Ohio State University Extension Fact Sheet

Ohio State University Extension Fact Sheet

Food, Agricultural and Biological Engineering

590 Woody Hayes Dr., Columbus, Ohio 43210

Ground- and Surface-Water Terminology


Larry C. Brown
Leonard P. Black

Ohio's surface and ground water resources provide a variety of water supply needs for the state. These water supply needs can be separated into the following categories: public, rural domestic and livestock, private industrial, and irrigation. Bounded by Lake Erie on the north and the Ohio River on the south, Ohio has 43,900 miles of streams and 2,200 lakes. These surface water resources supply the domestic water needs of about 58 percent of Ohio's population. Ground water resources supply these needs for the remaining 42 percent. However, in rural areas of Ohio, ground water resources supply 90 percent of the total rural domestic water use.

The right to use surface and ground water supplies, the quality and the availability of these water resources present complex problems and issues. To deal with these problems and issues, Ohio's citizens may find that they need a better understanding of surface and ground water terminology.

This publication presents some generally accepted definitions associated with water resources in Ohio. It is intended to serve as an educational guide, providing quick reference to the definitions. It is not intended to present legal definitions, and should not be used for legal purposes.


Aquiclude A geologic formation that is saturated but is incapable of transmitting sufficient quantities of water to a well. Also, this type of formation is not capable of transmitting enough water to be considered as a significant part of the regional ground water system.

Aquifer A geologic formation, group of formations, or part of a formation capable of storing, receiving and transmitting water. The formation is capable of yielding enough water to support a well or spring.

Aquifuge A geologic formation that is both impermeable and contains no water.

Aquitard A geologic formation that is saturated but is incapable of transmitting sufficient quantities of water to a well. However, this type of formation is capable of transmitting enough water to be considered as a significant part of the regional ground water system.

Artesian Aquifer See Aquifer, Confined.

Artesian Well A well in which water from a confined aquifer rises above the regional water table of the aquifer.

Baseflow The amount of water in a stream that results from ground water discharge.

Bedrock A general term for consolidated (solid) rock that underlies soils or other unconsolidated materials. See Formation.

Capillary Fringe The transition zone between the saturated and the unsaturated zone where the pore spaces in soil and/or rock layers are filled with water. However, the water will not flow in sufficient quantities to support a well.

Catchment A surface from which runoff is collected. Examples include roofs, paved surfaces, or constructed surfaces covered with plastic.

Channel The bed of a river, stream, drainage ditch, or other waterway that transports a concentrated flow of water.

Cistern A non-pressurized tank, usually underground, for storing water.

Concentrated Flow Runoff that accumulates or converges into well-defined channels.

Cone of Depression A depression in the potentiometric surface in the area around a well, or group of wells, from which water is being withdrawn.

Confined Aquifer See Aquifer.

Conjunctive Use The combined use of surface and ground waters to serve a particular purpose.

Consolidated Formation See Formation.

Consumptive Use Water that has been evaporated, transpired, incorporated into products, plant tissue, or animal tissue and, therefore, is not available for immediate reuse. Sometimes referred to as water consumption.

Contact Spring See Spring.

Contaminated Water Water that contains disease-causing or toxic substances. See Polluted Water.

Deep Percolation The downward movement of water through the soil below the plant root zone.

Depression Spring See Spring.

Diffused Water Water, usually resulting from rainfall and/or snow melt, that spreads over the land surface. Once diffused water enters a well defined channel, it is usually described as concentrated flow.

Diversion A channel constructed across the land slope to intercept surface runoff and to conduct it to an outlet.

Drainage The removal of excess water from the land surface and/or from the soil profile.

Drainage Area A general term for the land area drained by a ditch, creek, stream, or river. When reference is made specifically to a large surface water body like a river, the term Drainage Basin is used.

Drainage Basin The land area drained by a river.

Drawdown The vertical distance between the water level in a well before pumping and the water level in the well during pumping.

Erosion The detachment and movement of soil and rock particles by gravity, wind, water, freezing and thawing, and/or other natural phenomena.

Estuary A semi-enclosed coastal body of water that has a free connection with the open sea. It is strongly affected by tidal action, and within it sea water is mixed, and usually measurably diluted, with fresh water.

Evapotranspiration A collective term that describes water movement back to the atmosphere as a result of evaporation from soil surfaces and surface water bodies, and by plant transpiration.

Fault Spring See Spring.

Field Capacity The amount of water held in unsaturated soil pores after a period of free drainage.

Formation (Geologic) The two basic types of geologic formations are defined below:

Gaining Stream A stream that receives ground-water discharge. The flow increases as one moves downstream.

Geologic Formation See Formation.

Grass Waterway A natural or constructed watercourse or outlet that is shaped or graded and planted with suitable vegetation for the purpose of dispersing runoff without causing erosion.

Ground Water All subsurface water that fills the pores, voids, fractures, and other spaces between soil particles and in rock strata in the saturated zone of geologic formations.

Ground Water Discharge Point A place where ground water flows out from an aquifer and into a surface water body.

Ground Water Hydrology The subdivision of the science of hydrology that deals with the occurrence, movement, and quality of water beneath the Earth's surface.

Ground Water Recharge See Recharge.

Ground Water Table See Water Table.

Hydraulic Conductivity A measure of the rate at which water will move through a permeable soil or rock layer. For a particular soil or rock layer, the hydraulic conductivity may not be the same in the horizontal direction as in the vertical direction.

Hydrogeology The general definition of ground water hydrology applies here except that hydrogeology places a greater emphasis on geology.

Hydrologic Cycle The constant process of water movement from the Earth to the atmosphere by evaporation and transpiration, and from the atmosphere to the Earth in various forms of precipitation. This term includes movement of water on and beneath the Earth's surface. Sometimes the term Water Cycle is used.

Hydrology The science dealing with the waters of the Earth, their distribution and movement on the surface and underground, and the cycle involving evaporation and precipitation (Hydrologic Cycle).

Impermeable Layer A layer that does not permit water to flow through it.

Infiltration The downward entry of water into the Earth's surface. Infiltration usually refers to water movement into a soil or rock surface while the terms hydraulic conductivity, percolation, and permeability usually relate to water movement within a soil or rock layer.

Infiltration Capacity The maximum rate at which infiltration can occur under specific soil moisture conditions.

Interflow The lateral movement of a significant amount of water through the soil above the regional water table.

Leaching The natural process by which salts and other soluble materials are removed from the soil by percolating water.

Losing Stream A stream whose water seeps into an aquifer. The flow decreases as one moves downstream.

Nuisance Water Water that is safe, from a human or animal health standpoint, but is unpleasant to use.

Overdraft The reduction of ground water storage that occurs when withdrawals from an aquifer exceed recharge. Sometimes referred to as mining of ground water.

Overland Flow The quantity of water that moves across the land surface. Contributions to overland flow are from runoff and from the surfacing of subsurface flows before they reach a receiving stream or a defined drainage channel.

Parallel Flow Paths Layers of ground water flow moving at such slow speeds that significant mixing between layers does not occur.

Perched Water Table See Water Table.

Percolation The downward movement of water through layers of soil or rock.

Permeability A measure of the relative ease with which water will move through soil or rock.

Piezometric Surface See Potentiometric Surface.

Polluted Water Water containing a natural or human-made impurity. The water is classified as polluted when the concentration of the pollutant exceeds the acceptable standard for a particular use. Water that contains disease-causing or toxic substances is said to be contaminated.

Porosity The percentage of the volume of a material, such as soil or rock, that is occupied by pore spaces. Porosity is an indication of the capacity of the material to hold water.

Potable Water Water that is safe and palatable for human consumption.

Potentiometric Surface The level to which water rises in a tightly cased well constructed in a confined aquifer. In an unconfined aquifer, the potentiometric surface is the water table. The term piezometric is sometimes used in place of potentiometric.

Precipitation The process by which water vapor condenses in the atmosphere or onto a land surface in the form of rain, hail, sleet or snow.

Prior Appropriation See Water Rights.

Receiving Waters All distinct bodies of water that receive runoff, including channels, streams, rivers, ponds, lakes, estuaries, and in some cases, ground water.

Recharge The replenishment of ground water by seepage (deep percolation) of precipitation and runoff. Also stated as the process of addition of water to the saturated zone.

Regional Water Table See Water Table.

Return Flow The amount of water that reaches a surface or ground water source after it has been released from the point of use and thus becomes available for further reuse. Also called return water.

Riparian Rights See Water Rights.

River Basin See Drainage Basin.

Run-In Surface water that moves directly to ground water through vertical channels in the soil and/or rock layer.

Runoff The portion of precipitation or irrigation water that moves across land as surface flow and enters streams or other surface receiving waters. Runoff occurs when the precipitation rate exceeds the infiltration rate.

Safe Yield The amount of ground water that can be withdrawn continually from an aquifer in an economical and legal manner without having any adverse effect on the ground water resource or on the surrounding environment.

Saturated Zone The zone in a soil profile or geologic formation in which all pore spaces are filled with water.

Seepage The infiltration and percolation of surface water from overland flow, ditches, channels, ponds, lakes, streams, rivers, or other surface water bodies.

Sinkhole The cavities in bedrock that are open to the atmosphere. These usually result from the collapse of overlying soil or geologic material.

Soil Water Zone The soil water zone extends from the land surface down through the major root zone. Therefore, its total depth is variable and is dependent upon soil type and vegetation. This zone is unsaturated except during periods of heavy infiltration and percolation.

Sole-Source Aquifer An aquifer that supplies fifty percent or more of the drinking water of an area, as defined by the Environmental Protection Agency.

Spring A surface water body created by the natural emergence of ground water to the Earth's surface.

Subsurface Drainage See Drainage.

Surface Drainage See Drainage.

Surface Drains Ditches or swales that are designed to help remove excess water from the land surface to a conveyance channel. These are usually constructed as broad, shallow channels that can be crossed with field machinery.

Surface Water The water from all sources that occurs on the Earth's surface either as diffused water or as water in natural channels, artificial channels, or other surface water bodies.

Throughflow See Interflow.

Transmissivity A measure of the rate at which water will move through an aquifer. Transmissivity incorporates the hydraulic conductivity of the aquifer, aquifer thickness, water temperature and fluid properties to describe water movement.

Transpiration The process by which plants and animals loose water, as vapor, into the atmosphere.

Unconfined Aquifer See Aquifer.

Unconsolidated Formation See Formation.

Unsaturated Zone A soil or rock zone above the water table and extending to the land surface in which the pore spaces are only partially filled with water. Sometimes called the vadose zone.

Vadose Zone A term sometimes used in place of unsaturated zone.

Water Cycle See Hydrologic Cycle.

Water Rights The legal rights to the use of water.

Water Quality The chemical, physical, biological, and radiological condition of a surface or ground water body.

Watershed An area of land that drains to a single water outlet.

Water Table The upper boundary or top surface of the zone of saturation in a soil profile or geologic formation.

Waterway Any channel, natural or constructed, in which water flows.

Wellhead Protection Area A designated surface and subsurface area surrounding a well or well field that supplies a public water supply and through which contaminants or pollutants are likely to pass and eventually reach the aquifer that supplies the well or well field. The purpose of designating the area is to provide protection from the potential of contamination of the water supply. These areas are designated in accordance with laws, regulations, and plans that protect public drinking water supplies.

Wetland A land area that is inundated or saturated by surface and/or ground water with a frequency and duration sufficient to support an abundance of hydrophytic (water-loving) plants or other aquatic life that require permanently saturated or seasonally saturated soil conditions for growth and reproduction. Examples include swamps, marshes, bogs, sloughs, potholes, wet meadows, river overflow areas, mud flats, and natural ponds.


This publication presents some generally accepted definitions of common terms associated with water resources in Ohio. This is an educational guide; it is not intended to offer legal definitions. Numerous published texts, dictionaries, and glossaries offer definitions that may be appropriate for legal purposes and also may provide the reader with a more technical definition. A few of these are listed below. For more information about Ohio's water resources, contact your county Extension agent, the Ohio Department of Natural Resources, Division of Water (Fountain Square, Columbus, OH 43224), or the U.S. Geologic Survey, Water Resources Division (Ohio District, 975 West Third Ave., Columbus, OH 43212).

References and Associated Publications

Applied Principles of Hydrology. 1987. J.C. Manning. Merrill Publishing Company.

Basic Ground-Water Hydrology. 1984. R.C. Heath. U.S. Geological Survey Water Supply Paper 2220.

Gazetteer of Ohio Streams. 1960. Report No. 12, Ohio Water Plan Inventory. ODNR Division of Water.

Glossary (Ground-Water Quality). In: National Water Summary 1986. U.S. Geological Survey Water-Supply Paper 2325. pp. 548-552.

Glossary (Ground-Water Resources). In: National Water Summary 1984. U.S. Geological Survey Water-Supply Paper 2275. pp. 460-465.

Glossary (Surface-Water Resources). In: National Water Summary 1985. U.S. Geological Survey Water-Supply Paper 2300. pp. 500-502.

Glossary (Water Supply and Use). In: National Water Summary 1987. U.S. Geological Survey Water-Supply Paper 2350. pp. 546-549.

Ground Water. 1979. R.A. Freeze and J.A. Cherry. Prentice-Hall.

Ground-Water Resources of the United States. 1983. D.K. Todd. Premier Press.

Introduction to Ground Water Hydrology. 1988. R.C. Heath and F.W. Trainer. National Water Well Association.

Inventory of Ohio's Lakes. 1980. Ohio Water Inventory Report No. 26. ODNR Division of Water.

Ohio Surface-Water Resources. In: USGS National Water Summary 1985. U.S. Geological Survey Water-Supply Paper 2300. pp. 369-374.

Ohio Ground-Water Resources. In: USGS National Water Summary 1984. U.S. Geological Survey Water-Supply Paper 2275. pp. 341-346.

Ohio Ground-Water Quality. In: USGS National Water Summary 1986. U.S. Geological Survey Water-Supply Paper 2325. pp. 407-414.

Principles of Water Rights Law in Ohio. 1979. C.C. Callahan and C.V. Youngquist. (J.R. Hanson, Ed.). Division of Water, Ohio Department of Natural Resources. Out-of-print. (Copy on file at Division of Water, ODNR, and Agricultural Engineering Department, The Ohio State University).

Private Water Systems Handbook. 1987. MWPS-14, Midwest Plan Service, Ames, IA. (Available through the Agricultural Engineering Department, The Ohio State University).

Soil and Water Conservation Engineering. 1981. G.O. Schwab, R.K. Frevert, T.W. Edminster, and K.E. Barnes. John Wiley and Sons.


This publication was produced through the Water Resources Educational Materials Project funded by the Innovative Grant Program of the Ohio Cooperative Extension Service, The Ohio State University. Project Team: Larry C. Brown (Project Leader, OSU Extension), Ron Overmyer (Sandusky County, OSU Extension), John Hixson (Union County, OSU Extension), Gary Wilson (Hancock County, OSU Extension), Marcus Dresbach (Northwest District, OSU Extension), Glen Arnold (Putnam County, OSU Extension), Jay Johnson (Agronomy, OSU Extension), Robert Roth (School of Natural Resources, OSU), and Leonard Black and Margo Fulmer (ODNR, Division of Water). This publication was reviewed by: Water Resources Project Team; Division of Water, ODNR; Steve Workman and William Elliot (Agricultural Engineering Department, OSU); Robert Vertrees (School of Natural Resources, OSU); Dave Carpenter and Chris Reimer (National Water Well Association); and Robert Stiefel (Water Resources Center, OSU).

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.

TDD No. 800-589-8292 (Ohio only) or 614-292-6181

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