©Narain-Ford

The use of purpose-built underground irrigation systems reduces freshwater consumption by the Dutch agricultural sector by as much as 25%. This is evident from research by the universities of Amsterdam and Utrecht and KWR Water. These types of systems make use of wastewater that is purified by the soil.

Water problem

At present, 70% of the world’s fresh water is used in agricultural irrigation. This contributes enormously to the worldwide shortage of fresh water. Underground irrigation technology can reduce the amount of water used by this sector.

Water usage is particularly problematic during dry seasons. More water is needed for irrigation than what is actually available. During these seasons, water is used from streams, ditches, and lakes where sewage treatment plants discharge water into.

Dominique Narain-Ford, the main author of the study: “This wastewater degrades the quality of the world’s limited fresh water supplies. When using this wastewater in traditional aboveground irrigation methods, field workers and crops are directly exposed to contaminated water. This can pose serious health risks.”

Micropollutants

Standard sewage treatment plants are unable to remove micropollutants from water. Micropollutants are substances such as medicines, hormones, and pesticides. These micropollutants come into direct contact with crops when this water is used in aboveground irrigation systems.

Solution

These problems can be circumvented by using underground irrigation. In that case, field workers and crops do not come directly into contact with wastewater. Soil also functions as a purification system. Various breakdown processes take place in soil. Micropollutants can largely be removed from the water by the soil. The spread of chemicals is reduced to a minimum this way.

Nairin-Ford: “In underground irrigation systems, about a quarter of agricultural water supply requirements can be met by using wastewater during an average season, while the figure is 17 % during a dry season. In order to satisfy the demand for irrigation water, 7 to 13% of the annual amount of wastewater would need to be used for this purpose.”

“Although less water is lost due to evaporation in underground irrigation systems, more water is nevertheless still needed in comparison with aboveground irrigation. Groundwater must rise to a certain level before it can reach crops.” In the long run, underground irrigation will require less water owing to increased groundwater levels.

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