John R. Nimmo, Ph. D.

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.