John R Nimmo, Ph. D.


John Nimmo is a Research Physicist working toward establishment of a sound twenty-first century framework of water flow processes in soils and rocks. His specialty is the unsaturated zone, between the land surface and the water table. Applications of his work include aquifer recharge estimation, contaminant transport, ecohydrology, land-use evaluation, and climate-change. As Lead Scientist of the Unsaturated Zone Processes Team of the Water Cycle Branch, he supervises a USGS research group that pursues these objectives through field and lab experiments, mathematical modeling, and development of unsaturated-flow theory.



Problems of water quality, water availability, land-use evaluation, ecosystem preservation and restoration, and climate-change impacts require knowledge of the unsaturated-zone dynamics of water and substances it carries. Measurement, prediction, and understanding of the flow of water through soil and rock is crucial to this effort. Through collaboration with the geographically-based Water Science Centers, other units of the Water Resources Mission Area and the USGS as a whole, as well as outside research institutions, great progress is possible through in-depth investigations and field experiments applied to diverse locations. Beyond individual-site applications, this diversity affords a vital opportunity to synthesize and develop specific findings into needed fundamental and practical advances in unsaturated-zone hydrology.

Current and recent emphases include:

(1)  Preferential flow, including the influence of soil structure and rock fractures on water flow and contaminant transport.

(2)  Interactions of soil moisture, plants, and ecological habitat.

(3)  Aquifer recharge estimation, including episodic as well as continuous components.

(4)  Expert-guided automated techniques of hydrograph analysis for exchanges of water between aquifers and the land surface, the unsaturated zone, and streams and lakes.

(5)  Effects of climate change, especially storm characteristics and precipitation, on water resources.

(6)  Sound, widely-applicable theory and mathematical representation of flow behavior and properties.

(7)  Evaluation of recently-implemented stormwater control measures.

(8)  Transport of water and contaminants in thick and geologically complex unsaturated zones.  

(9)  Advancement of techniques for measuring hydraulic properties of the unsaturated zone, especially simple, low-technology methods for rapid characterization at 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. 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.

For a complete list of publications, download John Nimmo's CV  (2018, pdf format).