Spatiotemporal dynamics of cultivated land and its impact on water security in northern China

Cultivated land and water resources are vital to agricultural production, and changes in their spatial distribution significantly affect regional water security and food supply. This study analyzes the spatiotemporal dynamics of China’s cultivated land from 1995 to 2020 using land use data. Daily crop water demand is estimated via the Penman-Monteith equation and the crop coefficient method, enabling provincial-level assessments of total demand and deficits. The Water Security Index for Rainfed Agriculture (WSIR) is applied to evaluate how changes in land distribution affect water security. Results show that from 1995 to 2020, China’s cultivated land shifted from the southeast to the northwest, aggravating regional water imbalances, especially in arid northern areas. Water demand is highest in the eastern, southern, and northern regions; however, rainfall shortages in the north lead to significant deficits. The national average WSIR is 69 %; southeastern provinces have relatively abundant rainfall suitable for rainfed farming, while northwestern areas suffer from severe scarcity and depend on irrigation. As farmland expands northward, water resource pressure increases, highlighting the need for efficient utilization and rational allocation. The study emphasizes that spatial shifts in cultivated land have substantial impacts on water security and agricultural sustainability. Future strategies should align farmland distribution with water availability, enhance water transfers, and improve irrigation efficiency to alleviate water stress and ensure food and ecological security. • From 1995–2020, China’s farmland shifted north, worsening water scarcity. • Farmland expansion in arid north worsens severe water shortages. • Rainfed agriculture water security averages 69%, highest in southeast, lowest in northwest. • Urbanization, land policies, and climate change drive farmland relocation, affecting water balance.