Steve Chapra

GARDEN 2018

10 April 2018

“Building the Perfect Beast”

Water-Quality Modelingof Lake Garda

OUTLINE

Assumptions

Sediment-Water Interactions

HABs

Upper Food Web

Chemistry

The Po as a System

Conclusions

L2K: PHYSICAL MODEL

epi (1)

bottom

hypo

(4)

A0

A1

meta (2)

A3

top hypo (3)

A2H

H1

H2

H3

H4

Temp

cond

Qin

Qp Qe

Qout

STATE VARIABLES

(mass balances)Variable Units Variable Units

Temperature C Diatoms mgC/L

Specific conductance umhos Greens mgC/L

Inorganic suspended solids mgD/L Cyanobacteria fix mgC/L

Particulate organic carbon mgC/L Cyanobacteria-non fix mgC/L

Dissolved organic carbon mgC/L Nanoplankton mgC/L

Organic nitrogen mgN/L Herbivorous zooplankton mgC/L

Ammonia mgN/L Carnivorous zooplankton mgC/L

Nitrate mgN/L Dissolved methane mgCH4/L

Organic phosphorus mgP/L Sulfate mgSO4/L

Bioavailable phosphorus mgP/L Hydrogen Sulfide mgS/L

Detrital organic silica mgSi/L Calcium mgCa/L

Bioavailable available silica mgSi/L Total inorganic carbon

Dissolved oxygen mgO2/L Alkalinity mgCaCO3/L

mol/L

OTHER WATER-QUALITY

OUTPUTDerived variables Sediment-water fluxes Air-water gas fluxes

Carbonaceous BOD Oxygen Oxygen

Carbon dioxide Total inorganic carbon Carbon dioxide

Bicarbonate Bioavailable phosphorus Methane

Carbonate Ammonia Nitrous oxide

Total chlorophyll a Nitrate

Extinction coefficient Sulfate

Secchi depth Hydrogen sulfide

Turbidity Nitrogen gas

pH Nitrous oxide

Alkalinity Dissolved organic carbon

Specific conductance Dissolved methane

Total Kjeldahl N Methane gas

Total organic carbon

Particulate organic carbon

Hydrogen sulfide

WATER COLUMN KINETICS

ran

dn

s

mi

cd

h

hna

hpi

rnc

rpc

s

ap

s

nnn

rap

p

o

x

g

zc

o

sod

o

s

cp

no

s

po

s

zh

g

e

e

d

rca

r

r

r

rca

rpc

rnc

ASSUMPTIONSState of the art physics

Water motion

Heat budget & temperature

Boundary layers

State of the art biology & chemistry

Multiple algal groups (including HABs)

Upper food chain (grazers)

Macrochemistry (pH, major ions, calcite, etc.)

Sediment-water interactions

Gas transfer (SOD, methane flux, etc.)

Nutrient fluxes

Sediment chemistry (beyond nutrients)

MODELLING

Sediment/Water

Interactions in Lakes(SOD and Nutrient Fluxes)

sediments

epi

air

SEDIMENT-WATER PROCESSES“THE MISSING LINK OF WATER-QUALITY MODELLING”

Organic

Matter

SOD

Nutrients

N, P

Fluxes

SEWAGE,

RUNOFF PHOTOSYNTHESIS

hypo

Nutrients

Organic

Matter

Organic

Matter

Oxygen

Nutrients?

Short-term Effects:

O2 Depletion and

Internal Loading

Esthwaite Water, England

Mortimer (1971)

settling

p1

inflow outflow

SHAGAWA

LAKE,

MINNESOTA 0

20

40

60

1965 1967 1969 1971 1973 1975 1977 1979

NO RELEASE

RELEASE

burial

p2

release

WASTE TREATMENT

Long-term Effects:

Retarded Recovery

SOD

(g/m2/d)

0

4

8

0 100 200

COD (mgO/L)

THE “SQUARE-ROOT” RELATIONSHIP

OF SEDIMENT OXYGEN DEMAND

AND OVERENRICHMENT

SOD = a COD0.5

WHERE DOES NONLINEARITY

COME FROM?

Loss of carbon as methane

gas in anaerobic sediments

Competition between reaction

and diffusion in aerobic

surface sediment

LOSS OF CARBON AS METHANE GAS

IN ANAEROBIC SEDIMENTSA

CT

IVE

SE

DIM

EN

T L

AY

ER

WA

TE

R C

OL

UM

N

ANAEROBIC ZONE

AEROBIC ZONE

PRODUCTION OF

CH4(aq) CH4(aq) CH4(g)

If saturation exceeded

CH4(aq)

SOD

POC FLUX

POC

CO2

0

2

2 D

d c

dzSC

2 c JD s CCSODmax *

CSODmax

0

5

10

0 20 40 60

SOD

(g/m2/d)

Jc* (g/m2/d)

SOD = Jc*

SQUARE-ROOT EFFECT DUE

TO BUBBLE FORMATION

Mass Balance:

Flux

Mass Balance

COMPETITION BETWEEN REACTION AND

DIFFUSION IN AEROBIC SURFACE SEDIMENT

Flux Balance (divide by A):

1110

1

1 ckVAcvAcvdt

dcV b -- 1110

1

1 ckVAcvAcvdt

dcV b -- 1110

1

1 ckVAcvAcvdt

dcV b -- 1110s

1

1 ckVAcvAcvdt

dcV b --

10

1

1 cvcvdt

dcH b

--10s

1

1 kH1c1cvcvdt

dcH b

--

Jn = rnavaa + vonno

no1

no2 na2

na1

o

nn2

nn1 N2

N2

N2

aerobic

anaerobic

overlying water

deep sediments

ac

tive

sed

ime

nts

O2

overlying water

deep sediments

ac

tiv

e s

ed

imen

ts

NH4+

anaerobic

JN JNH 4

+

NO3–

aerobic

DIFFUSION/REACTION COMPETITION

IN THE AEROBIC LAYER

Diffusion

Reaction

water

aerobic

anaerobic

0 1 2 3 40

5

10

15

20

0

5

10

15

20

0 1 2 3 4

SOD

JN

SOD = 2.77 Jn

0.6Jn

0.6

R2

= 0.9827R2

= 0.9827

TOTAL SOD = CSOD + NSOD

1

22

2

'

1

22

2*SOD

1

1

SOD1

12SOD

nwo

n

C*noon

cwo

c

CsD

koD

DJar

koD

DJc

CSOD NSOD

0

5

10

0 20 40 60

Jc* (gO/m2/d)

SO

D

(gO

/m2/d

)

TOTAL SOD = CSOD + NSOD

SOD = Jc*

SODmax

SOD

o(0) = 10

o(0) = 4

OXIDATION-REDUCTION

Oxidation:

“REDOX”

Loss of electrons (energy)

Reduction:

Gain of electrons (energy)

Charge is “reduced”

[CH2O] + O2 CO2 + H2O

[CH2O] O2

e–

Oxidized

Reductant

Electron

donor

Reduced

Oxidant

Electron

acceptor

energy

“Aerobic respiration”

REDOX SEQUENCECH2O O2+ CO2

Aerobic respiration

Denitrification

Manganese

reduction

Iron reduction

Sulfate reduction

Methane formation

“methanogenesis”

NO3– N2 + CO2+

CH2O CH4 + CO2+

SO42– HS– + CO2+

FeOOH(s) Fe2+ + CO2+

MnO2(s) Mn2+ + CO2+

PON2

JN

JC

POC2

Aerobic

sediment

Anaerobic

sediment

Deep

sediment

Water

Atmosphere

LOW SULFATE SYSTEMS

(Most lakes)

O2,0

CH4,0

CH4,2

CO2,1

CO2,0

CO2,2

CH4,g

DOC2

DOC1 CH4,1

NH4,2

NH4,0

N2O

N2

NO3,1

NO3,1

O2,0

NH4,1

NH4,2

NH4,0

N2O

N2

NO3,1

NO3,1

O2,0

NH4,1

SO4,1

SO4,2HS2

HS0

HS1

O2,0 SO4,0

HIGH SULFATE SYSTEMS

(Estuaries)

O2,0

NH4,2

NH4,0

N2O

N2

CO2,1

CO2,0 NO3,1

NO3,1

O2,0

NH4,1

POC2

DOC1

CO2,2

JC

JN

PON2DOC2

O2,0

NH4,2

NH4,0

N2O

N2

CO2,1

CO2,0 NO3,1

NO3,1

O2,0

NH4,1

POC2

DOC1 SO4,1

SO4,2HS2

HS0

HS1

O2,0

CO2,2

SO4,0

JC

JN

CH4,0

CH4,2

CH4,1

PON2DOC2

CH4,g

SOME “SIGNIFICANT” LAKES(Iseo)

LAKE ISEO EXAMPLE

High (Present) Sulfate

SO4 = 48.4 mgSO4 L–1

SOD = 7.6285 gO2 m–2 d–1

NSOD = 0.4670 gO2 m–2 d–1

CSOD = 0.0023 gO2 m–2 d–1

SSOD = 7.1591 gO2 m–2 d–1

No Sulfate

SO4 = 0 mgSO4 L–1

SOD = 1.2069 gO2 m–2 d–1

NSOD = 1.1144 gO2 m–2 d–1

CSOD = 0.0926 gO2 m–2 d–1

SSOD = 0 gO2 m–2 d–1

Hypo O2 = 10 mg/L

JC* = 10 gO2 m–2 d–1

Temp = 6.3 oC

Depth = 150 m

Presence of SO4

Bad for lake

Increases SOD

Good for climate

Decreases loss of

methane to atmosphere

Further Research

Effect of meromixis on

sediment mixing

Effect of water motion on

sediment-water exchange

Incorporation of full

chemistry into sediment

models

Harmful Algal Blooms

(HABs)

(a) Diatoms (b) Greens

(d) non-N-fixing Bluegreens

“Microcystis”

(c) N-fixing Bluegreens

“Oscillatoria”

“Good Algae”(i.e., nontoxic,

edible phytoplankton)

Functional Groups

Cyanobacteria

(HABs)(AKA Blue Green Algae)

“The cockroaches

of the water”

Cyanobacteria

Greens

Diatoms

Seasonal Succession of Phytoplankton in Lakes

100

Percent

biomass

(b) Hypereutrophic

0M A M J J A S O N D

Cyano

Greens

Diatoms

0

100

Percent

biomass

(a) Oligotrophic

Temperature

Nutrient limitation

Grazing

Settling/buoyancy

Principal Components Governing

Seasonal Succession Patterns

Why do cyanobacteria win?

0

20

40

60

80

100

0

20

40

60

80

100

0

20

40

60

80

100

0 2010 30 40

oTemperature ( C)

Paerl & Otten 2012

Diatoms

Greens

Bluegreens

sy/x = 6.11

r2 = 0.974

sy/x = 4.44

r2 = 0.986

sy/x = 8.55

r2 = 0.940

NUTRIENT LIMITATION,

SETTLING & GRAZING

Total phytoplankton chlorophyll

DiatomsBluegreens

(Non N-fix)

Greens/

Others

Zooplankton

Bluegreens

(N-fix)

Nitrogen PhosphorusSilica

2050

2090

Critical HABs blooms in USA

High temperature kinetics

Scum formation

Research Issues

High Temperature Growth

Plateau

High-Growth

Temperatureinhibition

0 10 20 30 40

Temperature (oC)

0

0.5

1

1.5

kg,max

(/d)

SEDIMENTS SEDIMENTSSEDIMENTS

WIND

SCUM FORMATION

WIND

Upper Food Chain

FIRST FOOD CHAIN

Herbivorous Zooplankton

Phytoplankton

Carnivorous Zooplankton

SIMPLE HABs MODEL

DiatomsBlue

greens

Others

(Greens)

NitrogenPhosphorus Silica

Herbivorous Zooplankton

Carnivorous Zooplankton

UPPER TROPHIC LEVEL

Bottom-up versus top-down

Where did the zooplankton go?

Invasive species

WQ modeling’s dirty little secret

NITROGEN

SMALL

HERBIVOROUS

CLADOCERANS

LARGE

HERBIVOROUS

CLADOCERANS

SMALL

OMNIVORES

SMALL

HERBIVOROUS

COPEPODS

GREENSBLUE

GREENS

LARGE

DIATOMSSMALL

DIATOMS

PHOSPHORUSSILICON

NAUPLII

PREDATORS LARGE

OMNIVORES

ALEWIFE

NITROGEN

SMALL

HERBIVOROUS

CLADOCERANS

LARGE

HERBIVOROUS

CLADOCERANS

SMALL

OMNIVORES

SMALL

HERBIVOROUS

COPEPODS

GREENSBLUE

GREENS

LARGE

DIATOMSSMALL

DIATOMS

PHOSPHORUSSILICON

NAUPLII

PREDATORS LARGE

OMNIVORES

ALEWIFE

GENERAL, ISSUES, QUESTIONS

AND CHALLENGES(Please indulge me)

Data stewardship

Watershed modeling

Interdisciplinary cooperation

Systems approach

GREAT LAKES TP MODELLoading

Model

TP

Load

WQ

Model

TP

Conc

population,

land useCorrelations

Chla/SD

Conc

DECISION-SUPPORT MODEL

HURON

SUPERIOR

W

W

W

W W W

W

S

SSS

S

S

S

WEST ERIE CENT ERIE EAST ERIE

ONTARIO

MICHIGAN

TP CONCENTRATIONS

50

40

30

20

10

0

10

0

1800 1850 1900 19500

1800 1850 1900 1950

1800 1850 1900 1950

30

20

10

01800 1850 1900 1950

30

20

10

0

1800 1850 1900 1950

30

20

10

01800 1850 1900 1950

10

0

1800 1850 1900 1950

10

0

CENTRAL

ERIE

HURON

MICHIGAN

ONTARIO

EASTERN

ERIE

WESTERN

ERIE

SUPERIOR

eutrophic

nonpoint

point

oligotrophic

0

10

20

1800 1850 1900 1950 2000

TP

(mgP/L)

LAKE ONTARIO

Much better than expected!

(and maybe too much)

The Pre Alpine Italian “Great Lakes”

N

50 km

Garda

Gulf of Genoa

Torino

Pavia

Milano

Cremona

Parma Ferrara

Mantova

Brescia

Como Iseo

Maggiore

SWITZERLAND

FRANCE

PoPo

Po

Po

Lugano

Garda