Hydrogeology Definition

What does a hydrogeologist do?

By Darrel Dunn, Ph.D., PG, Hydrogeologist

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Dictionary Definition of Hydrogeology

The Merriam-Webster Dictionary defines hydrogeology as: a branch of geology concerned with the occurrence, use, and functions of surface water and groundwater.  This definition seems to conform with the history of the word and the practice of the discipline.

Use and Functions of Groundwater

Use and functions of groundwater include:

• Drinking water and other domestic use,

• Irrigation,

• Maintain the flow of streams during dry periods (by flow of groundwater into the streams),

• Maintain wetlands, and

• Store water (artificial recharge).

Use and Functions of Surface Water

Use and functions of surface water include:

• Drinking water and other domestic uses,

• Irrigation,

• Provide aquatic habitat (sustain ecological systems),

• Recreation,

• Transport municipal and industrial effluents, and

• Hydropower.

History of the Term Hydrogeology

The first use of the term hydrogeology was in 1802 by Lamark .  He applied the term to  phenomena of erosion and deposition by aqueous agencies (Davis and Dewiest, 1966).  Subsequently, the term hydrogeology has been used for the study of groundwater at least as early as 1874 when it was used by Joseph Lucas, who was working for the British Geological Survey (Wilson, 1985).   Joseph Lucas was a geologist involved with making maps of underground water resources.  The term hydrogeology does not seem to have been widely used until the publication of the textbook titled "Hydrogeology"  (Davis and DeWiest, 1966). 

Scope of Hydrogeology

The scope of hydrogeology is consistent with the Merriam-Webster definition given above.  It evolved from erosion and deposition by surface water to include groundwater resource evaluation and then expanded to cover technology related to groundwater, soil moisture, and surface water that benefits from a substantial amount of geologic knowledge. 

The textbook "Hydrogeology" covers the following topics:

• The hydrologic cycle, which includes precipitation, evaporation, plant transpiration, streamflow, overland flow, and infiltration water to soil and groundwater,

• Physical and chemical properties of water,

• Groundwater quality,

• Theory of groundwater flow and its applications to water well technology, petroleum hydrodynamics, and saltwater intrusion into aquifers,

• Exploration for groundwater, including such geophysical methods as magnetic surveys, gravity surveys, seismic surveys, and electrical surveys ,

• Groundwater systems in various geologic terrains (igneous rocks, metamorphic rocks, sedimentary rocks, and surficial sediments), and

• Groundwater in climatic extremes.

The textbook "Applied Hydrogeology" (Fetter, 1980) further defines the scope of hydrogeology by covering  computer modeling of groundwater flow.

Hydrogeology and the basic sciences

The scope of hydrogeology includes application of relevant aspects of the basic sciences: mathematics, physics, chemistry and biology.  The theory of groundwater flow is based on advanced mathematics.  Understanding this theory and its assumptions and limitations benefits from understanding advanced calculus (including vector calculus) and partial differential equations.  Analysis of data benefits from understanding statistics and probability.  Application and understanding of computer models of groundwater flow and surface water flow benefits from understanding computer methods of numerical analysis.  Knowledge of physics is applied in the theory of groundwater and surface water behavior and in the application of geophysical methods to groundwater exploration.  Chemistry is applied to studies of groundwater quality and the computer simulation of the movement of chemicals in groundwater systems.  Biology is applied to the understanding of the influence of organisms on the chemistry and quality of groundwater and surface water, and to understanding surface water ecosystems.

References

Davis, S. N. and R. J. M. DeWiest (1966): Hydrogeology; John Wiley & Sons.

Fetter C. W. Jr. (1980): Applied Hydrogeology; Charles E. Merrill Publishing Company.

Wilson, H. E. (1985): Down to Earth - One Hundred and Fifty Years of the British Geological Survey; Scottish Academic Press.