Water retention area with land use adapted to the ground water levels and flooding frequencies, at the primary sea wall (Research project 'COMTESS')
In the 19th and 20th century land was reclaimed from the sea to make use of the exposed fertile soils for agriculture through a process known as ‘impoldering’. The reclaimed land is now characterized by intensive grazing and cropland. This is a region where agriculture is the most important form of land use. However, the land needs to be regularly drained. Given the expected increase in precipitation in winter due to climate change, the corresponding increase in freshwater discharge needs to be managed. Furthermore, the periods when natural discharge into the sea oc-curs are likely to decrease – because of rising sea levels also caused by climate change. Consequently, in winter and spring, greater quantities of freshwater will need to be pumped into the sea rather than discharged naturally at the low or ‘ebb’ tide. Specially embanked water retention polders will be required to temporarily impound water as part of a multifunctional approach to coastal zone management.
Purpose of the Technology: These retention polders could be a cost-effective alternative to expensive invest-ments in extra pumping capacities to prevent submergence of low-lying cultivated areas. The primary aim is to restrict floods to the retention polders when the drain-age network is overburdened and cannot deal with the predicted extra demands in the future. The high evapotranspiration from the open waterbody, and the reeds growing within, will also help with reducing the amount of water. During dry sum-mers, the water in the retention polder could also be put to creative use as a source of irrigation. Another potential advantage is that subsurface saltwater intrusion in the region could be prevented by the freshwater-filled polders. During extreme storm surges and in the rare case of breaches in the sea wall, the retention polders would serve as an extra line of defence by holding seawater.
Establishment / maintenance activities and inputs: An embankment enclosing approx. 3,000 ha will be able to store up to 25,000,000 m³ of water. This will improve the drainage of an area of approx. 49,000 ha. The invest-ment for building this water retention area is high – but for the reasons stated it serves a necessary purpose at a cost which is lower than the alternative – increased pumped drainage installations. Maintenance costs will be lower than the drainage alternative as only the integrity of the embankment needs to be monitored regularly. Agricultural land use within the polders is adapted to higher water levels and occa-sional flooding.
Natural / human environment: However within the proposed retention polders – the areas enclosed by the em-bankment - a change from the current intensive grazing for dairy farming and cropland to extensive grazing, open waters and wetlands covered with reeds will take place. The reeds can be harvested for their commercial value as biomass for renewable energy generation, or for other applications (e.g. thatching of roofs or industrial raw material). According to recent investigations, natural reeds growing in brackish water produce as much biomass as maize cultivated for biogas use. In con-trast to maize, no investments in tillage, fertilizer or biocides are necessary for these naturally growing reed stands. Thus the proposed land use provides an economic alternative to the current production system.
Localização: Landkreis Aurich, Germany, Lower Saxony, Alemanha
Nº de sites de tecnologia analisados:
Difusão da tecnologia:
Em uma área permanentemente protegida?:
Data da implementação: 10-50 anos atrás
Tipo de introdução
| Especifique a entrada | Unidade | Quantidade | Custos por unidade (Euro) | Custos totais por entrada (Euro) | % dos custos arcados pelos usuários da terra |
| Mão-de-obra | |||||
| Labour | 1,0 | 21000000,0 | 21000000,0 | ||
| Equipamento | |||||
| Machine use | 1,0 | 9000000,0 | 9000000,0 | ||
| Material de construção | |||||
| 750000,0 | |||||
| Custos totais para a implantação da tecnologia | 30'000'000.0 | ||||
| Custos totais para o estabelecimento da Tecnologia em USD | 31'914'893.62 | ||||
| Especifique a entrada | Unidade | Quantidade | Custos por unidade (Euro) | Custos totais por entrada (Euro) | % dos custos arcados pelos usuários da terra |
| Mão-de-obra | |||||
| Labour | 800,0 | ||||
| Equipamento | |||||
| Machine use | 300,0 | ||||
| Material de construção | |||||
| Earth | 100,0 | ||||
Under wet conditions in the retention area a crop production is not possible any more.
Under wet conditions in the retention area an intensive fodder production is not possible any more.
Under wet conditions in the retention area the optiomal fodder quality can not ensured any more.
Quantidade anterior à GST: 49000 ha
Quantidade posterior à GST: 46000 ha
For the whole catchment area a loss of approx. 3,000 ha (size of retention area).
Due to reduction of saline influx
Only adjusted land use takes place within retention area, therefore the expenses are reduced.
Due to land use adapted to the conditions the typical land use is not possible and a diversitfication will take place with reed mowing and extensive grazing in the retention area.
Diversification of landscape by building the retention area will increase the attractivity for recreation and tourists.
Less intensive land use results in more diversity and conservation of regional species and habitats.
Typical for the region are wet situations. These typical wet conditions are restored by cessation of drainage system within the retention area.
Updwelling of saline groundwater is prevented by increased water level in the retention area.
By water in the retention are the recharge of groundwater will increase and prevent salinization.
Instead of pumping water into the sea a higher amount is evapotranspirated naturally.
Typical for the region are wet situations. These typical wet conditions are restored by cessation of drainage system within the retention area.
By water in the retention are the recharge of groundwater will increase and prevent salinization.
By wetter conditions the soil organic matter will be increased.
Growth of reeds
By diversification of land use the number of species will be increased, especially due to extensive land use.
By diversification of land use the number of species will be increased, especially due to extensive land use.
By diversification of land use the number of habitats will be increased.
Modelled is the global warming potential by gas emissions. Not yet clear if it is benefit or disadvantage. Model will show.
Water from retention area.
Water stored in retention area can be used for irrigation during dry summer months.
Measured m3 of excess water in the catchment area, leading to floods or needs to be pumped. Exact values from modelling will be added as soon as possible!
Retention area to tackle impact of climate change.
Retention area to tackle impact of climate change.
