Biography
Early Life and Education
Van Genuchten was born on February 13, 1945, in Vught, a small town in the southern Netherlands, during the final months of World War II when the southern part of the country had already been liberated. [1] He was the third of eleven children in a family that operated a small farm located approximately 400 meters from the only concentration camp in the Netherlands during the war. [1]
Growing up in a conservative rural environment, van Genuchten and his siblings frequently helped with farm work, including tending to vegetable and flower gardens, caring for cows and chickens, and working in the fields. [1] Despite the traditional farming background, his parents insisted that all their children, including the girls, attend high school—an uncommon practice for farming families at the time. [1]
Van Genuchten attended a five-year high school (HBS) in Boxtel, cycling approximately 10 kilometers from home daily regardless of weather conditions. [1] During this period, he was active in his school's volleyball team and participated in the boy scouts and a philately club. [1]
University Education
After completing high school in 1962, van Genuchten enrolled at Wageningen University (then called the Agricultural College or Landbouwhogeschool) to study tropical agriculture. [1] This decision was largely based on advice from a high school psychologist who, after asking him to draw a picture of a tree, concluded that van Genuchten was not qualified for a regular university and certainly not for physics and mathematics. [1]
However, upon beginning his studies at Wageningen, Professor Rootselaar of the mathematics department immediately noticed van Genuchten's interest and ability in mathematics. [1] Van Genuchten became a teaching assistant in the mathematics department from the very beginning until he received his Master of Science degree in early 1972. [1] Professor Rootselaar even suggested that he switch to the University of Amsterdam to study mathematics, where Rootselaar also held a faculty position, but van Genuchten remained in Wageningen. [1]
In 1967, as part of his studies, van Genuchten spent a year in Madagascar working on improved rice irrigation practices and conducting hydrological studies, including measuring flow rates in large rivers. [1] This experience profoundly changed his life, exposing him to the deprived living conditions of the local population and various diseases. [1] He contracted malaria, hepatitis, and other infections, which forced him to spend several months in hospitals in both Madagascar and the Netherlands. [1] For many years afterward, he had to watch his diet and refrain from consuming alcoholic beverages. [1]
The Madagascar experience dramatically shifted his attitude toward his studies, leading to much greater focus on academic excellence. [1] He completed his MS degree in 1971 under the supervision of Professors Nugteren (Irrigation and Drainage), de Wit (Theoretical Crop Ecology), and Rootselaar (Mathematics). [1] During this period, he wrote several research reports, including one documenting drip irrigation experiments using fine- and coarse-textured soils, along with analyses of moisture distributions using analytical solutions of the Richards equation derived by John R. Philip. [1]
Doctoral Studies
Due to health problems from his stay in Madagascar, van Genuchten was advised not to return to the tropics after receiving his MS degree. [1] His professors in Wageningen suggested writing to several people in the United States to obtain a paid fellowship. [1] He wrote to five people, and only two responded—Peter Wierenga from New Mexico State University (NMSU) in Las Cruces was the only one who offered funding. [1]
Van Genuchten went to Las Cruces, presumably for one year. [1] However, upon arrival, Wierenga informed him that funding would only be available if he entered the PhD program in Agronomy. [1] Although doing a PhD at NMSU was not his original objective, van Genuchten had no choice and consented. [1]
Initially, Wierenga wanted van Genuchten to work on field projects involving drip irrigation of various crops, partly because of his MS studies on trickle irrigation. [1] However, Wierenga quickly noticed that van Genuchten was not the best field experimentalist and asked him instead to work on mathematical analysis of various datasets, such as concentration effluent curves from laboratory soil columns. [1] This marked the beginning of van Genuchten's studies in soil physics and vadose zone hydrology. [1]
At NMSU, van Genuchten learned about chloride, boron, and pesticide transport processes in laboratory soil columns and how physical (e.g., soil aggregation) and chemical (e.g., kinetic sorption) nonequilibrium processes affect observed breakthrough curves. [1] His doctoral research focused on contaminant transport, particularly pesticides, leading to the formulation of chemical (one- and two-site) and physical (dual-porosity) type nonequilibrium models. [1] He received his PhD in January 1975. [1]
Career
Princeton University (1975-1978)
In late December 1974, just before formally receiving his PhD, van Genuchten moved to Princeton, New Jersey, to work as a postdoctoral researcher with George Pinder in the Department of Civil Engineering, Princeton University. [1] George Vachaud from Grenoble, France, had suggested this position during a visit to Las Cruces. [1]
At Princeton, Pinder and Bill Gray taught van Genuchten better numerical solutions for multiphase flow. [1] His main work focused on finite element solutions of the Richards equation using Hermitian (smooth cubic) finite element basis functions. [1] A persistent problem was how best to describe unsaturated soil hydraulic properties using analytical functions rather than interpolated data. [1] The Brooks and Corey (1964) formulations, popular at the time, were not overly compatible with Hermitian solutions due to a lack of first-order continuity in the soil water retention curve at the air entry value. [1]
This challenge led van Genuchten to develop alternative formulations better suited for Hermitian finite element solutions and more accurate in describing observed soil hydraulic data. [1] This work resulted in a Princeton research report in 1978. [1] Van Genuchten had been in contact with Yechezkel Mualem, who had published a paper on predicting the hydraulic conductivity function from soil water retention data (Mualem, 1976). [1] Van Genuchten wanted to publish the Princeton report jointly with Mualem, but for unknown reasons, that did not happen. [1]
Jacob Dane, impressed with the soil hydraulic property optimization program van Genuchten had developed, urged him to publish a formal research paper. [1] Van Genuchten initially hesitated but finally submitted a paper to the Soil Science Society of America Journal (SSSAJ) in 1979. [1] Unfortunately, the paper was returned for major revisions, with reviewers stating that the material was marginal and that even the title was not original. [1] Van Genuchten nearly gave up but eventually revised and resubmitted the manuscript. [1]
The resulting 1980 paper describing the Mualem-van Genuchten equations became extremely popular and profoundly changed van Genuchten's career. [1] The hydraulic functions are now used in numerous unsaturated flow studies focusing on soil, environmental, hydrogeologic, and atmospheric research, as well as applications in fuel cells, fluid infiltration into fabrics and diapers, bio-membranes, and ink infiltration processes. [1] According to Google Scholar, the paper has gathered approximately 35,000 citations. [1]
U.S. Salinity Laboratory (1978-2008)
After three years at Princeton, George Pinder told van Genuchten it was time to move on. [1] Van Genuchten applied to three places, but after meeting Chris Dirksen at a conference in Houston, he was convinced to join the U.S. Salinity Laboratory (USSL), a national laboratory of the Agricultural Research Service (ARS) of the U.S. Department of Agriculture (USDA) in Riverside, California. [1] Van Genuchten had heard much about USSL and admired the work of three Dutch scientists working there: Jan van Schilfgaarde, Peter Raats, and Chris Dirksen. [1]
Van Genuchten was hired by the University of California, Riverside (UCR) as a research scientist in 1978 and served as adjunct professor in the Department of Environmental Sciences between 1987 and 2005. [3] The position was initially implemented through an appointment in the Soils Department of UCR because van Genuchten did not have U.S. citizenship, which had become mandatory for federal positions. [1]
After seven years in Riverside, van Genuchten needed to change his formal association from UCR to USSL. [1] To become Research Leader of his research unit, he needed to become a U.S. citizen. [1] The Dutch government immediately revoked his Dutch citizenship since, at the time, they did not allow dual citizenship. [1] Fortunately, he was able to regain his Dutch citizenship in 2008 when the Netherlands changed its laws for certain cases that applied to him, giving him dual citizenship of the United States and the Netherlands. [1]
After becoming Research Leader, what van Genuchten describes as a "golden age" in research began. [1] He worked with many colleagues on better describing subsurface fluid flow and contaminant transport processes, including:
- Modeling and experimental work on preferential flow with Horst Gerke and Binayak Mohanty [1]
- Improved analytical modeling with Feike Leij, Nobuo Toride, Todd Skaggs, and Jesus Pérez Guerrero [1]
- Better numerical solutions with Kangle Huang and especially Jiri Šimůnek [1]
- Colloid and colloid-facilitated transport with Scott Bradford [1]
- Alternative parameter optimization methods with Karim Abbaspour [1]
- Improved descriptions of soil hydraulic functions with Marcel Schaap, Feike Leij, and Tom Vogel [1]
- More general multicomponent transport formulations with Diederik Jacques, Dirk Mallants, and Jiri Šimůnek [1]
Van Genuchten also conducted numerous laboratory and field tracer experiments with Binayak Mohanty, Marcel Schaap, and Peter Shouse. [1]
One highlight during his stay in Riverside was a large international conference on soil hydraulic properties organized in 1989, which attracted participants from all parts of the world representing different disciplines. [1] A follow-up workshop was organized in 1997, attended by more than 220 participants. [1]
Van Genuchten also participated in several international teams visiting foreign areas affected by natural or man-made problems. [1] In 1988, he traveled to the former Soviet Union to improve collaboration between American and Soviet soil physicists in addressing irrigation problems, particularly those in the Aral Sea drainage basin. [1] In 1993, he visited Ukraine with an American team to review alternative remediation scenarios for soil and groundwater pollution by radionuclides released during the Chernobyl nuclear accident in April 1986. [1] In 2005, he participated in a trip to Sri Lanka to investigate the impacts of the December 26, 2004 tsunami on coastal groundwater resources following a magnitude 9.3 earthquake off the south coast of Sumatra, which killed approximately 50,000 people, primarily on the east coast of Sri Lanka. [1]
Development of HYDRUS Software
A critically important ongoing effort during van Genuchten's time at USSL was the continuous improvement of the numerical HYDRUS code for solving water flow and transport of various agricultural and other contaminants in the subsurface. [1] The software development involved long-term collaboration with Jiri Šimůnek and Miroslav Šejna, who worked especially on graphical interfaces that made the codes much more accessible and user-friendly. [1]
Much of the earlier versions of HYDRUS and its precursors were coded in Fortran but were later augmented with graphical user interfaces. [1] Van Genuchten and his colleagues supported the codes with short courses and workshops since the mid-1990s, given on all continents. [1] While the codes were initially made available through cooperative agreements between USSL and others, they were later commercialized by Mirek Šejna's PC-Progress company in Prague, Czech Republic. [1]
HYDRUS has become one of the most widely used software packages for simulating water, heat, and solute movement in variably saturated porous media. [4] The software is now used by thousands of researchers, engineers, and educators worldwide. [4]
Rio de Janeiro and Utrecht Years (2008-)
Van Genuchten's tenure at the U.S. Salinity Laboratory ended in 2008. [1] He was then welcomed at the Federal University of Rio de Janeiro in Brazil by Renato Cotta and Su Jian, and at Utrecht University in the Netherlands by Majid Hassanizadeh and many others. [1] The positions at these universities were mostly courtesy (non-paying) appointments that allowed him to continue working on various fluid flow and contaminant transport problems. [1]
In Brazil, one major focus was on radioactive materials, including environmental aspects of mining and milling activities using "naturally occurring radioactive materials" (NORMs). [1] Other projects involved radioactive waste from uranium mining activities and mishandling of cesium-containing teletherapy equipment. [1] Van Genuchten also examined the fluid flow properties of carbonate rocks using NMR and microCT data along with pore network modeling, often in collaboration with Amir Raoof at Utrecht University. [1]
At Utrecht University, his collaboration with Majid Hassanizadeh and Amir Raoof facilitated interactions with many students on a variety of topics, several not necessarily focused on subsurface fluid flow and/or contaminant transport. [1]
Scientific Contributions
van Genuchten Equation
Van Genuchten's most significant contribution is the closed-form equation published in 1980 for predicting the hydraulic conductivity of unsaturated soils. [5] This mathematical model, known as the Mualem-van Genuchten equation, describes the relationship between soil water content, capillary pressure, and hydraulic conductivity in unsaturated porous media.
The van Genuchten model has become the most widely used expression for describing soil water retention curves and is implemented in numerous numerical models for simulating variably saturated flow. The 1980 paper has become one of the most cited publications in soil physics, with approximately 35,000 citations according to Google Scholar. [1]
The model is used extensively in:
- Agricultural and environmental sciences for simulating soil water dynamics
- Predicting groundwater contaminant transport
- Climate change research for land surface process modeling
- Non-soil applications including fuel cells, fabric infiltration, bio-membranes, and ink infiltration processes
HYDRUS Software Package
Van Genuchten, together with Jiri Šimůnek and Miroslav Šejna, developed the HYDRUS suite of software packages for simulating water, heat, and solute movement in variably saturated porous media. [4] The HYDRUS family includes HYDRUS-1D for one-dimensional problems and HYDRUS-2D/3D for two- and three-dimensional simulations. [4]
The HYDRUS software uses finite element methods to numerically solve the Richards equation for variably saturated water flow and convection-dispersion equations for solute transport. [4] The software incorporates the van Genuchten equations for describing soil hydraulic properties and has been continuously expanded to include numerous additional processes. [4]
HYDRUS has become an international standard tool used by thousands of researchers and practitioners worldwide for applications ranging from agricultural water management to environmental remediation. [4]
Other Major Contributions
Van Genuchten made numerous other contributions to soil physics and vadose zone hydrology, including:
- Development of the CXTFIT software for parameter estimation from laboratory column breakthrough curves [1]
- Development of the CHAIN code for describing subsurface transport of solutes subject to consecutive first-order decay reactions [1]
- Analytical solutions for preferential advective-dispersive transport through cylindrical macropores [1]
- Contributions to understanding preferential flow, colloid transport, root water uptake under stress conditions, and multicomponent reactive transport [1]
