Maija Paasonen-Kivekäs

Sven Hallins forskningsstiftelse Sven Hallin Research Foundation

Vattendagen, Uppsala 30.1.2014

Odlingslandskapets avvattning –

miljö – och produktionsaspekter i ett nordiskt perspektiv

Avvattning från miljöperspektiv i Finland

Drainage from the point of the enviroment in Finland

Outline

• General features of land drainage • Potential environmental impacts of land

drainage • Status of surface waters, loading and water

protection targets • Clay soils, acid sulfate soils, organic soils • Measures for water pollution control • Concluding remarks

Land drainage in Finland

Subsurface drainage 58% of the total field area, 1.29 milj. ha Open drainage 27%, 0.62 milj. ha Undrained 15%, 0.35 milj. ha Basic drainage network Clearing and restoration Clay soils 25-33% Organic soils 11% Acid sulfate soils 2-6% Slope 1% 57% of the field area

> 7% 3.4% of the field area

Field drainage

Recipient of drainage waters from agricultural fields

• From 68% of the total field area drainage waters discharge to main ditches

• from 13% of the field area waters discharge immediately to surface water bodies

• from 6% of the field area waters discharge to pipe drains

• from 13% of the field area waters discharge to terrain

Reference: Puustinen et al. 1994. Kuivatustila, viljelykäytäntö ja vesistökuormitukseen

vaikuttavat ominaisuudet Suomen pelloilla. Vesi- ja ympäristöhallituksen julkaisusarja A.

Rainer Rosendahl

Potential environmental impacts of land drainage

• Hydrology • Soil properties: clay soils, organic soils, AS soils • Water quality of runoff waters • Channel morphology • Nutrient loading to surface waters • Eutrophication of surface waters • Acid and metal loads from acid sulfate soils to surface waters • GHG emissions • Decrease of biodiversity

Human-induced phosphorus

and nitrogen loads into surface waters

in Finland

SYKE 2012

Phosphorus

4004 t/a, 71%

of the total load*

Nitrogen

69 595 t/a, 63%

of the total load *

Finnish Environment Institute *Human induced + natural background load

Diffuse pollution

Unit loads from different land use types1) kg ha-1 a-1

Total nitrogen Total phosphorus

• Natural areas 0.3…2.3 0.02…0.15 • Forestry 2) 0.5…3.5 0.02…0.5 • Agriculture 12…20 0,5…2 • Peat production 10 0.27 • Urban areas 5…9 0.2…0.6

1) Average values from different research projects in Finland

2) Loading after foresty measures during 10 years

d o d

Finland’s Water Protection

Policy Outlines

• Reduction of nutrient emissions that lead to eutrophication, especially from agricultural sources (phopshorus)

• Reduction of risks associated with hazardous substances

• Reducing the harmful impacts of hydrological engineering

• Conservation of aquatic biodiversity • Water body restoration

Ecological status

of surface waters

Agri-environmental programme

Objectives • Reduce water pollution • Increase biodiversity Periods 1995-1999, 2000-2006, 2007-2013(14), 2015-2020 Measures • Basic measures • Supplementary measures • Special measures Total amount of support 348 milj. € in 2011 • 90% of the farmers in 2007-2013 • 95% of the total field area in 2007-2013 • Basic and supplementary measures 294 milj. € • Special measures 47 milj. € Subsidies for land drainage measures • Controlled drainage • Subirrigation and recycling of drainage waters • Environmental river engineering and restoration • Support for investments and maintenance

Clay soils

• Clayey soils (> 30% clay) about 30 % of the total agricultural land area • Major part subsurface drained • High erosion and phosphorus losses • Benefits of subsurface drainage Lowering of ground water table Maintenance and development of soil structure Enhance infiltration Enhance root development and crop growth Reduction of surface runoff and erosion Reduction of particle phosphorus loading to surface waters Reduction of soluble mineral P leaching to surface waters Reduction of GHG emissions

Nutrient loading from

subsurface drained clay soils: experimental results in Finland

• Runoff fractions depend on soil properties, topography, season and weather conditions

• Water logging and increase of surface runoff under soil

compaction and aging subsurface drainage systems

• Supplementary drains or renewal of the old drainage system needed

• High losses of nitrogen via drains, especially after drain

installation • High losses of suspended solids and particle P via tile drains,

measured max. load 2.5-4 kg tot-P ha-1 a-1

• Preferential flow via cracks and other macropores from the tillage layer to bottom soil and tile drains

Research on subsurface drainage, Nummela field site 2007-2013

X ha

D Reference plot 32 m drain space, 3,4 ha

A Renewal of drainage 16 m -> 6 m drain space + thin textile, 2,9 ha

B Reference plot 16 m drain space, 1,3 ha

C Supplementary drainage 16 m -> 8 m drain space + gravel, 1,7 ha

- New pipe lines between the old tile drains, June 2008

- Drain spacing 16 m → 8 m - Average drain depth 1 m - Gravel as envelope - Gravel deposits every 7 m - Trench installation machine

Supplementary drainage, plot C

- Drain spacing 16 m → 6 m, June 2008 - Average drain depth 0.9 m - Thin textile as envelope - The old tile pipes were cut off - Trenchless installation/drainage plow - Subsoiling in autumn 2009

Renewal of drainage, plot A

Annual drain flow and tillage layer runoff, Nummela

Precipitation in different periods: Calibration 715 mm Exp I 646 mm Exp II 575 mm Exp III 526mm Exp IV 693 mm Exp V 573 mm

Nutrient loads in drain flow, Nummela

FLUSH-model

Reference: Lassi Warsta and Mika Turunen Aalto University, School of Engineering

3-D two-domain model Hydrology Soil temperature Snow accumulation and melt Erosion Nitrogen

Acid sulfate (AS) soils

The Litorina Sea (5000-1000 BP); today Baltic Sea Anaerobic conditions → Sulfide-bearing sediments (clay, silt) Oxidation of sulfide soils → Acid sulfate soils Elevation < 60 m above sea level Area of cultivated AS soils in Finland 43 000-130 000 ha (Soil Taxonomy, ILRI,FAO/UNESCO; (Yli-Halla et al. 1999)

Weppling, K. et al. (eds.) 1999.

WWF Finland Report No 11.

Environmental impacts of AS soils

Oxidation of sulfide soil under low groundwater table due to - Natural land uplift - Drainage - Evapotranspiration - Extreme drought → Release of acidity → Dissolution of metals High nitrogen storage in the bottom soil → High N loading potential to surface waters Deterioration of water quality and ecological status of surface waters Potentially high N2O emissions

pH 6.2 → pH 3.5

pH 3.9

Reduction of environmental loading from agricultural AS soils

Prevention of oxidation of potential AS soils by raising groundwater table depth Lower drainage intensity Controlled drainage Controlled + subirrigation Problem: Lateral seepage losses in oxidized soil layers Investigation of potential AS soils important

Use of controlled drainage and subirrigation

in AS soil, Lapfjärden experimental site EU Catermass Life+/BEFCASS projects

Figure ©Seija Virtanen, Finnish Drainage Foundation

CDP controlled subsurface drainage + pumping + plastic sheet

CD controlled subsurface drainage

ND normal subsurface drainage

Increased pH, decreased Al concentrations and acidity

under higher water table

Organic soils

• About 11% of the total agricultural field area • Efficient drainage needed • Drainage + fertilisation, liming and tillage → Higher microbiological activity → Decomposition of organic matter → Release of mineral nutrients → Increase of nutrient loading

(N, soluble P) → Increase of GHG emissions

emissions 50% of the total agricultural emissions; agriculture 17% of the total GHG emissions

Reduction of environmental loading from organic soils

• Lower drainage intensity higher groundwater restricts the biologically

active layer on the soil surface • Controlled drainage • Less fertilisation, liming and tillage → Lower microbiological activity → Lower release of nutrients → Lower GHG emissions → Less runoff

Reference: Merja Myllys and Kristiina Regina, Agrifood Research Finland MTT

Objectives

• Reduce nutrient loading to surface waters

• Reduce acid and metal loading from AS soils

to surface waters

• Enhance crop growth

Implementation

• 600 000 ha, 26% of total agricultural land

could be theoretically implemented

Criteria: slope < 2 %, good hydraulic conductity

• 50 000 ha implemented since 1995

• Support to farmers for investments and

maintenance

Questions in Finnish conditions: Impacts on

• Water balance and runoff components?

• Nutrient loading to surface waters?

• Crop yield and quality?

• Soil structure?

Controlled drainage

Controlled drainage, subirrigation and recycling of drainage waters

Irrigated field,

2-level pipe system

Reservoir for drainage waters

and irrigation water from the river

Wetlands and ponds

Objectives

• Flow retention

• Load reduction to surface waters

• Increase of biodiversity

• Diversification of landscape

• Storage of drainage waters for recycling by irrigation

• Multipurpose wetlands

Implementation

• 50 000 wetlands could be theoretically implemented

• Approximately 500 implemented

• Investment and maintenance support to farmers

Questions:

Impacts on water quality?

Design criteria?

Maintenance?

Chemical treatment of drainage waters

Boost retention of dissolved phosphorus

In agricultural wetlands and field ditches

Precipitation of dissolved P

- by dosing ferric sulfate to runoff water

- by contacting runoff water with solid P

sequestrial materials

Pour efficiency

in practice

Special locations

with high loading

Reference

Uusitalo et al. 2013

MTT Report 92

Restoration of basic drainage network

Environmental river engineering

Photo: Rainer Rosendahl

Objectives Increase biodiversity Improve water quality Diversify landscape Decrease need for restoration and maintenance of main ditches Means Sedimentation ponds, bottom dams re-meandering, 2 stage channels, biological erosion control Implementation Support for investments Research and demonstration projects Guidances Trained advisors and planners Questions Impact on water quality and loading? Impact on field drainage intensity?

Environmental river engineering and restoration

Järvenpää, SYKE 2004

A Natural small river

B Ditching

C The ditch needs restoration

D New restoration

Environmental river engineering

Photos: Kaisa Västilä

Ritobäcken, Sibo

Flow-plant-sediment interactions in environmentally preferable channels:

vegetative resistance modeling and cohesive sediment processes

Reference: Kaisa Västilä and Juha Järvinen Aalto University, School of Engineering

Concluding remarks • Land drainage induces both beneficial and harmful impacts on the environment • Environmental changes due land drainage vary between locations • Role of land drainage in environmental changes partly unknown • Subsurface drains are an important route for nitrogen and phosphorus

losses from field sections to surface water bodies

• Reduction of particle P transport to tile drains in clayey soils needed; means in drainage design and technique? • Adjustment of drainage intensity and use of controlled

drainage/subirrigation are expected to diminish harmful effects e.g. in AS soils and organic soils • Integration of land drainage and cultivation measures important (tillage, fertilisation, crop type, …) • Integration of water pollution control measures within field drainage and basic drainage network • Efficiency of e.g. controlled drainage, wetlands and environmental river

for pollution control in Finnish conditions?

Tack så mycket!

Photo Kaisa Västilä, Aalto University