Technologies

Submerged drains [Netherlands]

Onderwaterdrains (NL)

technologies_1704 - Netherlands

Completeness: 80%

1. معلومات عامة

1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Key resource person(s)

SLM specialist:

Van de Akker Jan J.H.

Wageningen Environmental Research (Alterra)

Netherlands

SLM specialist:
Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)
Preventing and Remediating degradation of soils in Europe through Land Care (EU-RECARE )
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Wageningen Environmental Research (Alterra) - Netherlands
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Provincie Holland Zuid - Netherlands
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Provincie Utrecht - Netherlands
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
LTO NOORD - Netherlands
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Waterschap Amstel, Gooi en Vecht - Netherlands

1.3 Conditions regarding the use of data documented through WOCAT

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:

نعم

2. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

Submerged drains are drains installed in grassland on peatsoils with the aims to decrease soil subsidence and emission of CO2 and N2O due to the oxidation of peat soil, and to maintain suitable groundwater levels in fields for grassland production and grazing.

2.2 Detailed description of the Technology

Description:

Contrary to usual drains, submerged drains are installed below ditchwater level. Submerged drains diminish the differences between ditch level and groundwater level in the fields by enabling the infiltration from ditch to field and the drainage from field to ditch.
In summer and dry periods the infiltration from ditch to field is much lower than the evapotranspiration of the grass, resulting in a lowering of the groundwater level some decimetres below ditch water level. With submerged drains the groundwater level is lowered less drastically because infiltration from ditch to field is improved. In winter and wet periods, fields are drained more quickly compared to conventional drainage.

Purpose of the Technology: Submerged drains diminish the differences between ditch level and groundwater level in the fields by enabling the infiltration from ditch to field and the drainage from field to ditch. Under peak rainfall events groundwater levels become less high and remain at high levels for shorter times than in fields without submerged drains.
Due to the increased groundwater level in summer the decomposition of the peat soil is reduced. As a result, the rate of soil subsidence is decreased and also the emission of greenhouse gases and of N and P released to the surface water.

Establishment / maintenance activities and inputs: The installation of submerged drains is done with common drainage installation machines. Submerged drains should be installed between 15 and 25 cm below the ditch water level, and between 45 and 75 cm below the soil surface. The drain pipes should have a diameter of at least 6 cm. The distance between drains is at most 6 m. Drain length is at most 300 m. Submerged drains can be installed in the length or width direction of a field. Drains must be installed level.

Natural / human environment: Submerged drains were designed for peat soils under permanent pasture for dairy farming. More than 70 % of Dutch peat soils are under this land use. Drainage of these peat soils results in subsidence, mainly by decomposition (oxidation) of the peat (partly by shrinkage and consolidation). This is an ongoing process, because every 10 to 15 year ditchwater levels are adapted to the lowered surface in order to enable dairy farming and to prevent the conversion to wetlands. Soil subsidence causes several problems: decreased suitability for grazing and grassland farming, increased flood risk, emission of greenhouse gases, damage to infrastructure (dikes, roads, foundations, sewerage networks) and increased cost of water management.

Submerged drains were tested with a network of practitioners and 10 dairy farmers in the Dutch peat soil area between 2011 and 2013 on an area of 20 ha.

2.3 Photos of the Technology

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment

بلد:

Netherlands

Region/ State/ Province:

The Netherlands/Province of Zuid-Holland

Further specification of location:

Krimpenerwaard

Specify the spread of the Technology:
  • evenly spread over an area
If the Technology is evenly spread over an area, specify area covered (in km2):

0,054

Comments:

Total area covered by the SLM Technology is 0.054 m2.

The measure was tested in three pilots in the areas Krimpenerwaard, Keulevaart and Demmerkiksekade. Each pilot covered two fields: one with submerged drains and one without. The area given refers to the pilot in the Krimpenerwaard.

2.6 Date of implementation

If precise year is not known, indicate approximate date:
  • less than 10 years ago (recently)

2.7 Introduction of the Technology

Specify how the Technology was introduced:
  • during experiments/ research
  • through projects/ external interventions
  • stimulated by regional authorities
Comments (type of project, etc.):

Since 2003 submerged drains have been applied on several experimental farms in The Netherlands. Implementations over larger areas (i.e. a water management unit, 'peilval' in Dutch) will be done in 2016.

2007: research on soil subsidence in the Western peat area following the large scale groundweter level lowering in the 1960s and 1970s signalled the high rate of soil subsidence (5-12 mm/y) (Van den Akker et al., 2007a)

2008: concerns about soil subsidence in the western peat area from the provincial autorities of Noord-Holland, Utrecht and Zuid-Holland in the policy document 'Voorloper Groene Hart' (2008)

2008-2012: various research projects to test the effectiveness of submerged drains to reduce soil subsidence and to improve conditions for dairy farming, and on the effects for water quality: www.waarheenmethetveen.nl, Hoving et al. (2008), Woestenburg (2009), EU project EUROPEAT, Woestenburg et al. 2009; Jansen et al., 2010; Hendriks and Van den Akker, 2012; Hoving et al. (2008, 2009, 2013)

2011-2012: research on the Peat Area Innovation Centre (VIC) to test effects of submerged drainage in combination with dynamic groundwater level management (Hoving et al., 2013)

2012- testing by research instsiutes of economic viability of submerged drains with regard to water level management and agricultural productivity, on assignment of the province Noord-Holland, waterboard Hollands Noorderkwartier.

2009-2011: various modelling studies assigned by the provinces and water boards of the western peat meadow area on the effects of submerged drains for the demand for inlet and discharge of water and effects on the decomposition of peat and the water quality.

2011: model research on effects of submerged drains on the water demand of the western peat area until 2050 under climate change (Van den Akker et al., 2011)

2010-2013 experimental research in 3 pilots initiated by the province of Utrecht and Zuid-Holland, four water boards and the farmers' organisation LTO Noord. Aim: to test if the application of submerged drains results in larger amounts of water to supply and to discharge from the peat meadow area, and to test if the submerged drains result in a larger load of nutrients to ditches,

3. Classification of the SLM Technology

3.2 Current land use type(s) where the Technology is applied

Grazing land

Grazing land

Intensive grazing/ fodder production:
  • Improved pastures
  • cows
Comments:

Major land use problems (compiler’s opinion): The major land use problems in the Western Dutch peat soil area is soil subsidence due to the lowering of the groundwater level in the 1960s and 1970s. The soil subsidence amounts to 0-2.5 cm per year. It is mainly caused by the oxidation of peat soil, which releases nutrients to soil and surface water, and CO2 and N2O to the atmosphere. The soil subsidence causes several problems:
- damage to buildings and infrastructure
- increasing costs of water management: high groundwater levels require pumping of water to enable agricultural use, and storage of rainfall excess water during peak rainfall events
- drainage of nature reserves to lowered agricultural land
- water pollution: the lowering of the groundwater level causes upward seepage of nutrient-rich water to polders
- greenhouse gas emissions (2-3% of total CO2 emissions in The Netherlands)
- loss of peat soils (2% per year in the NL)
- increased flood risk (due to combination with sealevel rise)

Major land use problems (land users’ perception): Grassland and arable farming are hampered by high groundwater levels due to a lowered bearing capacity and too wet conditions for crops. Maintaining the groundwater level at a level high enough to prevent the decomposition of peat soil would imply a conversion to wetlands and forest swamps. This is not acceptable to various kinds of land users (nature managers, farmers, users of built-up area). This would also mean the loss of the cultural historic open landscape and habitat for meadow birds, strongly reduced economic possibilities and an increased demand of water from the rivers (view of water managers and governments).

Future (final) land use (after implementation of SLM Technology): Grazing land: Gi: Intensive grazing/ fodder production

Longest growing period in days: 270Longest growing period from month to month: April-October
Livestock density: > 100 LU /km2

3.3 Has land use changed due to the implementation of the Technology?

Has land use changed due to the implementation of the Technology?
  • Yes (Please fill out the questions below with regard to the land use before implementation of the Technology)
Grazing land

Grazing land

  • Intensive grazing/ fodder production

3.4 Water supply

Water supply for the land on which the Technology is applied:
  • rainfed

3.5 SLM group to which the Technology belongs

  • water diversion and drainage
  • ground water management

3.6 SLM measures comprising the Technology

structural measures

structural measures

  • S4: Level ditches, pits
management measures

management measures

  • M7: Others
Comments:

Main measures: management measures

Specification of other management measures: maintaining high groundwater level

3.7 Main types of land degradation addressed by the Technology

chemical soil deterioration

chemical soil deterioration

  • Cn: fertility decline and reduced organic matter content (not caused by erosion)
physical soil deterioration

physical soil deterioration

  • Pw: waterlogging
  • Ps: subsidence of organic soils, settling of soil
water degradation

water degradation

  • Hg: change in groundwater/aquifer level
  • Hp: decline of surface water quality
Comments:

Main type of degradation addressed: Cn: fertility decline and reduced organic matter content, Ps: subsidence of organic soils, settling of soil

Secondary types of degradation addressed: Pw: waterlogging, Hg: change in groundwater / aquifer level, Hp: decline of surface water quality

Main causes of degradation: other human induced causes (specify) (lowering of the groundwater level to enable agricultural use of the peat soils results in soil subsidence and detioration of ground- and surface water quality due to capillary rise)

Secondary causes of degradation: change in temperature (higher temperatures under climate change increase the decomposition rate of peat soil; subsidence and CO2 emissions will increase by 75%), change of seasonal rainfall (decrease in summer rainfall (23% in warm and dry CC scenario for NL)), inputs and infrastructure: (roads, markets, distribution of water points, other, …) (maintenance of high water levels in built-up and natural areas increases the difference in groundwater level with agricultural land onb peat soils)

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:
  • reduce land degradation

4. Technical specifications, implementation activities, inputs, and costs

4.1 Technical drawing of the Technology

Technical specifications (related to technical drawing):

The picture shows a cross section through an agricultural field, bounded by two ditches. A submerged drain (yellow bar in the picture) is installed at 80 cm below the soil surface. It ends in the ditch on the left side at 20 cm below the water level in the ditch. The dotted line indicates the position of the groundwater table in the situation without the submerged drain; the continuous blue line indicates the position in the situation where the submerged drain is installed. The lines show that in summer the groundwater level is raised to nearly the level of the ditch water by the submerged drain, whereas the level would be approximately 30 cm lower without the drain.
In winter, in the situation with the submerged drain, the groundwater level is around 40 cm below the soil surface. This enables the farmer to use the field for grazing or to traffic the field. However, in the situation without the drain, the groundwater level nearly reaches the soil surface in the centre of the field, impeding traffic or grazing on the field.

Technical knowledge required for field staff / advisors: moderate (Estimates of economic benefits due to increased grass production and grazing periods vary between years with meteorological conditions.)

Technical knowledge required for land users: moderate (Specific conditions apply to the dimensions and positioning of submerged drains in the fields. Level position and lebgth are critical.)

Technical knowledge required for companies installing the drains: moderate (Specific conditions apply to the dimensions and positioning of submerged drains in the fields. Level position and lebgth are critical. Soil must have sufficient bearing capacity during installation.)

Technical knowledge required for water board: moderate (submerged drains increase the water supply and discharge from groundwater level management units. Additional pumping effort can be prevented by informed water level management.)

Technical knowledge required for researchers: (the implications of submerged drains on the water management in an entire management unit should be explored using coupled hydraulic and rainfall-runoff models.)

Main technical functions: improvement of topsoil structure (compaction), maintaining soil organic matter

Secondary technical functions: increase of infiltration, increase / maintain water stored in soil, drainage of excess rainfall

Other type of management: Maintaining high groundwater levels.

Author:

Jan van den Akker, Alterra, Droevendaalsesteeeg 3, 6708 PB Wageningen, The Netherlands

4.2 General information regarding the calculation of inputs and costs

other/ national currency (specify):

euro

If relevant, indicate exchange rate from USD to local currency (e.g. 1 USD = 79.9 Brazilian Real): 1 USD =:

1,09

4.3 Establishment activities

Activity Timing (season)
1. maintenance of drains and outlet in ditch
2. installation of submerged drains in dry periods

4.4 Costs and inputs needed for establishment

Specify input Unit Quantity Costs per Unit Total costs per input % of costs borne by land users
Labour maintenance of drains and outlet in ditch ha 1,0 30,14 30,14 100,0
Labour installation of submerged drains ha 1,0 1980,0 1980,0 100,0
Total costs for establishment of the Technology 2010,14
Total costs for establishment of the Technology in USD 1844,17
Comments:

Lifespan of the drains: 30 years

4.5 Maintenance/ recurrent activities

Activity Timing/ frequency
1. maintenance of submerged drains several times in lifetime of drains (30 y)

4.6 Costs and inputs needed for maintenance/ recurrent activities (per year)

Specify input Unit Quantity Costs per Unit Total costs per input % of costs borne by land users
Other Annual cost incl maintenance ha 1,0 127,0 127,0 100,0
Total costs for maintenance of the Technology 127,0
Total costs for maintenance of the Technology in USD 116,51
Comments:

Machinery/ tools: establishment and installation require specific skills and machinery; hired, not done by the farmer himself

Investment costs of 1500-1800 €/ha are based on submerged drains at 6 m distance. Costs per m of drain establishment based on drains of 6 cm diameter. Costs based on practical experience from farmers. Drains may have a lifetime of 30 years and require little maintenance.

Specific skills and machinery are required for installation and maintenance, hired from a drainage company. The farmer must only ensure that the outlets of the drains in the ditches remain open and undamaged.

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

We do not have information on specific cost items, only on establishment costs ad between 1500 and 1800 euro/ha, and annual cost of 117 €/ha incl maintenance, assuming a 20-year life time. Establishment costs can also be expressed per m of drain, i.e. 1.10 EURO per m including materials (drain of 6 cm diameter).

Determinate factors include size and geometry of fields; installation in the length direction is cheaper, and results in fewer outlets in the receiving ditch.

5. Natural and human environment

5.1 Climate

Annual rainfall
  • < 250 mm
  • 251-500 mm
  • 501-750 mm
  • 751-1,000 mm
  • 1,001-1,500 mm
  • 1,501-2,000 mm
  • 2,001-3,000 mm
  • 3,001-4,000 mm
  • > 4,000 mm
Specifications/ comments on rainfall:

Distribution of rainfall over the year: 23% (winter), 19% (spring), 27% (summer) and 31% (autumn)

Agro-climatic zone
  • humid
  • sub-humid

Thermal climate class: temperate

5.2 Topography

Slopes on average:
  • flat (0-2%)
  • gentle (3-5%)
  • moderate (6-10%)
  • rolling (11-15%)
  • hilly (16-30%)
  • steep (31-60%)
  • very steep (>60%)
Landforms:
  • plateau/plains
  • ridges
  • mountain slopes
  • hill slopes
  • footslopes
  • valley floors
Altitudinal zone:
  • 0-100 m a.s.l.
  • 101-500 m a.s.l.
  • 501-1,000 m a.s.l.
  • 1,001-1,500 m a.s.l.
  • 1,501-2,000 m a.s.l.
  • 2,001-2,500 m a.s.l.
  • 2,501-3,000 m a.s.l.
  • 3,001-4,000 m a.s.l.
  • > 4,000 m a.s.l.
Comments and further specifications on topography:

Altitudinal zone: 0-100 m a.s.l. (Submerged drains are designed for polders in lowland areas on peat soils)
Landforms: Plateau/plains (submerged drains are designed to drain level fields)
Slopes on average: Flat (submerged drains are designed to drain flat terrain, based on hydraulic prressure head differences between field and ditch)

5.3 Soils

Soil depth on average:
  • very shallow (0-20 cm)
  • shallow (21-50 cm)
  • moderately deep (51-80 cm)
  • deep (81-120 cm)
  • very deep (> 120 cm)
Soil texture (topsoil):
  • fine/ heavy (clay)
Topsoil organic matter:
  • high (>3%)
If available, attach full soil description or specify the available information, e.g. soil type, soil PH/ acidity, Cation Exchange Capacity, nitrogen, salinity etc.

Soil depth on average: Very deep (if the peat substrate is considered as part of the soil profile, soils are deeper than 120 cm, with peat packages up to 13 m in some parts of the western Dutch peatland area) and shallow (If the top of the C-horizon is considered as the bottom of the soil profile. C-horizons typically start at 15-30 cm below the soil surface)
Soil texture is fine/heavy (for peat soils with a clayey top layer. In peat soils without such a top layer, a soil texture indication is not applicable. Peat soils are defined as having at least 40 cm of peat in the top 80 cm)
Soil fertility is very high (peat soils are able to supply ample nutrients to plants provided that they are well drained)
Topsoil organic matter is high (Organic matter contents in the topsoil are above 20%. Peat soils are defined as having at least 40 cm of peat in the top 80 cm according to the Dutch soil classification system)
Soil drainage/infiltration is poor/none (peat soils inherently have poor drainage due to their low position with reference to the groundwater level in the regional water system. Values of Ksat reported 2.9-5.0 cm/d)
Soil water storage capacity is very high (the soil water storage capacity is very high due to the large pore space (0.70-0.90 m3/m3))

5.4 Water availability and quality

Ground water table:

< 5 m

Availability of surface water:

good

Water quality (untreated):

for agricultural use only (irrigation)

Comments and further specifications on water quality and quantity:

Ground water table: <5m (Average lowest grondwater level in the pilot region is 5-10 cm below the soil surface; average highest level 55-65 cm)
Availability of surface water is good (surface water is amply available due to the low position of the peat soil area compared to the mean sea level, and due to the dense network of ditches and other surface water conveyors and bodies) and excess (surface water levels are under continuous control by the water boards. Therefore flood situations do not occur, but under high-intensity rainfall events fields may submerge)
Water quality (untreated) is for agriculutral use only (Irrigation, surface and groundwater can be used for agriculture without treatment. Nutrient rich water emerging by capillary rise in polders may not be suitable for nature.)
Biodiversity is medium (the grasslands in the western peatsoil area are suitable habtitats for meadow birds)

5.5 Biodiversity

Species diversity:
  • medium

5.6 Characteristics of land users applying the Technology

Market orientation of production system:
  • commercial/ market
Off-farm income:
  • less than 10% of all income
Relative level of wealth:
  • average
Individuals or groups:
  • individual/ household
Indicate other relevant characteristics of the land users:

Difference in the involvement of women and men: Executives of agricultural enterprises in The Netherlands are usually men.
Population density: 200-500 persons/km2
Annual population growth: 1% - 2%
100% of the land users are average wealthy and own 100% of the land.
Off-farm income specification: Dairy farmers in this part of The Netherlands spend 100% of their time on the farm. Sometimes their wives have jobs earning off-farm income.
Market orientation is commercial/market (intensive dairy farming in the NL produces for the market)

5.7 Average area of land used by land users applying the Technology

  • < 0.5 ha
  • 0.5-1 ha
  • 1-2 ha
  • 2-5 ha
  • 5-15 ha
  • 15-50 ha
  • 50-100 ha
  • 100-500 ha
  • 500-1,000 ha
  • 1,000-10,000 ha
  • > 10,000 ha
Comments:

On average, Dutch dairy farms have 50 ha grazing land for 90 dairy cows (2013).

5.8 Land ownership, land use rights, and water use rights

Land ownership:
  • individual, titled
Land use rights:
  • individual
Water use rights:
  • leased

5.9 Access to services and infrastructure

health:
  • poor
  • moderate
  • good
education:
  • poor
  • moderate
  • good
technical assistance:
  • poor
  • moderate
  • good
employment (e.g. off-farm):
  • poor
  • moderate
  • good
markets:
  • poor
  • moderate
  • good
energy:
  • poor
  • moderate
  • good
roads and transport:
  • poor
  • moderate
  • good
drinking water and sanitation:
  • poor
  • moderate
  • good
financial services:
  • poor
  • moderate
  • good

6. Impacts and concluding statements

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

fodder production

decreased
increased
Quantity before SLM:

10.7-12.4 tons DM/ha11575

Quantity after SLM:

9.8-12.4 ton DM/ha10975

Comments/ specify:

Net grass yields (DM) measured on experimental plots. May slightly decrease due to SMD, but less loss due to trampling, increased length of grazing season. This delivers 500 kg DM/ha extra fodder produced and 30 extra grazing days.
But also loss possible: From 11575 kg DM/ha to 10975 kg DM/ha Decrease in grass yield is possible between 3 and 9%. This does not take into account losses due to tramping in situation without drains and longer grazing season under SMD.

fodder quality

decreased
increased
Quantity before SLM:

275-417 kg N/ha

Quantity after SLM:

235-389 kg N/ha

Comments/ specify:

Slight decrease in N and P content of grass, but quality of grass is expected to improve due to better drained soil and improved bearing capacity

risk of production failure

increased
decreased
Comments/ specify:

SMD enable a longer grazing season, increased bearing capacity and reduced risk of flooding of fields

Income and costs

expenses on agricultural inputs

increased
decreased
Comments/ specify:

reduced additional feedstock; benefits of extra grass yields and grazing days amount to 171 euro/ha

farm income

decreased
increased
Comments/ specify:

net benefits of installing SMD are approx. 54 euro per ha per year

workload

increased
decreased
Comments/ specify:

trafficability and workability of fielfds improved due to drier topsoil conditions and increased bearing capacity

Other socio-economic impacts

inlet and drainage of water

Comments/ specify:

SMD require an increased inlet and drainage of water in the ditches by the water board, increased pumping hours: 10-22% in dry years; 7-12% in wet years.
Inlet: extra 36-86 mm/y in dry years, 19-45 mm in wet years
Drainage: 17-59 mm in dry years; 33-60 in wet year

Socio-cultural impacts

community institutions

weakened
strengthened
Comments/ specify:

Community of Practice on SMD in peat soils enabled knowledge transfer between land users, research insttitutes, farmer's association and authorities

national institutions

weakened
strengthened
Comments/ specify:

The CoP has informed water boards and provinces in the part of The Netherlands with problems due to soil subsidence

Improved livelihoods and human well-being

decreased
increased
Comments/ specify:

The long-term experiments in The Netherlands, pilots and activities of the farmers organisation LO Nederland, the Veenweide Informatie Centrum and the Community of Practice Submerged Drainage on Peat soils have increased the understanding of participating farmers of submerged drainage, the water accounting of their land, soil and soil quality. Tjey acquired practical knowledge on the implementation of the technology. Participating farmers continue to exchange knowledge and intend to extend the area under SMD. As a result of the pilots and the activities of the Community of Practice, interest for submerged drainage was raised among other dairy farmers, policy makers and authorities.

Ecological impacts

Water cycle/ runoff

water quality

decreased
increased
Comments/ specify:

slight decrease of export of N, P and SO4 to the surface water

excess water drainage

reduced
improved
Comments/ specify:

SMD increased drainage by 20-65 mm per year in 2011 and 2012

Soil

soil moisture

decreased
increased
Comments/ specify:

SMD increased infiltration by 8-93 mm per year in 2011 and 2012

soil compaction

increased
reduced
Comments/ specify:

decreased soil subsidence to 50% (reductions of 3-6 and 5-8 mm/year)

Biodiversity: vegetation, animals

animal diversity

decreased
increased
Comments/ specify:

no direct impact on breeding conditions for meadow birds

Climate and disaster risk reduction

emission of carbon and greenhouse gases

increased
decreased
Comments/ specify:

decreased GHG emissions in CO2 eq: 6.8-13.5 t/ha per year (pilot Keulevaart) and 11.3-18.1 (pilot Demmeriksekade)

Other ecological impacts

Hazard towards adverse events

improved
reduced
Comments/ specify:

quicker lowering of groundwater table after extreme rainfall events (1-5 days)

Water management

harder
easier
Comments/ specify:

More easy water management in polders: Fewer sub-polders with fixed ditch water level; possibility to create areas with high and low surface levels

6.2 Off-site impacts the Technology has shown

damage on public/ private infrastructure

increased
reduced
Comments/ specify:

reduced costs of infrastructure protection (30% or 3.5 M€/year until 2100 in the Frisian peat meadow area)

Cost of regional water management

increased
decreased
Comments/ specify:

due to smaller differences in water levels between water management units

6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Gradual climate change

Gradual climate change
Season increase or decrease How does the Technology cope with it?
annual temperature increase well

Climate-related extremes (disasters)

Meteorological disasters
How does the Technology cope with it?
local rainstorm well
local windstorm well
Climatological disasters
How does the Technology cope with it?
drought not known
Hydrological disasters
How does the Technology cope with it?
general (river) flood well

Other climate-related consequences

Other climate-related consequences
How does the Technology cope with it?
reduced growing period well
Comments:

Under extreme rainfall events, submerged drains cannot prevent that the groundwater level rises to above the soil surface. However, the groundwater level will fall more quickly with submerged drainas than without, on average to 10 cm lower levels.

Effects of dry summers have not yet been measured in experiments.

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?
Short-term returns:

slightly positive

Long-term returns:

positive

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?
Short-term returns:

slightly positive

Long-term returns:

positive

Comments:

A longer grazing season and the extra yield of fodder are the basis for a viable implementation of submerged drainage for land users. The CBA considers establishment and maintenance costs together: establishment costs of € 1800,-/ha, discounted over 20 years, including maintenance, result in annual cost of € 117,-/ha (6.5% of the investment). Benefits include 500 kg DM/ha extra grass use and 30 extra grazing days. This would yield € 171/ha, resulting in a net saldo of € 54,-. In addition SMD are an investment in sustainable soil management, resulting in an increased economic value of the land in the long term.

6.5 Adoption of the Technology

If available, quantify (no. of households and/ or area covered):

13

Of all those who have adopted the Technology, how many did so spontaneously, i.e. without receiving any material incentives/ payments?
  • 91-100%
Comments:

13 land user families have adopted the Technology without any external material support

Comments on spontaneous adoption: The area under submerged drainage implemented by the 10 dairy farmers from the Community of Practice is 20 ha. The area under SMD in the three pilots described in this questionnaire is roughly an additional 0.05 km2 per farm.

There is a moderate trend towards spontaneous adoption of the Technology

Comments on adoption trend: Due to the growing interest in the peat soil area because of the relevance for climate mitigation and the economic risks of soil subsidence there is growing interest in SMD in combination iwth dynamic groundwater level management to reduce the rate of soil subsidence. Subsidy arrangements are in preparation, which will stimulate adoption of the technology by more dairy farmers.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
Submerged drains increase the number of days with a good bearing capacity of grassland, and therefore enable a longer grazing season and less trampling of grass.
Higher effective yield in total.
Short term: slightly cost effective. Long term: good cost effective.
Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Submerged drains allow a strong reduction of soil subsidence and GHG emissions (at least 50%, even >50% if combined with higher ditch water levels).

How can they be sustained / enhanced? Further implementation by dairy farmers in the peat-meadow area. For this purpose the Community of Practice is recommended, as well as the arrangement of subsidies and the active involvement of regional government and water board. This applies to all mentioned advantages.
The quality of surface water in ditches will slightly improve.
Less problems with difference between subsiding soil surfaces and constant water levels in lakes and high water ditches (along houses).
Less sub-polders with a certain fixed ditch water level, and possibility to create areas with a high surface level (with submerged drains) and a low surface level (without SD).

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

Weaknesses/ disadvantages/ risks in the land user’s view How can they be overcome?
Grass yield is lower due to reduced mineralization of nitrogen. Yield could be increased due to better usage of manure (better NUE). On the other hand yield is increased due to increased number of days with a good bearing capacity of grassland, and a longer grazing season and less trampling of grass.
Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view How can they be overcome?
Submerged drains require more inlet water to polders. Reduction of inlet requirement is possible by smart water management. This implies water level margins of +/- 10 cm and the use of weather forecasting.
Submerged drains require a bit more pumping to drain water under extreme rain events.

7. References and links

7.1 Methods/ sources of information

7.2 References to available publications

Title, author, year, ISBN:

Several reports on submerged drainage are available from Alterra, Wageningen UR (in Dutch). The report used for this WOCAT QT is:Effecten van onderwaterdrains in peilvak 9 van polder Groot-Wilnis Vinkeveen : modelstudie naar de effecten van onderwaterdrains op maaivelddaling, waterbeheer, wateroverlast en waterkwaliteit in peilvak 9 Author(s)Hendriks, R.F.A.; Akker, J.J.H. van den; Jansen, P.C.; Massop, H.Th.L. SourceWageningen : Alterra Wageningen UR, 2014 (Alterra-rapport 2480) - p. 124Other literature (in Dutch): Waarheen met het veen. Woestenberg, M. 2009. Uitegeverij Landwerk and Alterra, Wageningen URhttp://www.levenmetwater.nl/static/media/files/Boek_wmhv_def.pdf

Available from where? Costs?

Alterra Reports are available atlibrary.wur.nl

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