Optimizing crop planting structure for balancing water, ecology, and economy in groundwater over-exploited ecologically sensitive regions

Bashang Plateau in China serves as an ecological barrier against wind-driven sand invasion and is a vital water conservation area in the Beijing-Tianjin-Hebei region. Since the 1990s, the expansion of the vegetable industry has increased irrigation demand and actual groundwater extraction, threatening regional water security and ecological stability. This study aims to quantify crop-specific water consumption and explore sustainable planting structures that reduce agricultural water use while maintaining economic and ecological viability. We analyzed the temporal dynamics of dominant crop planting areas (corn, beans, naked oats, oilseeds, coarse cereals, sugar crop, potatoes, and vegetables), and the spatial-temporal characteristics of regional precipitation, temperature, and soil moisture distribution from 2000 to 2020. Crop-specific evapotranspiration (ET) was measured through field experiments (2021–2022), and the nondominated sorting genetic algorithm II (NSGA-II) was employed to generate sustainable planting structures under 10 %, 20 %, and 30 % regional water-saving targets. Over two decades, planting structure shifted toward water-intensive crops, peaking during 2013–2016 before declining due to water scarcity and market dynamics. The 10 % water reduction scenario (S1) proved feasible by reducing the planting area of potatoes and vegetables and increasing coarse cereals (particularly in Shangyi and Kangbao, with lower precipitation), maintaining economic benefits and ecosystem service value. However, 20 % and 30 % reduction (S2, S3) caused economic losses of 6 % and 12.7 %, respectively, due to coarse cereals could not fully offset losses from reduced potato and vegetable production. Balancing groundwater sustainability with agricultural productivity requires optimizing planting structures, supported by improved irrigation technologies and policy incentives. The findings emphasize the need for a balanced crop restructuring strategy, prioritizing high-value crops while limiting water-intensive crops to ensure a sustainable agricultural system in this ecologically sensitive region.