The study looked at how water is moved between different regions in China through trading crops, and whether this movement is efficient and sustainable. They found that while overall water transfers increased slightly, the amount of inefficient transfers decreased. However, unsustainable transfers also increased in some areas. Wheat, rice, maize, and cotton were identified as the main crops contributing to both inefficient and unsustainable water transfers. It's important to consider both efficiency and sustainability when managing crop production and water resources to make sure we're using water wisely.