The study looked at different ways to grow crops in North China to save groundwater. They used a computer model to see how much water and crops different farming methods would need. They found that growing winter wheat and summer maize every year with limited irrigation is the best for saving water and getting good crops. Other methods with less crops or more water didn't work as well. In the future, all methods will produce less crops because of less water, but the best method will still be growing winter wheat and summer maize every year with limited water. This method saves water, gives good crops, and is the best choice for farming in North China.