Watershed management_Lecture 16-20
M odu le 4 – ( L1 2 - L1 8 ) : “ W a t e r sh e d M ode lin g”
St a n da r d m ode lin g a ppr oa ch e s a n d cla ssifica t ion s, syst e m con ce pt St a n da r d m ode lin g a ppr oa ch e s a n d cla ssifica t ion s, syst e m con ce pt
for w a t e r sh e d m ode lin g, ove r a ll de scr ipt ion of diffe r e n t h ydr ologic
pr oce sse s, m ode lin g of r a in fa ll, r u n off pr oce ss, su bsu r fa ce flow s a n d gr ou n dw a t e r flow gH ydr ologic M ode lin g H ydr ologic M ode lin g 1 6 1 6
L1 6 L1 6 L1 6 – L1 6 H ydr ologic M ode lin g H ydr ologic M ode lin g
Topics Cove r e d Topics Cove r e d
Rainfall runoff modeling, Runoff Rainfall runoff modeling, Runoff
g, process, Physical modeling, process, Physical modeling, Distributed model Distributed model
g,
Rainfall runoff modeling, Rainfall runoff modeling,
K K Keywords: Keywords: d d Physical modeling, distributed model. Physical modeling, distributed model.
W a t e r sh e d M ode l Rainfall watershed
I nterception ET
( Ba se d on : M cCu e n , 1 9 8 9 , & Ra j V ir Sin gh , 2 0 0 0 ) Surface storage
Surface runoff Direct
ET Infiltration runoff
Interflow Percolation 0.00 3.00 6.00 9.00 12.00 15.00 D is c har ge( m 3 /s e c ) 0.0 5.0 10.0 15.0 20.0 R a in fa ll i n te rn s ity (m m /hr) GW Channel 200 400 600 Time(min) Rainfall Observed Simulated
W a t e r sh e d m ode ls Rainf Channel flow al l
Formulation
Calibration Calibration
Infiltration
Application
Overland flow Interflow
W a t e r sh e d m ode l con st it u t e s
1. Input function
2 Output function
2. Output function
3. Transform function
Ph ysica lly ba se d w a t e r sh e d m ode ls Ph ysica lly ba se d w a t e r sh e d m ode ls Overland flow
Channel flow Channel flow
D e t e r m in ist ic H ydr ologic M ode l
Three main categories: Lumped, Semi- distributed & Distributed
Parameters do not vary spatially
Lumped models:
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 processes
- – Discharge prediction at outlet only Di h di ti t tl t l
- – Simple & minimal data requirements, easy use
- – Eg. SCS-CN based models; IHACRES, WATBAL etc. g
D e t e r m in ist ic H ydr ologic M ode l..
Se m i – dist r ibu t e d m ode ls:: 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 subbasins number of smaller subbasins number of smaller subbasins number of smaller subbasins
Mainly two types: Kinematic wave theory models (eg. Mainly two types: Kinematic wave theory models (eg.
HEC HEC--HMS model) HMS model) -- simplified version of surface flow simplified version of surface flow equations of physically based model equations 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 lumped models lumped models l l d d d l d l
Less demanding on input data than distributed models Less demanding on input data than distributed models
Eg: SWMM, HEC HMS, TOPMODEL, SWAT etc. Eg: SWMM, HEC Eg: SWMM HEC--HMS TOPMODEL SWAT etc Eg: SWMM HEC HMS, TOPMODEL, SWAT etc. HMS TOPMODEL SWAT etc
D e t e r m in ist ic H ydr ologic M ode l
D ist r ibu t e d m ode ls: 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
Requires large amount of data l f d
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. Physically based Watershed Model… Ph ysica lly ba se d de t e r m in ist ic m ode ls: Ph i ll b d d i i i d l
Aim: Gain better understanding of hydrologic
p e o phenomena operating in a watershed and how changes e a ope a g a a e s ed a d o c a ges in watershed may affect these phenomena
Complex processes simplified by lumping process in space and time space 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.
distribution and storage of water and their variability in space and time space and time
Te ch n ology of Ph ysica l M ode lin g gy y g
Hydrodynamic Models theoretical, physical based or hydraulic models. e.g Dynamic wave model for overland flow flow
Overland / channel flow By continuity equation and momentum equation
Modeling: May be in 1D, 2D or 3D
Based on requirements & data availability
Ph ysica lly Ba se d Ph ysica lly Ba se d M ode l M ode l -- Flow Flow Equ a t ion s Equ a t ion s First proposed First p p proposed by p p by St y y St.. Venant Venant in in 1871 1871 based based on on fundamental laws fundamental laws of of continuity continuity & & conservation conservation of momentum of momentum Con t in u it y e qu a t ion Con t in u it y Con t in u it y e qu a t ion Con t in u it y e qu a t ion e qu a t ion M om e n t u m Equ a t ion M om e n t u m Equ a t ion
De Saint-Venant (1797-1886) St. Venant Equations - Assumptions
Flow is one-dimensional
Hydrostatic pressure prevails and Hydrostatic pressure prevails and vertical accelerations are negligible
Discretization as Channel rectangular g network t k
Streamline curvature is small Streamline curvature is small
strips 1 in the 2 3 d watershe 2 1
Bottom slope of the channel is small 3 4 4 4 Channel meeting
Overland flow Single discretized point strip channel with
Steady uniform flow equation such
W L overland flow
as Manning’s / Chezy equation can
adding at channel
be used to describe resistance be used to describe resistance
nodes Overland flow
effects
Channel flow element element
The fluid is incompressible The fluid is incompressible
Terms in Momentum Equation
2
1 1
1 1 Q Q Q Q y y
g g ( S S ) o f
A t A x A x
Loca l Con ve ct ive Pr e ssu r e Gr a vit y Fr ict ion a cce le r a t ion a cce le r a t ion for ce for ce for ce t e r m t e r m t e r m t e r m t e r m
V V y V g g ( S S ) o f
t t x x x x Kin e m a t ic W a ve D iffu sion W a ve D yn a m ic W a ve St. Venant Equations
Applica t ion s of diffe r e n t for m s of m om e n t u m e qu a t ion V V y
V V g g g g S S S S ( ( ) ) o o f f
t x x
Kin e m a t ic w a ve : when gravity forces and
friction forces balance each other (steep slope channels with no back water effects)
Diffusion wave: when pressure forces are
important important in in addition addition to to gravity gravity and and frictional forces
Dynamic wave: when both inertial and
pressure forces f are important i t t and d backwater effects are not negligible (mild slope channels with downstream control) Overland Flow (St. Venant’s equations) u h v h h
Continuity equation:
r e r r f e i i x y t
Where, h-depth of flow;
- infiltration re-excess rainfall (mm); f
i Momentum equations in 2-D u u u h u
u v g g ( s s ) r
ox fx e t x y x h
v v v h v u v g g s s r
( ) oy fy e
t x y y h
g-acceleration due to gravity; S -slope of watershed
ox
element in x-direction; S
- slope in y-direction; S
oy fx
frictional slope in x-direction Overland Flow – Diffusion & Kinematic D iffu sion w a ve for m in 1 D
α β-coefficients obtained
Kin e m a t ic w a ve for m 1 D
; t x
f S S re t h x q
Boundary conditions
Initial conditions
3
q=0 at all nodal points
h h u q
5
h h u q t x
Initial condition, t=0, h=0, ll d l
α, β-coefficients obtained from Manning’s equation
e r t h x q
S S x h f
Gov. Equation for Channel Flow
Equation of continuity
Q A
q q x t
Momentum equation
2
Q Q h
gA gA S S S S gA gA
f
t x A x
q-lateral inflow; Q-discharge in the channel;
A-area of flow in the channel, S -bed slope; S S -friction slope of channel friction slope of channel.
f f Channel Flow- Diffusion & Kinematic Kinematic Q A
Diffusion
q q h h S S
x t o f
x
Initial conditions
1
1
2 2 / /
3
3
1 1 / /
2
2
B Boundary conditions d diti
Q R S A h f n
Kinematic: Kinematic:
Q A S =S
q f
x t
Use of N u m e r ica l Sim u la t ion M ode ls
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 methods and 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
Improves quality of modeling using spatial I li f d li i i l characteristics
Examples of Hydrodynamic & Empirical Models Ph ysica l Pr oce ss H ydr odyn a m ic
M ode ls
Em pir ica lM ode ls
Surface runoff i. Kinematic ii. Diffusion i. Rational method ii. Unit Hydrograph iii. Dynamic iv. Conceptual models iii. SCS method Infiltration i. Richards equation ii. Kinematic
G i. SCS method ii. SCS-CN C iii. Green-Ampt iv. Philip-two term iii. HEC iv. Algebraic Groundwater runoff i. Model based on i. Algebraic G ou d ate u o
(Base flow)
ode based o
Groundwater flow equation geb a c e.g.Horton eqn. ii. Algebraic equations E t i ti i P M t lith i Bl iddlEvapotranspiration i. Penmann-Montelith i. Blaney criddle
Ex a m ple s of H ydr odyn a m ic & Em pir ica l M ode ls M d l
Ph ysica l Pr oce ss H ydr odyn a m ic M ode ls Em pir ica l
i.Kinematic wave Flow over porous bed SCS model ii. Dynamic wave iii. iii.
Volume balance Volume balance i. Kinematic Muskingum Flow in channel ii.
Diffusion
Hydrograph analysis Hydrograph analysis iii.
Dynamic
Solute transport Model p based on Algebraic g advection- dispersion Fickianmodels
i.Sediment graph Sediment transport i. Kinematic models
ii. Dynamic ii.
Regression iii. iii Einstein bed load Einstein bed load equation ti
- Single Single--event model event model
- Components Components : : overland runoff overland runoff , , channel channel routing etc. routing etc.
PSRM PSRM
Overland Flow Overland Flow
Conceptualized view of urban drainage system Conceptualized view of urban drainage system
Developed for original application to the San Developed for original application to the San Francisco master drainage plan Francisco master drainage plan
(Storage (Storage Treatment Treatment O l d Fl O l d Fl
D l d f i i l li ti t th S D l d f i i l li ti t th S
Simulations for both quality and quantity Simulations for both quality and quantity S Simulation imulation P Program rogram-- F Fortran) ortran)
Continuous or Single Continuous or Single--event model by EPA event model by EPA
((H Hydrologic ydrologic S Simulation imulation
H SPF H SPF
))
((P Penn enn S State tate R Runoff unoff M Model) odel)
Limitation Limitation : Constant Outflow from detention facility : Constant Outflow from detention facility
Routines for estimating detention storage volumes Routines for estimating detention storage volumes
design rainstorm, layout of sewer network are inputs) design rainstorm, layout of sewer network are inputs)
ILLinois inois U Urban rban D Drainage rainage A Area rea S Simulator) imulator)
((ILL
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)
ILLinois inois U Urban rban
I LLUD AS ((ILL
I LLUD AS
H ydr ologic M ode ls H ydr ologic M ode ls
STORM STORM
STORM STORM
Contd…. SW M M SW M M
Routing for surface, subsurface and groundwater Routing for surface, subsurface and groundwater ((S Storm torm W Water ater M Management anagement M Model) odel)
Fully dynamic hydraulic flow routing Fully dynamic hydraulic flow routing
H EC H EC -- 1
1 H EC H EC-- H M S H M S
DOS/ Window (difference between two models) DOS/ Window (difference between two models)
- Including models like HEC Including models like HEC--1, TR 1, TR--55, TR 55, TR--20 etc. 20 etc.
Calculates runoff hydrograph at each component Calculates runoff hydrograph at each component i e channels pumps conduits etc i e channels pumps conduits etc i.e. channels, pumps, conduits etc. i.e. channels, pumps, conduits etc.
W M S W M S
Provide the link between spatial terrain data (GIS) Provide the link between spatial terrain data (GIS) d h d l i d l d h d l i d l and hydrologic models and hydrologic models
I H ACRES
Si l ti f t fl f b i f i Si l ti f t fl f b i f i
I H ACRES
Simulation of stream flows from basins of various Simulation of stream flows from basins of various sizes sizes
Unit hydrograph approach to lumped modeling Unit hydrograph approach to lumped modeling
Steps In Watershed Simulation Analysis
Selection of model
I nput data collection: rainfall, infiltration, physiography, land use, channel characteristics etc
Evaluate the study objectives under various watershed simulation conditions simulation conditions
Selection of methods for obtaining basin hydrographs and channel routing channel routing
Calibration and verification of model
Model simulations for various conditions
Sensitivity analysis
Evaluate usefulness of model and comment on needed changes
Ex: Overland flow model: Kinematic wave ( Got t a r di a n d V e n u t e lli 1 9 9 3 ; Ja be r a n d M oh t a r , 2 0 0 3 ; Re ddy model model e t a l. 2 0 0 7 ) :
S f n o
5
5
3 Analytical solution for one-dimensional
kinematic wave equations is given by time step 30 sec Kinematic wave model above equations (Jaber and Mohtar, 0 . 0 0 2 5 time step 180 sec Kinematic wave model i f i
2003); t c is t im e of concent rat ion 2003) i ︶ 0 . 0 0 2 0 Analytical model ( sec) ; t r is rainfall durat ion ( sec) ; t f is m s e / / 3 ^ 0 . 0 0 1 5 c t he sim ulat ion t im e (sec); Lw is t he m o w ︵ lengt h of lengt h of w at ershed ( m ) in t he t e hed ( m ) in t he l n d f a l e r 0 . 0 0 1 0 direct ion of m ain slope. O 0 . 0 0 0 5 v
400 m x 500 m, slope So = 0.0005, -1/3 0 . 0 0 0 0
Manning’s coefficient = 0 02 m Manning s coefficient = 0.02 m sec, sec 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0 2 2 0 2 4 0 2 6 0 2 8 0 3 0 0 3 2 0
T i m e m i n ︵ ︶Ca se st u dy: Banaha Watershed
(Venkata Reddy et al., 2007) (Venkata Reddy et al., 2007) Location- Chatra district in Jharkhand State, India
2 Area- 16.72 km ; Major Soil class – Sandy loam. j y
Remotely Sensed Data- IRS1D LISSIII imagery of Jan. 1998 Thematic Maps- Drainage, Slope and LU/LC Map generation & analysis- ERDAS IMAGINE & ArcGIS S ope Slope map- ArcGIS; LU/LC map - ERDAS IMAGINE ap cG S; U/ C ap S G Manning’s roughness map- Based on LU/LC map Finite 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 of adjacent element values
2 2 6
6 Banaha Watershed : y 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 )
Results and Discussion
9.00 12.00 15.00 m 3 /s e c ) 0.0 5.0 e rns it y r)
0.00 3.00 6.00 9.00 D is c ha rg e( m 10.0 15.0 20.0 R a in fa ll in te (mm/ h r 60.00 200 400 600 Time(min) Rainfall Observed Simulated
20.00 30.00 40.00 50.00
h
ar
ge
(m
3
/s
e
c
)
5 10 15 Rainfall 20 inf al l i n te n s it y (mm /h r) Observed Simulated Calibration event, July 24, 1996 Validation event, August 17, 1996 0.00 10.00 100 200 300 400 Time(min)Di
s
c
h
25 30 Ra iObserved and simulated hydrographs of rainfall events (Banha), (Venkata Reddy et al., 2007)
Validation event, August 17, 1996
( y , )
Re fe r e n ce s Re fe r e n ce s Raj Vir Singh (2000), Watershed Planning and Management, Yash Publishing • House
J.V.S Murthy (1991), Watershed Management, New Age international • Publications Publications
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, 2765-2777 Chow, 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. St orm Wat er Managem ent Model User’s Manual Version 5.0, EPA/600/R-05/040
Mark, O., Weesakul, S., Apirumanekul, C., Aroonnet, S.B., Djordjevic, S. (2004).
“ Pot ent ial and lim it at ions of 1D m odeling of urban flooding ” J Hydrology 299 Pot ent ial and lim it at ions of 1D m odeling of urban flooding. J.Hydrology, 299,
284-299.Tu t or ia ls - Qu e st ion !.?.
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.Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
Se lf Eva lu a t ion - Qu e st ion s!. Q
Describe different categories of deterministic hydrologic models?. hydrologic models?.
What is the importance of physically based watershed modeling?.
Describe the St. Venant equations with its b h h 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 model. disadvantages of each model
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay P f T I Eldh D t t f Ci il E i i
IIT B b
Assign m e n t - Qu e st ion s?. 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 & limitations. advantages & limitations
What are the important steps in the watershed simulation analysis?.
Illustrate various types of hydrodynamic & empirical models used in hydrology.
Un solve d Pr oble m !. Un solve d Pr oble m !.
For your watershed area, discuss the For your watershed area, discuss the possibility of applying a physically based possibility of applying a physically based
model for runoff/ flood analysis. Identify the model for runoff/ flood analysis. Identify the d l f d l f ff/ fl ff/ fl d d l l i Id i Id tif th tif th
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 evapo--transpiration, Identify how to model evapo 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 rainfall-- Discuss how to add these processes in the rainfall runoff modeling. runoff modeling.
Dr. T. I. Eldho Dr. T. I. Eldho Professor, Professor, Department of Civil Engineering, Department of Civil Engineering, p p g g g g Indian Institute of Technology Bombay, Indian Institute of Technology Bombay, Mumbai, India, 400 076. Mumbai, India, 400 076. Email: Email: Email: Email: eldho@iitb.ac.in eldho@iitb.ac.in eldho@iitb.ac.in eldho@iitb.ac.in