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not reflect current scientific knowledge
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Agricultural Sciences and should be
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Copyright 2005, Board of Trustees, University
,' ( Circular 862
A Glossary of Terms for
Water Resource Management
Donald J. Pitts
Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
John T. Woeste, Dean for Extension
Florida's rapidly increasing population and its expanding
agriculture have placed increasing pressure on existing water
supplies. These conditions make efficient water management
essential to the long-term sustainability of our way of life.
Water is essential to all of earth's life forms. Florida's
ecosystems are often sensitive to small changes in the
hydrologic process. Many people are becoming more aware
of issues related to environmental quality.
A majority of the water use in the world and in Florida is
the result of irrigation for agriculture. Florida pumps more
water for irrigation than all other states east of the Mississippi
River combined. Irrigation has contributed more to
increasing food production worldwide than any other single
farm input. Therefore, agriculture and society in general
have a major interest and responsibility to ensure adequate
quantities of high quality water remain available.
Water management practices should lean toward
increasing the efficiency of water use, rather than toward
increasing the supply of water. Water supply is ultimately
limited. Attempting to increase supply merely postpones the
inevitable crisis. Many human activities have been
contributing to the degradation of water supplies. Although
pollution of surface water (rivers and lakes) is potentially
reversible, that may not be the case for groundwater. Once
polluted, the restoration of the vast groundwater supplies in
Florida would be very difficult and expensive. Prevention of
contamination is the only rational approach.
Science can illuminate the issues related to water
management but can not usually resolve them. Solutions
must often be worked out through the political process. The
success of the political process is enhanced by
communication. It is our hope that this glossary can aid in
that process by providing some common language.
A GLOSSARY OF
TERMS FOR WATER RESOURCE MANAGEMENT
D. J. Pitts*
Acre-foot: A unit of volume measure equal
to 43,560 ft3; 1 foot of water covering 1 acre
of surface area; also acre-inch = 27,154
Sulfates from fossil
are washed out of
by rain, acidifying lakes
Adiabatic Process: A process occurring
without the addition or loss of energy
Advective Energy Transfer: Process of
energy transfer by means of the mass motion
of the atmosphere.
Albedo: Ratio of the amount of solar
radiation reflected by a surface to the amount
incident upon it.
Algal Bloom: Excessive growth of algae in
lakes and other freshwater bodies, caused
by excessive nutrient enrichment.
Anaerobic: A condition with the absence of
Aquiclude: An impermeable geological
formation that confines water in an adjoining
Aquifer: A geological formation that is
saturated with water and consists of highly
permeable material that will yield significant
volumes of water to a well or spring.
Aquaculture: Commercial agriculture
practiced in an aquatic environment.
or well): Water that is held
in porous rock or soil
Artesian Pressure: Pressure within a
groundwater aquifer developed as a result of
Autotrophs: Organisms that utilize CO2 in the
direct production of organic matter usually
from solar radiation as the primary energy
Available Soil Water: Difference between soil
water content at field capacity and that at
Base Flow: The ground water contribution to
stream flow that comes from springs or
seepage into a stream channel.
Basin: An area drained by a river and its
tributaries, also termed catchment or
* D. J. Pitts is an Agricultural Engineer located at the Southwest Florida Research and Education Center in
Immokalee, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.
Bedload: Coarse material moving on or near
the bottom of a flowing stream.
Biochemical Oxygen Demand (BOD): The
quantity of dissolved oxygen required for the
aerobic decomposition of organic matter in
Bog: A peat-accumulating wetland that has
no significant inflows or outflows and
supports mosses that require an acidic
Bottomland: Lowlands along streams and
rivers, usually alluvial floodplains that are
Brackish: A description of water with a high
content of soluble salts, often caused by the
mixing of seawater with freshwater.
Canopy: A vegetative cover formed by the
tops of plants.
Capillarity: The process by which the
surface of a liquid in a very narrow tube rises
against the pull of gravity (related to
unsaturated hydraulic conductivity).
Capillary Fringe: The zone immediately
above the water table that is nearly saturated.
Capillary Water: Water which remains in the
soil pore spaces after gravity drainage has
Catchment: The watershed, drainage basin,
or area drained.
Celsius (C): A unit of measure of
temperature; 0 degrees C equals the freezing
point of water, 100 degrees C equals the
boiling point of water at sea level.
Channel: The flow path of a river or stream
that meanders through an area, transporting,
eroding, and depositing alluvial sediments.
Channelization: The digging of a channel
through the center of a stream bed to
increase flow velocity or expedite the removal
of flood water.
Channel Capacity: Flow rate of a ditch,
canal, or natural channel when flowing full.
Channel Stabilization: The prevention of
erosion by the use of jetties, drop structures,
vegetation or other means.
Chemical Oxygen Demand (COD): A
measure of the oxygen equivalent to the
organic matter content of a sample that can
be oxidized by a strong chemical oxidant.
Clay: A soil particle less than .002 mm in
Coagulation: The process of individual
particles coming together to form clusters
Coefficient of Roughness: A factor in fluid
flow formulas expressing the character of a
channel surface and its frictional resistance to
Cone of Depression: A depression of conical
shape produced in a water table by the
extraction of water from a well.
Confined Water: Groundwater, under
pressure, that is constrained by an overlying
Connate Water: Water present in rocks at
Consumptive Use: Water withdrawn from a
source and evaporated, transpired, or
otherwise made unavailable.
Confining Bed: A related less permeable
zone adjacent to an aquifer.
Convective Storms: A meteorological
phenomena associated primarily with surface
Conveyance Losses: Water lost from a canal
or ditch by evaporation or downward
Crop Coefficient: A factor that relates actual
evapotranspiration to potential evapotrans-
piration given crop, age and cultural practice.
Darcy's Law: A mathematical description of
fluid flow through a permeable media
(velocity of flow is equal to the hydraulic
gradient multiplied by the flow characteristics
of the media).
Depression Storage: Initial storage of rain in
small surface puddles.
Deep Percolation: Water which percolates
below the root zone and can not be used by
Desalination: The process to separate a
saline solution into pure fresh water and a
Detention Basin: A constructed basin for the
temporary storage of surface runoff and
drainage water that will be released at a
Doctrine of Appropriation: A legal doctrine of
water rights which asserts that all rights are
based on use.
Dissolved Oxygen: Atmospheric oxygen that
is held in solution within water.
Drainage Basin: The area from which a
stream collects water and through which it
Drawdown: The change in the static ground
water level due to pumping from a well.
Ecosystem: The interconnected community
of organisms and the natural environment in
which they exist.
Effective Rainfall: The portion of rainfall that
infiltrates into the soil and is stored for plant
use within the root zone.
Effluent Stream: A stream intersecting the
water table and receiving groundwater flow.
Electrical Conductance: A method for
approximating the total dissolved solids within
water using the conductivity of the water.
Electrodialysis: The electrochemical process
where water is desalinated by ions passing
through a semipermeable membrane from a
less concentrated to a saturated solution.
Elevation Head: Energy possessed by a fluid
due to its position above some reference
Energy Gradient: The change in energy per
unit length in the direction of flow or motion.
Ephemeral Stream: A stream that goes dry
during protracted rainless periods.
Erosion: The detachment and movement of
soil from the land surface by wind, water or
Estuary: A partially enclosed body of
brackish water with a connection to the sea.
Eutrophication: The condition of high
concentration of nutrients within a water body
that results in the consumption of available
Evaporation: The change of liquid water to
water vapor in the atmosphere.
Evaporative Cooling: Cooling or reduction in
temperature caused by evaporation from a
Evapotranspiration (ET): The combined loss
of water to the atmosphere from evaporation
Fen: A peat-accumulating wetland that
receives some drainage from surrounding
mineral soil and usually supports marsh-like
Field Capacity: Moisture content of the soil
after gravitational flow has ceased.
Flocculation: The process of small particles
coming together in water to form aggregates.
Floodplain: Area that is adjacent to a
channel and that may be inundated during
Flume: A device for measuring the flow of
Furrow: A small ditch for the conveyance of
irrigation or drainage water.
Gaining Stream: A stream where flow
increases due to inflow from ground water.
Grade: The degree of slope of a ground
Gradient: The change of elevation, velocity,
pressure, energy or temperature per unit
Greenhouse Effect: A reduction in the net
loss of energy from the earth's upper
atmosphere resulting in an increase in the
earth's mean temperature.
Ghyben-Herzberg Principle: Principle is
based on the fact that freshwater is 2.5
percent less dense than seawater, and
consequently seawater will tend to intrude
into coastal freshwater aquifers.
Gravitational Water: Water that moves
through the root zone under the influence of
Ground Water: Water beneath the surface of
the ground contained in a soil saturated
condition as opposed to surface water and
Halophytes: Plants with a high tolerance for
Hardness: Relates to the encrusting potential
of a water and is measured by the
concentration of calcium and magnesium.
Headwaters: The upstream source of a river
or other moving body of water.
Hurricane: A cyclone type storm with winds
in excess of 74 MPH.
Hydraulic Conductivity: The measure of the
ease with which water can flow through a soil
profile expressed in units of length per time
Hydraulic Head: A measure of the soil water
potential on an energy per unit weight basis.
Hydrograph: A graphical representation of
stream flow, stage (water level), or velocity.
Hydrological Cycle: The path through which
water passes from the ocean to the
atmosphere and on to the land and then
back to the ocean.
Hydrology: The science that deals with the
properties, distribution and flow of water on,
in or above the earth's surface.
Hydroperiod: Seasonal pattern of the water
level of a wetland; is like a hydrologic
signature for each wetlands type.
Hydroscopic Water: Water that is held
strongly by bonding to soil particles and is
not available to plants.
Hydrostatic Pressure: A measure of the
weight that a column of water with a unit
cross sectional area exerts on a unit area at
the base of the column while the fluid is at
Impermeable Boundary: A restrictive layer
which defines either the upper or lower limit
of the aquifer which restricts the passage of
Influent Stream: A stream that contributes to
Infiltration: Movement of water into the soil.
Infiltration Rate: Quantity of water that will
enter a particular soil per unit time (i.e.,
Interception: Precipitation caught and held
(as on plant leaves) before it reaches the
Interflow: That portion of rainfall which
infiltrates into the soil and moves laterally
within the upper soil horizons until
intercepted by a stream channel or until it
returns to the surface at point down slope
from its point of infiltration.
Intrinsic Permeability: A measure of the
ability of the soil to transmit a fluid.
Leaky Aquifer: An aquifer with upper or
lower boundaries that allow significant
passage of water.
Leaching: Removal of soluble material from
the soil by the passage of water through it.
Losing Stream: A stream or portion of a
stream that loses water to its bed or banks.
Lysimeter: A device to measure the rate of
water movement from a block of soil.
Manning Equation: A method for estimating
open channel flow.
Marsh: A frequently or continually inundated
wetlands characterized by emergent
herbaceous vegetation adapted to soil
Meandering Stream: A stream which flows in
large loops, not in a straight line.
Meteoric Water: Groundwater deriving from
Mire: Peat-accumulating wetland (European
Moisture Release Curve: A graph plotting
soil water potential against soil water content
for a particular soil.
Moor: Synonymous with peatland (European
Muck: An organic soil.
National Geodetic Vertical Datum (NGVD):
Distance above sea level.
Natural Levees: Deposits of coarse materials
adjacent to a channel that are left on the
river bank during floods.
Nonpoint Source Pollution: Pollution that is
discharged over a wide area and enters into
receiving waters at generally irregular
intervals as a consequence of storm runoff.
Oligotrophic: A low-nutrient state of a lake or
Osmosis: The tendency of a fluid to pass
through a semipermeable membrane into a
solution where its concentration is lower, thus
equalizing the conditions on either side of the
Osmotic Potential: The force or negative
pressure created by osmosis.
Overland Flow: Water flowing over the
ground surface and over a wide area.
Oxbows: Permanently standing bodies of
water that result from the cutoff of river
Peat: Organic soils mainly composed of
Peatland: A generic term for wetlands that
accumulates partially decayed plant matter.
Perched Groundwater: A locally saturated
zone above an impervious layer of limited
Percolation: Downward movement of water
in the soil due to gravity.
Permeability: The physical structure and
texture of the soil that allows water to move
pH: A measure of the free hydrogen ion
concentration within a solution.
Phloem: The principal food-conducting tissue
of vascular plants, basically composed of
sieve elements, parenchyma cells and fibers.
Phreatic Water: Another term for
groundwater; water occurring in a zone of
Phreatophytes: Plants that derive a majority
of their water from groundwater as opposed
to soil moisture (e.g., cottonwoods, cypress).
Piezometric Level: The level water would rise
in an unconfined tube equivalent to the
Point Source Pollution: Pollution being
discharged into the environment from a
Porosity: Ratio of the pore volume to the
total volume of a material.
Evapotranspiration that would occur
well vegetated surface if water is not
Potable Water: Water that is fit for human
Potentiometric Surface: The level to which
water will rise within a cased well.
Rainfall Intensity: The amount (depth) of
rainfall per unit of time.
Rainfall Duration: The length of time during
which rain fell.
Recharge: Inflow of water into an aquifer.
Recharge Area: An area that is connected to
the aquifer by a highly porous media and
has an ample source of surface water.
Relative Humidity: The ratio of the water
content of the air to the maximum water
holding capacity of the air at a given
Reservoir: An open area where water is
Residence Time: The average time period
water remains in a wetlands; reciprocal of the
Return Period: The reciprocal of the
probability of an event (i.e., a 5 year storm).
Reverse Osmosis: A method of desalinization
and filtration of water.
Riparian: Pertaining to the land adjacent to
a body of water.
Root Zone: That depth of soil occupied by
Run-off: The component of rainfall not
immediately infiltrated into the soil.
Run-off Hydrograph: A curve showing the
time distribution of runoff rates.
Run-on: The component of a water budget
consisting of run-off from an adjacent field.
Saltwater Intrusion: The phenomenon
occurring when saltwater moves laterally from
the ocean into the ground water to displace
Sedimentation: The act or process of
accumulation of sediments in layers.
Sensible Heat: Energy absorbed by a
substance which results in a change in
temperature rather than a change in state.
Slope: Degree of deviation of a surface from
Sinkhole: In Florida an area where the
surface of the land has subsided or
collapsed as a result of the underlying
limestone being dissolved.
Sloughs: Areas of standing water that form
in meanders and along valley walls.
Soil Water: The total water existing in soil
not in a saturated state after gravitional flow
has ceased (soil moisture).
Soil Aeration: Movement of air into a soil as
water is drained out.
Soil Water Deficiency: The amount of water
required to raise the moisture content of a
soil to field capacity.
Soil Water Potential: The work required to
move a unit mass of water in a soil from on
arbitrary datum to the point in question.
Specific Yield: The amount of water that a
unit volume of an aquifer will yield when
Stage: The elevation of a water surface in a
stream or reservoir in reference to an
Sublimation: The direct change of state of
ice or snow to water vapor.
Supercooling: The process in which a liquid
goes below its freezing point without forming
a solid. An example would be water which
goes below 0 C (32 F), remains liquid, and
does not form ice.
Surface Water: Water on the surface of the
ground, including water in man-made
Suspended Sediment: Sediment carried by
stream flow and is a function of the stream
velocity, particle size and density.
Swamp: Wetlands dominated by trees and
Tensiometer: A device for measuring soil
water potential; it contains a ceramic cup, a
column of water, and a vacuum gage.
Terrace: Floodplains that may have once
been formed by the rivers alluvial deposits
but are not now in hydrologic connection
with the present river.
Transmissivity: The rate at which water
moves through an aquifer at a specific
Transpiration: The process by which plants
lose water vapor.
Tributary: A branch of a river, stream or
channel which contributes flow to the main
Turgor: The normal distension or rigidity of
plant cells caused by the pressure of the cell
contents exerted against the cell walls.
Some turgor is necessary for cell expansion
and growth. Loss of turgor pressure can
Turnover Rate: The ratio of flow through
volume to average volume within a wetlands
or a reservoir.
Vadose Zone: The portion of the soil that is
above the water table and unsaturated.
Vapor Pressure Deficit: Difference between
the existing vapor pressure and that of a
saturated atmosphere 7 t the same
Viscosity: The cohesive forces existing
between particles of a fluid which causes the
fluid to offer resistance to flow.
Water Budget: An account of additions and
subtractions of water from a particular area
Water Potential: The chemical potential of
water. An indication of the driving force of
water through a plant or soil. It is one
measure of the amount of water stress a
plant experiences and is expressed in units
of pressure such as atmospheres, bars, or
Water Table: The surface level of an
Water Well: An excavation, where the
intended use is for the location, acquisition,
"MAiRSTO SCIENCE LIBRARY
UNIVER3 1262 05130 9077
3 1262 05130 9077
development, or artificial recharge of ground
Wetlands: An area where the soil is
saturated for a significant period of time such
as swamps, marshes, bogs, wet meadows,
and tidal flats.
Wet Meadow: Grassland with waterlogged
soil near the surface but without standing
water for most of the year.
Wilting Point: A point at which soil water is
no longer available to the plant varies
Xerophyte: A plant adapted to a limited
supply of water.
Xylem: The principal water conducting tissue
in vascular plants. The xylem can also be a
supporting tissue, especially the secondary
This publication was produced at a cost of $578.50, or 30.0 cents per copy, to enhance communications
among various groups in society. 5-2M-90
COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, John T. Woeste,
director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the May 8 and June
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is available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesville, Florida 32611. Before publicizing ...,. oEo.
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