Measures of streamflow timing

Half-flow dates, defined as the dates on which half of the year's total stream-flow has passed, appear to be useful measures of streamflow ‘timing.’ For studying possible changes in streamflow regime caused by watershed management practices, especially vegetational manipulation aimed at increasing snowpack and delaying snowmelt, half-flow dates seem to be more suitable than the date of momentary maximum flow. They are more sensitive to change in regime than another criterion in general use, the percentage of flow occurring during one or more fixed months.