Land use effect on nutrient loading – nutrient models new assessment tools

Inese Huttunen, Markus Huttunen and Bertel Vehviläinen

Finnish Environment Institute

Basic structure of WSFS-Vemala

Hydrological WSFS-model:• Inputs daily precipitation and temperature• Simulates hydrological cycle on daily time step• Covers all Finland, 6200 sub-basins, 58 000 lakes• Simulated daily• Data-assimilation, ensemble forecasts

Water quality simulation with Vemala• Diffuse loading (agriculture and non-agriculture)• Point load, settlements, atmospheric deposition• Simulates transport in rivers and lakes• Total phosphorus, total nitrogen, suspended solids,

organic carbon (TOC)

Relationship between concentration and runoff / use of VIHMA annual loads

• Runoff r (= r1+r2+r3+r4+r5) is divided into 5 classes rx,

each class has Ptot concentration cx,x which is calibrated• r1: runoff in runoff class 1, 0-1 mm/day• r2 runoff in runoff class 2, 1-3 mm/day• r3 runoff in runoff class 3, 3-6 mm/day• r4 runoff in runoff class 4, 6-10 mm/day• r5 runoff (unlimited) in runoff class 5, > 10 mm/day

• Concentration relationship with runoff

Example of concentration runoff relationship for one out of four seasons

0

200

400

600

800

1000

1200

1400

1600

1800

0 5 10 15 20 25

Runoff, mm

Co

ncen

trati

on

, m

ikro

g/l

Agriculture

Non-agriculture

Total concentration

rcrcrcrcrcr

cx5544332211

VIHMA tool (Puustinen, SYKE) is used to simulate annual agricultural load and Vemala load is adjust

1 100 000 field plots are simulated separately by knowing slope, plant, soil type, P soil

Nutrient balance in lakes

rAVccQtIdtdm

out )(Inflow loading

Outflowingload

Sedimentation

Internal

load

Accumulation = Loading – outflow – sedimentation + internal loading

Annual Phosphorus balance for Karhijärvi

Inflow loading 10.2 t

Outflow load 8.9 t

Sedimentation 5.9 t Internal loading

3.2 t

Calibration

Calibration is the process of modifying the parameters to a model until the difference between output from the model and observed data sets is minimum

Optimization criteria is:

all observation points located at the same calibration area are taken into calibration:• + there is a need to use all available

observations in the calibration even if the are very infrequent (few times per year),

• − more frequently observed points gets more weight in the calibration procedure.

appropriate weights for each type of observations are found and tested to reach the best possible calibration result

Water quality observations are not daily

wq wqn

i

n

isimobssimobs iloadiloadwiconciconcwOC

1 1

22 21

Phosphorus concentration

Phosphorus load

Agricultural load 59% of the total loading into Archipelago Sea

59%

28%

10%

3%

Phosphorus load to Archipelago Sea, 329 t/year

Agriculture, 195 t

Non-agriculture, 91 t

Scattered settlements, 33 t

Point load, 9t

Use of VEMALA to simulate different scenarios

Vemala can be used to simulated present situation

We can change present loadings and simulate concentrations and loadings in the river catchments in changed conditions:

Possible changes are:• Crop management changes by VIHMA / ICECREAM• Wetland effect• Scattered settlement loading changes• Point load changes• Climate change scenarios• Combination of above mentioned

Scenario simulations has been done in TEHO project for Aurajoki, Loimijoki and Eurajoki

Wetland simulation

All possible small ditch catchments with area 20 – 200 ha

Which has at least 20% of agricultural fields

Its possible to simulate the effect of all possible wetlands, we can simulate nutrient sedimentaion in wetland, plant uptake

Present Buffer strips

30% of vegeta-

tion cover in-crease in

winter

50% of vegeta-

tion cover in-crease in

winter

70% of vegeta-

tion cover in-crease in

winter

30% of vegeta-

tion cover in-crease in winter on steeper fields

50% of vegeta-

tion cover in-crease in winter on steeper fields

70% of vegeta-

tion cover in-crease in winter on steeper fields

mannure applica-

tion stoped

double applica-tion of

mannure

P-test values

de-creased

nyky-il-masto

0 -381 0 1177 4561 0 459 4054 -2699 2697 -3016

2010-39

7396 6953 7396 8774 12779 7396 7927 12173 4245 10542 3846

2020-49

11297 10822 11297 12782 17109 11297 11866 16445 7905 14679 7463

2040-69

18708 18173 18708 20389 25289 18708 19347 24547 14865 22541 14354

2070-99

25581 24989 25581 27434 32846 25581 26287 32034 21325 29812 20744

-2500

2500

7500

12500

17500

22500

27500

32500

nykyilmasto2010-39

2020-492040-69

2070-99

TEHO scenarios for Aurajoki, change of Ptot loading from present loading, present loading 60784 kg/year

PT

OT

lo

ad,

kg/y

ear

Scenarios of agricultural practices in TEHO Buffer zones Increase of vegetation cover during the winter (30%, 50%, 70% of

the total agricultural area):• Equally in all catchment• On the steeper sloped fields

Using of mannure decreased by 50% Decresed using of P fertilizer

Conclusions from TEHO scenarios: There is no one single method to reduce agricultural loading,

seceral reduction methods need to be combined The best reduction can be achieved by combination of:

• Increased vegetation cover on fields over 3% slope• Buffer zones are established• Reduced P fertilizer application, that P soil < 14 mg/l• Best management practices of mannure apllication

Summary Agricultural load needs to be reduced to improve the

state of the Baltic Sea Mitigation measures are done on the field scale and

there are needed tools to estimate what is the effect of mitigation measures on the river catchment scale

Nutrient load models (Vemala) can be used to simulate different scenarios how should the agricultural practices be changed to reduce the agricultural loading

There are no one single method to reduce agricultural loading, its a combination of methods

More detailed process description improves the models capability to simulate climate change or agricultural management scenarios

Thank You!

www.environment.fi/waterforecast