Temporal and Spatial Changes of Hydrographic Connectivity with the Development of Agriculture, Industry, and Urban Areas: A Case Study of the Yellow River Basin in Henan Province during the Last Two Decades

Hydrographic connectivity stands as a crucial indicator for analyzing the structural dynamics within river and lake systems. Nevertheless, the impact of changes in hydrographic connectivity, including structural and functional connectivity within extensive river basins, on the progression of agriculture, industry, and habitation remain scarcely explored. To bridge this gap, Henan province in China, traversed by the Yellow River, was selected as a case study. The extraction of water information was facilitated by employing a remote sensing-based Modified Normalized Difference Water Index (MNDWI), while Set Pair Analysis was utilized to construct a hydrographic connectivity evaluation system for the study area spanning the preceding two decades (2000-2020). The results revealed that for structural connectivity, agricultural land covers over 50% and prevails as the primary land-use type; reservoir and lake areas initially increased before subsequently decreasing. Human activities have exerted a profound influence on these changes. Meanwhile, the structural form of the water system has gradually improved, exhibiting an increasing complexity of river networks and a stabilizing connectivity configuration. As for functional connectivity, the natural function remains well-preserved, while the social function demonstrates a positive correlation with the expansion of industrial activities, eventually achieving an excellent level from a moderate level. Overall, agriculture dominated the water usage structure, with residential water consumption steadily increasing, thereby positively impacting hydrographic connectivity in the studied area.