Important information regarding the origin and evolution of water is contained within the chemical composition of the water. Perhaps no other individual contributed so much to the use of natural water chemistry as a tool in hydrological studies than John Hem. An equally important contribution made by Hem was the realization of the benefits of a multidisciplinary approach—in this case, chemistry and hydrology —to scientific studies.
In 1940, after receiving a bachelor's degree in chemistry, Hem was given a field assignment in the U.S. Geological Survey as a Junior Chemist. His first project focused on the Gila River in Arizona, where he immediately distinguished himself by demonstrating the value of water chemistry as a tool to better understand how the Gila River system operated. His work clearly showed how interrelated groundwater and surface water were in the Gila River system. *
By his own admission, this early work continued to motivate him throughout his professional career with the Geological Survey where his early formal training in chemistry provided insights not available to many other hydrologists at the time. Hem is considered largely responsible for the integration of natural water chemistry into the science of hydrogeology.
Among Hem's scientific contributions is his work describing the geo-chemistry of iron, manganese, and aluminum in water, particularly factors that control the solubility of these metals in a water environment. Throughout his career, Hem applied both theory and laboratory experiments to understanding natural water chemistry.
Hem is best known for his book the Study and Interpretation of the Chemical Characteristics of Natural Water, first published in 1959 and revised in 1968 and again in 1985. Published as a U.S. Geological Survey Water-Supply Paper, the book has been used widely as a reference and textbook and has gone through over a dozen printings. The utility of the publication, other than being the first book on the geochemistry of water, is that it provides significant information on the composition of natural waters (e.g., lakes, streams, springs) in a variety of settings as well as highly useful information on the controls of natural water composition.
Hem received the O. E. Meinzer Award from the Geological Society of America in 1990 for his publication, noting the benefit the work provided to the science of chemical hydrogeology. He has also received the Distinguished Science Award from the National Water Well Association and the Distinguished Service Award from the U.S. Department of the Interior.
Dennis O. Nelson
Hem, John D. Study and Interpretation of the Chemical Characteristics of Natural Water, 3rd ed. Alexandria, VA: Department of the Interior, U.S. Geological Survey, Water-Supply Paper 2254, 1985.
* See "Colorado River Basin" for a map that includes the Gila River.