The scientists used a computer model called ISAREG to figure out when and how much water to give to crops in the Hetao area in northern China. By looking at the weather, soil, and available water, they tested different irrigation methods for four main crops. They found that by using a bit less water than usual (about 45 mm less), they were able to save water but still get good crop yields. This means that farmers in Hetao could use less water for irrigation and still grow crops effectively.