Socioeconomic development dominates changes in runoff response over 1/3 of global river basins

Global warming and human activities are altering the global hydrologic cycle, raising concerns about water availability. The rainfall-runoff relationship (RRR), determining how much rainfall becomes runoff, remains poorly understood globally, particularly regarding the influence of socioeconomic development. Here, we analyze rainfall and runoff data from 1,492 global basins over the period 1990–2015, finding that 80.5% experienced significant changes in RRRs. Using a hydrologic model-based attribution framework, we attribute these changes to natural environmental factors in 67.7% of basins and to socioeconomic factors in 32.3% of basins. Notably, among basins where socioeconomic factors dominate RRR changes, 65.9% show reduced runoff coefficients, indicating that human activities are decreasing runoff generation. Our findings demonstrate that socioeconomic developments such as population growth and GDP increase—reduce runoff by enhancing water withdrawals and consumption, thereby exacerbating water scarcity. This study highlights the substantial human impact on hydrologic processes under climate warming.