CE 374 K – CE 374 K – HydrologyHydrology

Second Quiz ReviewSecond Quiz Review

Daene C. McKinneyDaene C. McKinney

Runoff ProcessesRunoff Processes WatershedWatershed

TerminologyTerminology ConceptsConcepts

StreamflowStreamflow Components of Components of

hydrologic cycle hydrologic cycle affecting itaffecting it

Atmospheric Moisture

Interception

Snowpack

Surface

Soil Moisture

Groundwater

Streams and Lakes

Runoff

RainSnow

Evaporation

Evapotranspiration

Evaporation

Throughfall and Stem Flow

Snowmelt

Infiltration

Overland Flow

Percolation

Groundwater Flow

Channel Flow

Pervious Impervious

Energy

WatershedBoundary

HydrographsHydrographs

Peak

Ris

ing L

imb

Recessio

n L

imb

Time

Dis

ch

arg

e,

Q

Beginning of Direct Runoff

BaseflowRecession Baseflow

Recession

Centroid of Precipitation

Basin Lag

Time of Rise

End of Direct Runoff

InflectionPoint

Baseflow SeparationBaseflow Separation

Three techniquesThree techniques Straight – line methodStraight – line method Fixed Base MethodFixed Base Method Variable Slope MethodVariable Slope Method

Time

Dis

ch

arg

e,

Q

A B

Baseflow

Direct Runoff

Time

Dis

ch

arg

e,

Q

A B

D

C

2.0AN

Baseflow

Direct Runoff

Time

Dis

ch

arg

e,

Q

A BC

E

Baseflow

Direct Runoff

Abstraction (Losses) Abstraction (Losses) EstimationEstimation

Phi – Index MethodPhi – Index Method

M

mmd tRr

1

A

Qt

A

Vr

N

nn

dd

1

0

2000

4000

6000

8000

10000

12000

7:30 PM 9:00 PM 10:30 PM 12:00 AM 1:30 AM 3:00 AM 4:30 AM 6:00 AM

Time

Stre

amflo

w (c

fs)

0

0.5

1

1.5

2

2.5

t=0.27

interval time

runoffdriecttongcontributi

rainfallofintervals#

indexPhi

rainfall observed

runoffdirect ofdepth

t

M

R

r

m

d

Abstraction (Losses) Abstraction (Losses) EstimationEstimation

SCS Curve SCS Curve Number MethodNumber Method

101000

CN

S

Time

Pre

cip

itati

on

pt

aI aF

eP

aae FIPP

StorageMaximumPotentialS

nAbstractioContinuing

nAbstractioInitial

Excess Rainfall

Rainfall Total

a

a

e

F

I

P

P

SP

SPPe 8.0

2.0 2

)(

)(

SIP

IPSF

a

aa

SIa 2.0

Hydrologic MeasurementHydrologic Measurement ClimateClimate PrecipitationPrecipitation Surface Water Surface Water

FlowFlow StageStage Rating CurveRating Curve

Unit HydrographUnit Hydrograph Time – Area RelationshipTime – Area Relationship

A

B

C

D

G

DPCBAQ

DPCPBAQ

DPCPBPAQ

DPCPBPAPQ

DPCPBPAPQ

CPBPAPQ

BPAPQ

APQ

58

457

3456

23455

12344

1233

122

11

*0*0*0

*0*0

*0

2P

1P

3P

Time, t

Excess

Rain

fall

4P5P

Unit HydrographUnit Hydrograph DerivationDerivation

n

mmnmn UPQ

11

9182739

8172638

7162537

6152436

5142335

4132234

3122133

21122

111

UPUPUPQ

UPUPUPQ

UPUPUPQ

UPUPUPQ

UPUPUPQ

UPUPUPQ

UPUPUPQ

UPUPQ

UPQ

Reservoir RoutingReservoir Routing

Storage - Storage - Discharge Discharge RelationshipRelationship

Level Pool RoutingLevel Pool Routing

QQt

Sand,

2

jj

jj

jj

Qt

SII

Qt

S

2

2

1

11

jjj

QQt

S

112

jj

jjj

Qt

SQQ

t

S 22

21

1

1

11

22j

jj

jjj Q

t

SQ

t

SII

River RoutingRiver Routing

Muskingum Muskingum MethodMethod Prism StoragePrism Storage Wedge StorageWedge Storage

])1([ QXXIKS

jjjj QCICICQ 32111

tXK

tXKC

tXK

KXtC

tXK

KXtC

)1(2

)1(2

)1(2

2

)1(2

2

3

2

1

SCS Dimensionless SCS Dimensionless HydrographHydrograph

SCS developed a parametric UH model based on averages of UHs from a large number of small agricultural watersheds in the US.

pp T

ACU

lagp tt

T

2

A – watershed area C – conversion factor for

unit system Tp- time to peak t – excess precip

duration tlag - basin lag, time

between center of rainfall excess and UH peak

Given ER hyetograph and time lag, then solve for time of UH peak, then UH peak

Frequency AnalysisFrequency Analysis Recurrence Recurrence

IntervalInterval Return Period: Return Period:

Average Average recurrence interval recurrence interval

Probability of an Probability of an extreme event is extreme event is related to the related to the return periodreturn period

TxX ofocurrencesbetweenTime

pTE

1)(

)(E

Extreme Value Extreme Value DistributionsDistributions

EV-I, EV-II, and EV-IIIEV-I, EV-II, and EV-III Extreme Value Type I (Gumbell) Extreme Value Type I (Gumbell)

DistributionDistribution

s6 5772.0xu

ux

y

yxF expexp)(

1lnln

T

TyT TT yux

Frequency FactorsFrequency Factors In generalIn general

NormalNormal

EV-IEV-I

LP-III: See tableLP-III: See table

szxx TT

sKxx TT

deviationstandardSample

meanSample

periodReturn

factorFrequency

magnitudeeventEstimated

s

x

T

K

x

T

T

1lnln5772.0

6

T

TKT

TT zK

Hydrologic DesignHydrologic Design

Depth-Duration-Frequency Estimates TP-40, Hydro-35, Asquith

I – D – F CurvesI – D – F Curves

Design Hyetographs: Design Hyetographs: distribute rainfall over time SCS HyetographHyetograph Triangular HyetographTriangular Hyetograph Alternating Block Method Alternating Block Method

fT

ci

ed

cbt

ai