[Enviro-lunch] Next Monday (11/15): John Nimmo presenting preferential flow in unsaturated zone

[Kyungjin Min]

[image: image.png]

Hello all,



Next Monday (11/15) Dr. John Nimmo from USGS will present about unsaturated
zone preferential flow. Please join us between 12-1 pm (pacific) via zoom.





Title: Unsaturated zone preferential flow-Unexpected effects for ecosystems
and hazardous-waste containment

Abstract: Preferential flow along common subsurface paths such as wormholes
and fractures moves water through the unsaturated zone faster and more
directly than diffuse or capillary flow through the bulk of soil matrix
material. In ecosystems preferential flow is vital for the efficient
distribution of water through the root zone for the optimal use of plants.
Field experiments in a restored tropical dryland forest in Hawaii
demonstrate that the plants themselves, through their ordinary growth and
decay processes, can modify the soil over several years to enhance the
preferential flow that is beneficial to them. At near-surface hazardous
waste sites, minimization of preferential flow is important for contaminant
containment. Field experiments at a simulated waste trench in Idaho show
that common landfill construction practices can effectively destroy
macropore preferential flowpaths, though additional effects such as
destruction of flow-inhibiting natural layer boundaries may offset the
beneficial effects of macropore destruction. Ongoing research on the
processes of preferential flow has produced significant insights in recent
decades. A major current need is for predictive methods to incorporate the
improved understanding that has been achieved.
[image: John Nimmo.png]

Bio: John Nimmo is active in Unsaturated Flow Research in Menlo Park,
California, USA. He also is Research Physicist Emeritus with the U.S.
Geological Survey, having been actively employed at the USGS from 1981 to
2020. During most of his USGS career, he was Chief of the Unsaturated Flow
Processes Project. His research primarily pursues process understanding and
estimation methods for fundamental unsaturated-zone flow processes, with
particular emphasis on preferential flow. This work is directed toward
applications in water-resource assessment, subsurface contaminant fluxes
and vulnerabilities, and soil-water dynamics of natural and altered
ecosystems. He pursues these largely through mathematical modeling and
development of theory, and additionally in collaborations involving field
and lab experiments. He writes review articles and basic reference
materials that draw on his knowledge and experience gained during more than
four decades of research on unsaturated flow (jrnimmo at usgs.gov)



Sincerely,

co-host: KJ Min, Manisha Dolui, Toshiyuki Bandai, Jennifer Alvarez

faculty coordinator: Asmeret Asefaw Berhe

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Fall 2021 Enviro-Lunch Schedule

*date*

*speaker*

*title*

*11/15*

John Nimmo

@USDA

Preferential flow through unsaturated soil: How can we understand and
predict it?

*11/22*

Michael Kaiser

 @U of Nebraska

SOM dynamics

*11/29*

Thanksgiving

*12/6*

Carl Adair

@ U of Vermont

Litter decay and soil organic matter formation
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