Hydrologic Overview & Hydrologic Overview & QuantitiesQuantities
It is important to understand the big It is important to understand the big picture when attempting to forecast. picture when attempting to forecast.
This includes the interactive This includes the interactive components and hydrologic quantities.components and hydrologic quantities.
The complexity of what we are trying to The complexity of what we are trying to accomplishaccomplish……..
Infiltration
Evaporation & Condensation
The Water Budget
Photosynthesis & Respiration
Antecedent Moisture
Conditions
Transpiration & Interception
Variable Source Area
Time of Concentration The “sphere” concept was borrowed
from Dr. Peter Black:Watershed Hydrology – 2nd Edition, Peter Black, 1996, Ann Arbor Press (ISBN# 1-5704 027-1)
Models try to mimic this!Models try to mimic this!
Basin Process Representation
Infiltration
Excess Precip.
Interception
StorageTime Series
Time Series
From A Basin ViewFrom A Basin View
Excess Precip. Model
Excess Precip.
Basin “Routing”
Unit Hydrograph
Stream “Routing”
Runoff Hydrograph
The Runoff PictureThe Runoff Picture
•• Hydrology is long term and short termHydrology is long term and short term……..•• In this course we will mainly focus on the In this course we will mainly focus on the
shortshort term:term:•• Floods & flood flows.Floods & flood flows.•• Generating runoff/high flows.Generating runoff/high flows.•• Predicting/forecasting flows.Predicting/forecasting flows.•• Space/time scales.Space/time scales.
Recipe(s) for a Flood/High FlowsRecipe(s) for a Flood/High Flows
•• What causes a flood / high flow?What causes a flood / high flow?•• What are the conditions?What are the conditions?•• What are the types of flooding situations?What are the types of flooding situations?•• Your area or other areasYour area or other areas……....
What Are the Defining What Are the Defining Characteristics of a Flood?Characteristics of a Flood?•• Timing Timing –– rise time, recession, duration.rise time, recession, duration.•• Flows Flows –– peak flows, magnitude peak flows, magnitude
(statistical).(statistical).•• Precipitation Precipitation –– intensity, duration, intensity, duration,
frequencyfrequency……..
What Controls the Timing, Flow, What Controls the Timing, Flow, and Precipitation?and Precipitation?•• The hydrology The hydrology –– short term and long term.short term and long term.•• The meteorology The meteorology –– short term short term
(weather/storm type) and long term (weather/storm type) and long term (climate).(climate).
Short TermShort TermWeather (storm type) & Weather (storm type) & ““current hydrologic current hydrologic conditionsconditions””
Watershed CharacteristicsWatershed Characteristics
•• AreaArea•• SlopeSlope•• Land UseLand Use•• SoilsSoils•• GeologyGeology•• ClimateClimate•• GeomorphologyGeomorphology
Some of the Some of the ““RightRight””CombinationsCombinations……..•• Precipitation Precipitation ––vs.vs.-- infiltrationinfiltration
–– Precipitation intensity > infiltration ratePrecipitation intensity > infiltration rate–– Precipitation total > infiltration capacityPrecipitation total > infiltration capacity–– ““StorageStorage”” in the system is fullin the system is full–– Human induced high water or flowsHuman induced high water or flows–– Natural alterations to the watershedNatural alterations to the watershed
Our Focus Our Focus -- ForecastingForecasting
•• Must be both short & long term..Must be both short & long term..•• The combination(s) of precipitation and The combination(s) of precipitation and
hydrologic conditions that lead create a hydrologic conditions that lead create a potential flooding situationpotential flooding situation……
•• ““basin hydrologybasin hydrology”” –– basin hydrology looks basin hydrology looks at the hydrologic budget in both the short at the hydrologic budget in both the short and long term.and long term.
How much water is there?How much water is there?
Distribution of Earth's Waters and Residence TimesDistribution of Earth's Waters and Residence Times........Location of
Storage Percent of
Fresh Residence
Time (years)
Total water on earth
Oceans Total Fresh
Water 100.0 6977
Ice and Glaciers
75.4 5210
Groundwater Deep
14.0 973
Groundwater Shallow
11.0 764
Lakes 0.3 21 Biosphere 0.24 17.1
Soil Moisture 0.06 4.17 Atmosphere 0.035 2.43
Rivers 0.003 2.1
WaterWater ResourcesResources
•• Mean Mean annualannual precipitationprecipitation
726 726 mmmm//yearyearAsiaAsia
670 670 mmmm//yearyearNorthAmericaNorthAmerica
1648 1648 mmmm//yearyearSouthAmericSouthAmericaa
686 686 mmmm//yearyearAfricaAfrica
734 734 mmmm//yearyearEuropeEurope
HydrologicalHydrological processesprocesses
•• CloudsClouds andand atmosfericatmosfericmovementmovement
•• PrecipitationPrecipitation•• LossesLosses
–– InterceptionInterception–– EvapotranspirationEvapotranspiration–– InfiltrationInfiltration–– DepressionDepression storagestorage
•• RainfallRainfall –– runoffrunoff•• FloodFlood RoutingRouting
Units & Properties of WaterUnits & Properties of Water
Property Symbol Value Comments Density
(mass/volume) ~1.94 slugs/ft3
~ 1.0 g/cm3 Slug = lb*s2/ft
Specific Weight (weight/volume)
62.4 Lbs/ft3
9.81 kN/m3 g
Specific Volume Specific Gravity s.g. 1.0 for water
@ 0o C s.g.fluid = gfluid/gwater
Solar Solar RadiationRadiation
•• DifferencesDifferences accordingaccording toto thethe latitudelatitude
Solar Solar RadiationRadiation
•• DiferencesDiferences betweenbetween JuneJune andand SeptemberSeptember
EffectiveEffective RadiationRadiation
•• DifferenceDifference betweenbetween receivedreceived andand back back radiationradiation
RRnn = = RRii (1(1--) ) –– RRee
•• RiRi, solar , solar radiationradiation•• , albedo, albedo•• RRe,e,, back , back radiationradiation
CloudCloud structurestructure
•• WaterWater dropsdrops fromfrom 0.01 0.01 toto 0.03 mm0.03 mm•• WeightWeight fromfrom 0,5 0,5 toto 1 1 grgr/m/m33
•• GrowingGrowing processesprocesses up up toto 10.000 10.000 toto100.000 times 100.000 times initialinitial valuesvalues
•• WaterWater in in cloudsclouds can can explainexplain 10 10 toto 12 12 mmmm
DropletDroplet aggregationaggregation
•• RaindropsRaindrops up up toto 3 3 toto 4 4 mmmm
•• Terminal Terminal velocityvelocity9 a 12 m/s9 a 12 m/s
TypesTypes ofof rainfallrainfall
•• CiclonicalCiclonical / Frontal / Frontal rainrain
•• OrographicOrographic
•• ConvectiveConvective cellscells
Frontal Frontal rainrain•• Cold Cold andand hot hot airair massesmasses movingmoving alongalong thethe
planeteplanete
Frontal Frontal precipitationsprecipitations
•• AssociatedAssociated toto largelarge areasareas ((tenstens ororhundredshundreds ofof miles miles ofof KmKm22))
•• LongLong durationsdurations ((daysdays) ) andand highhigh total total rainfallsrainfalls butbut withwith lowlow rainfallrainfall intensitiesintensities
OrographicOrographic PrecipitationsPrecipitations
•• TypicalTypical MediterraneanMediterranean patternpattern•• DuringDuring thethe fallfallHot Hot airair comingcoming fromfrom thethe MagrebMagreb, , MountainsMountains closeclose toto seasideseaside
HeavyHeavy rainfallsrainfalls
ConvectiveConvective cellscells
•• AfectingAfecting toto smallsmall areasareas•• ConvectiveConvective cellscells appearingappearing andand
disappearingdisappearing duringduring thethe rainrain periodperiod•• Can produce Can produce veryvery intense intense rainfallsrainfalls
RainfallRainfall measurementsmeasurements
•• PrecipitationPrecipitation: mm l/m: mm l/m22
•• IntensityIntensity mmmm/h/h•• Temporal Temporal registerregister: : pluviographpluviograph oror
hyetographhyetograph
GreatestGreatest precipitationprecipitation datadata
•• Data Data onon differentdifferent observatoriesobservatories
ReuniReunióón, n, FebruaryFebruary 196419641350 mm1350 mm12 h 12 h
ReuniReunióón, n, MarchMarch 195219521870 mm1870 mmDayDay
HoltHolt, Missouri, , Missouri, JuneJune 19471947300 mm300 mm42 minutes42 minutes
CherrapunjiCherrapunji, , JulyJuly 186118619300 mm9300 mmMonthMonth
CherrapunjiCherrapunji, 1860, 1860--010126470 mm26470 mmYearYear
HawaiiHawaii, , MountMount WaialealeWaialeale11680 mm11680 mmAnnualAnnual precipitationprecipitation
47.0425DP
RainfallRainfall envelopeenvelope
•• MathematicalMathematical relationshiprelationship
•• P, mmP, mm D, D, hourshours
IntensityIntensity
•• IntensityIntensity, ratio , ratio betweenbetween precipitationprecipitationandand timetime
•• HyetographHyetograph
RainfallRainfall monitoringmonitoring
•• SatellitesSatellites, , qualitativequalitative observationobservation
MeasurementMeasurement networksnetworks
•• INM, INM, rainfallrainfall data in 24 hdata in 24 h•• SMC, SMC, shortershorter time seriestime series•• RainfallRainfall radarsradars
RainfallRainfall data data analysisanalysis
•• HypothesisHypothesis: : toto studystudy thethe historicalhistoricalrainfallrainfall data data toto predictpredict futurefuture rainfallrainfall
•• WeWe assumeassume thethe futurefuture rainfallrainfall willwill be be thethe samesame as as thethe previousprevious oneone
•• ClimaticClimatic changechange effecteffect: : toto studystudy•• ApplicationApplication in in hydrologicalhydrological studiesstudies
Data Data analysisanalysis
•• Time series Time series analysisanalysis•• QualitativeQualitative analysisanalysis
–– FillingFilling gapsgaps–– ConsistencyConsistency testtest ((doublesdoubles massmass))
•• StatisticalStatistical analysisanalysis
StatisticalStatistical analysisanalysis II
•• AnnualAnnual rainfallrainfall seriesseries•• ExtremalExtremal distributionsdistributions
–– GumbelGumbel–– Log Pearson IIILog Pearson III–– SQRT SQRT –– ETET
•• AssociatedAssociated valuesvalues toto returnreturn periodperiod ofof N N yearsyears
•• PartialPartial durationduration series, (series, (peakpeak overoverthresholdthreshold) )
•• AppropriatedAppropriated toto returnreturn periodsperiods belowbelow 10 10 yearsyears
StatisticalStatistical analysisanalysis IIII