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Vadose Zone Journal
Vol. 4, No: xx, 2005; Pages: 798–810

Ecohydrology Monitoring and Excavation of Semiarid Landfill Covers a Decade after Installation

David D. Breshears,* John W. Nyhan, and David W. Davenport

Institute for the Studyof Planet Earth, and Department of Ecology & Evolutionary Biology,University of Arizona, Tucson, AZ 85721-0043.


Landfill covers are intended to protect buried waste from waterseepage and biointrusion for thirty to thousands of years, yet mostcover studies are limited to a few years and do not directly investigatenet changes in the soil profile that affect changing landfill performance.We evaluated water balances, vegetation cover, rooting patterns, andsoil profiles of two landfill-cover designs (two plots each) more than adecade after installation at semiarid Los Alamos National Laboratory,NM, USA: a conventional design of 20 cm of topsoil over compactedcrushed-tuff and an integrated design of 71 cm of topsoil over anengineered barrier designed to induce lateral flow (geotextile overlying 46 cm of gravel). Water balances for both designs had ~3% ofprecipitation as seepage; the integrated plots lost <1% of water asinterflow, probably because the barrier interface had only a 5% slope.The conventional design had a net loss of stored soil water and proportionally more evapotranspiration than the integrated design. Aftermore than a decade, (i) vegetation changes included increased biomassand species diversity on most plots, with proportionally fewer invadingspecies and more extensive rooting in the integrated plots; (ii) thegeotextile was largely unchanged; and (iii) infiltration and subsequentwater penetration occurred primarily via macropores, including rootchannels and animal burrows. Both cover designs effectively minimized seepage during their initial decade, but observed effects ofenvironmental processes such as succession and burrowing are expected to become progressively more important determinants of coverperformance over additional decades.

Keywords:landfill performance;macropores;fewer invadingspecies;Ecohydrology Monitoring;root penetration;radionuclide.

Corresponding author:

E-mail: daveb@ag.arizona.edu


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