Technologies

Submerged drains [Pays-Bas]

Création : 30 oct. 2015 12:29
Mise à jour : 5 juin 2019 15:44
Compilateur : Simone Verzandvoort
Rédacteur : –
Examinateurs : Fabian Ottiger, Alexandra Gavilano

Onderwaterdrains (NL)

technologies_1704 - Pays-Bas

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1. Informations générales

1.2 Coordonnées des personnes-ressources et des institutions impliquées dans l'évaluation et la documentation de la Technologie

Personne(s)-ressource(s) clé(s)

Spécialiste GDT:

Van de Akker Jan J.H.

Wageningen Environmental Research (Alterra)

Pays-Bas

Spécialiste GDT:

Simone Verzandvoort

Nom du projet qui a facilité la documentation/ l'évaluation de la Technologie (si pertinent)

Preventing and Remediating degradation of soils in Europe through Land Care (EU-RECARE )

Nom du ou des institutions qui ont facilité la documentation/ l'évaluation de la Technologie (si pertinent)

Wageningen Environmental Research (Alterra) - Pays-Bas

Nom du ou des institutions qui ont facilité la documentation/ l'évaluation de la Technologie (si pertinent)

Provincie Holland Zuid - Pays-Bas

Nom du ou des institutions qui ont facilité la documentation/ l'évaluation de la Technologie (si pertinent)

Provincie Utrecht - Pays-Bas

Nom du ou des institutions qui ont facilité la documentation/ l'évaluation de la Technologie (si pertinent)

LTO NOORD - Pays-Bas

Nom du ou des institutions qui ont facilité la documentation/ l'évaluation de la Technologie (si pertinent)

Waterschap Amstel, Gooi en Vecht - Pays-Bas

1.3 Conditions relatives à l'utilisation par WOCAT des données documentées

Le compilateur et la(les) personne(s) ressource(s) acceptent les conditions relatives à l'utilisation par WOCAT des données documentées:

Oui

2. Description de la Technologie de GDT

2.1 Courte description de la Technologie

Définition de la Technologie:

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 Description détaillée de la Technologie

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 de la Technologie

Galerie Médias

2.5 Pays/ région/ lieux où la Technologie a été appliquée et qui sont couverts par cette évaluation

Pays:

Pays-Bas

Région/ Etat/ Province:

The Netherlands/Province of Zuid-Holland

Autres spécifications du lieu:

Krimpenerwaard

Spécifiez la diffusion de la Technologie:

répartie uniformément sur une zone

Si la Technologie est uniformément répartie sur une zone, précisez la superficie couverte (en km2):

0,054

Commentaires:

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 de mise en œuvre de la Technologie

Si l'année précise est inconnue, indiquez la date approximative: :

il y a moins de 10 ans (récemment)

2.7 Introduction de la Technologie

Spécifiez comment la Technologie a été introduite: :

au cours d'expérimentations / de recherches
par le biais de projets/ d'interventions extérieures

stimulated by regional authorities

Commentaires (type de projet, 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 de la Technologie de GDT

3.2 Type(s) actuel(s) d'utilisation des terres, là où la Technologie est appliquée

Pâturages

Pâturage intensif/ production fourragère :

Prairies améliorées

cows

Commentaires:

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 Est-ce que l’utilisation des terres a changé en raison de la mise en œuvre de la Technologie ?

Est-ce que l’utilisation des terres a changé en raison de la mise en œuvre de la Technologie ?

Oui (Veuillez remplir les questions ci-après au regard de l’utilisation des terres avant la mise en œuvre de la Technologie)

Pâturages

Intensive grazing/ fodder production

3.4 Approvisionnement en eau

Approvisionnement en eau des terres sur lesquelles est appliquée la Technologie:

pluvial

3.5 Groupe de GDT auquel appartient la Technologie

dérivation et drainage de l'eau
gestion des eaux souterraines

3.6 Mesures de GDT constituant la Technologie

structures physiques

S4: Fossés isohypses, trous

modes de gestion

M7: Autres

Commentaires:

Main measures: management measures

Specification of other management measures: maintaining high groundwater level

3.7 Principaux types de dégradation des terres traités par la Technologie

dégradation chimique des sols

Cn: baisse de la fertilité des sols et réduction du niveau de matière organique (non causée par l’érosion)

dégradation physique des sols

Pw: saturation en eau des sols
Ps: affaissement des sols organiques, tassement des sols

dégradation hydrique

Hg: changement du niveau des nappes phréatiques (eaux souterraines) et des aquifères
Hp: baisse de la qualité des eaux de surface

Commentaires:

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 Prévention, réduction de la dégradation ou réhabilitation des terres dégradées

Spécifiez l'objectif de la Technologie au regard de la dégradation des terres:

réduire la dégradation des terres

4. Spécifications techniques, activités, intrants et coûts de mise en œuvre

4.1 Dessin technique de la Technologie

Spécifications techniques (associées au dessin technique):

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.

Auteur:

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

4.2 Informations générales sur le calcul des intrants et des coûts

autre/ monnaie nationale (précisez):

euro

Indiquez le taux de change des USD en devise locale, le cas échéant (p.ex. 1 USD = 79.9 réal brésilien): 1 USD = :

1,09

4.3 Activités de mise en place/ d'établissement

	Activité	Calendrier des activités (saisonnier)
1.	maintenance of drains and outlet in ditch
2.	installation of submerged drains	in dry periods

4.4 Coûts et intrants nécessaires à la mise en place

	Spécifiez les intrants	Unité	Quantité	Coûts par unité	Coût total par intrant	% des coût supporté par les exploitants des terres
Main d'œuvre	maintenance of drains and outlet in ditch	ha	1,0	30,14	30,14	100,0
Main d'œuvre	installation of submerged drains	ha	1,0	1980,0	1980,0	100,0
Coût total de mise en place de la Technologie					2010,14
Coût total de mise en place de la Technologie en dollars américains (USD)					1844,17

Commentaires:

Lifespan of the drains: 30 years

4.5 Activités d'entretien/ récurrentes

	Activité	Calendrier/ fréquence
1.	maintenance of submerged drains	several times in lifetime of drains (30 y)

4.6 Coûts et intrants nécessaires aux activités d'entretien/ récurrentes (par an)

	Spécifiez les intrants	Unité	Quantité	Coûts par unité	Coût total par intrant	% des coût supporté par les exploitants des terres
Autre	Annual cost incl maintenance	ha	1,0	127,0	127,0	100,0
Coût total d'entretien de la Technologie					127,0
Coût total d'entretien de la Technologie en dollars américains (USD)					116,51

Commentaires:

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 Facteurs les plus importants affectant les coûts

Décrivez les facteurs les plus importants affectant les coûts :

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. Environnement naturel et humain

5.1 Climat

Précipitations annuelles

< 250 mm
251-500 mm
501-750 mm
751-1000 mm
1001-1500 mm
1501-2000 mm
2001-3000 mm
3001-4000 mm
> 4000 mm

Spécifications/ commentaires sur les précipitations:

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

Zone agro-climatique

humide
subhumide

Thermal climate class: temperate

5.2 Topographie

Pentes moyennes:

plat (0-2 %)
faible (3-5%)
modéré (6-10%)
onduleux (11-15%)
vallonné (16-30%)
raide (31-60%)
très raide (>60%)

Reliefs:

plateaux/ plaines
crêtes
flancs/ pentes de montagne
flancs/ pentes de colline
piémonts/ glacis (bas de pente)
fonds de vallée/bas-fonds

Zones altitudinales:

0-100 m
101-500 m
501-1000 m
1001-1500 m
1501-2000 m
2001-2500 m
2501-3000 m
3001-4000 m
> 4000 m

Commentaires et précisions supplémentaires sur la topographie:

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 Sols

Profondeur moyenne du sol:

très superficiel (0-20 cm)
superficiel (21-50 cm)
modérément profond (51-80 cm)
profond (81-120 cm)
très profond (>120 cm)

Texture du sol (de la couche arable):

fin/ lourd (argile)

Matière organique de la couche arable:

abondant (>3%)

Si disponible, joignez une description complète du sol ou précisez les informations disponibles, par ex., type de sol, pH/ acidité du sol, capacité d'échange cationique, azote, salinité, 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 Disponibilité et qualité de l'eau

Profondeur estimée de l’eau dans le sol:

< 5 m

Disponibilité de l’eau de surface:

bonne

Qualité de l’eau (non traitée):

uniquement pour usage agricole (irrigation)

Commentaires et précisions supplémentaires sur la qualité et la quantité d'eau:

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 Biodiversité

Diversité des espèces:

moyenne

5.6 Caractéristiques des exploitants des terres appliquant la Technologie

Orientation du système de production:

commercial/ de marché

Revenus hors exploitation:

moins de 10% de tous les revenus

Niveau relatif de richesse:

moyen

Individus ou groupes:

individu/ ménage

Indiquez toute autre caractéristique pertinente des exploitants des terres:

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 Superficie moyenne des terres utilisées par les exploitants des terres appliquant la Technologie

< 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

Commentaires:

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

5.8 Propriété foncière, droits d’utilisation des terres et de l'eau

Propriété foncière:

individu, avec titre de propriété

Droits d’utilisation des terres:

individuel

Droits d’utilisation de l’eau:

loué

5.9 Accès aux services et aux infrastructures

santé:

pauvre
modéré
bonne

éducation:

pauvre
modéré
bonne

assistance technique:

pauvre
modéré
bonne

emploi (par ex. hors exploitation):

pauvre
modéré
bonne

marchés:

pauvre
modéré
bonne

énergie:

pauvre
modéré
bonne

routes et transports:

pauvre
modéré
bonne

eau potable et assainissement:

pauvre
modéré
bonne

services financiers:

pauvre
modéré
bonne

6. Impacts et conclusions

6.1 Impacts sur site que la Technologie a montrés

Impacts socio-économiques

Production

production fourragère

en baisse

en augmentation

Quantité avant la GDT:

10.7-12.4 tons DM/ha11575

Quantité après la GDT:

9.8-12.4 ton DM/ha10975

Commentaires/ spécifiez:

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.

qualité des fourrages

en baisse

en augmentation

Quantité avant la GDT:

275-417 kg N/ha

Quantité après la GDT:

235-389 kg N/ha

Commentaires/ spécifiez:

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

risque d'échec de la production

en augmentation

en baisse

Commentaires/ spécifiez:

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

Revenus et coûts

dépenses pour les intrants agricoles

en augmentation

en baisse

Commentaires/ spécifiez:

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

revenus agricoles

en baisse

en augmentation

Commentaires/ spécifiez:

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

charge de travail

en augmentation

en baisse

Commentaires/ spécifiez:

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

Autres impacts socio-économiques

inlet and drainage of water

Commentaires/ spécifiez:

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

Impacts socioculturels

institutions communautaires

affaibli

renforcé

Commentaires/ spécifiez:

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

institutions nationales

affaibli

renforcé

Commentaires/ spécifiez:

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

Commentaires/ spécifiez:

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.

Impacts écologiques

Cycle de l'eau/ ruissellement

qualité de l'eau

en baisse

en augmentation

Commentaires/ spécifiez:

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

drainage de l'excès d'eau

réduit

amélioré

Commentaires/ spécifiez:

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

Sols

humidité du sol

en baisse

en augmentation

Commentaires/ spécifiez:

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

compaction du sol

en augmentation

réduit

Commentaires/ spécifiez:

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

Biodiversité: végétale, animale

diversité animale

en baisse

en augmentation

Commentaires/ spécifiez:

no direct impact on breeding conditions for meadow birds

Réduction des risques de catastrophe et des risques climatiques

émissions de carbone et de gaz à effet de serre

en augmentation

en baisse

Commentaires/ spécifiez:

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

Autres impacts écologiques

Hazard towards adverse events

improved

reduced

Commentaires/ spécifiez:

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

Water management

harder

easier

Commentaires/ spécifiez:

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 Impacts hors site que la Technologie a montrés

dommages sur les infrastructures publiques/ privées

en augmentation

réduit

Commentaires/ spécifiez:

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

Commentaires/ spécifiez:

due to smaller differences in water levels between water management units

6.3 Exposition et sensibilité de la Technologie aux changements progressifs et aux évènements extrêmes/catastrophes liés au climat (telles que perçues par les exploitants des terres)

Changements climatiques progressifs

	Saison	Augmentation ou diminution	Comment la Technologie fait-elle face à cela?
températures annuelles		augmente	bien

Extrêmes climatiques (catastrophes)

Catastrophes météorologiques

	Comment la Technologie fait-elle face à cela?
pluie torrentielle locale	bien
tempête de vent locale	bien

Catastrophes climatiques

	Comment la Technologie fait-elle face à cela?
sécheresse	pas connu

Catastrophes hydrologiques

	Comment la Technologie fait-elle face à cela?
inondation générale (rivière)	bien

Autres conséquences liées au climat

	Comment la Technologie fait-elle face à cela?
réduction de la période de croissance	bien

Commentaires:

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 Analyse coûts-bénéfices

Quels sont les bénéfices comparativement aux coûts de mise en place (du point de vue des exploitants des terres)?

Rentabilité à court terme:

légèrement positive

Rentabilité à long terme:

positive

Quels sont les bénéfices comparativement aux coûts d'entretien récurrents (du point de vue des exploitants des terres)?

Rentabilité à court terme:

légèrement positive

Rentabilité à long terme:

positive

Commentaires:

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 de la Technologie

Si disponible, quantifiez (nombre de ménages et/ou superficie couverte):

De tous ceux qui ont adopté la Technologie, combien d'entre eux l'ont fait spontanément, à savoir sans recevoir aucune incitation matérielle, ou aucune rémunération? :

91-100%

Commentaires:

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 Points forts/ avantages/ possibilités de la Technologie

Points forts/ avantages/ possibilités du point de vue de l'exploitant des terres
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.

Points forts/ avantages/ possibilités du point de vue du compilateur ou d'une autre personne ressource clé
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 Faiblesses/ inconvénients/ risques de la Technologie et moyens de les surmonter

Faiblesses/ inconvénients/ risques du point de vue de l’exploitant des terres	Comment peuvent-ils être surmontés?
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.

Faiblesses/ inconvénients/ risques du point de vue du compilateur ou d'une autre personne ressource clé	Comment peuvent-ils être surmontés?
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.