China's electricity transmission reduces carbon emissions but causes water resource depletion

China's rapid growth in electricity demand intensifies the twin challenges of water conservation and carbon reduction in a system where production and consumption are spatially mismatched. We develop a novel evaluation framework to quantify how electricity generation and interprovincial transmission redistribute “virtual” water and carbon. The method integrates national water/carbon footprints by technology with a dimensionless provincial resource stress index (SI) that scales footprints to local resource conditions, and couples these with observed electricity flows among 30 provinces (2010, 2015, 2020). We further apply Kaya–LMDI decomposition to attribute changes to average water/carbon intensity, generation efficiency, industrial progressiveness, economic level, and population. Our results show electricity generation and supply concentrated in northern, eastern, and southwestern China, with northern provinces dominated by thermal power and southern provinces by hydropower. In 2020, interprovincial transfers embodied 7.8 billion m³ of virtual water and 758.6 Mt of virtual carbon. Transmission supported national decarbonization by increasing carbon-reduction benefits from 63.6 Mt (2010) to 164.0 Mt (2020), but also increased pressure on water resources, with water depletion rising from 1.2 to 1.9 billion m³. A significant negative correlation between water-conservation and carbon-reduction benefits indicates a persistent trade-off, although its strength weakened over time as provincial mixes diversified. The scenario analysis suggests that province-specific, “balanced” adjustments to the electricity mix can deliver larger joint gains than single-objective (water- or carbon-prioritized) strategies. Overall, our study provides policy implications, including optimizing interprovincial trading patterns, differentiating targets by regional resource endowments, and adopting shared-responsibility mechanisms and compensation instruments for exporting regions. The proposed assessment framework also provides a scalable basis for aligning electricity planning with SDGs and China's carbon-neutrality goals.