Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17CE4505 – Surface Water Quality EngineeringCE4505 Surface Water Quality EngineeringModeling Lecture 2. Model DevelopmentEmpirical ModelsSecchi disk and chlorophyll(Chapra 1997, Figure 29.6) CE4505 – Surface Water Quality EngineeringEmpirical ModelsVollenwieder plot (Chapra 1997, Figure 29.1) CE4505 – Surface Water Quality Engineering(Chapra 1997, Figure 29.4) Linked Empirical-Mechanistic ModelsCE4505 – Surface Water Quality EngineeringMechanistic Mass Balance Models(Chapra 1997, Figure 1.5) accumulation loadings transport reactions= � �in out reactiondmm m mdt= - �g g g1 1 1' ( ) ' ( )nii i i i i idCV W Q C Q C E C C E C C V k Cdt- - += + � - � + � - + � - + ��CE4505 – Surface Water Quality Engineering(Chapra 1997, Figure 18.8) Temporal ResolutionCE4505 – Surface Water Quality EngineeringSpatial Resolution(Chapra 1997, Figure 16.1) CE4505 – Surface Water Quality EngineeringTime and Space Scale of Water Quality Problems(Chapra 1997, Figure 18.9) CE4505 – Surface Water Quality EngineeringKinetic ResolutionTotalPhosphorusAvailableParticulatePhosphorusRefractoryParticulatePhosphorusDissolvedOrganicPhosphorusSolubleReactivePhosphorusCE4505 – Surface Water Quality EngineeringThings should be made as simple as possible -- but no simpler. Albert Einsteinimage source: www.physik.uni-frankfurt.de/~jr/physpiceinstein.htmlThe Guiding PrincipleCE4505 – Surface Water Quality Engineeringunlimited costcostcost + $desired reliabilityModel ComplexityModel ReliabilityDefensible, Credible, Cost-EffectiveCE4505 – Surface Water Quality EngineeringModel ComplexityScreening  Management  ResearchStriking a BalanceCE4505 – Surface Water Quality Engineering1925-1960 (Streeter-Phelps)• Problems: untreated and primary effluent• Pollutants: BOD• Systems: streams and estuaries (1D)• Kinetics: linear, feed forward• Solutions: analyticalModeling: Historical Development(Chapra 1997) CE4505 – Surface Water Quality Engineering1960-1970 (Computerization)• Problems: primary and secondary effluent• Pollutants: BOD• Systems: streams and estuaries (1D/2D)• Kinetics: linear, feed forward• Solutions: analytical and numericalModeling: Historical Development(Chapra 1997) CE4505 – Surface Water Quality Engineering1970-1977 (Biology)• Problems: eutrophication• Pollutants: nutrients• Systems: streams, lakes and estuaries (1D/2D/3D)• Kinetics: nonlinear, feedback• Solutions: numericalModeling: Historical Development(Chapra 1997) CE4505 – Surface Water Quality Engineering1977- 2000 (Toxics)• Problems: toxics• Pollutants: organics, metals• Systems: sediment-water interactionsfood chain interations, streams, lakes and estuaries• Kinetics: linear, feed forward• Solutions: analyticalModeling: Historical Development(Chapra 1997) CE4505 – Surface Water Quality Engineering2000 - present (Ecosytems)• Problems: ecosystem change, climate, invasives• Pollutants: natural components – carbon, nutrients, organisms• Systems: primary production, food web interactions• Kinetics: nonlinear, feedback• Solutions: numericalModeling: Historical Development(Chapra 1997) Benthic InvertebratesPhytoplanktonWhitefishCE4505 – Surface Water Quality