CE5504 – Surface Water Quality Modeling

CE5504 Surface Water Quality Modeling

General Lecture 2. Model Development

Empirical Models

CE5504 – Surface Water Quality Modeling

Secchi disk and chlorophyll

(Chapra 1997, Figure 29.6)

Empirical Models

CE5504 – Surface Water Quality Modeling

Vollenwieder plot

(Chapra 1997, Figure 29.1)

(Chapra 1997, Figure 29.4)

Linked Empirical-Mechanistic Models

CE5504 – Surface Water Quality Modeling

Mechanistic Mass Balance Models

CE5504 – Surface Water Quality Modeling (Chapra 1997, Figure 1.5)

accumulation loadings transport reactions

in out reactiondm m m mdt

1 1 1' ( ) ' ( ) nii i i i i i

dCV W Q C Q C E C C E C C V k Cdt

(Chapra 1997, Figure 18.8)

Temporal Resolution

CE5504 – Surface Water Quality Modeling

Spatial Resolution

CE5504 – Surface Water Quality Modeling (Chapra 1997, Figure 16.1)

Time and Space Scale of Water Quality Problems

CE5504 – Surface Water Quality Modeling (Chapra 1997, Figure 18.9)

Kinetic Resolution

CE5504 – Surface Water Quality Modeling

TotalPhosphorus

AvailableParticulate

Phosphorus

RefractoryParticulate

Phosphorus

DissolvedOrganic

Phosphorus

SolubleReactive

Phosphorus

Things should be made as simple as possible -- but no simpler.

Albert Einstein

image source: www.physik.uni-frankfurt.de/~jr/physpiceinstein.html

The Guiding Principle

unlimited cost

cost

cost + $

desired reliability

Model Complexity

Mod

el R

elia

bilit

y

Defensible, Credible, Cost-Effective

Model Complexity

Screening Management Research

Striking a Balance

1925-1960 (Streeter-Phelps)• Problems: untreated and primary effluent• Pollutants: BOD• Systems: streams and estuaries (1D)• Kinetics: linear, feed forward• Solutions: analytical

Modeling: Historical Development

CE5504 – Surface Water Quality Modeling (Chapra 1997)

1960-1970 (Computerization)• Problems: primary and secondary effluent• Pollutants: BOD• Systems: streams and estuaries (1D/2D)• Kinetics: linear, feed forward• Solutions: analytical and numerical

Modeling: Historical Development

CE5504 – Surface Water Quality Modeling (Chapra 1997)

1970-1977 (Biology)• Problems: eutrophication• Pollutants: nutrients• Systems: streams, lakes and estuaries

(1D/2D/3D)• Kinetics: nonlinear, feedback• Solutions: numerical

Modeling: Historical Development

CE5504 – Surface Water Quality Modeling (Chapra 1997)

1977- 2000 (Toxics)• Problems: toxics• Pollutants: organics, metals• Systems: sediment-water interactions

food chain interations, streams, lakes and estuaries

• Kinetics: linear, feed forward• Solutions: analytical

Modeling: Historical Development

CE5504 – Surface Water Quality Modeling (Chapra 1997)

2000 - present (Ecosytems)• Problems: ecosystem change, climate, invasives• Pollutants: natural components – carbon, nutrients, organisms• Systems: primary production, food web interactions• Kinetics: nonlinear, feedback• Solutions: numerical

Modeling: Historical Development

CE5504 – Surface Water Quality Modeling (Chapra 1997)

Benthic Invertebrates

Phytoplankton

Whitefish