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Title: B2. The Isotopic Age of Runoff in Natural Flow Systems
Authors: Duffy, Christopher
Issue Date: May-2012
Publisher: Internet-First University Press
Abstract: This paper outlines a theory describing fundamental controls on the isotopic “age” of runoff from watersheds. In this context “age” is defined as the time since the water and environmental tracer entered the system as precipitation. The paper first examines the theoretical basis for directly modeling “age” of environmental tracers, and explains how subsurface flow (Boussinesq equation) and transport processes affect age dynamics. Solutions for the age of watershed runoff are presented for storm events, seasonal and stochastic tracer inputs. Through a simple analogy to boundary layer theory and potential flow, a strategy to estimate the effective depth and corresponding age of groundwater circulation is presented. The approach reveals an important relationship for flow-depth and age, which can be used to define the practical mixing layer for environmental tracers contributing to runoff. Extension of the model to the unsaturated zone and the effects of mobile-immobile on flow and transport on the age of runoff are briefly outlined. Preliminary results from a field experiment for stable isotopes at the Shale Hills Critical Zone Observatory provides some initial validation and estimates for the “dynamic” age of runoff.
Description: Once downloaded, these high definition QuickTime videos may be played using a computer video player with H.264 codec, 1280x720 pixels, millions of colors, AAC audio at 44100Hz and 29.97 frames per second. The data rate is 5Mbps. File sizes are on the order of 600-900 MB. (Other formats may be added later.) Free QuickTime players for Macintosh and Window computers may be located using a Google search on QuickTime. The DVD was produced by J. Robert Cooke.
Appears in Collections:Hydrologic Discovery - Oral Presentations (Videos)

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streaming_29554.htmlView Streaming Video8.2 kBHTMLView/Open
B2_Duffy_SLIDES.pdfPDF of slides used in the lecture11.11 MBAdobe PDFView/Open
B2_Duffy_Runoff_SD_for_Apple_Devices.m4vDownload small version of Video156.72 MBM4v VideoView/Open
B2_Duffy_Runoff-HD_for_Apple_Devices_5Mbps.m4vDownload HD Video for Apple Devices487.6 MBM4v VideoView/Open

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