John R. Nimmo is a Research Physicist Emeritus for the USGS Water Resources Mission Area.
John R. Nimmo, Research Physicist Emeritus, is working toward establishment of a sound twenty-first century framework of water flow processes in soil and rock. His specialty is the unsaturated zone, between land surface and the water table. He collaborates with other USGS scientists to advance hydrologic science through observation and experiment, mathematical modeling, and development of theory.
Research overview
Problems of water availability and water quality require measurement, prediction, and understanding of the unsaturated-zone dynamics of water and substances it carries—applications include aquifer recharge estimation, ecosystem preservation and restoration, contaminant transport, and hydrologic impacts of land-use and climate change. Through collaboration with the geographically-based Water Science Centers, other units of the Water Mission Area, and the larger scientific community, great progress is possible through in-depth investigations, theory and method development, and field experiments.
Current and recent emphases include:
(1) Preferential flow through unsaturated soil and rock.
(2) Aquifer recharge estimation, including episodic as well as continuous components.
(3) Expert-guided automated techniques of hydrograph analysis for exchanges of water between aquifers and the land surface, the unsaturated zone, and streams and lakes.
(4) Effects of climate change, especially storm characteristics and precipitation, on water resources.
(5) Vulnerability of aquifers to contamination through unsaturated-zone transmission.
(6) Advancement of measurement techniques for unsaturated hydraulic properties, especially simple, low-technology methods for rapid characterization of areally-diverse field sites.
Career Overview
I earned a Ph.D. in physics in 1983 at the University of Wisconsin, with a specialty in porous media physics and minor in soil science. I then began full-time work in the USGS. My early career focused mainly on lab experiments and measurement techniques related to soil hydraulic properties, with the main application being aquifer-recharge estimation. Since the 1990s I have broadened my research efforts: (1) topically, to permit a more complete treatment of the inherently multidisciplinary concerns of earth science, (2) methodologically, to select from a large toolbox of lab, field, theoretical, and modeling techniques to best approach a given problem, and (3) geographically, to broaden the applicability of my work to a wide range of climate, geology, soils, hydrology, vegetation, and land use. Besides research, I contribute much effort to teaching, consultation, review of research papers and programs, and leadership of scientific groups within and outside the USGS.
Science and Products
Hydrologic Investigations near the Remote Handled Low-Level Waste Facility
Hydraulic Property Data at the Santa Rosa Island Cloud Forest Restoration Site 2017-2019, Channel Islands National Park, California, USA
Rapid-response unsaturated zone hydrology: Small-scale data, small-scale theory, big problems
Imperatives for predicting preferential and diffuse flow in the unsaturated zone: 1. Equal emphasis
Imperatives for predicting preferential and diffuse flow in the unsaturated zone: 2. Disparate formulation
Does the Darcy-Buckingham Law apply to flow through unsaturated porous rock?
The processes of preferential flow in the unsaturated zone
UZIG research: Measurement and characterization of unsaturated zone processes under wide-ranging climates and changing conditions
Episodic master recession evaluation of groundwater and streamflow hydrographs for water-resource estimation
Vegetation influences on infiltration in Hawaiian soils
Property transfer from particle and aggregate size to water retention [property-transfer models]
Preferential flow, diffuse flow, and perching in an interbedded fractured-rock unsaturated zone
Evaluation of diffuse and preferential flow pathways of infiltratedprecipitation and irrigation using oxygen and hydrogen isotopes
Quantitative framework for preferential flow initiation and partitioning
Science and Products
- Science
Hydrologic Investigations near the Remote Handled Low-Level Waste Facility
The U.S. Department of Energy has proposed a location for a new facility to store waste at the INL. In the unlikely event that waste leaks from the facility, it will be important to monitor whether the contamination reaches the aquifer and baseline information is need before the facility is built. Because we need to know how water and contaminants may travel through the aquifer, we need to gather... - Data
Hydraulic Property Data at the Santa Rosa Island Cloud Forest Restoration Site 2017-2019, Channel Islands National Park, California, USA
Santa Rosa Island, part of Channel Islands National Park off the coast of California, has a undergone a history of ecologic degradation due to introduced ungulate grazing for ranching (cattle and sheep) and hunting (deer and elk) purposes. Grazing in many parts of the island has resulted in widespread vegetation loss and subsequent erosion presumably causing changes in infiltration/runoff relation - Publications
Filter Total Items: 82
Rapid-response unsaturated zone hydrology: Small-scale data, small-scale theory, big problems
The unsaturated zone (UZ) extends across the Earth’s terrestrial surface and is central to many problems related to land and water resource management. Flow of water through the UZ is typically thought to be slow and diffusive, such that it could attenuate fluxes and dampen variability between atmospheric inputs and underlying aquifer systems. This would reduce water resource vulnerability to contAuthorsJohn R. Nimmo, Kimberlie Perkins, Michelle R. Plampin, Michelle A. Walvoord, Brian A. Ebel, Benjamin B. MirusImperatives for predicting preferential and diffuse flow in the unsaturated zone: 1. Equal emphasis
No abstract available.AuthorsJohn R. NimmoImperatives for predicting preferential and diffuse flow in the unsaturated zone: 2. Disparate formulation
No abstract available.AuthorsJohn R. NimmoDoes the Darcy-Buckingham Law apply to flow through unsaturated porous rock?
The Darcy–Buckingham (DB) law, critical to the prediction of unsaturated flow, is widely used but has rarely been experimentally tested, and therefore may not be adequate in certain conditions. Failure of this law would imply that the unsaturated hydraulic conductivity is not constant for a given water content, as assumed in nearly all subsurface flow models. This study aims to test the DB law onAuthorsAntonietta C. Turturro, Maria C. Caputo, Kimberlie Perkins, John R. NimmoThe processes of preferential flow in the unsaturated zone
Preferential flow, a major influence in unsaturated soil and rock almost everywhere, occurs by multiple phenomenologically distinct hydraulic processes. For the mode known as funneled flow, concentrated in particularly conductive portions of the medium, the surface-tension/viscous-flow processes of traditional unsaturated flow theory predominate. Fingered flow, through conductive paths of higher wAuthorsJohn R. NimmoUZIG research: Measurement and characterization of unsaturated zone processes under wide-ranging climates and changing conditions
Unsaturated zone properties and processes are central to understanding the interacting effects of land-use change, contamination, and hydroclimate on our ability to grow food, sustain clean water supplies, and minimize loss of life and property. Advances in unsaturated zone science are being achieved through collaborations across traditional boundaries where information from biological, physical,AuthorsJared J. Trost, Benjamin B. Mirus, Kimberlie Perkins, Wesley R. Henson, John R. Nimmo, Rafael Munoz-CarpenaEpisodic master recession evaluation of groundwater and streamflow hydrographs for water-resource estimation
Hydrograph analysis tools using a master recession curve (MRC) can produce many types of hydrologically important watershed-response quantifications, including aquifer recharge and stormflow characterization. An MRC is the relation between the value of a measured response R and its rate of change with time, dR/dt, occurring on the falling limb when there is no infiltration or other water input. WeAuthorsJohn R. Nimmo, Kimberlie PerkinsVegetation influences on infiltration in Hawaiian soils
Changes in vegetation communities caused by removing trees, introducing grazing ungulates, and replacing native plants with invasive species have substantially altered soil infiltration processes and rates in Hawaii. These changes directly impact run-off, erosion, plant-available water, and aquifer recharge. We hypothesize that broad vegetation communities can be characterized by distributions ofAuthorsKimberlie Perkins, Jonathan D. Stock, John R. NimmoProperty transfer from particle and aggregate size to water retention [property-transfer models]
No abstract available.AuthorsJohn R. NimmoPreferential flow, diffuse flow, and perching in an interbedded fractured-rock unsaturated zone
Layers of strong geologic contrast within the unsaturated zone can control recharge and contaminant transport to underlying aquifers. Slow diffuse flow in certain geologic layers, and rapid preferential flow in others, complicates the prediction of vertical and lateral fluxes. A simple model is presented, designed to use limited geological site information to predict these critical subsurface procAuthorsJohn R. Nimmo, Kaitlyn M Creasey, Kimberlie Perkins, Benjamin B. MirusEvaluation of diffuse and preferential flow pathways of infiltratedprecipitation and irrigation using oxygen and hydrogen isotopes
Subsurface-water flow pathways in three different land-use areas (non-irrigated grassland, poplar forest, and irrigated arable land) in the central North China Plain were investigated using oxygen (18O) and hydrogen (2H) isotopes in samples of precipitation, soils, and groundwater. Soil water in the top 10 cm was significantly affected by both evaporation and infiltration. Water at 10–40 cm depthAuthorsBin Ma, Xing Liang, Shaohua Liu, Menggui Jin, John R. Nimmo, Jingxin LiQuantitative framework for preferential flow initiation and partitioning
A model for preferential flow in macropores is based on the short-range spatial distribution of soil matrix infiltrability. It uses elementary areas at two different scales. One is the traditional representative elementary area (REA), which includes a sufficient heterogeneity to typify larger areas, as for measuring field-scale infiltrability. The other, called an elementary matrix area (EMA), isAuthorsJohn R. Nimmo