A farm in Anna Paulowna in the Netherlands is pioneering new methods to conserve fresh water and reduce agricultural pollution through an ambitious project known as Zoetwaterboeren. At the Hoeve Lotmeer farm, experts have installed and tested a circular water system as well as a drainage water purification system designed to protect crops during dry periods and improve local water quality.
The project is a joint effort involving Wageningen University and Research, research centre Vertify, Deltares, and installation specialist Pipelife, working in close cooperation with local arable farmer Klaas Schenk.
Storing winter water below ground for use in dry seasons
The circular system captures fresh drainage water from the fields, stores it underground during winter, and later pumps it up for irrigation when dry conditions develop. According to project leader Vince Kaandorp from Deltares, the team has built an Aquifer Storage and Recovery system, which is relatively new in arable farming.
“We first had to examine the depth of the subsurface, how to pre-treat the water, and the volume we could store. At a depth of twenty three metres, we found a suitable layer of coarse sand,” Kaandorp explained. Water is now being stored at a rate of eight cubic metres per hour.
The full system includes adjustable drainage pipes to collect water, a surface storage basin with a capacity of one thousand cubic metres, and an infiltration system to place the water into the subsurface. Online monitoring tools help researchers see water movement and track changes in groundwater levels in real time.
Increasingly unpredictable rainfall patterns and longer dry periods pose major risks for farms located below sea level, such as Hoeve Lotmeer. Salty groundwater is rising into the root zone, reducing the availability of fresh irrigation water. At the same time, stricter European water quality rules require farmers to reduce nutrients flowing into nearby waterways.
“Collecting and storing drainage water means fewer nutrients enter local waters, including the nearby Amstel Lake,” Kaandorp said.
Farmer Klaas Schenk believes the system will strengthen the future of farming in the area. “It removes the need for external fresh water sources and reduces our environmental impact. This gives new possibilities for arable farming in a changing climate.”
New filter removes almost all nitrate and phosphate from drainage water
In late 2024, Hoeve Lotmeer also became the first location in the world to install a combined woodchip and iron sand filter to cleanse drainage water. Early test results show that the filter removes almost all nitrate and phosphate before the water reaches surrounding surface waters.
Researchers say this method is particularly useful for crops such as onions, potatoes, vegetables, and flower bulbs, where nutrient leakage to water is difficult to avoid. Woodchips encourage naturally present bacteria to break down nitrate, while iron sand, a leftover product from drinking water treatment, traps phosphate.
“Both nitrate and phosphate were entering surface water through field drainage,” said Deltares expert Stefan Jansen. “Combining woodchips with iron sand gives a powerful result.”
The filter also prevents unwanted side effects. In earlier woodchip-only systems, researchers found sulphide could form, which has a strong smell and is harmful in large amounts. Iron sand helps block this process while capturing released phosphate.
Initial tests took place in January and February 2025 and showed consistently high removal rates for more than a month. Research will continue during the winter of 2025 and 2026 to see how the filter performs over longer periods.
“We are learning where these systems work best and how they can support sustainable agriculture,” Jansen said. “This is a low-cost and low-technology way to protect water while meeting the goals of the European Water Framework Directive.”
The Zoetwaterboeren project aims to demonstrate practical solutions for farming in areas facing climate stress and water shortages. If successful, the technology could be adopted by farms across the Netherlands and other regions facing similar environmental pressures.