Evaluation of Multiple Groundwater Management Targets by Applying Frequency, Duration, and Magnitude Metrics to Water Table Depth Targets

Abstract

Groundwater resource management faces significant challenges due to groundwater overdraft and waterlogging. Establishing thresholds of the water table depth (WTD) is crucial to ascertain whether WTDs align with ranges conducive to the health of social-ecological systems. However, existing studies often overlook multiple protection targets, dominant targets across different seasons, and spatial variations of thresholds. The long-term effects of WTDs exceeding threshold ranges of the WTD also need to be further explored. Here we propose a novel framework for calculating grid-scale thresholds across seasons, incorporating multiple targets. This framework calculates frequency, duration, and magnitude metrics, offering an evaluation of multiple groundwater management targets over decades. We apply this framework to the lower Tao'er River Basin in China, revealing threshold depths for shallow water tables ranges of 1.16–2.05 m and 1.16–4.05 m during non-growth and growth periods, while threshold depths for deep water tables ranges from 6.28–33.54 m and 1.96–30.72 m, respectively. Climate change scenarios demonstrate minimal frequency changes but significant deterioration in duration and magnitude compared to the historical scenario. Grids with duration of transgressions more than 12 months expand by 1–2 times, while grids exceeding thresholds of the WTD by 2 m increase by 37%–81% under climate change and intensified pumping scenarios. A 20% increase in groundwater pumping leads to an average rise of 151%, 224%, and 147% deterioration in frequency, duration, and magnitude. Furthermore, 1%–6% of grids face dual challenges of groundwater storage reduction and waterlogging. These findings can inform groundwater resource management under various potential futures.