Baseflow residence time (often mean baseflow residence time) is a parameter useful in describing the mixing of waters from the infiltration of precipitation and pre-event groundwater in a watershed. It describes the average amount of time that water within the transient water supply resides in a watershed. Many methods of determining baseflow residence time have been developed, mostly involving mathematical models using a convolution integral approach with isotopic or chemical data as the input.[1] Other methods that do not require such extensive and expensive data collection include Brutsaert and Nieber,[2] which uses aquifer parameters as inputs, and Vitvar et al., which uses the stream flow hydrograph to determine baseflow recession parameters.