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Vadose Zone Journal
Vol. 4, No: xx, 2005; Pages: : 811–818


Assessing Contaminant Transport Vulnerability in Complex Topography Using a Distributed Hydrologic Model

Scott N. Martens and David D. Breshears*

Earthand Environmental Sciences Division, Mail Stop J495, Los AlamosNational Laboratory, Los Alamos, NM 87545 and School of NaturalResources, Institute for the Study of Planet Earth, and Departmentof Ecology & Evolutionary Biology, University of Arizona, Tucson,AZ85721-0043.

Abstract

Modeling of vadose zone hydrology is required to address a varietyof applied problems in general and risk assessments associated withcontaminants in particular. Risk assessments increasingly must focuson multisite, multipathway analyses as opposed to single-site, singlepathway analyses. Such assessments can be particularly challengingwhen contaminants are widely dispersed in complex topography. Here we highlight how a set of contaminated sites situated within complextopography can be effectively prioritized relative to vulnerability ofcontaminant transport from surface and subsurface flows. We useda distributed hydrologic model, SPLASH, to assess the lateral flowsof surface and subsurface water following the simulation of a 100-yearprecipitation event, which could correspond to an intense thunderstorm. Our case study was conducted in the North Ancho watershedof Los Alamos National Laboratory, in northern New Mexico, USA,an area with widely dispersed contaminants and diverse topography.Simulated surface flows generally exceeded subsurface flows by morethan four orders of magnitude, indicating the relative importance ofpotential redistribution of contaminants by surface flows for this typeof precipitation event. For the 18 potential contaminant release sitesinvestigated, the maximum surface flow varied by more than an orderof magnitude across the sites. Half of the sites had surface flows<25% of the maximum surface flow for a site, allowing for prioritization ofthose sites with the greatest vulnerability. Our results highlight howrisks of contaminant transport can be effectively assessed in complextopography using distributed hydrologic modeling.

Keywords:vadose zone hydrology;distributed hydrologic model;Topography;SPLASH;hydrologic modeling;radionuclide.


Corresponding author:

E-mail: daveb@ag.arizona.edu

 

 
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