The South-to-North Water Diversion Project and Tianhe Project in China aim to address the unequal distribution of water resources between the north and south regions. A study compared the sustainability of these projects using a simple game model. It found that the Tianhe Project is more beneficial in the short term, while the South-to-North Water Diversion Project is more sustainable in the long term. To maximize economic sustainability, both projects should be built together. They can improve arid areas environmentally and socially. However, there are challenges in implementing the Tianhe Project, and the study suggests policy recommendations to address them.