Modeling Lecture 1. Modeling and Sustainability CE4505 Surface Water Quality Engineering CE4505 –...
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Transcript of Modeling Lecture 1. Modeling and Sustainability CE4505 Surface Water Quality Engineering CE4505 –...
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Modeling Lecture 1. Modeling and Sustainability
CE4505 Surface Water Quality Engineering
CE4505 – Surface Water Quality Engineering
Sustainability
In our every deliberation we must consider the impact of our decisions on the next seven generations.Iroquois Confederacy
http://www.interspecies.com/pages/7th_gen.htmlhttp://www.bathtram.org/tfb/tE04.htm
Meeting the needs of the present without compromising the ability of future generations to meet their own needs. World Commission on Environment and Development, 1987
CE4505 – Surface Water Quality Engineering
…a mathematical model is an idealized formulation that represents the response of a physical system to external stimuli.
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Chapra 1997, p. 10
Modeling
CE4505 – Surface Water Quality Engineering
Toward Sustainability
1) a knowledge of the way a system works.
We might think of this as a research model.
2) a manner of predicting cause and effect.
We might think of this as a management model.
Decisions supporting a sustainable future require:
CE4505 – Surface Water Quality Engineering
Understanding the System
http://www.wordinfo.info/words/index/info/view_unit/1/?letter=B&spage=3
The Blind Men and the ElephantJohn Godfrey Saxe, 1816-1887
CE4505 – Surface Water Quality Engineering
It was six men of Indostan To learning much inclined,
Who went to see the Elephant (Though all of them were blind),
That each by observation Might satisfy his mind
The First approached the Elephant, And happening to fall
Against his broad and sturdy side, At once began to bawl:
“God bless me! but the Elephant Is very like a wall!”
The Second, feeling of the tusk, Cried, “Ho! what have we here
So very round and smooth and sharp? To me ’tis mighty clear
This wonder of an Elephant Is very like a spear!”
The Third approached the animal, And happening to take
The squirming trunk within his hands, Thus boldly up and spake:
“I see,” quoth he, “the Elephant Is very like a snake!”
To Better See the Elephant …
The Fourth reached out an eager hand, And felt about the knee.
“What most this wondrous beast is like Is mighty plain,” quoth he;
“ ‘Tis clear enough the Elephant Is very like a tree!”
The Fifth, who chanced to touch the ear, Said: “E’en the blindest man
Can tell what this resembles most; Deny the fact who can
This marvel of an Elephant Is very like a fan!”
The Sixth no sooner had begun About the beast to grope,
Than, seizing on the swinging tail That fell within his scope,
“I see,” quoth he, “the Elephant Is very like a rope!”
And so these men of Indostan Disputed loud and long,
Each in his own opinion Exceeding stiff and strong,
Though each was partly in the right, And all were in the wrong!
So oft in theologic wars, The disputants, I ween,
Rail on in utter ignorance Of what each other mean,
And prate about an Elephant Not one of them has seen!
CE4505 – Surface Water Quality Engineering
To provide a better understanding of the mechanisms and interactions that give rise to various types of water quality behavior, such understanding to be sharpened by the formulation and testing of hypotheses of the cause-effect relationships between residual inputs and resulting water quality.
(Thomann and Mueller 1987)
Research Models
CE4505 – Surface Water Quality Engineering
FieldObservations
MathematicalModel
ProcessStudies
ConceptualFramework
To Validate our Understanding of System Response
Why model? The research perspective –
CE4505 – Surface Water Quality Engineering
Cause and Effect: achieving sustainability
by Build and MeasureCE4505 – Surface Water Quality Engineering
underdesign -
…the environmental engineering equivalent of building a bridge that falls down.
www.civil.columbia.edu/ce4210/bridgecollapse.html
(Thomann and Mueller 1987, p. ix)
Undesirable Outcomes
CE4505 – Surface Water Quality Engineering
overdesign -
…the environmental engineering equivalent of building a bridge to nowhere.
http://www.zen39641.zen.co.uk/ps/
(Thomann and Mueller 1987, p. ix)
Undesirable Outcomes
CE4505 – Surface Water Quality Engineering
Cause and Effect: firing a projectile
20 sin 2
vR
g
by Applying a Model
angle
dis
tan
ce
CE4505 – Surface Water Quality Engineering
Linking …
Action and ReactionPerturbation and ResponseCause and Effect
by Applying a Model
Cause and Effect: achieving sustainability
CE4505 – Surface Water Quality Engineering
Specify water use
Establish water quality criteria
Determine cause and effect
Identified engineered alternatives
Conduct cost-benefit analysis
Evaluate socioeconomic impact
A Water Quality Management Plan
CE4505 – Surface Water Quality Engineering
To provide a more rational basis for making water quality control decisions, such a basis to include a defensible, credible, predictive framework, within the larger framework of cost-benefit analysis.
(Thomann and Mueller 1987)
Why Model?
CE4505 – Surface Water Quality Engineering
Why model?
CE4505 – Surface Water Quality Engineering
Guidance for Management Actions
Quantificationof
Loads
Characterizationof
Fate & Transport
Mathematical Model
Engineered Solutions
Model Implementations
CE4505 – Surface Water Quality Engineering
, , ,c f W physics chemistry biology
1c W
a
Define “a” as an assimilation factor, L3·T-1
Simulation Mode
W a c Design Mode 1 – assimilative capacity
Wa
c Design Mode 2 – environmental modification
(Chapra 1997, Figure 1.1)
Water and Wastewater in an Urban Setting
CE4505 – Surface Water Quality Engineering
(Chapra 1997, Figure 1.2)
The Water Quality Management Process
CE4505 – Surface Water Quality Engineering