The amount of water that flows into streams and rivers soon after a rainfall, causing the stream to rise above its stable condition. Sometimes called stormflow, quickflow, or direct runoff , this flow of water occurs relatively quickly to channels and causes water levels to rise, peak, and then recede as the storm water drains from the watershed following the storm. Storm runoff is the sum of precipitation falling directly on the channel, overland flow, and subsurface flow. Groundwater generally takes a long period of time to contribute to streamflow and does not appreciably affect streamflow rise immediately after the storm; therefore, it is not considered a part of stormflow. When water levels rise above the banks of a stream or river, storm runoff is considered to cause a flood. In technical hydrology terms, stormflow is the portion of the hydrograph that is above base flow.