The scientists used a computer model to study how water moves in an arid area with a lot of farming. They focused on a big watershed in Southern California and Mexico. By adjusting the model, they found a better way to predict water flow in different parts of the area. They tested the model on both natural areas and farmland, and found that changing some values made the predictions more accurate for some places. This research helps us understand how water is used in dry regions and can help manage water resources better in the future.