A hydrograph is a graph showing the change in the amount of flowing water over time. A hydrograph of a stream in a desert would be different from a forest stream hydrograph in that it would only show a value for flow only for a short time each year. Deserts receive little rainfall and so there would most likely be no flow for many months of the year. Forest ecosystems are different in that rainfall is higher and so the flow will be present all year round except for variations in the dry season and the wet season.