A new model called GISMOD was created to study how water moves through different layers of soil. It includes five parts to help understand things like how water evaporates, runs off, and recharges the ground. The model was tested in the Heihe River area and showed that water mainly soaks into the ground in the upper areas and then flows out in the middle. The model also did a good job predicting how much water would run off at a specific station.