Crit­i­cal assess­ment of mega-​​projects is emerg­ing as a much-​​needed dis­ci­pline in an era when, in many places, resource demands exceed envi­ron­men­tal capac­ity. This techno-​​economic study, using the Desali­na­tion Eco­nomic Eval­u­a­tion Pro­gram devel­oped by the Inter­na­tional Atomic Energy Agency, shows that by 2030, China will have the capac­ity to pro­duce 23.1 bil­lion m3 of water annu­ally, at $0.86/m3, as a co-​​product of elec­tric­ity gen­er­a­tion through nuclear power, pro­vided that the coun­try favors desali­na­tion over water diver­sion. We cal­cu­late that the result­ing water pro­duc­tion and sup­ply chain needed to erad­i­cate absolute scarcity for 0.16 bil­lion peo­ple will cost between $0.99/m3 and $1.79/m3, and we prove that this will be afford­able, even for the poor­est  inhab­i­tants. We then com­pare both coal and nuclear desali­na­tion with the cur­rently planned South–North Water Trans­fer Mega-​​Project and show that, while the short-​​run cost of water diver­sion is lower, crit­i­cal vul­ner­a­bil­i­ties and future resource demands favor nuclear desalination.