Linking Land-Use and Water Quality -

Modelling Results and Discussion

Lisa Norton, Stephen Maberly, Linda May and

Alex Elliott

with help from John Rockliffe, Leslie Webb, farmers and householders

in the catchment

What is a model?

A model is a simulation of reality

which:

looks like the real thing

provides an opportunity to look at something in its

totality (which might be difficult to do in real life)

provides information on how different parts of an

object relate to one another

A model does not necessarily

function like the real thing it represents

contain all the detailed internal workings of the thing it

represents

Scientists use models to:

Represent reality

Understand how things work

Test how things might work under different (including future) conditions

(because it’s easier than doing it in reality)

What do we want the

Loweswater catchment

model to do?

What are the building blocks for a

Loweswater model?

Land cover information

Land management information and soil P

levels for farmed land

Numbers of people

Septic tank condition, use and

management

Rainfall

Lake discharge

Wind speed

Air temperature/humidity

Cloud cover

Lake data for validation

Tell us how what is done in the

catchment is related to the

algal blooms in the lake

Data/information that is likely to be important but which we don’t

have/ haven’t been able to incorporate

Slurry tank/midden stead condition

Yard water /waste arrangements

Connectivity between waste storage

and water bodies (under normal

conditions)

Connectivity between waste storage

and water bodies (under extreme

weather conditions)

Locations of animal feeders in relation

to water bodies

Animal access to water bodies in lake

feeder streams

Outline of modelling approach

Collect farm

data

Create farm

nutrient budget

(PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff

model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations

(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as

point or diffuse)

Create farm

management

scenario data

Status quo

Scenario testing

Local weather

Land cover

Land cover and land management

Each land cover type has an associated average nutrient

export value

Nutrient Exports on managed farmland depend heavily on

inputs and stocking levels

Hence specialist farmer nutrient budgeting software

was used to calculate nutrient exports from the farmland

using John Rockliffe’s information on farming practice and

soil nutrient status

Land cover type Area

(km2)

P

(mg P m-3)

Nitrate

(mg N m-3)

A High production grass 2.79 32 3,540

B Broadleaved woodland 0.65 10 190

C Coniferous woodland 0.35 10 190

D Natural grass 1.39 5 2,100

E Urban 0.12 56 0

F Arable 0.03 17 2,900

G Moors and heathland 2.29 7 190

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

Calculate nutrient excess on each farm

1. Collect data from farmers

2. Enter data into PLANET

(Planning Land Application of

Nutrients for Efficiency and the

Environment)

3. Calculate phosphorus and

nitrogen balance for each farm,

based on ‘imports’ and ‘exports’

of :

1. Fertiliser

2. Livestock

3. Feedstuffs

4. Bedding

5. etc.

1. Predict nutrient excess on each

farm

1 & 2

3 & 4Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

Example: predicting the P excess on each farm

Farm

5 kg P y-1 50 kg P y-1

N

U

T

R

I

E

N

T

S

O

U

T

N

U

T

R

I

E

N

T

S

I

N

NUTRIENT

EXCESS

IN – OUT = 400 – 250 =150 kg P y-1

Bedding/feed Bedding/feed

Fertiliser/manure/slurry

Sheep

Cattle

Fertiliser/manure/slurry

Sheep

Cattle

Revise annual net P surplus

1. P surplus for each farm minus soil P deficit

(calculated in PLANET) (as calculated from John Rockliffe’s soil sampling)

(calculated by farm – on the assumption that P deficit = capacity for P uptake by soil)

Update P surplus values to take account of soil uptake and septic tank

discharges:

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

2a. Either- add P from septic tanks on farms into the above sum (data from Leslie

Webb)

(P from septic tanks is taken up the soil in the same way as farm nutrient surplus

– a diffuse source)

2b. Or add P from septic tanks in as a direct input to streams (a point source)

Farm no. Surplus P Soil P deficitP from septic

tanksNet P surplus

1134 375 3.1 0

2356 161 2.0 197

3. Summed to produce an annual P-load for all the farms

Outline of modelling approach

Collect farm

data

Create farm

nutrient budget

(PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff

model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations

(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as

point or diffuse)

Create farm

management

scenario data

Status quo

Scenario testing

Local weather

Land cover

•Last data available for Loweswater in 2001

• 2009 data reconstructed from adjacent gauging stations

y = 0.060x + 0.087

R2 = 0.843

0

0.5

1

1.5

2

2.5

3

0 20 40 60

Park Beck outflow to Crummock (m3 s-1)

Lo

we

sw

ate

r o

utflo

w (

m3

s-1

)

y = 0.076x + 0.094

R2 = 0.832

0

0.5

1

1.5

2

2.5

3

3.5

0 10 20 30 40

Scalehill outflow from Crummock (m3 s-1)

Lo

we

sw

ate

r o

utflo

w (

m3

s-1

)

Loweswater flow (discharge) for validation- 1

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

0

0.5

1

1.5

2

2.5

3

09/02/19

99

28/08/19

99

15/03/20

00

01/10/20

00

19/04/20

01

05/11/20

01

Dis

ch

arg

e (

m3 s

-1)

Loweswater

Lowes from Park Beck

Lowes from Scalehill

0

2

4

6

8

10

12

31/12/20

08

10/04/20

09

19/07/20

09

27/10/20

09

04/02/20

10

Dis

ch

arg

e (

m3 s

-1)

Scalehill simulation

Park Beck simulation

Loweswater flow (discharge) for validation- 2

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

Predict streamflow from rainfall

1. Generate modelled streamflow

from rainfall (local rain gauge plus

Ken) and air temperature (buoy)

2. Values compared to simulated

discharge for Loweswater

0

0.5

1

1.5

2

2.5

Sep-99 Dec-99 Mar-00 Jun-00 Sep-00 Dec-00 Mar-01 Jun-01

Dail

y d

isch

arg

e (m

3s

-1)

Date

Modelled values

Measured values

Str

ea

mfl

ow

(m

3s

-1)

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

Calculate daily nutrient runoff values for each scenario

1. Annual P-inputs from the farms

added to annual P-input from the

other land in the catchment (export

coefficient) to produce a total

annual load of P (kg y-1)

2. Different scenarios of possible land

management were investigated

(each with/without direct septic tank

input) and annual P-load calculated

3. GWLF hydrological model (daily

discharge) combined with these P-

loads to produce daily loads of P

(also using a similar approach

nitrogen and silica)

0

2

4

6

8

10

12

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Estim

ate

d P

load t

o la

ke (

kg P

d-1

)

2009

S1 S2 S3

S4 S5E

stim

ate

d P

in

pu

t to

lake

(kg P

d-1

)

Scenario Description

S1 Status quo

S2 All farmland to deciduous forest

S3 All improved grassland to natural grassland

S4 Remove cattle; double sheep

S5 Double cattle; halve sheep

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

0

100

200

300

400

S1

S1A

S2

S2A

S3

S3A

S4

S4A

S5

S5A

Phosphorus-load (kg y-1)

Scen

ario

P-loads predicted by the different scenarios

Scenario Description

S1Current land cover & stocking densities

(A = Septic tanks as point sources)

S2All farmland changed to deciduous forest

(A = Septic tanks as point sources)

S3

All improved grassland changed to natural

grassland

(A = Septic tanks as point sources)

S4No cattle; double sheep

(A = Septic tanks as point sources)

S5Double cattle; half sheep

(A = Septic tanks as point sources)

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

Light

What controls phytoplankton growth?

Algae

Wind

Heat flux

Nutrients

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

The phytoplankton used in this PROTECH simulation

Asterionella

Aulacoseira

Chlorella

Plagioselmis

Dinobryon

Anabaena

Planktothrix

Aphanizomenon

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

-5.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

31

-Dec-0

81

4-J

an

-09

28

-Ja

n-0

91

1-F

eb

-09

25

-Feb

-09

11

-Ma

r-0

92

5-M

ar-0

90

8-A

pr-0

92

2-A

pr-0

90

6-M

ay

-09

20

-Ma

y-0

90

3-J

un

-09

17

-Ju

n-0

90

1-J

ul-

09

15

-Ju

l-0

92

9-J

ul-

09

12

-Au

g-0

92

6-A

ug

-09

09

-Sep

-09

23

-Sep

-09

07

-Oct-

09

21

-Oct-

09

04

-No

v-0

91

8-N

ov

-09

02

-Dec-0

91

6-D

ec-0

93

0-D

ec-0

9

T (

°C)

Loweswater, 2009

A…

0

4

8

12

16

20

31

-Dec-0

81

4-J

an

-09

28

-Ja

n-0

91

1-F

eb

-09

25

-Feb

-09

11

-Ma

r-0

92

5-M

ar-0

90

8-A

pr-0

92

2-A

pr-0

90

6-M

ay

-09

20

-Ma

y-0

90

3-J

un

-09

17

-Ju

n-0

90

1-J

ul-

09

15

-Ju

l-0

92

9-J

ul-

09

12

-Au

g-0

92

6-A

ug

-09

09

-Sep

-09

23

-Sep

-09

07

-Oct-

09

21

-Oct-

09

04

-No

v-0

91

8-N

ov

-09

02

-Dec-0

91

6-D

ec-0

93

0-D

ec-0

9

mea

n w

ind

sp

(m

/s)

Loweswater windspeed, 2009

Meteorological data from buoy input into PROTECH

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

Loweswater, 2009

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

31

-De

c-0

8

14

-Ja

n-0

9

28

-Ja

n-0

9

11

-Fe

b-0

9

25

-Fe

b-0

9

11

-Ma

r-0

9

25

-Ma

r-0

9

08

-Ap

r-0

9

22

-Ap

r-0

9

06

-Ma

y-0

9

20

-Ma

y-0

9

03

-Ju

n-0

9

17

-Ju

n-0

9

01

-Ju

l-0

9

15

-Ju

l-0

9

29

-Ju

l-0

9

12

-Au

g-0

9

26

-Au

g-0

9

09

-Se

p-0

9

23

-Se

p-0

9

07

-Oc

t-0

9

21

-Oc

t-0

9

04

-No

v-0

9

18

-No

v-0

9

02

-De

c-0

9

16

-De

c-0

9

30

-De

c-0

9

Su

rf P

FD

um

ol

m-2

s-1

surf PFD surf PFD after 16Jan09

Surface lightAir temperature

Windspeed

In-lake temperatures for PROTECH validation

Loweswater, 2009

0

5

10

15

20

25

30

31-D

ec-0

8

14-J

an

-09

28-J

an

-09

11-F

eb

-09

25-F

eb

-09

11-M

ar-

09

25-M

ar-

09

08-A

pr-

09

22-A

pr-

09

06-M

ay-0

9

20-M

ay-0

9

03-J

un

-09

17-J

un

-09

01-J

ul-

09

15-J

ul-

09

29-J

ul-

09

12-A

ug

-09

26-A

ug

-09

09-S

ep

-09

23-S

ep

-09

07-O

ct-

09

21-O

ct-

09

04-N

ov

-09

18-N

ov

-09

02-D

ec-0

9

16-D

ec-0

9

30-D

ec-0

9

T (

°C)

0.1m 1m 2m 3m 4m 5m 6m 7m 9m 11m 13m 15mCollect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

Met data inputs

0

5

10

15

20

25

0 50 100 150 200 250 300 350 400

Tem

per

atu

re in

to

p 5

m (

oC

)

Day of year

Buoy data

Series2PROTECH

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

0

5

10

15

20

25

1 31 61 91 121 151 181 211 241 271 301 331 361

Ch

loro

ph

yll a

(m

g m

-3)

Day of year

Total

Chlorella

Plagioselmis

Asterionella

Aulacoseira

Anabaena

Aphanizomenon

Planktothrix

Dinobryon

PROTECH output for S1 scenario

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

0

5

10

15

20

25

1 31 61 91 121 151 181 211 241 271 301 331 361

Ch

loro

ph

yll a

(m

g m

-3)

Day of year

Total

Chlorella

Plagioselmis

Asterionella

Aulacoseira

Anabaena

Aphanizomenon

Planktothrix

Dinobryon

0

5

10

15

20

25

1 31 61 91 121 151 181 211 241 271 301 331 361

Ch

loro

ph

yll a

(m

g m

-3)

Day of year

Total

Chlorella

Plagioselmis

Asterionella

Aulacoseira

Anabaena

Aphanizomenon

Planktothrix

Dinobryon

PROTECH output for S3 (low P load) & S5 (high P load) scenarios

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

0

5

10

15

20

1 31 61 91 121 151 181 211 241 271 301 331 361

SRP

(m

g m

-3)

Day of year

S5

S3

S1

PROTECH output of SRP concentration for scenarios S1, S3 and S5

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

Validation against monthly data: Total Chlorophyll

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

Validation against monthly data: Cyanobacteria

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

0

2

4

6

8

10

12

14

0 100 200 300 400

An

nu

al m

ea

n c

hlo

rop

hy

ll a

(mg

m-3

)

Phosphorus load (kg SRP y-1)

H:G

G:M

M:P

Chlorophyll production vs SRP load for the scenarios

0

2

4

6

8

10

12

14

0 100 200 300 400

An

nu

al m

ea

n c

hlo

rop

hy

ll a

(mg

m-3

)

Phosphorus load (kg SRP y-1)

H:G

G:M

M:P

S3

S2

S3A

S2A

S1

S1AS5

S4

S5AS4A

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

0

2

4

6

8

10

12

0 100 200 300 400

An

nu

al m

ea

n c

hlo

rop

hy

ll a

(mg

m-3

)

Phosphorus load (kg SRP y-1)

Cyanobacterial Chlorophyll vs SRP load

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

y = 0.16x + 30.75R² = 0.98

0

20

40

60

80

100

0 100 200 300 400

% tim

e o

r %

Ch

la

Phosphorus load (kg SRP y-1)

Percent cyanobacteria Percent of year> 10 mg Chl a m-3

Cyanobacterial Chl as % of total and % of year chlorophyll > 10 mg m-3

Collect farm

data

Create farm

nutrient budget (PLANET)

Calculate farm

nutrient excess

Collect rainfall

& flow data

Calibrate

rainfall/runoff model (GWLF)

Generate daily

runoff values

Calculate nutrient

runoff concentrations(= nutrient excess/flow)

Generate daily nutrient

inputs to lake (GWLF)

Predict lake response

(PROTECH)

Adjust for soil P

deficit

Add P losses from

septic tank (as point or diffuse)

Create farm

management scenario data

Status quo

Scenario testingLocal weather

Land cover

Conclusions

• All models are simplifications of reality but,

despite the simplifying assumptions and inevitable

non-perfect data, the three models, PLANET,

GWLF and PROTECH were successfully linked to

produce a reasonable simulation of the effect of

the land on the lake

• Currently, observations and models suggest that

the lake is at moderate ecological status for WFD

with a total annual load of about 200 kg P y-1.

• The models suggests that if the load was halved,

the lake could be brought to good ecological status

(time……). The model could be used as a tool to

inform future land-management decisions.

• Septic tanks have a relatively small effect on P

and phytoplankton today, but- they can be

improved without major changes to way of life and

would become increasingly important if P-losses

from the land were reduced.

Discussion

• Discuss these and other scenarios

• Are their any actions that LCP could instigate following on from the modelling?

• Sources of funding for further improvements (septic tanks, slurry/ waste

management)

• Known unknowns

• Can it help with the ‘tension’ between economy and ecology?

•

0

5

10

15

20

25

1980 1990 2000 2010

To

tal p

ho

sp

horu

s (u

g L

-1)

W Sp

Su A

0

5

10

15

20

25

1990 1995 2000 2005 2010P

hyto

pla

nkto

n C

hl a

(µg

L-1

)

W Sp Su A

Long-term trends