A stage-based groundwater-threshold framework for drought-year irrigation management in deep confined aquifers of the North China Plain

The North China Plain relies heavily on deep confined groundwater to alleviate irrigation water shortages during drought years. However, conventional static groundwater control levels are often unable to reflect intra-seasonal changes in groundwater storage and stage-specific water demand, and therefore cannot directly support pumping control during drought periods. To address this issue, this study develops a stage-based groundwater-threshold framework for drought-year irrigation management in deep confined aquifers. The framework adopts a dual temporal structure consisting of a drought management period and rolling guarantee periods. It combines a sliding baseline groundwater level with staged drought-limit groundwater levels (DLGWLs), and determines stage-specific regulation thresholds based on groundwater abstraction, relative recharge, aquifer storage conditions, and planned water demand. The framework was applied to two representative study areas in the North China Plain. The results show that, in the recovering-type groundwater system, the overall supply adjustment factor α was 1, and the DLGWLs mainly served as tools for verifying the planned abstraction scheme and supporting early-warning verification. In the declining or unstable-recovery groundwater system, the overall supply adjustment factor α and pumping adjustment factor β were 0.9756 and 0.9695, respectively, indicating that the framework can identify regulation trigger points and determine the required intensity of pumping reduction. Monte Carlo analysis showed that, under the no-regulation scenario, the probabilities of groundwater levels falling below the sliding baseline groundwater level at the end of the drought management period were 8.30% in Jizhou District and 60.22% in Xinji District, indicating a higher baseline-breach risk in the declining or unstable-recovery groundwater system. The proposed framework provides an operational basis for safe deep confined groundwater supply, stage-specific threshold management, and pumping control during drought years.