sentences:  Whitewater kayakers generally need specific water flows to do their sport, and creeking takes this requirement very strictly, as too little or too much water in a stream will have massive impacts on ease and safety.In eastern North America creeks usually only run in the spring as the rivers are fed by snow melt, and in the fall as this is generally the rainy season.In parts of the world where there are glaciers creeks may run in the spring, the heat of summer and then again in the fall giving kayakers three time windows to run the rivers.