Alphabets of Hydrology[1]

8/16/2019 Alphabets of Hydrology[1]

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BULACAN STATE UNIVERSITY

COLLEGE OF ENGINEERING

CE463 HYDROLOGY

PROJECT1 DIFFERENT TERMS AND

TERMINOLOGIES USED IN HYDROLOGY

SCORE

SUBMITTED BY: SUBMITTED TO:

DAYANAN, GHIOVANI J. / CE 4C ENGR.GAUDENCIO C. PASCUAL

JANUARY 22, 216



1. A!"#$%&' ( The process by which ice and snow dissipate owing to melting and

evaporation.

2. A!)$*+'$ ( The part of a valley or canyon wall against which a dam is constructed.

Right and left abutments are those on respective sides of an observer looking

downstream.

3. A!)$*+'$ S++#-+ ( Reservoir water that moves through seams or pores in the natural

abutment material and exits as seepage.

4. A+(0&&$- the volume of water required to cover 1 acre to a depth of 1 foot. One acre-

foot is equal to !"#$% cubic feet or 1"&!!.# cubic meters.

. A'$+++'$ &'%$%&'- the conditions prevailing prior to an event. This description is

normally used to characteri'e basin wetness.

6. A$$+')#$%&'- the reduction in the peak of a hydrograph as it moves downstream"

resulting in a more broad" flat hydrograph.

. A+(0&&$ (The amount of water required to cover one acre to a depth of one foot. (n

acre-foot equals !&$")#1 gallons" or !"#$% cubic feet.

5. A$%+ C&'+#$%&' S$&#-+ ( The portion of water stored in a reservoir that can be

released for all useful purposes such as municipal water supply" power" irrigation"

recreation" fish" wildlife" etc. *onservation storage is the volume of water stored between

the inactive pool elevation and flood control stage.

7. A$%+ 8U#!"+9 S$&#-+ C##%$ ( The total amount of reservoir capacity normally

available for release from a reservoir below the maximum storage level. +t is total or reservoir capacity minus inactive storage capacity. ,ore specifically" it is the volume of

water between the outlet works and the spillway crest.



1. A%&'#; T+ S'&< S#*"%'- S+$ ( ( snow sampler consisting of a #-foot

fiberglass tube" ! inches in diameter" with a serrated-edge steel cutter at one end and a

twisting handle at the other. This sampler has a $%-inch snow depth capacity.

11. ADVIS ( ( program which combines the (ntecedent recipitation +ndex (+/ method of

estimating runoff with unit hydrograph theory to estimate streamflow for a headwater

basin.

12. A%!&'+ S'&< S)+ P&-#* (*enter 0OR2*/ program that makes airborne

snow water equivalent and soil moisture measurements over large areas of the country

that are sub3ect to severe and chronic snow melt flooding.

13. A%!&'+ S'&< =#$+ E>)%#"+'$ M+#)+*+'$ T?+& (( theory based on the fact

that natural terrestrial gamma radiation is emitted from the potassium" uranium" and

thorium radioisotopes in the upper eight inches of the soil. The radiation is sensed from

low flying aircraft #%% feet above the ground. 4ater mass in the snow cover attenuates

the terrestrial radiation signal. The difference between airborne radiation measurements

made over bare ground and snow-covered ground can be used to calculate a mean areal

snow water equivalent value with a root mean square error of less than a half inch.

14. A"!+& (The portion of incoming radiation which is reflected by a surface.

1. ALERT F"&& =#'%'- S$+* (( cooperative" community-operated flood warning

system5 the acronym stands for (utomated 6ocal 7valuation in/ Real Time.

16. B#+ 0"&<- the sustained flow in a channel because of subsurface runoff.

1. B#+"%'+ *&'%$&%'- - The establishment and operation of a designed surveillance

system for continuous or periodic measurements and recording of existing and changing

conditions that will be compared with future observations after 0R*" 18)&/.

15. B+#;$?&)-? )+ - ( plot of relative concentration versus time" where relative

concentration is defined as *9*o with * as the concentration at a point in the

groundwater flow domain" and *o as the source concentration.



17. B)%") - The vertical distance the water table or potentiometric surface is raised" or the

increase of the pressure head due to the addition of water.

2. B+-%''%'- &0 F++@) -:ate on which ice forming a stable winter ice cover is first

observed on the water surface.

21. B+'?*#; 8BM9 -( permanent point whose known elevation is tied to a national

network. These points are created to serve as a point of reference. ;enchmarks have

generally been established by the <2=2" but may have been established by other >ederal

or local agencies. ;enchmarks can be found on <2=2 maps.

22. B"#; I+ -Transparent ice formed in rivers and lakes" or on roads and bridges.

23. B&+ %+ -(n ice sheet in the form of a long border attached to the bank or shore.5

shore ice.

24. B#;%? I+ -+ce formed from ;rackish water.

2. B#%+ S$+#* -*haracteri'ed by successive division and re3oining of streamflow with

accompanying islands. ( braided stream is composed of anabranches.

26. C#"%!#$%&' -The process of using historical data to estimate parameters in a hydrologic

forecast technique such as 2(*2,(" routings" and unit hydrographs.

2. C#%""#%$ -1/The degree to which a material or ob3ect containing minute openings or

passages" when immersed in a liquid" will draw the surface of the liquid above the

hydrostatic level. <nless otherwise defined" the liquid is generally assumed to be water.

&/The phenomenon by which water is held in interstices above the normal hydrostatic

level" due to attraction between water molecules.

25. C#%""# F%'-+ -The soil area 3ust above the water table where water can rise up

slightly through the cohesive force of capillary action. This layer ranges in depth from a

couple of inches" to a few feet" and it depends on the pore si'es of the materials. The

capillary fringe is also called the capillary 'one.



27. C#%""# P&$+'$%#" -The work required to move a unit mass of water from the reference

plane to any point in the soil column.

3. C#%""# &'+ -The soil area 3ust above the water table where water can rise up slightly

through the cohesive force of capillary action. This layer ranges in depth from a couple of

inches" to a few feet" and it depends on the pore si'es of the materials. The capillary 'one

is also called the capillary fringe.

31. C#$?*+'$ A+# -(n area having a common outlet for its surface runoff also see

:rainage (rea or ;asin" 4atershed/.

32. CFS 8C)!% F++$ + S+&'9 -The flow rate or discharge equal to one cubic foot of

water" usually/ per second. This rate is equivalent to approximately ?.) gallons per

second. This is also referred to as a second-foot.

33. C0(D# -The volume of water discharged in twenty four hours" with a flow of one cubic

foot per second is widely used5 1 cfs-day is & x $% x $% @ )$"%%% cubic feet" 1.8)!?1

acre-feet" or $$"!1? gallons. The average flow in cubic feet per second for any time

period is the volume of flow in cfs-days.

34. C?#''+" 8<#$+&)+9 -(n open conduit either naturally or artificially created which

periodically" or continuously contains moving water" or forms a connecting link between

two bodies of water. River" creek" run" branch" anabranch" and tributary are some of the

terms used to describe natural channels. 0atural channels may be single or braided. *anal

and floodway are some of the terms used to describe artificial channels.

3. C?#''+" I'0"&< -4ater" which at any instant" is flowing into the channel system form

surface flow" subsurface flow" base flow" and rainfall that has directly fallen onto the

channel.

36. C?#''+" L+# -(n elongated opening in the ice cover caused by a water current.

3. C?#''+" R&)$%'- -The process of determining progressively timing and shape of the

flood wave at successive points along a river.



35. C?#''+"%@#$%&' -The modification of a natural river channel5 may include deepening"

widening" or straightening.

37. C"&+ B#%' -( basin draining to some depression or pond within its area" from which

water is lost only by evaporation or percolation. ( basin without a surface outlet for

precipitation.

4. C"&+ B#%' L#;+ F"&&%'- ->looding that occurs on lakes with either no outlet or a

relatively small one. 2easonal increases in rainfall cause the lake level to rise faster than

it can drain. The water may stay at flood stage for weeks" months" or years.

41. D#* -(ny artificial barrier which impounds or diverts water. The dam is generally

hydrologically significant if it is-

a. 1. &# feet or more in height from the natural bed of the stream and has a storage of

at least 1# acre-feet.

b. &. Or has an impounding capacity of #% acre-feet or more and is at least six feet

above the natural bed of the stream.

42. D#* F#%")+ -*atastrophic event characteri'ed by the sudden" rapid" and uncontrolledrelease of impounded water.

43. D+# S$&#-+ -The volume in a reservoir below the lowest controllable level.

44. D++ P+&"#$%&' L& -4ater that percolates downward through the soil beyond the

reach of plant roots.

4. D++ S++#-+ -+nfiltration which reaches the water table.

46. D++ <+"" -( well whose pumping head is too great to permit use of a suction pump.

4. D+0&*+ I+ -( general term for ice which has been squee'ed together and forced

upwards and downwards in places. 2ubdivisions are rated ice" ridge ice" hummocked ice"

and other similar deformations.



45. D+-##$%&' -The geologic process by means of which various parts of the surface of the

earth are worn down and carried away and their general level lowered" by the action of

wind and water.

47. D+"$# -(n alluvial deposit" often in the shape of the =reek letter AdeltaA" which is formed

where a stream drops its debris load on entering a body of quieter water.

. D+'%$+ -Thin branch-like growth of ice on the water surface.

1. D+'%$% -The form of the drainage pattern of a stream and itBs tributaries when it

follows a treelike shape" with the main trunk" branches" and twigs corresponding to the

main stream" tributaries" and subtributaries" respectively" of the stream.

2. D+'%$ C)+'$ -( flow of water maintained by gravity through a large body of water"

such as a reservoir or lake" and retaining its unmixed identity because of a difference in

density.

3. D+'%$ &0 S'&< -The ratio" expressed as a percentage" of the volume which a given

quantity of snow would occupy if it were reduced to water" to the volume of the snow.

4hen a snow sampler is used" it is the ratio expressed as percentage of the scale reading

on the sampler to the length of the snow core or sample.

4. D+"+$%&' C)+ -That part of the hydrograph extending from the point of termination of

the Recession *urve to the subsequent rise or alternation of inflow due to additional

water becoming available for stream flow.

. D++%&' S$&#-+ -The volume of water contained in natural depressions in the land

surface" such as puddles.

6. E(3, F"&& S$#-+ R+&$ -( form that a 2ervice ydrologist9 ydrology >ocal oint

completes to document the dates in which forecast points are above flood stage" as well

as the crest dates and stages. :iscussion of the flood event must also be included in the 7-

#" ,onthly Report of River and >lood conditions. (n 7-! report is sent to Regional

eadquarters" the appropriate R>*" as well as the Office of ydrology O/.



. E(, M&'$?" R+&$ &0 R%+ #' F"&& &'%$%&' -( monthly narrative report

covering flooding which occurred over the past month. >lood stage" flood crest and dates

in which flooding occurred is covered within this report for each data point which was in

flood. +f the flooding involved a forecast point" an 7-! must be filled out as well. +f no

flooding has occurred within the past month" a climatic summary of the past month can

be included as well as other interesting non-flood events" such as water supply" ice 3ams

and the occurrence of drought. (n 7-# report is sent to Regional eadquarters" the

appropriate R>*" as well as the Office of ydrology O/.

5. E(, F"&& D#*#-+ R+&$ -( report to be completed anytime there is reported flood

damage or loss of life as a direct result of flooding. (n 7-? report is sent to Regional

eadquarters" as well as the Office of ydrology O/.

7. E(17, R+&$ &' R%+ G#-+ S$#$%&' -( report to be completed every # - 1% years

providing a complete history of a river station and all gages that have been used for

public forecasts since the establishment of the station. 2hould be updated anytime a

significant change occurs at a forecast point.

6. E(17#, A!%-+ R+&$ &' R%+ G#-+ S$#$%&' -(n abridged version of an 7-18" an 7-

18a used to be used to update the 7-18 as additional information" or changes occur at thestation during the intervening five year period. 0o longer relevant since 7-18s can be

updated and produced rapidly on computers or on (4+2. (n 7-18a can also be used to

take the place of an 7-18 in documenting any gage history" or information of any non-

forecast point i.e5 data point/.

61. E#$?+' 8& E#$?0%""9 D#* -(n embankment dam in which more than #%C of the total

volume is formed of compacted fine-grained material. ( homogeneous earthen dam is

constructed of similar earthen material throughout. These are the most common type of

dam because their construction involves using materials in the natural state" requiring

little processing.



62. E00+$%+ P&&%$ -The ratio" usually expressed as a percentage" of the volume of water

or other liquid which a given saturated volume of rock or soil will yield under any

specified hydraulic condition" to the given volume of soil or rock.

63. E00+$%+ P+%%$#$%&' 8R#%'0#""9

a. That part of the precipitation that produces runoff

b. ( weighted average of current and antecedent precipitation that is AeffectiveA in

correlating with runoff.

c. That part of the precipitation falling on an irrigated area that is effective in

meeting the consumptive use requirements.

64. E00")+'$ S++#-+ -:iffuse discharge of ground water to the ground surface.

6. E00")+'$ S$+#* -(ny watercourse in which all" or a portion of the water volume came

from the hreatic 'one" or 'one of saturation by way of groundwater flow" or base flow.

66. E'-%'++ L++" -( telescope which is attached to a spirit-tube level" all revolving

around a vertical axis and is mounted on a tripod. (n 7ngineerBs 6evel is used for

determining the difference in elevation between two points. The telescope on the level

has a vertical cross hair and a hori'ontal cross hair. Once the instrument is leveled" the

sighting through the hori'ontal cross hair represent a hori'ontal plane of equal elevation.

6. E'+*!"+ H&"&-% F&+#$%'- -( process whereby a continuous hydrologic model

is successively executed several times for the same forecast period by use of varied data

input scenarios" or a perturbation of a key variable state for each model run. ( common

method employed to obtain a varied data input scenario is to use the historicalmeteorological record" with the assumption that several years of observed data covering

the time period beginning on the current date and extending through the forecast period

comprises a reasonable estimate of the possible range of future conditions.



65. E>)%"%!%)* D#<&<' -The ultimate" constant drawdown for a steady rate of pumped

discharge.

67. E>)%"%!%)* S)0#+ D%?#-+ -The steady rate of surface discharge which results

from a long-continued" steady rate of net rainfall" with discharge rate equal to net rainfall

rate.

. E>)%"%!%)* T%*+ -The time when flow conditions become substantially equal to those

corresponding to equilibrium discharge or equilibrium drawdown.

1. F"&&"#%' - lowland areas ad3oining lakes" wetlands" and rivers that are susceptible to

inundation of water during a flood. >or regulatory purposes" the floodplain is the area

covered by the 1%%-year flood or the area that has a 1 percent chance of flooding every

year. +t is usually divided into districts called the floodway and flood fringe. (reas where

the floodway and flood fringe have not been determined are called approximate study

areas or general floodplain. 6ocal units of government administer ordinances that guide

development in floodplains.

2. F"&& $#-+ - The 0ational 4eather 2ervice defines flood stage as the river level that

begins to impact life and9or property. ( River flood warnings will be issued when river

levels are forecast to reach flood stage at any official national weather service river

forecast location.

3. F++#" E*+-+' M#'#-+*+'$ A-+' 8FEMA9 ((n agency of the federal

government having responsibilities in ha''ard mitigation5 >7,( also administers the

0ational >lood +nsurance rogram.

4. F++#" S'&< S#*"+ (( snow sampler consisting of five or more sections of sampling

tubes" one which has a steel cutter on the end. The combined snowpack measuring depth

is 1#% inches. This instrument was formerly the ,ount Rose Type 2now 2ampling 2et.

. F+$? ((n area of the sea surface over which a wind with constant direction and velocity

is blowing.



6. F%+" 8M&%$)+9 C##%$ (The amount of water held in soil against the pull of gravity.

. F%+" M&%$)+ D+0%%+' (The quantity of water" which would be required to restore

the soil moisture to field moisture capacity.

5. F%"" D#* ((ny dam constructed of excavated natural materials or of industrial wastes.

7. F%' 8S'&<9 (Old snow on top of glaciers" granular and compact and not yet converted

into ice. +t is a transitional stage between snow and ice. (lso called 0eve.

5. F%' L%'+ (The highest level to which the fresh snow on a glacierBs surface retreats

during the melting season. The line separating the accumulation area from the ablation

area.

)1. G#-+

a. ( device for indicating the magnitude or position of a thing in specific units"

when such magnitude or position undergoes change" for example- The elevation

of a water surface" the velocity of flowing water" the pressure of water" the amount

or intensity of precipitation" the depth of snowfall" etc.

b. The act or operation of registering or measuring the magnitude or position of a

thing when these characteristics are undergoing change.

c. The operation" including both field and office work" of measuring the discharge of

a stream of water in a waterway.

52. G#-+ D#$)* (The arbitrary 'ero datum elevation which all stage measurements are made

from.

53. G#-+ H+%-?$ (The water-surface elevation referred to some arbitrary gage datum. =age

height is often used interchangeably with the more general term stage" although gage

height is more appropriate when used with a reading on a gage.



54. G#-%'- S$#$%&' (( particular site on a watercourse where systematic observations of

stage and9or flow are measured.

5. G#""+ (( passageway within the body of a dam or abutment.

56. G#$+ (( device in which a leaf or member is moved across the waterway from an

external position to control or stop flow. There are many different kinds of gates used on

a dam. 2ome include- ;ulkhead" *rest or 2pillway/" 7mergency" >ixed 4heel" >lap"

>lood" =uard" Outlet" Radial" Regulating" and 2lide =ates.

5. G+&?&"&- (That branch of hydrology relating to subsurface" or subterranean waters.

55. G+&?% (The study of the physical characteristics and properties of the earth5including geodesy" seismology" meteorology" oceanography" atmospheric electricity"

terrestrial magnetism" and tidal phenomena.

57. G"#%+ (;odies of land ice that consist of recrystalli'ed snow accumulated on the surface

of the ground" and that move slowly downslope.

7. G"#%+ D#**+ L#;+ (The lake formed when a glacier flows across the mouth of an

ad3oining valley and forms an ice dam.

71. GOES 8G+&$#$%&'# O!%$%'- E'%&'*+'$#" S#$+""%$+9 (

72. 2atellite orbiting at &&"%%% miles above the earthBs surface that remains above the same

location on the earth. :*s transmit river and rainfall data to the =O72 for relay to a

ground-receive site in 4allops +sland" D(.

73. GOES DCS 8D#$# C&""+$%&' S$+*9 (( data collection system under 072:+2 which

is comprised of the :*s" and the 072:+2 *ommand and :ata (cquisition *:(/

2ystem components. This satellite-based system collects a variety of environmental data

from locations in the 4estern emisphere. The system is a data relay network for more

than 1%"%%% :*s which transmits data to one of two =O72 satellites 7ast and 4est/.

These data are relayed to the 072:+2 *:( ground station located at 4allops +sland" D(.



The data are then relayed over to 2ilver 2prings" ,:" where the data is then distributed to

the appropriate recipients.

74. G#%$ D#* (( concrete structure proportioned so that its own weight provides the

ma3or resistance to the forces exerted on it.

7. G&)' ++%+ %$+ (( satellite dish and associated computer which receives signals

from the =O72 satellite" decodes the information" and transmits it to another site

for further processing. The =O72 satellite ground-receive site is located at

4allops +sland" D(5 and the information is relayed to a mainframe computer at

042 for processing.

76. H+# (The difference between the pool height and tailwater height. <sually expressed in

feet of head" or in lbs.9sq. inch.

7. H+# L& (The decrease in total head caused by friction" entrance and exit losses.

75. H+# R#+ (( channel which directs water to a water wheel5 a forebay.

77. H+#<# E&%&' (7rosion which occurs in the upstream end of the valley of a stream"

causing it to lengthen its course in such a direction.

1. H+#<#$+ (2treams at the source of a river.

11. H+#<#$+ A%& P&-#* 8ADVIS9 (( rogram which uses the (ntecedent

recipitation +ndex (+/ method of estimating runoff" unit hydrograph theory

and stage-discharge ratings to produce hydrologic forecasts for headwater basins.

12. H+#<#$+ A%& T#!"+ (( table developed by a River >orecast *enter for a

eadwater =uidance oint5 a pre-computed matrix of values allows a forecaster

to ascertain an anticipated crest or rise on a small river or stream for a variety of

rainfall events and soil moisture conditions.



13. H+#<#$+ !#%' (( basin at the headwaters of a river. (ll discharge of the

river at this point is developed within the basin.

14. HSA 8H&"&-% S+%+ A+#9 (( geographical area assigned to 4eather

2ervice >orecast OfficeBs94eather >orecast OfficeBs that embraces one or

more rivers.

1. H)**&; (( hillock of broken ice which has been forced upward by

pressure.

16. H)**&;+ I+ (+ce piled hapha'ardly one piece over another to form an

uneven surface.

1. H#)"% F%"" D#* (( dam constructed of materials" often dredged" that

are conveyed and placed by

15. suspension in flowing water.

17. H#)"% G#+ L%'+ (( line whose plotted ordinate position represents the

sum of pressure head plus elevation head for the various positions along a

given fluid flow path" such as along a pipeline or a ground water streamline. +n open channels" the hydraulic grade line is equal to the water surface.

11%. H#)"% H+#

a. The height of the free surface of a body of water above a given point beneath the

surface.

b. The height of the water level at the headworks" or an upstream point" of a

waterway" and the water surface at a given point downstream.

c. The height of a hydraulic grade line above the center line of a pressure pipe" at a

given point.



111. H#)"% M+#' D+$? (The right cross-sectional area of a stream of

water divided by the length of that part of its periphery in contact with its

containing conduit5 the ratio of area to wetted perimeter. (lso called

ydraulic Radius.

112. H#)"% P+*+#!%"%$ (The flow of water through a unit cross- sectional area

of soil normal to the direction of flow when the hydraulic gradient is unity.

113. H#)"% R#%) (The right cross-sectional area of a stream of water divided

by the length of that part of its periphery in contact with its containing conduit5

the ratio of area to wetted perimeter. (lso called ydraulic ,ean :epth.

114. H&-#? (( graph showing the water level stage/" discharge" or other

property of a river volume with respect to time.

11. H&-#? S+##$%&' (The process where the storm

hydrograph is separated into baseflow components and surface runoff

components.

116. I+ B&&* (( floating structure designed to retain ice.

11. I+ B%-+ (( continuous ice cover of limited si'e extending from shore to shore

like a bridge.

115. I+ G&-+ (The gorge or opening left in a 3am after it has broken.

117. I+ #* (( stationary accumulation that restricts or blocks streamflow.

12. I+ P)? (*ompression of an ice cover particularly at the front of a moving

section of ice cover.

121. I+ R)' (>low of ice in a river. (n ice run may be light or heavy" and may

consist of fra'il" anchor" slush" or sheet ice.



122. I+ T<%$? (:ownstream movement of a small section of an ice cover. +ce

twitches occur suddenly and often appear successively.

123. I+ S?&+ (On-shore ice push caused by wind" and currents" changes in

temperature" etcetera.

124. IFLO=S (The +ntegrated >lood Observing and 4arning 2ystem.

12. I*+*+#!"+ (,aterial that does not permit fluids to pass through it.

126. I*+%&) (The ability to repel water" or not let water infiltrate.

12. I*&$ (4ater piped or channeled into an area.

125. I'#$%+ S$&#-+ C##%$ (The portion of capacity below which the reservoir is

not normally drawn" and which is provided for sedimentation" recreation"

fish and wildlife" aesthetic reasons" or for the creation of a minimum controlled

operational or power head in compliance with operating agreements or

restrictions.

127. I'?(D+-++ (The product of inches of rainfall multiplied by the temperature in

degrees above free'ing >ahrenheit 2cale/" used as a measure of the

snowmelting capacity of rainfall.

13. I'?+ &0 R)'&00 (The volume of water from runoff of a given depth over the

entire drainage.

131. J+$$ (( structure e.g.5 a pier" or mole of wood or stone/ extending into a sea"

lake" or river to influence the current or tide or to protect a harbor.

132. J&;)"?"#) ((n +celandic term meaning glacier dammed lake outburst flood.

133. J)+'%"+ =#$+ (4ater formed chemically within the earth and brought to the

surface in intrusive rock.



134. L#- 8&0 # !#%'9 (The measure of the time between the center of mass of

precipitation to the center of mass of runoff on the hydrograph/5 basin lag is a

function of not only basin characteristics" but also of storm intensity and

movement. 2ome hydrologic texts define lag from the center of mass of

rainfall to the hydrograph peak.

13. L#- 8T%*+9 (The time it takes a flood wave to move downstream.

136. L#*%'# F"&< (2treamline flow in which successive flow particles follow

similar path lines and head loss varies with velocity to the first power.

13. LARC 8L%*%$+ A)$&*#$% R+&$ C&""+$&9 ((n electronic device that

interfaces a river or precipitation gage with a telephone line making it

possible for remote computers to call a gaging site and retrieve data.

135. L+'-$? (The distance in the direction of flow between two specific points

along a river" stream" or channel.

137. L+'$% S$+* (( nonflowing or standing body of fresh water" such as a lake

or pond. *ompare lotic system.

14. L+++ 8D%;+9 (( long" narrow embankment usually built to protect land

from flooding. +f built of concrete or masonry the structure is usually

referred to as a flood wall. 6evees and floodwalls confine streamflow

within a specified area to prevent flooding. The term AdikeA is used to describe an

embankment that blocks an area on a reservoir or lake rim that is lower than the

top of the dam.

141. LF=S (( generic term for any type of 6ocal >lood 4arning 2ystem.

142. L%*%$+ A)$&*#$% R+*&$+ C&""+$& 8LARC9 ((n electronic device that

interfaces a river or precipitation gage with a telephone line making it

possible for remote computers to call a gaging site and retrieve data.



143. L%*'&"&- (The branch of hydrology that pertains to the study of lakes.

144. L%$?&?++ (That part of the earth which is composed predominantly of

rocks either coherent or incoherent" and including the disintegrated rock

materials known as soils and subsoils/" together with everything in this rocky

crust.

14. L%$$&#" &'+ (The area on" or near the shore of a body water.

146. M#%' S$+* (The reach of a river9stream formed by the tributaries that flow into

it.

14. M#& F"&&%'- (( general term including extensive inundation and propertydamage. <sually characteri'ed by the evacuation of people and livestock and

the closure of both primary and secondary roads./

145. MAP 8M+#' A+#" P+%%$#$%&'9 (The average rainfall over a given area"

generally expressed as an average depth over the area.

147. M# C)+ (( graph of the cumulative values of a hydrologic quantity such

as precipitation or runoff/" generally as ordinate" plotted against time or date.

1. M#%*)* S%""<# D%?#-+ (2pillway discharge cfs/ when reservoir is at

maximum designed water surface elevation.

11. M+#' D+$? (The average depth of water in a stream channel or conduit. +t is

equal to the cross-sectional area divided by the surface width.

12. M+#'+ (The winding of a stream channel.

13. M+#'+ B+"$ (The area between lines drawn tangential to the extreme limits

of fully developed meanders.

14. M+'%) (The curved surface of the liquid at the open end of a capillary

column.



1. M+$+&% =#$+ (4ater derived from precipitation.

16. M%'+ I'? (( rate of discharge through an orifice one inch square under a

specific head.

1. M%'& F"&&%'- (( general term indicating minimal or no property

damage but possibly some public inconvenience.

15. M%%&' &0 $?+ N#$%&'#" =+#$?+ S+%+ (To provide weather and flood

warnings" public forecasts and advisories for all of the <nited 2tates" its

territories" ad3acent waters and ocean areas" primarily for the protection of life

and property. 042 data and products are provided to private meteorologist for

the provision of all speciali'ed services.

17. M%%&' &0 $?+ H&"&-% S+%+ P&-#* (To provide river and flood

forecasts and warnings for the protection of life and property and to provide basic

hydrologic forecast information for the 0ationBs economic and environmental

well-being.

16. N#$)#" C&'$&" (( stream gaging control which is natural to the stream

channel" in contrast to an artificial control structure by man.

161. N#$%&'#" E'%&'*+'$#" S#$+""%$+, D#$#, #' I'0&*#$%&' S+%+

8NESDIS9 ( 072:+2 collects" processes" stores" analy'es" and disseminates

various types of hydrologic" meteorologic" and oceanic data. 072:+2

is also responsible for the development of analytical and descriptive

products so as to meet the needs of itBs users.

162. N+$ R#%'0#"" (The portion of rainfall which reaches a stream channel or the

concentration point as direct surface flow.

163. NOHRSC(The 0ational Operational ydrologic Remote 2ensing *enter. (n

organi'ation under the 0ational 4eather 2ervice Office of ydrology O/

that mainly deals with snow mapping.



164. O!+#$%&' =+"" (( non-pumping well used for observing the elevation of

the water table or pie'ometric surface.

16. O-++ (( reverse curve" shaped like an elongated letter 2. Th7 downstream faces

of overflow dams are often made to this shape. >rom the >rench word Ogive/.

166. OH (The Office of ydrology" located in 2ilver 2prings" ,:.

16. OML ((n Operations ,anual 6etter. These serve as updates to policy and

procedure for the 042ervice Operations ,anual 42O,/.

165. O'+ P++'$ C?#'+ F"&& 8O'+ H)'+ Y+# F"&&9 (>lood magnitude that

has one chance in 1%% of being exceeded in any future 1-year period. Theoccurrence of floods is assumed to be random in time" or regularity of occurrence

is implied. The exceeding of a 1-percent chance is no guarantee" therefore" that a

similar si'e flood will not occur next week. The risk of experiencing a large flood

within time periods longer than 1 year increases in a nonadditive fashion. >or

example" the risk of exceeding a 1-percent chance flood one or more times during

a !%-year period is &# percent and during a ?%-year period is #% percent.

1$8. O%0%+ (

a. (n opening with closed perimeter" usually sharp edged" and of regular form in a

plate" wall" or partition through which water may flow" generally used for the

purpose of measurement or control of water.

b. The end of a small tube" such as a itot tube" pie'ometer" etc.

1. O&-#?% P+%%$#$%&' (recipitation which is caused by hills ormountain ranges deflecting the moisture-laden air masses upward" causing them

to cool and precipitate their moisture.

11. O)$0"&< C?#''+" (( natural stream channel which transports reservoir

releases.



12. O)$"+$ ((n opening through which water can be freely discharged from a

reservoir.

13. O)$"+$ D%?#-+ S$)$)+ (rotects the downstream end of the outlet pipe

from erosion and is often designed to slow down the velocity of released

water to prevent erosion of the stream channel.

14. P#"*+ D&)-?$ S++%$ I'+ ((n index whereby excesses or deficiencies of

precipitation are determined in relation to average climate values. The index

takes in to account precipitation" potential and actual

7vapotranspiration" infiltration of water into the soil" and runoff.

1. P##*+$% D#$# (:ata such as rating curves" unit hydrographs" and

rainfall9runoff curves which define hydrologic variables in models.

16. P##+$ =#"" (( solid wall built along the top of the dam for ornament"

safety" or to prevent overtopping.

1. P#$%#"(D)#$%&' F"&& S+%+ (( list of all flood peaks that exceed a chosen

base stage or discharge" regardless of the number of peaks occurring in a year.

=enerally however" selected to result in one per year on average" with some

years having none and others having several.

15. P#'#;+ I+ (*ircular flat pieces of ice with a raised rim5 the shape and rim

are due to repeated collisions.

17. P+#; D%?#-+ (ighest rate of discharge of a volume of water passing

a given location during a given period of time during the year" or a flood event"

etc../.

15. P+?+ G&)'<#$+ (6ocal saturated 'ones above the water table which

exist above an impervious layer of limited extent.



151. P+?+ =#$+ T#!"+ (The water table of a relatively small ground-water

body supported above the general ground water body.

152. P+&"#$%&' (The movement of water" under hydrostatic pressure" through the

interstices of a rock or soil" except the movement through large openings such

as caves.

153. P+&"#$%&' D++ (+n irrigation or farming practice" the amount of water that

passes below the root 'one of the crop or vegetation.

154. P+&"#$%&' P#$? (The course followed by water moving or percolating

through any other permeable material" or under a dam which rests upon a

permeable foundation.

15. P+&"#$%&' R#$+ (The rate" usually expressed as a velocity" at which water

moves through saturated granular material. The term is also applied to

quantity per unit of time of such movement" and has been used erroneously to

designate +nfiltration Rate or +nfiltration *apacity.

156. P++''%#" S$+#* (( stream that flows all year round. *ompare intermittent

stream.

15. P+*#'+'$ C&'$&" (( stream gaging control which is substantially

unchanging and is not appreciably affected by scour" fill" or backwater.

155. P+*#'+'$ M&')*+'$ (>ixed monuments placed away from the dam which

allow movements in hori'ontal and vertical control points on the dam to be

monitored by using accurate survey procedures.

157. PF 8)#'$%$#$%+ P+%%$#$%&' F&+#$9 (( spatial and temporal precipitation

forecast that will predict the potential amount of future precipitation for a

specified region" or area.



17. R#%&%&$&+ S'&< G#-+ (( snow water equivalent gage based on the

absorption of gamma radiation by snow5 this gage can measure up to ##

inches water equivalent with a & to # percent error.

171. R+-)"#$& F"&&<# (2ome maps show an area where construction regulations

require special provisions to account for this extra ha'ard. This is a regulatory

floodway.

172. R+*&$+ O!+%'- S$+* A)$&*#$%&' 8ROSA9 (( type of automated data

transmitter used by 042 *ooperative rogram observers.

173. R++&% (( man-made facility for the storage" regulation and controlled release

of water.

174. R#$%'- C)+ (( graph showing the relationship between the stage" usually

plotted vertically E-axis/ and the discharge" usually plotted hori'ontally

F-axis/.

17. R#$%'- T#!"+ (( table of stage values and the corresponding discharge for a

river gaging site.

176. R+#? (The distance between two specific points outlining that portion of the

stream" or river for which the forecast applies. This generally applies to the

distance above and below the forecast point for which the forecast is valid.

17. R++%&' C&'$#'$ (*onstant used to reduce the (+ value daily in the

(+ method of estimating runoff.

175. R%+ S$+* ((ll of the streams and channels draining a river basin.

177. R%+ R++#$%&' S$#$+*+'$ 8RVR9 (( statement released by the 042

to inform river users of current and forecast river and lake conditions. These

statements are especially useful for planning purposes.



2. R%+ S$#$+*+'$ 8RVS9 (( product issued to communicate notable

hydrologic conditions which do not involve flooding" i.e." within river bank

rises" minor ice 3ams" etc.

21. R&;0%"" D#* ((n embankment dam of earth or rock in which the material is

placed in layers and compacted by using rollers or rolling equipment. 2ame as

Rolled >illed :am.

22. R& (( graduated staff used in determining the difference in elevation

between two points. The two most common types of rods are the hiladelphia

Rod" graduated in feet and hundredths of a foot" and a *alifornia Rod" graduated in

feet" inches" and eights of an inch.

23. R&""+ F%""+ D#* ((n embankment dam of earth or rock in which the

material is placed in layers and compacted by using rollers or rolling equipment.

2ame as Rockfill dam.

24. ROML (Regional Operations ,anual 6etter. These serve as updates to

regional policy and procedure for the 0ational 4eather 2ervice Operations

,anual 42O,/.

2. R&$$+' I+ (+ce in an advanced stage of disintegration.

26. R&)$%'- (The methods of predicting the attenuation of a flood wave as it

moves down the course of a river.

2. R)'&00 (That part of precipitation that flows toward the streams on the surface of

the ground or within the ground. Runoff is composed of baseflow and surface

runoff.

25. S##*+'$& S&%" M&%$)+ A&)'$%'- M&+" 8SACSMA9 (( hydrologic

model which simulates the movement and occurrence of water in and on top of

the ground.



27. S#$+""%$+ H&"&- P&-#* (( 0OR2* program that uses satellite data

to generate areal extent of snow cover data over large areas of the western

<nited 2tates.

21. SCS (The 2oil *onservation 2ervice" now known as the 0R*2 0ational

Resources *onservation 2ervices/.

211. S+&'(D# F++$ (The volume of water represented by a flow of one cubic foot

per second for & hours5 equal to )"%%% cubic feet. This is used

extensively as a unit of runoff volume. Often abbreviated as 2:>.

212. S+%*+'$ S$&#-+ C##%$ (The volume of a reservoir planned for the

deposition of sediment.

213. S++#-+ (The interstitial movement of water that may take place through a

dam" its foundation" or abutments.

214. S+%+ H&"&-%$ (The designated expert of the hydrology program at a

4>O.

21. S?++$ F"&< (>low that occurs overland in places where there are no definedchannels" the flood water spreads out over a large area at a uniform depth. This

also referred to as overland flow.

216. S?&+ %+ ((n ice sheet in the form of a long border attached to the bank or

shore5 border ice.

21. S%$+(S+%0% (Term used in con3unction with AforecastA or AwarningA to convey

the fact that a hydrologic stream/ forecast is produced for an individual streamgage location as opposed to a general area e.g." a city" 'one" or county/ as is

commonly done in many types of weather forecasts.

215. T#%"<#$+ H+%-?$ (eight of water immediately downstream of the dam. Darious

datums may be used./



217. T?#"<+- (The line of maximum depth in a stream. The thalweg is the part that

has the maximum velocity and causes cutbanks and channel migration.

22. T?+&&"%$+ ((n instrument used in surveying to measure hori'ontal and vertical

angles with a small telescope that can move in the hori'ontal and vertical planes.

221. T?+?&" R)'&00 (The runoff in inches from a rain of specified duration that

causes a small stream to slightly exceed bankfull. 4hen available" flood stage is

used instead of slightly over bankfull.

222. T%%'-(B);+$ R#%' G#-+ (( precipitation gage where collected water is

funneled into a two compartment bucket5 %.%1" %.1 mm" or some other designed

quantity of rain will fill one compartment and overbalance the bucket so that it

tips" emptying into a reservoir and moving the second compartment into place beneath

the funnel. Tipping buckets provide a measurement of both intensity and amount

of precipitation.

223. T&+ &0 D#* 8U$+#* #' D&<'$+#*9 (The 3unction of the face of a dam

with the ground surface.

224. T&+ D#%' 8& O)$0#""9 (( drain which carries seepage away from the dam and

can allow seepage quantities to be measured.

22. T&$#" G& R++&% C##%$ (The total amount of storage capacity

available in a reservoir for all purposes from the streambed to the normal

water or normal water or normal pool surface level. +t does not include surcharge"

but does include dead storage.

226. T#+ (( hydrograph or similar plot for an extended-range time hori'on

showing one of many scenarios generated through an ensemble forecast

process.

22. T#+ 8&0 P+%%$#$%&'9 (( rainfall amount less than %.%1 of an inch.



225. T#'%#$%&' (4ater discharged into the atmosphere from plant surfaces.

227. T#? R#; (( screen located at an intake to prevent debris from entering.

23. T#+" T%*+ (The time required for a flood wave to travel from one location toa subsequent location downstream.

231. T)!%%$ (The thickness or opaqueness of water caused by the suspension of

matter. The turbidity of rivers and lakes increases after a rainfall.

232. T)'%'- P&%'$ (( temporary point whose elevation is determined by additions

and subtractions of backsights and foresights respectively.

233. T#'%#$%&' (4ater discharged into the atmosphere from plant surfaces.

234. T#? R#; (( screen located at an intake to prevent debris from entering.

23. T#+" T%*+ (The time required for a flood wave to travel from one location to

a subsequent location downstream.

236. T)!%%$ (The thickness or opaqueness of water caused by the suspension of

matter. The turbidity of rivers and lakes increases after a rainfall.

23. T)'%'- P&%'$ (( temporary point whose elevation is determined by additions

and subtractions of backsights and foresights respectively.

235. U'+0"&< (The lateral motion of water through the upper layers until it enters a

stream channel. This usually takes longer to reach stream channels than runoff.

This also called subsurface storm flow.

237. U'%$ H&-#? 8& U'%$-#?9 (The discharge hydrograph from one inch of

surface runoff distributed uniformly over the entire basin for a given time

period.



24. U'%$ H&-#? D)#$%&' (The time over which one inch of surface runoff

is distributed for unit hydrograph theory.

241. U'%$ H&-#? T?+& (<nit ydrograph Theory states that surface runoff

hydrographs for storm events of the same duration will have the same shape" and

the ordinates of the hydrograph will be proportional to the ordinates of the unit

hydrograph. >or example" the hydrograph for GA of storm runoff will be half that

of that from the unit hydrograph.

242. U'%+#" T+ =+%-?$%'- #' R+&%'- G#-+ (( gage which collects

precipitation and then converts the weight onto an inked pen movement which

traces on graph paper fixed to a clock driven drum.

243. U$+#* S"&+ (The part of the dam which is in contact with the reservoir

water. On earthen dams" this slope must be protected from the erosive

action of waves by rock riprap or concrete.

244. U!#' F"#? F"&& G)%#'+ (( specific type of flash flood guidance

which estimates the average amount of rain needed over an urban area

during a specified period of time to initiate flooding on small" ungaged streams

in the urban area.

24. U!#' F"&&%'- (>looding of streets" underpasses" low lying areas" or storm

drains. This type of flooding is mainly an inconvenience and is generally not

life threatening.

246. U.S. A* C& &0 E'-%'++ 8USACE9 ((s part of the :epartment of the

(rmy" the *orps has responsibilities in civil and military areas. +n civil works"

the <2(*7 has authority for approval of dredge and fill permits in navigable

waters and tributaries thereof5 the <2(*7 enforces wetlands regulations" and

constructs and operates a variety of water resources pro3ects" mostly

notably levee" dams and locks.



24. U.S. G+&"&-%#" S)+ 8USGS9 (The >ederal (gency chartered in 1)?8 by

congress to classify public lands" and to examine the geologic structure"

mineral resources" and products of the national domain. (s part of its

mission" the <2=2 provides information and data on the 0ationBs rivers and

streams that are useful for mitigation of ha'ards associated with floods and

droughts.

245. V#&+ &'+ (The locus of points 3ust above the water table where soil

pores may either contain air or water. This is also called the 'one of aeration.

247. V#"+ (( device fitted to a pipeline or orifice in which the closure member is

either rotated or moved in some way as to control or stop flow.

2. V+"&%$ &'+ ((reas within the floodplain sub3ect to potential high damage

from waves. These sometimes appear on flood insurance rate maps.

21. =#$+&)+ ((ny surface flow such as a river" stream" or tributary.

22. =#$+?+ (6and area from which water drains toward a common watercourse in

a natural basin.

23. =#$+ E>)%#"+'$ (The amount of water" in inches" obtained by melting a

snow sample.

24. =#$+ P&"")$%&' (The alteration of the constituents of a body of water by man

to such a degree that the water loses its value as a natural resource.

2. =#$+ S)" O)$"&&; (( seasonal volume forecast" generally for a period

centered around the time of spring snowmelt e.g." (pril-Huly/. The outlooks are

in units of acre-feet and represent the expected volume of water to pass by a

given point during a snowmelt season. The outlook categories include ,ost

robable" Reasonable ,aximum" and Reasonable ,inimum.



26. =#$+ S)" O)$"&&; 8ESS9 P&)$ (( public product issued by a >orecast

Office which contains narrative and numeric information on current and

extended water supply conditions.

2. =#$+ T#!"+ (The level below the earthBs surface at which the ground

becomes saturated with water. The water table is set where hydrostatic

pressure equals atmospheric pressure.

25. =#$+ Y+# (The time period form October 1 through 2eptember !%.

27. =+%-?%'-($+ P+%%$#$%&' G#-+ (( rain gage that weighs the rain or snow

which falls into a bucket set on a platform of a spring or lever balance. The

increasing weight of its contents plus the bucket are recorded on a chart. The

record thus shows the accumulation of precipitation.

&$%. =+%

a. ( low dam built across a stream to raise the upstream water level fixed-

crest weir when uncontrolled/5

b. ( structure built across a stream or channel for the purpose of measuringflow measuring or gaging weir/5

c. ( structure built into a levee or river bank that allows water to flow from the

main river channel into a bypass channel during time of high flows.

261. =+$ F"&&&&0%'- ((n approach to floodproofing which usually is a last resort.

>lood waters are intentionally allowed into the building to minimi'e water

pressure on the structure. 4et floodproofing can include moving a fewvaluable items to a higher place or completely rebuilding the floodable area.

4et floodproofing has an advantage over other approaches- no matter how

little is done" flood damage will be reduced. Thousands of dollars in damage can

be avoided 3ust by moving furniture and appliances out of the flood-prone

area.



262. =+$"#' ((n area that is regularly wet or flooded and has a water table that

stands at or above the land surface for at least part of the year.

263. =%+ =+%-?$ G#-+ (( river gage comprised of a weight which is lowered to the

water level. The weight is attached to a cable5 and as the weight is lowered" a

counter indicates the length of cable released. The stage is determined from the

length of cable required to reach the water level.

264. /R R+"#$%&'?% (The empirical conversion relationship between radar

reflectivity and precipitation rate.

26. +& D#$)* (( reference A'eroA elevation for a stream or river gage. This

A'eroA can be referenced usually within ten feet of the bottom of the

channel/ to mean sea level" or to any other recogni'ed datum.

266. &'+ E*!#';*+'$ D#* ((n embankment dam which is comprised of

'ones of selected materials having different degrees of porosity" permeability and

density.

26. &'+ &0 A+#$%&' (The locus of points 3ust above the water table where soil

pores may either contain air or water. This is also called the vadose 'one.

265. &'+ &0 S#$)#$%&' (The locus of points below the water table where soil

pores are filled with water. This is also called the phreatic 'one.

Alphabets of Hydrology[1]

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