acre-feet: a measure of water volume, one acre-foot being the amount required to cover one acre to a depth of one footcfs: cubic feet per second, a common way of expressing river dischargedischarge: the rate of river flow, expressed as a volume of water per unit of timehydrograph: a graph showing river stage or discharge over a certain period of timehydrology: the scientific study of the distribution, circulation and properties of the waters of the earth100-year flood: the flood expected to occur on average once every 100 years, or having a 1% chance of occurring any given yearpeak discharge: the highest river level reached during a flood eventstage: the height of the river surface, usually express in feet above a reference elevation