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