered a 33.2 percent increase in the dynamic weight of this indicator compared to its entropy weight. Conversely, in the same year, the ecological-environmental water use ratio exceeding its threshold by 27 percent resulted in a 52.9 percent reduction in its dynamic weight, thereby precisely quantifying the temporal effects of drought impact and policy intervention. (2) Subsystem scores exhibited dynamic differentiation: The socioeconomic water use subsystem exhibited the highest mean score, while significant interannual fluctuations were observed in the agricultural water use and food security subsystem and the ecosystem health and sustainability subsystem, collectively revealing the stability of regional water use structure and the heightened sensitivity of ecological and agricultural systems to climate fluctuations. (3) The basin's comprehensive water resources system score evolved through three distinct phases: a slow ascent phase (2005–2008), a fluctuating rise phase (2009–2017), and a high-quality development phase (2018–2023). This trajectory confirms the presence of a compound regulatory mechanism within the Shule River Basin's water resources system, characterized by "ecological hysteresis, policy-driven interventions, and technical compensation". This study establishes a novel dynamic analytical framework for assessing arid region water resource systems, substantiated the methodological advantage of this dynamic weighting approach in the non-stationary environments typical of arid zones.