The 2018 drought affected agriculture heavily, especially in the sandy Eastern part of the Netherlands where freshwater supply by rivers is not possible. Treated wastewater is increasingly being considered as freshwater source for irrigation. Our experimental site in Haaksbergen clearly showed the benefits for crop yields of subsurface irrigation using treated wastewater. Additionally, the drought provides insight in the ‘worst case’ emissions of wastewater and its contaminants to the environment.
Exploitation of alternative freshwater resources
Not only in semi-arid regions, but also in humid temperate regions as the Netherlands, agriculture may suffer from water shortages. The 2018 drought emphasizes our vulnerability to limited rainfall combined with a high evaporative demand for water. Agriculture was impacted heavily, especially there where freshwater resources for irrigation were not available, or (ground)water abstractions were prohibited. When natural precipitation is inadequate, alternative freshwater resources could be exploited.
Subsurface irrigation with treated wastewater using CAD
Controlled drainage systems allow to actively control the groundwater levels and soil moisture conditions at an agricultural field. An advanced technology is anticipatory or Climate Adaptive Drainage (CAD), which allows active ‘remote control’ of drainage levels. Additionally, CAD allows to increase freshwater availability by subirrigation of water with underground supply through drains. In Haaksbergen, this technique is being tested, using sewage effluent which is normally quickly discharged from the area.
The system showed its benefits for the extreme dry summer of 2018. Crop yields of adjacent fields clearly lagged behind that of the subirrigated field, as is shown by satellite data (see figure).
While the system shows its value in terms of freshwater availability and crop growth, reuse of treated wastewater as resource is not without risks, due to the presence of a wide range of contaminants. The emissions of contaminants to the deeper groundwater are being monitored from 2015 onwards. With recent funding from the Netherlands Organisation for Scientific Research (NWO) we are able to increase our fundamental knowledge of how to manage subirrigation systems using effluent, in order to diminish potential emissions of contaminants of emerging concern to crops, groundwater and surface water.
- NWO Closed Cycles
- WiCE Zuinig met Zoet
- Monitoring Haaksbergen
- Deltafact Hergebruik van effluent
- Programma Lumbricus