Groundwater storage can play a significant role in defining the annual stream flow hydrograph. Groundwater is an important source of water for streams, and the amount of water stored in the ground can affect the amount of water that flows into a stream during different seasons.

During periods of high precipitation or snowmelt, groundwater storage can act as a buffer, absorbing excess water and slowly releasing it over time. This can result in a more sustained stream flow during drier periods, as the stored groundwater continues to feed the stream.

Conversely, during periods of low precipitation, groundwater recharge may be limited, and the amount of water available to streams may be reduced. This can result in lower stream flow, or even the drying up of streams in some cases.

Overall, the amount of water stored in the ground can have a significant impact on the annual stream flow hydrograph, affecting both the timing and amount of water that flows into a stream throughout the year.