The study analyzed how a large dam affected the long-term runoff of a river basin using a computer model. They used data on rainfall, evapotranspiration, and the landscape to simulate the changes. By comparing data from before and after dam construction, they found that the amount of water flowing into the river slightly increased upstream of the dam due to environmental changes. The dam also reduced flood peak flows by storing water, but increased low flows by releasing water in a regulated manner.