Residence Time Distributions in Dynamically Changing Hydrologic Systems

Dr. John L. Wilson, Department of Earth and Environmental Science,
New Mexico Tech,Socorro, NM 87801, USAAbstract:Spatial and temporal variability of weather and climatic forcings induce a dynamic response in hydrologic systems. Regional groundwater systems, mountain watersheds, and stream hyporheic zones are examples of hydrologic systems driven by forcings varying at several time scales, from daily to seasonal to decadal and longer. Hydrologic systems are also characterized by a suite of flow paths, with positions further along flow paths exhibiting older residence time statistics. If a hydrologic flow system is in steady state the flow paths do not change in time and water present at a given point has a stable residence time distribution. But hydrologic flow paths and residence times can change dynamically with weather and climate temporal variability. Traditionally, this dynamic response is ignored and modeled and observed residence times are evaluated as if the flow was in steady state. In dynamic systems the residence time distribution depends on the time of observation and the time at which the water entered the system; in other words, it depends on two different times. A finite element scheme is used to model the transient flow and transport of an ideal tracer into a Thóthian-like domain, and to illustrate the effect of dynamically changing systems on residence-time estimation. Further applications of these concepts to atmospheric and ocean residence times, are also discussed.

Location: Kaprielian Hall (KAP) - 209

Audiences: Everyone Is Invited

Contact: Evangeline Reyes