The Netherlands is the largest exporter of agricultural products in Europe and the second-largest in the world. More than half of the country’s territory is covered by agricultural land, and the government, agribusinesses and farmers keep working together to ensure sustainable development of the sector. Amongst the challenges that still have to be tackled is soil salinization in coastal areas. Together with several research partners, Pipelife is currently testing self-sustaining drainage systems that might help prevent soil salinization in the future while storing freshwater for the summer months.
Historically, the flood-prone coastal areas in the Netherlands have been drained by placing horizontal drainage pipes in the soil and diverting the excess water to a ditch from where it eventually flows into the sea.
However, this approach has become problematic, especially during the dryer summer months. Freshwater from rainfall being transported into the sea and the high water needs of agriculture and other industries have resulted in lower groundwater levels and increased salinization in some regions of the country.
Maurice Meester, the Product Manager at Pipelife Netherlands explains: “There is less and less freshwater in the ground. Normally, if you dig into the ground a few centimeters deep, you would find freshwater. But nowadays, we use so much water that groundwater cannot restore itself sufficiently. Freshwater floats on saltwater, and with enough fresh water in the top layers of the soil, we can keep the saltwater at a normal depth. Nowadays, however, the saltwater slowly moves upwards since there is less and less freshwater on top to keep it at bay. That results in saltwater slowly seeping into the land, and, eventually, there are areas so salty that you cannot grow anything there anymore.”
A new, four-year pilot jointly launched by the research institutes Vertify and Deltares together with the University of Wageningen and Pipelife Netherlands is exploring a possible solution. The initial phase of the project focuses on the potential of rainwater harvesting for Dutch farmers, and the first harvesting system has already been installed.
The idea behind the pilot project is to turn existing drainage pipes into a closed network that can manage the groundwater levels within the field. All drainage pipes are connected to the main pipe, which leads into a collection well. By having all the water pass one central point, the groundwater level can be controlled at all times. Excess water after heavy rainfall can be infiltrated into the ground, stored in an enclosed ditch or put into a reservoir.
The innovative system is currently tested in an 8-acre field owned by a local farmer. The area already had a drainage system of around 8 km of pipes installed previously. Now, the drainage system has been closed to prevent the loss of water, and 6 km of Pipelife’s drainage pipes have been installed additionally. The installation works were completed in March.
Meester comments on the new system: “Normally, drainage is very simple; the idea is to get rid of the water. Now, we want to turn it around. We want to keep the water because it is becoming more and more scarce, but we need it for the future. And we need it for the farms which are an integral part of the Netherlands’ economy.”
The rainiest months in the Netherlands are October, November and December — during this period, the system’s capacity to collect water will be tested. Afterward, it will be possible to explore how efficiently the collected water can be returned to the soil during the drier summer months.
In addition, the new system has to be economically feasible to ensure that farmers are willing to use it. Therefore, the project focuses not only on potential environmental benefits but also on how closed drainage systems could help increase yields.
“We want to have as much water stored underground as possible at minimal investment costs for farmers — the return of investment has to be within 10 years,” Meester emphasizes, “The goal is to make sure that the farmer is the one who benefits most. Only then can we convince most farmers to invest in such systems.”
After the first testing year, it is also planned to research how closed drainage systems can be combined with irrigation systems and how they can help prevent nutrient loss from soils.
In addition, the pilot has a strong focus on transparency and education, informing farmers about the results and giving them an opportunity to share their own experiences.
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