Water is the lifeblood of every greenhouse business. It is not only essential for the growth and health of crops, but also plays a major role in the reliability and efficiency of operations. As such, the availability and quality of irrigation water are direct success factors for stable and sustainable cultivation.
Horticultural businesses rely on four different water sources: rainwater, city water, groundwater, and surface water. Each of these sources has its own characteristics, advantages and disadvantages, and requires a specific approach to storage and purification. What factors should growers consider? How can each source be used most effectively? And how should the water from each source be treated?
For many growers, rainwater is the ideal primary water source. It is freely available and has a low EC value. This makes it particularly suitable for closed cultivation systems where all drain water is reused. Another benefit is that rainwater generally does not require chemical purification.
However, the availability of rainwater depends on the season. During dry periods, such as hot summers or extended droughts, tanks or reservoirs may run empty quickly.
It is therefore important to have sufficient rainwater storage capacity. Preferably, this storage should be covered to prevent contamination by algae or organic material. Collecting rainwater also supports sustainability goals, as it reduces dependence on other sources and makes rainwater a very environmentally friendly option.
Before it can be used, rainwater should be filtered. Filters can remove coarse particles and organic debris.
As a result, rainwater is not only sustainable and affordable, but—if properly stored and disinfected—also a high-quality source for plant health.
Another commonly used source is city water, which is typically available at all times. This source offers reliable availability and usually has a stable and controlled quality, which is important for crop cultivation.
Using city water can simplify greenhouse operations, since it generally does not require dedicated storage or complex purification systems.
Still, city water has its drawbacks. It is more expensive than alternatives such as rainwater or surface water. The EC value is often higher, and it may contain sodium—making treatment necessary, especially when drain water is reused, as salt accumulation can become a problem.
Furthermore, using drinking water does not align well with the sector’s sustainability goals. Due to environmental regulations, growers are not always permitted to use large volumes of city water.
Groundwater is an attractive source due to its consistent availability. Regardless of the season, supply is usually stable, which can make it a valuable source in areas with limited rainfall.
However, groundwater does come with technical and legal considerations. Its quality can vary significantly depending on the location, and it often contains high concentrations of iron, sodium, or other minerals. Extracting groundwater also usually requires a permit, and in some areas it may be restricted or even prohibited due to environmental concerns. On top of that, groundwater is becoming increasingly scarce worldwide.
Treatment almost always begins with aeration, as groundwater typically contains very little oxygen. This oxygen-poor condition can lead to biofilm and algae growth and creates a favorable environment for fungal development.
Groundwater should also be filtered to remove coarse particles and organic matter. If mineral concentrations are too high, reverse osmosis is required to make the water suitable for use.
Another possible water source is surface water. This includes water from ditches, rivers, or lakes and can be a good supplement to rainwater—especially in water-rich regions.
Surface water, however, is a complex and challenging source. It is often contaminated with organic material, chemical substances, or plant pathogens. Removing these impurities typically requires multiple treatment steps, which drives up costs. Additionally, surface water often has a high EC value.
Before surface water can be used safely, several filtration steps are usually necessary. It is wise to regularly test surface water quality so that treatment can be adjusted to current conditions.
In addition to external water sources, the reuse of drain water plays an increasingly important role. Rather than discharging this stream, growers can save water and retain valuable nutrients by purifying and reusing it.
Reusing drain water offers major benefits, but it does require proper treatment. Since this water comes from the cultivation system, it typically contains a mix of fertilizers, organic matter, and potentially harmful microorganisms such as fungi, bacteria, and viruses.
To reuse drain water safely, disinfection is essential. However, this requires investment in filtration and disinfection equipment. At ErfGoed, for instance, the cultivation floor functions as a biofilter when recovering drain water. A portion of the organic matter is filtered out before the water is collected.
Properly treating and reusing drain water reduces the need for fresh water, which leads to lower water costs and decreased environmental impact.
Rainwater is a sustainable and inexpensive source, making it an ideal choice for many growers. In most cases, especially when combined with drain water reuse, rainwater is the preferred source. But every situation is different. The optimal water strategy depends on factors such as location, type of crop, technical systems, and long-term vision. Often, a combination of multiple water sources offers the best solution.
At ErfGoed, we look beyond just the choice of water source. Effective water management includes storage, disinfection, treatment, and fertilization—but also irrigation, and the capture and reuse of drain water.
By managing and purifying water flows wisely, growers not only improve the resilience of their crops but also enhance the sustainability of their operations.