Groundwater Hydrology
Groundwater hydrology studies water beneath the land surface, how it is stored in aquifers, how it flows through porous and fractured rock under Darcy's law, and how it is extracted and contaminated.
Definition
Groundwater hydrology (hydrogeology) is the study of the occurrence, movement, and quality of water in the saturated zone beneath the land surface, governed by Darcy's law and the storage and transmission properties of geologic materials.
Scope
This area covers the properties of aquifers and the porous-media flow law that governs subsurface water, the analysis of groundwater flow systems and their recharge, the hydraulics of pumping wells, and the transport of dissolved contaminants. It addresses the saturated subsurface as a flow domain, complementing surface-water hydrology and the soil-water partitioning treated in the hydrological-cycle area.
Sub-topics
Core questions
- What is an aquifer, and how do Darcy's law and hydraulic conductivity describe flow through it?
- How do groundwater flow systems organize themselves between recharge and discharge areas?
- How does pumping a well lower heads, and what do pumping tests reveal about an aquifer?
- How do dissolved contaminants move and spread in groundwater?
Key concepts
- Aquifers, aquitards, and porosity
- Hydraulic head and hydraulic conductivity
- Darcy's law
- Recharge and discharge
- Well hydraulics and drawdown
- Advection and dispersion of contaminants
Key theories
- Darcy's law
- The volumetric flow of water through a porous medium is proportional to the hydraulic gradient and the hydraulic conductivity; this empirical law is the constitutive foundation for nearly all quantitative groundwater analysis.
- Transient well hydraulics (Theis solution)
- The Theis solution describes the time-dependent drawdown caused by pumping a well in a confined aquifer, enabling estimation of aquifer transmissivity and storativity from pumping-test data.
- Advection-dispersion of solutes
- Dissolved contaminants migrate with the mean groundwater velocity (advection) while spreading by mechanical dispersion and molecular diffusion, a framework that underlies prediction of plume movement and aquifer remediation.
Clinical relevance
Groundwater supplies a large share of drinking water and irrigation worldwide; this area underpins the development and protection of well fields, the assessment and remediation of contaminated aquifers, the management of aquifer depletion and saltwater intrusion, and the analysis of groundwater-dependent ecosystems.
History
Quantitative groundwater hydrology began with Darcy's 1856 experiments on flow through sand, was extended by Dupuit, Thiem, and others to wells, and was transformed by Theis's 1935 transient solution. The 1979 text by Freeze and Cherry synthesized the field and helped establish modern hydrogeology, including the study of contaminant transport.
Key figures
- R. Allan Freeze
- John A. Cherry
- Charles V. Theis
- Henry Darcy
Related topics
Seminal works
- freeze1979
- fetter2001
- theis1935
Frequently asked questions
- What is the difference between an aquifer and groundwater?
- Groundwater is the water itself in the saturated zone, while an aquifer is a body of rock or sediment permeable enough to store and transmit usable quantities of that water; low-permeability layers that impede flow are called aquitards or aquicludes.
- Does groundwater flow underground in rivers?
- Usually not. Except in some cavernous limestone settings, groundwater moves slowly through the pores and fractures of rock and sediment following hydraulic gradients, often only metres per year, rather than as open underground streams.