Terms of Hydrology (P)

pan coefficient :

Ratio of evaporation from a large body of water to that measured in an evap ...

pancake ice :

Pieces of newly-formed ice, usually approximately circular, and with raised ...

parameter :

Coefficient in some hydrological model, formula or other relationship which ...

partial contraction :

Reduced contraction resulting from the approach walls being so close to the ...

partial duration series :

Series of values of independent events, such as floods, occurring above a b ...

partial volume :

In soils, the ratio of the volume of a phase (air, water, solid matrix) to ...

partially penetrating well :

Well in which the length of water entry is less than the thickness of the s ...

particle size :

Dimension which is representative of the size of an individual particle.

passive sensing system :

Sensing system that detects or measures radiation emitted by the target. (M ...

path line :

Curve described by a moving particle of water.

Pavlovsky's approximation :

Similar to Dupuit's approximation, except that the stream lines are assumed ...

peak discharge :

Maximum instantaneous discharge of a given hydrograph.

peak-to-mean flow ratio :

Ratio of the peak discharge of a flow hydrograph, or a unit hydrograph, to ...

Pearson distribution :

Group of probability distributions of varying skewness and other properties ...

pendular water :

Water film surrounding solid particles at their points of contact, forming ...

perched groundwater :

Groundwater body, generally of moderate dimensions, supported by a relative ...

perched stream :

Stream that is separated from the underlying groundwater by a zone of unsat ...

Percolation :

Flow of a liquid through an unsaturated porous medium, e.g. of water in soi ...

perennial stream :

Stream which flows continuously all through the year.

perforated casing :

Casing, installed in a well, that has slots or perforations through which w ...

periphyton :

Association of aquatic organisms attached or clinging to rooted water plant ...

permafrost :

Layer of soil or rock in which the temperature has been continuously below ...

permeability coefficient :

Used for coefficient of hydraulic conductivity but not recommended in this ...

permeameter :

Instrument for measuring hydraulic conductivity.

persistence :

Tendency of a hydrological process or time-series to recur or continue. The ...

pF :

Decimal logarithm of the capillary head expressed in cm.

pH :

Absolute value of the decimal logarithm of the hydrogen-ion concentration ( ...

phreatic cycle :

Period of rise and the succeeding period of decline of a water table or pie ...

phreatic water :

Groundwater occurring in the zone of saturation and having a water table.

phreatophytes :

Water-loving plants that grow mainly along stream courses and/or where thei ...

piezometer :

Observation well in which the water table level or the piezometric head can ...

piezometric head :

(1) Elevation to which water will rise in a piezometer connected to a point ...

piezometric surface :

Surface joining points which are at an elevation equal to the piezometric h ...

Pitot tube :

Tube one end of which is open and held facing directly into a liquid stream ...

pixel :

Abbreviation for "picture element". Smallest element on the ground distingu ...

plane flow :

Flow the streamlines of which are contained in parallel planes.

playa :

Lake bed found in arid or desert regions in the lowest part of an enclosed ...

point data :

Observations at a geographical site, e.g. the site of a rain gauge or a str ...

point gauge; point gage (A) :

Adjustable water-level gauge consisting of a pointed metallic rod pointing ...

point precipitation :

Precipitation at a particular site.

polar orbit :

Orbit which passes directly over both geographic poles of the Earth.

polder :

A mostly low-lying area artificially protected from surrounding water and w ...

polje :

Large, isolated depression, generally several kilometres long, covered with ...

Pollutant :

A substance which impairs the suitability of water for a considered purpose ...

pollution :

Addition of pollutant to water.

polynya :

Water area enclosed in ice, generally fast ice; this water area remains con ...

Pond :

Small storage reservoir or body of water.

pondage :

Short-term holding back of water in a surface storage reservoir.

ponding :

(1) Natural formation of a pond in a water course. (2) Creation of free sta ...

ponor :

Hole or opening in the bottom or side of a depression where a surface strea ...

porosity :

Ratio of the volume of the interstices in a given sample of a porous medium ...

porous medium :

Permeable medium containing connected interstices which may be considered a ...

potamology :

That branch of hydrology dealing with surface streams and their regime. It ...

potential evaporation :

Quantity of water vapour which could be emitted by a surface of pure water ...

potential evapotranspiration :

Maximum quantity of water capable of being evaporated in a given climate fr ...

powder snow :

Dry snow surface which is composed of loose, fresh ice crystals.

precipitable water :

Amount of water, expressed as a depth or as a mass, which would be obtained ...

precipitation :

(1) Liquid or solid products of the condensation of water vapour falling fr ...

precipitation gauge; precipitation gage (A) :

General term for any device that measures the amount of precipitation princ ...

precipitation intensity :

Amount of precipitation collected in unit time interval.

precipitation station :

Station at which observations of precipitation only are made. (TR)

precision :

(1) Quality associated with the degree to which repeated computations, esti ...

pressure head :

Height of a column of static water that can be supported by the static pres ...

pressure ice :

General term for floating ice which has been squeezed together and in place ...

primary data processing :

Processing of raw observational data such as cleaning, checking, correcting ...

principal climatological station :

Climatological station at which hourly readings are taken, or at which obse ...

principal hydrometric station :

Hydrometric station at which one or a number of elements are observed for a ...

probabilistic process :

Process in which the probability of occurrence of the variables is taken in ...

probability :

Basic statistical concept either expressing in some way a "degree of belief ...

probability distribution :

Distribution giving the probability of a value of a variate as a function o ...

probability of forecast :

The chance of occurrence of a quantified assessment (in real time) of futur ...

probability paper :

Graph paper designed in such a way that the cumulative probability of a the ...

probable (possible) maximum precipitation (PMP) :

Amount of precipitation that is the statistical (physical) upper limit for ...

probable error :

Measure of sampling variability equal to 0.6745 times the standard error. O ...

propeller-type current meter :

Current meter the rotor of which is a propeller rotating around an axis par ...

psychrometer :

Instrument used for measuring the water-vapour content of the atmosphere. I ...

puddle :

Accumulation of melt water on ice, mainly due to melting snow but in the mo ...

pulse dilution gauging :

Determination of flow characteristics (velocity or discharge) by means of a ...

pumped storage :

(1) Arrangement whereby electric power is generated during peak load period ...

pumping test :

Pumping of water from a well at one or more selected discharge rates, durin ...

pumping water level :

Elevation at which water stands in a well when the well is being pumped at ...

Purification :

Treatment of water (or sewage) to change harmful or undesirable physical pr ...