Analyses of background nitrogen concentrations in Sweden: evolution of landscape processes and hydrology

Alena BartosovaBerit Arheimer, Johan Strömqvist, Göran Lindström

15 November 2016

International Workshop on Estimation of nitrogen loads to the marine environment around the time of the year 1900Sandbjerg Estate, Sønderborg, Denmark

Historical perspectiveLand use change:

• 2 449 lowered or drained lakes I Sweden during 1800s and 1900s.• 29 864 drainage companies• End of 1800s: 10 000 ha (100 km2) new arable land per year.

SMHI, 1995, SMHI Hydrologi, Report No. 62

Previously estimated effect on nitrogen reduction:

2500 reduced/drained lakes: reduced natural capacity to capture N by 30 000 ton

Hoffman, M., Johnsson, H., Gustafson, A. & Grimvall, A. 2000. Leaching of nitrogen in Swedish agriculture – historic perspective. Agriculture Ecosystems and Environment, 80, 277-290.

Drainage: natural N removal reduced by 20%

Andersson, L. and Arheimer, B., 2003. Modelling of human and climatic impact on nitrogen load in a Swedish river 1885-1994. Hydrobiologia 497(1-3):63-77.

Sources Andersson, L. and Arheimer, B., 2003. Modelling of human and climatic impact

on nitrogen load in a Swedish river 1885-1994. Hydrobiologia 497(1-3):63-77 Andersson, L. and Arheimer, B., 2001. Consequences of changed wetness on

riverine nitrogen – human impact on retention vs. natural climatic variability. Regional Environmental Change 2:93-105

Andersson, L. and Arheimer, B., 2002. Modelling of regional changes of riverivenitrogen flow in the Svartå River, Sweden. FRIEND 2002 --- Regional Hydrology. Bridging the Gap between Research and Practice. Proceedings of the 4th

Internation FRIEND Conference, Cape Town, South Africa, March 2002. IAHS Publ. no. 274, 2002

Lindström, G. & Bergström, S. (2004) Runoff trends in Sweden 1807-2002. Hydrological Sciences Journal, Vol. 49, No. 1, pp. 69-83.

Unpublished work from Soils2Sea project (http://www.soils2sea.eu/) SMHI Vattenwebb (http://vattenwebb.smhi.se/)

N retention Long-term difference between

The sum of all N emissions and soil leaching Total river basin outflow

Lumped description Biological uptake Sedimentation Denitrification Other biogeochemical processes

Highly affected by residence times Lakes in southern Sweden

Retention rate 30-40 kg/ha-year (Arheimer and Brandt 1998)

Svartån study 1400 km2 Upper part: hilly forested morraine with several lakes Lower part: farmland with very little lakes Shallow groundwater with relatively short residence times (months-few years)

#

##

Lake Sommen

Lake Roxen

Linköping

Marsta

Ledberg

Mjölby

Agricultural dominatedForest dominatedLakesRiversUrban areas

N

EW

S

0 10 20 30Kilometers

L.Roxen

L.Sommen

N

SWED

EN

Baltic Sea

Model setup HBV-N

Process-based. Semi-distributed conceptual model Based on HBV-96, also simulates N

Diffuse soil leaching, point sources, rural households, atmosphericdeposition

Physiography: 1885, 1905, 1927, 1956, 1976, 1994 40 subbasins

Climate data 10-year period 1985-1994 110-year time series (with 1994 data only for physiography)

Modeling results

#

##

Lake Sommen

Lake Roxen

Linköping

Marsta

Ledberg

Mjölby

Agricultural dominatedForest dominatedLakesRiversUrban areas

0 10 20 30 Kilometers

N

EW

S

0 10 20 30Kilometers

L.Roxen

L.Sommen

N

Ledberg (main stream)R2=0.81

0255075

100125150

jan-

85

jan-

86

jan-

87

jan-

88

jan-

89

jan-

90

jan-

91

jan-

92

jan-

93

jan-

94

simulationobservation

Marsta (upper branch)R2=0.65

0

1

2

3

jan-

85

jan-

86

jan-

87

jan-

88

jan-

89

jan-

90

jan-

91

jan-

92

jan-

93

jan-

94

simulationobservation

Wat

er fl

ow (m

3s-

1 )

Wat

er fl

ow (m

3s-

1 )

Skenaån (upper branch) R2=0.36

0

4

8

12

16

jan-

85

jan-

86

jan-

87

jan-

88

jan-

89

jan-

90

jan-

91

jan-

92

jan-

93

jan-

94

simulationobservation

Tota

l Nitr

ogen

Con

c. (m

g L-

1 )

Svartåfors (main stream)R2=0.24

0123456

jan-

85

jan-

86

jan-

87

jan-

88

jan-

89

jan-

90

jan-

91

jan-

92

jan-

93

jan-

94

simulationobservation

Tota

l Nitr

ogen

Con

c. (m

g L-

1 )

SWED

EN

Baltic Sea

Water discharge and Nitrogen concentration modelled with HBV-N

Agriculture activities

Total leaching comparable Increase in crop production compensated by decrease in fallow

0%

25%

50%

75%

100%

1885 1905 1927 1956 1975 1995

Clay Loam Loamy sand

0

100

200

300

400

500

600

1885 1905 1927 1956 1975 1995

km2

Total areacrops grassland fallow

Total agric. area in Sweden increased from 0,8 mil.ha in 1800 to 3,5 mil,ha in 1925

Human impact on retention

Agriculture statistics for parishes Information on tile drainage and drainage projects (lowering of lakes, open

ditch drains) No significant changes in tile drainage after 1927

Human impact on retention 75% drainage projects completed between 1770 and 1950

0

2

4

6

8

1885 1900 1915 1930 1945 1960

km2Lowering of lakes

agriculture dominated forest dominated

0

2

4

6

8

1885 1900 1915 1930 1945 1960

km2

New damsagricultural dominated forest dominated

Population

012345

tot-N

(kg/

capi

ta-y

ear)

Production per personPoint sources contributionDiffuse sources contribution

0

10000

20000

30000

40000

50000

60000

020406080

100120140160180200

1927 1956 1976 1994

Pop

ulat

ion

tot-N

(ton

/yea

r)

Point source emissions Rural source emissions Total emissionsUrban population Rural population Total population

Urbanization and migrationIncreased N-content of the dietIncreased used of toiletsSewage systems (small portion exported

outside the watershed)Wastewater treatment (1959)

20% removal at WWTP does not compensate for 50% increase of per capita N emission

Changes in load and retention by source

0250500750

100012501500

1885 1905 1927 1956 1976 1994

tot‐N (ton

/year)

Total load

Net load Retention

0250500750

100012501500

1885 1905 1927 1956 1976 1994

tot‐N (ton

/year)

Agriculture

Net load Retention

1994: net load 753 t/yr (69% arable, 17% urban point sources, 9% other land, 5% rural PS, 1% atm.dep.retention 29% (18% in groundwater, 7% in lakes, 4% in mainstem)

0

50

100

150

200

1885 1905 1927 1956 1976 1994tot‐N (ton

/year)

Deposition on lakes

Net load Retention

0

50

100

150

200

1885 1905 1927 1956 1976 1994

tot‐N (ton

/year)

Point sources

Net load Retention

0

50

100

150

200

1885 1905 1927 1956 1976 1994

tot‐N (ton

/year)

Other land

Net load Retention

Long-term simulation 110 years (change in gaging not evaluated) 1994 conditions

0250500750

1000125015001750

tot-N

(ton

/yea

r)

0500

10001500200025003000

tot-N

(ton

/yea

r)

y = ‐0.0001x + 0.4465R² = 0.6204

0%5%10%15%20%25%30%35%40%

500 1000 1500 2000

Retention of N, %

tot‐N (ton/year)

1825-1934:Low flowsHigh temperature

Runoff anomalies

Trend in runoff anomalies

Impact of rating curve

Individual impact on N transport

17

11/17/2016

-30-20-10

01020304050

A B C D E F G H I J K L

Cha

nge

of N

-load

(%)

Hydrological and climate related

Variables related to changes of land use, arable practices, and household emissions

Ara

ble

prac

tices

1927

Clim

ate

1905

-191

4

Und

rain

ed s

oil

No

WC

Eatin

gha

bits

188

5

No

low

ered

lake

s

Atm

.dep

. 190

0

Land

cov

er 1

985

No

dam

s

Land

cov

er 1

976

Ara

ble

prac

tices

1976

Clim

ate

1974

-198

5

TN retention in S-HYPE Retention in groundwater only Method compatible with Daisy/MIKE-SHE

Inputs to groundwater includehorizontal flows in S-HYPE

No retention for horizontal flows Preliminary unpublished results On-going work for Soils2Sea project

Background simulation with S-HYPE

Atmospheric deposition of nitrogen is reset Emissions from point sources and private sewers set to 0. Urban and semi-urban land is replaced with "other land". Farmland (spring sowing, autumn sowing, potato / sugar beet, oilseed rape and

grass) are replaced by extensive grassland. Secondary crops are removed. Forest clearings replaced with forest.

0.00001

0.001

0.1

10

1000

100000

10000000

0.001 0.1 10 1000 100000 10000000

Backgrou

nd Gross N Loa

d

Present Gross N Load

Total

Background Gross N Load Perfect Fit

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

Backgrou

nd re

tention

Present retention

Total

Perfect Fit Background retention

110100100010000

100000100000010000000100000000

1 100 10000 1000000 100000000

Backgrou

nd N re

tained

Present N retained

Total

Perfect Fit Background N retained

Summary Climate has a significant impact on N loads and retentions

Retention in Sweden mostly driven by processes in surface water (lakes) Possible negative effects of increasing TN retention in surface waters

Eutrophication of inland waters Change in silicate loads Change in algae composition Change in internal loading of other nutrients