Characteristics of the evolution of water security patterns in agricultural areas under the scenario of large-scale agricultural expansion

Sanjiang Plain (China). With the rapid development of the social economy and the increasingly severe impact of climate change, the contradiction between water supply and demand has become one of the core challenges affecting the sustainable development of various countries in the 21st century. However, the water security pattern and its evolution trend under changing scenarios remain unknown. Based on the theory of ecosystem service flow, this paper analyzes the evolution characteristics of the water security pattern in the Sanjiang Plain from 1985 to 2020 through spatial superposition methods and builds a regional comprehensive water security pattern. We find (1) Water production in the region increased from 161.73 × 10⁸ m³ /km² yr⁻¹ (cubic meters per year) in 1985–220.52 × 10⁸ m³ yr⁻¹ by 2020, with a historical peak of 223.17 × 10⁸ m³ yr⁻¹ in 2019. Water demand followed a multi-stage growth pattern with an average annual value of approximately 130 × 10⁸ m³ yr⁻¹ . (2) The spatial distribution of water resource surplus (source) and deficit (sink) areas exhibited counter-phase oscillations, following a dynamic sequence of 'encapsulation - integration - re-encapsulation'. The center of gravity of the 'source' area migrated at an average rate of 7.13 km/a, while the 'sink' area center showed a more active movement at 3.37 km/a, mainly in the Songhua River Basin and Muling Xingkai Plain. (3) The region identified two major water resource contradiction areas, three potential risk areas, 89 ecological nodes, and 40 early warning nodes. High-risk node clusters were found in the middle reaches of the Woken River (8 nodes), the Jiamusi section of the Songhua River (5 nodes), and the Jixi section of the Muling River (3 nodes). (4) The Heilongjiang River plays a crucial role in alleviating the region’s water supply-demand contradiction, while Qihulin River, with high-risk levels, require priority protection. This study provides a scientific basis for water resources management and policy-making, emphasizing the importance of identifying and monitoring water resource risk areas. These findings offer important guidance for governments and relevant stakeholders in formulating interventions and strategic planning for water security. • Reduced errors arising from groundwater base flow issues in the water security framework. • A long-term water security analysis framework was created. • Identified years of acute water resource conflict by analyzing the centroid migration of surplus and deficit areas. • Incorporating river network hierarchy improved water ecology node location identification. • Incorporating river network hierarchy improved water ecology node location identification.