Module 4 – (L12 - L18): “Watershed Modeling”Standard modeling approaches and classifications, system concept Standard modeling approaches and classifications, system concept for watershed modeling, overall description of different hydrologic processes, modeling of rainfall, runoff process, subsurface flows and groundwater flowg
16 Hydrologic Modeling111
16 Hydrologic Modeling
L16L16– Hydrologic ModelingL16L16 Hydrologic Modeling
Topics Covered Topics Covered Rainfall runoff modeling, Runoff Rainfall runoff modeling, Runoff g,g,
process, Physical modeling, process, Physical modeling, Distributed modelDistributed model
K dK d Keywords:Keywords: Rainfall runoff modeling, Rainfall runoff modeling, Physical modeling, distributed model.Physical modeling, distributed model.
22Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Watershed ModelRainfall watershed
Interception ET (Based on: McCuen, 1989,& Raj Vir Singh, 2000)
Surface storage
Surface runoff
Direct
ET
Infiltrationrunoff
Interflow
Percolation 0.00
3.00
6.00
9.00
12.00
15.00
Dis
char
ge(m
3 /sec
)
0.0
5.0
10.0
15.0
20.0
Rai
nfal
l int
erns
ity(m
m/h
r)
33Prof. T I Eldho, Department of Civil Engineering, IIT BombayGW storage
Channel flow
Base Flow
0 200 400 600
Time(min)RainfallObservedSimulated
Watershed models
Formulation Calibration
Rainfall Channel flow
Calibration Application Infiltration
Overland flowInterflow
Watershed model constitutes 1. Input function 2 Output function 2. Output function 3. Transform function
Physically based watershed modelsPhysically based watershed models
Overland flowChannel flow
44
Channel flow
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Deterministic Hydrologic Model Three main categories: Lumped, Semi-
distributed & Distributed Lumped models: Parameters do not vary spatially
within the basin & response is evaluated only at the outlet, without explicitly accounting for the response outlet, without explicitly accounting for the response of individual subbasins.– Parameters do not represent physical features of
hydrologic processes; model parameters – area weighted hydrologic processes; model parameters – area weighted average
– Not applicable to event based processesDi h di ti t tl t l– Discharge prediction at outlet only
– Simple & minimal data requirements, easy use– Eg. SCS-CN based models; IHACRES, WATBAL etc.
55
g
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Deterministic Hydrologic Model.. Semi – distributed models:: parameters are partially parameters are partially
allowed to vary in space by dividing the basin into a allowed to vary in space by dividing the basin into a number of smaller subbasinsnumber of smaller subbasinsnumber of smaller subbasinsnumber of smaller subbasins
Mainly two types: Kinematic wave theory models (eg. Mainly two types: Kinematic wave theory models (eg. HECHEC--HMS model) HMS model) -- simplified version of surface flow simplified version of surface flow equations of physically based modelequations of physically based model
Probability distributed models Probability distributed models –– spatial resolution is spatial resolution is accounted for by using probability distributions of input accounted for by using probability distributions of input accounted for by using probability distributions of input accounted for by using probability distributions of input parameters across the basin. parameters across the basin.
Advantage: structure is more physically based than Advantage: structure is more physically based than l d d ll d d llumped modelslumped models
Less demanding on input data than distributed modelsLess demanding on input data than distributed models Eg: SWMM HECEg: SWMM HEC--HMS TOPMODEL SWAT etcHMS TOPMODEL SWAT etc
66
Eg: SWMM, HECEg: SWMM, HEC HMS, TOPMODEL, SWAT etc.HMS, TOPMODEL, SWAT etc.
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Deterministic Hydrologic Model Distributed models: parameters are fully allowed to vary
in space at a resolution chosen by the user. Attempts to incorporate data concerning the spatial Attempts to incorporate data concerning the spatial
distribution of parameters variation together with computational algorithms
l f d Requires large amount of data Governing physical processes are modeled in detail. Results at any location & time Results at any location & time Highest accuracy in the rainfall-runoff modeling – if
accurate data is available High computational time, Cumbersome, experts required Eg. HYDROTEL; MIKE11/SHE, WATFLOOD etc.
77Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Physically based Watershed Model…Ph i ll b d d i i i d lPhysically based deterministic models: Aim: Gain better understanding of hydrologic
phenomena operating in a watershed and how changes p e o e a ope a g a a e s ed a d o c a gesin watershed may affect these phenomena
Complex processes simplified by lumping process in space and timespace and time
Laws of Physics Conservation of mass, momentum and energy
Continuity equation, equation of motion, equation of energy
One or more of these laws and several empirical One or more of these laws and several empirical relations are used in physical model development– Models may be fully distributed or semi distributed.
88Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Physically based Watershed Model…Scope of physical modeling Occurrence, movement,
distribution and storage of water and their variability in space and timespace and time
Technology of Physical Modelinggy y g Hydrodynamic Models theoretical, physical based or
hydraulic models. e.g Dynamic wave model for overland flowflow
Overland / channel flow By continuity equation and momentum equation
Modeling: May be in 1D, 2D or 3D Based on requirements & data availability
99Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
PhysicallyPhysically BasedBased ModelModel --FlowFlow EquationsEquationsFirstFirst proposedproposed byby StSt.. VenantVenant inin 18711871 basedbased ononp pp p yyfundamentalfundamental lawslaws ofof continuitycontinuity && conservationconservationofof momentummomentumContinuityContinuity equationequationContinuityContinuity equationequation
MomentumMomentum EquationEquation
De Saint-Venant (1797-1886)
1010Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
St. Venant Equations - Assumptions Flow is one-dimensional
Hydrostatic pressure prevails and Hydrostatic pressure prevails and vertical accelerations are negligible
Streamline curvature is small
Discretization asrectangular Channel
t k Streamline curvature is small
Bottom slope of the channel is small
gstrips
Channel 4
32
11
2
3
4
network in the watershed
Steady uniform flow equation such as Manning’s / Chezy equation can be used to describe resistance
Overland flow strip
meetingpoint Single discretized
channel with overland flow adding at channel
W
4
L
be used to describe resistance effects
The fluid is incompressible
Channel flow element
Overland flow element
nodes
1111
The fluid is incompressible
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
11 2 yQQTerms in Momentum Equation
0)(11
fo SSgxyg
AQ
xAtQ
ALocal acceleration term
Convective acceleration term
Pressure force term
Gravity force term
Friction force term
0)(
fo SSgxyg
xVV
tV
xxtKinematic Wave
Diffusion Wave
Dynamic Wave
1212Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
St. Venant Equations Applications of different forms of
momentum equation0)(
fo SSgygVVV
Kinematic wave: when gravity forces andfriction forces balance each other (steep
0)( fo SSgx
gx
Vt
slope channels with no back water effects) Diffusion wave: when pressure forces are
important in addition to gravity andimportant in addition to gravity andfrictional forces
Dynamic wave: when both inertial andf i t t dpressure forces are important and
backwater effects are not negligible (mildslope channels with downstream control)
1313Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Overland Flow (St. Venant’s equations)
Continuity equation:Where, h-depth of flow;
erth
yhv
xhu
iie frr re-excess rainfall (mm); fi-infiltration
Momentum equations in 2-D
0)(
hurssg
xhg
yuv
xuu
tu
efxox
0)(
hvrssg
yhg
yvv
xvu
tv
efyoy
g-acceleration due to gravity; Sox-slope of watershed element in x-direction; Soy-slope in y-direction; Sfx-frictional slope in x-direction
1414Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Overland Flow – Diffusion & Kinematic
Diffusion wave form in 1D α β-coefficients obtained hhuq
SSxh
f
0
erth
xq
α, β-coefficients obtained from Manning’s equation
Initial condition, t=0, h=0, ll d l
hhuqtx 5
q=0 at all nodal points Kinematic wave form 1D
3
Initial conditions Boundary conditions fSSre
th
xq
0;tx
1515Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Gov. Equation for Channel Flow
Equation of continuity0
qAQ
q
tx
Momentum equation
hgASSgAQQ
2
x
gASSgAAxt f
0
q-lateral inflow; Q-discharge in the channel; A-area of flow in the channel, S0-bed slope; Sf-friction slope of channel
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Sf friction slope of channel.
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Channel Flow- Diffusion & KinematicKinematic Diffusion h0
qAQ
Initial conditions B d diti
fo SSxh
2/13/21
q
tx
Boundary conditions
Kinematic:
ASRn
Q fh2/13/21
Kinematic:S0=Sf 0
q
tA
xQ
1717Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Use of Numerical Simulation Models Hydrologic simulation models use mathematical
equations to calculate results like runoff volume or equations to calculate results like runoff volume or peak flow
Computer models allows parameter variation in space and time with use of numerical methodsand time – with use of numerical methods
Ease in simulation of complex rainfall patterns and heterogeneous watersheds
Evaluation of various design controls and schemes Effective use of land use and land cover parameters
I li f d li i i l Improves quality of modeling using spatial characteristics
1818Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Examples of Hydrodynamic & Empirical Models
Physical Process Hydrodynamic
Models
Empirical
ModelsSurface runoff i. Kinematic
ii. Diffusion
i. Rational method
ii. Unit Hydrograph
iii. Dynamic
iv. Conceptual models
iii. SCS method
Infiltrationi. Richards equation
ii. Kinematic
G
i. SCS method
ii. SCS-CN
Ciii. Green-Ampt
iv. Philip-two term
iii. HEC
iv. AlgebraicGroundwater runoff i. Model based on i. Algebraic G ou d ate u o
(Base flow)
ode based oGroundwater flow equation
geb a ce.g.Horton eqn.
ii. Algebraic equationsE t i ti i P M t lith i Bl iddl
1919
Evapotranspiration (ET)
i. Penmann-Montelith
i.Morten method
i. Blaney criddle
Examples of Hydrodynamic & Empirical M d lModels
Physical Process Hydrodynamic Models EmpiricalFlow over porous bed i. Kinematic wave
ii. Dynamic waveiii. Volume balance
SCS model
iii. Volume balance
Flow in channel i. Kinematicii. Diffusion
Muskingum
Hydrograph analysis iii. Dynamic
Hydrograph analysis
Solute transport Model based on Algebraic padvection-dispersion Fickian models
g
Sediment transport i. Kinematic
ii. Dynamiciii Einstein bed load
i. Sediment graph models
ii. Regression ti
2020
iii. Einstein bed load equation
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Hydrologic ModelsHydrologic ModelsILLUDASILLUDAS
((ILLILLinoisinois UUrban rban •• Sizing of storm sewers (basin runoff characteristics, Sizing of storm sewers (basin runoff characteristics, design rainstorm layout of sewer network are inputs)design rainstorm layout of sewer network are inputs)((ILLILLinoisinois UUrban rban
DDrainage rainage AArea rea SSimulator)imulator)
design rainstorm, layout of sewer network are inputs)design rainstorm, layout of sewer network are inputs)•• Routines for estimating detention storage volumesRoutines for estimating detention storage volumes•• LimitationLimitation: Constant Outflow from detention facility: Constant Outflow from detention facility
PSRMPSRM((PPenn enn SState tate RRunoff unoff MModel) odel)
•• SingleSingle--event modelevent model•• ComponentsComponents: : overland runoffoverland runoff , , channelchannel routing etc.routing etc.
))HSPFHSPF
((HHydrologic ydrologic SSimulation imulation
•• Continuous or SingleContinuous or Single--event model by EPAevent model by EPA•• Simulations for both quality and quantity Simulations for both quality and quantity
SSimulation imulation PProgramrogram--FFortran)ortran)
STORMSTORM D l d f i i l li ti t th S D l d f i i l li ti t th S STORMSTORM(Storage (Storage Treatment Treatment O l d Fl O l d Fl
•• Developed for original application to the San Developed for original application to the San Francisco master drainage planFrancisco master drainage plan•• Conceptualized view of urban drainage systemConceptualized view of urban drainage system
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9/7/2012 21
Overland Flow Overland Flow and Runoff and Runoff model)model)
Contd….SWMMSWMM •• Routing for surface, subsurface and groundwaterRouting for surface, subsurface and groundwater
((SStorm torm WWater ater MManagement anagement MModel)odel)
•• Fully dynamic hydraulic flow routingFully dynamic hydraulic flow routing
HEC HEC --11HECHEC--HMSHMS
•• DOS/ Window (difference between two models)DOS/ Window (difference between two models)•• Calculates runoff hydrograph at each componentCalculates runoff hydrograph at each componenti e channels pumps conduits etc i e channels pumps conduits etc i.e. channels, pumps, conduits etc. i.e. channels, pumps, conduits etc.
WMSWMS •• Provide the link between spatial terrain data (GIS)Provide the link between spatial terrain data (GIS)d h d l i d ld h d l i d land hydrologic modelsand hydrologic models
•• Including models like HECIncluding models like HEC--1, TR1, TR--55, TR55, TR--20 etc.20 etc.
IHACRES Si l ti f t fl f b i f i Si l ti f t fl f b i f i IHACRES •• Simulation of stream flows from basins of various Simulation of stream flows from basins of various sizessizes•• Unit hydrograph approach to lumped modelingUnit hydrograph approach to lumped modeling
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9/7/2012 22Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Steps In Watershed Simulation Analysis Selection of model Input data collection: rainfall, infiltration, physiography, land
use, channel characteristics etc Evaluate the study objectives under various watershed
simulation conditionssimulation conditions Selection of methods for obtaining basin hydrographs and
channel routingchannel routing Calibration and verification of model Model simulations for various conditions Sensitivity analysis Evaluate usefulness of model and comment on needed
2323changes
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Ex: Overland flow model: Kinematic wavemodelmodel (Gottardi and Venutelli 1993; Jaber and Mohtar, 2003; Reddyet al. 2007):
f
o
Sn
535
Kinematic wave model time step 30 sec
Kinematic wave model
Analytical solution for one-dimensional kinematic wave equations is given by above equations (Jaber and Mohtar, 2003) i i f i
0.0015
0.0020
0.0025 time step 180 sec Analytical model
︵m^3
/sec
/m
︶
2003); tc is time of concentration (sec); tr is rainfall duration (sec); tf is the simulation time (sec); Lw is the length of te hed (m) in the
0.0005
0.0010
Ove
rland
flow
length of watershed (m) in the direction of main slope.400 m x 500 m, slope So = 0.0005, Manning’s coefficient = 0 02 m-1/3 sec
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0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 3200.0000
Time ︵min ︶
Manning s coefficient = 0.02 m sec, uniform excess rainfall R = 0.33 mm/ min, and duration of rainfall 200 min.
Case study: Banaha Watershed (Venkata Reddy et al., 2007)(Venkata Reddy et al., 2007)
Location- Chatra district in Jharkhand State, India Area- 16.72 km2 ; Major Soil class – Sandy loam.j yRemotely Sensed Data- IRS1D LISSIII imagery of Jan. 1998 Thematic Maps- Drainage, Slope and LU/LCMap generation & analysis- ERDAS IMAGINE & ArcGIS Slope map- ArcGIS; LU/LC map - ERDAS IMAGINE S ope ap cG S; U/ C ap S GManning’s roughness map- Based on LU/LC mapFinite Element Grid map- ArcGIS; Grid map overlaid on slope & Manning’s roughness maps overlaid on slope & Manning s roughness maps Mean value of slope and Manning’s roughness-Each element of the grid; Nodal values- Average of adjacent element values
2525
of adjacent element values
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Case study: Banaha Watershed
2626
Results and Discussion Diffusion wave- Philip model Calibration - 4 Rainfall events Calibration - 4 Rainfall events Validation - 3 Rainfall events
Calibrated parameters for rainfall events (Banha Watershed)
2727
Results and Discussion
9.00
12.00
15.00
m3 /s
ec)
0.0
5.0
erns
ityr)
0.00
3.00
6.00
9.00
Dis
char
ge(m 10.0
15.0
20.0
Rai
nfal
l int
e(m
m/h
r
60.00 00 200 400 600
Time(min)RainfallObservedSimulated
20.00
30.00
40.00
50.00
harg
e(m
3 /sec
) 5
10
15
20 infa
ll in
tens
ity(m
m/h
r)
RainfallObservedSimulated
Calibration event, July 24, 1996
Validation event, August 17, 1996
0.00
10.00
0 100 200 300 400Time(min)
Dis
ch
25
30
Rai
Observed and simulated hydrographs of rainfall events (Banha),(Venkata Reddy et al., 2007)
Validation event, August 17, 1996
2828
( y , )
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
ReferencesReferences• Raj Vir Singh (2000), Watershed Planning and Management, Yash Publishing
House• J.V.S Murthy (1991), Watershed Management, New Age international
PublicationsPublications Venkata Reddy K., Eldho T. I., Rao E.P. and Hengade N. (2007) “A kinematic
wave based distributed watershed model using FEM, GIS and remotely sensed data.” Journal of Hydrological Processes, 21, 2765-2777Chow V T Maidment D R and Mays L W (1988) Applied Hydrology McGraw Chow, V.T., Maidment, D.R., and Mays, L.W. (1988). Applied Hydrology, McGraw-Hill, Inc., New York.
Bedient, P.B. and Huber W.C.(1988). Hydrology and flood plain analysis, Addison-Wesley Publishing Company., London
Cunderlik, J. M. (2003). “Hydrologic model selection for the CFCAS project: Assessment of Water Resources Risk and Vulnerability to changing Climatic Conditions – Project Report 1”, Department of Civil and Environmental engineering, University of Western Ontario
USEPA SWMM. June 2007. Storm Water Management Model User’s Manual Version 5.0, EPA/600/R-05/040
Mark, O., Weesakul, S., Apirumanekul, C., Aroonnet, S.B., Djordjevic, S. (2004). “Potential and limitations of 1D modeling of urban flooding ” J Hydrology 299
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Potential and limitations of 1D modeling of urban flooding. J.Hydrology, 299, 284-299.
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Tutorials - Question!.?. Illustrate various hydrological processes from
rainfall to runoff in watershed based modeling. For a typical watershed, assess the important For a typical watershed, assess the important
hydrological processes and discuss various hydrological processes and discuss various models available to analyze these processes models available to analyze these processes models available to analyze these processes. models available to analyze these processes. Describe the merits & demerits of each models.Describe the merits & demerits of each models.
For a selected watershed, how to find the runoff For a selected watershed, how to find the runoff for a given rainfall event?. Illustrate with for a given rainfall event?. Illustrate with examples.examples.
3030
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Self Evaluation - Questions!.Q Describe different categories of deterministic
hydrologic models?.hydrologic models?. What is the importance of physically based watershed
modeling?.b h h Describe the St. Venant equations with its
applications, assumptions and importance. Compare the following lumped, semi distributed and Compare the following lumped, semi distributed and
distributed models: HEC-HMS; SWMM & MIKE 11 models. Discuss the applications, advantages & disadvantages of each modeldisadvantages of each model.
P f T I Eldh D t t f Ci il E i i IIT B b3131
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Assignment- Questions?.g Q Differentiate between lumped, semi distributed and
distributed models used in hydrologic modeling.distributed models used in hydrologic modeling. How physically based watershed modeling is done?.
Illustrate the step by step procedure. What are advantages & limitationsadvantages & limitations.
What are the important steps in the watershed simulation analysis?.
Illustrate various types of hydrodynamic & empirical models used in hydrology.
3232Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Unsolved Problem!.Unsolved Problem!.
For your watershed area, discuss the For your watershed area, discuss the possibility of applying a physically based possibility of applying a physically based
d l f ff/ fl d l i Id tif th d l f ff/ fl d l i Id tif th model for runoff/ flood analysis. Identify the model for runoff/ flood analysis. Identify the data required for physical modeling. data required for physical modeling. Develop a conceptual model by giving the Develop a conceptual model by giving the Develop a conceptual model by giving the Develop a conceptual model by giving the detailed steps for rainfall runoff modeling. detailed steps for rainfall runoff modeling.
Identify how to model evapoIdentify how to model evapo--transpiration, transpiration, interception & infiltration for the area considered. interception & infiltration for the area considered. With respect to available data, choose specific With respect to available data, choose specific models to model these processes.models to model these processes.models to model these processes.models to model these processes.
Discuss how to add these processes in the rainfallDiscuss how to add these processes in the rainfall--runoff modeling.runoff modeling.
3333Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Dr. T. I. EldhoDr. T. I. EldhoProfessor,Professor,Department of Civil Engineering, Department of Civil Engineering, p g gp g gIndian Institute of Technology Bombay,Indian Institute of Technology Bombay,Mumbai, India, 400 076.Mumbai, India, 400 076.Email:Email: [email protected]@iitb.ac.in
3434
Email: Email: [email protected]@iitb.ac.inPhone: (022) Phone: (022) –– 25767339; Fax: 2576730225767339; Fax: 25767302http://www.http://www.civil.iitb.ac.incivil.iitb.ac.in