Holistic Water Management in Agriculture: Tackling Salinization and Water Scarcity in Dutch Farmlands

As the world's second-largest exporter of agricultural products, the Netherlands has earned a reputation for its innovative farming practices. However, climate change now poses a significant threat to crop production, particularly in low-lying coastal regions where salinization and droughts are becoming more severe. To address these challenges, the "Freshwater Farmers" pilot project, launched two years ago in North Holland, is investigating how sustainable water management techniques — such as closed drainage systems, subsurface irrigation, and soil nutrient retention — can help farmers adapt to extreme weather conditions while maintaining their competitiveness.

_{Battling Salinization of Farmlands}

One-quarter of the Netherlands' territory lies below the sea level, making coastal Dutch farmlands vulnerable to both flooding and salinization. Increasing water demand, rising sea levels and more frequent droughts have exacerbated these issues in recent years. Most of the traditionally cultivated crops in the country are not salt-tolerant; therefore, salinized soils lead to stunted growth and lower yields.

In 2022, the research institutes Vertify and Deltares, along with the University of Wageningen and Pipelife Netherlands, launched a pilot project, "Freshwater Farmers," to explore a possible solution to the increasing soil salinization. The pilot is being conducted on a 30-hectare coastal farm in Anna Paulowna, owned by farmer Klaas Schenk. 

_{Closed Drainage Systems: A New Approach to Water Management} 

Conventionally, the coastal areas in the Netherlands have been drained by placing horizontal drainage pipes in the soil and diverting the excess water into the sea. While the method protects fields from flooding, it also leads to nutrient leaching and increased saltwater infiltration, decreasing soil fertility. 

In March 2022, the first closed drainage system was installed in Schenk's farm — the existing 8-kilometer drainage system was sealed using 6 kilometers of PVC pipes, allowing rainwater to be retained rather than discarded. After two seasons of use, both soil salinity and nutrient loss have been greatly reduced, highlighting the potential of closed drainage systems in agriculture.

_{Rainwater Reuse for Subsurface Irrigation}

The next stage of the pilot will begin this year, focusing on harvesting and storing larger volumes of rainwater to ensure freshwater availability year-round and reusing it for subsurface irrigation. Seven closed drainage systems will be tested on Schenk's lands, enabling comparison of various system sizes and irrigation schemes while meeting the national requirements for crop rotation.

"The rainwater harvested from the fields will undergo a two-step purification process and afterward be injected 20 meters below the surface level," explains Maurice Meester, Product Manager of Infrastructure and Network Management at Pipelife Netherlands. "At this depth, a layer of sand between two nonporous clay layers will serve as a natural well for storing large amounts of water. These water reserves will be replenished during the rainy winter months and gradually reused during the summer."

The groundwater levels in the test fields will be continuously monitored using sensors. A water-level control system installed into the collector wells will allow Schenk to remotely adjust the levels as needed to maintain optimal groundwater levels for various crop types, growth stages or agricultural equipment access.  

_{Preventing Nutrient Loss from Agricultural Runoff}

Conventional drainage systems can remove water-soluble nutrients together with the surplus water, making the topsoil layer less fertile while increasing eutrophication in nearby water bodies. To address the issue, the pilot will test a single-point solution to halt agricultural runoff and nutrient loss. 

A 70-m3 nutrient catcher will be added to the system and used when the precipitation amounts exceed the system's underground storage capacity and, consequentially, must be disposed of. Filled with organic filtering material, the catcher is expected to trap nutrients present in the runoff, preventing them from entering the environment. Once saturated, the organic, compostable filtering material will be returned to the fields, reducing the need for chemical fertilizers.

_{Next Steps in Testing} 

The final stage of the pilot is set to begin by the end of the year, pending approval from the local water board for injecting and storing water underground. The goal is to collect enough freshwater during the winter and early spring to support crops during summer droughts. 

The major study will conclude in the fall of 2025. In addition to evaluating the technical aspects and environmental impact of closed drainage systems, the project aims to demonstrate that these solutions can be made financially viable for farmers. If successful, similar systems could benefit coastal farms not only in the Netherlands but also in Belgium, Denmark, Germany, Poland and Sweden.

"Our goal is to achieve a return on investment within five years," emphasizes Meester. "With summer droughts now lasting for months and winter rainfall becoming more intense, closed drainage systems may soon be essential for coastal farmers to stay competitive. Storing freshwater underground for reuse has been proven before, but this project takes it further by testing an end-to-end water management solution to address the wide range of climate-related risks farmers face today."