When Does Moving Computing West Save Water? A Project-Specific Cooling and Break-Even Analysis of China’s East–Data–West–Computing Strategy

China’s East–Data–West–Computing strategy places data centers in cooler climates, but climate alone does not determine water savings. This study combines public cooling evidence, hourly weather data for 2015–2024, a physical heat-rejection model, and provincial electricity-water factors in a project-specific break-even analysis. An audit of 93 mapped records identifies 12 unique western hub projects and four named or cluster-level eastern alternatives, yielding 48 comparisons. Cooling operation is reconstructed from public evidence where possible and otherwise represented by explicit climate-based scenarios. Under the central assumptions, western combined operational water intensity is lower in 27 of 48 pairs, with changes ranging from −63.5% to +110.4%. Against Guangdong, matched wet-tower designs and facility energy efficiency yield higher mean western consumption because of electricity-related water use. Low-water configurations can reverse this penalty, but their advantage depends on the eastern alternative, facility energy overhead, and electricity supply. Local water stress adds a separate constraint on residual campus demand. Westward siting therefore saves operational water only when the destination project crosses the threshold set by the eastern alternative it replaces.