Reusing reclaimed water for irrigation: sustainability solution to alleviate growing water scarcity under climate change?

Climate change and increased pressure on natural resources have been identified as some of the major challenges that will affect Europe in the coming decades. This will cause consequences such as migration, food price shocks, water scarcity and imbalances in energy markets. Food and energy security require large amounts of fresh water. Water is one of the essential resources in both sectors, acting as a crucial driver for irrigation. The demand for natural resources is likely to increase over the coming decades due to growing global population numbers and economic development. At the same time, climate change may lead to lower overall water availability. Consequently, water scarcity, variability and uncertainty are becoming more prominent, which could lead to vulnerabilities within the energy and food sectors. In this sense, The EU is promoting initiatives to address water scarcity, such as investments to improve water use efficiency and the reuse of wastewater for irrigation. The objective of this research is twofold. Firstly, we assess the impact of changes in irrigation water availability, crop water requirements and yields under climate change on EU agriculture. Secondly, we analyse how promoting the reuse of treated water for agriculture may contribute to the reduction of water stress in coastal areas.

Using agro-economic modelling (CAPRI), we implement climate change scenarios (RCP7.0 and RCP8.5) - taking into account not only yield changes but also changes in irrigation water availability and crop water requirements - to assess the impact of climate change on agricultural production and water stress across EU regions (NUTS2 regions). Furthermore, to capture the contribution of water reuse for irrigation to mitigate climate change impact on water scarcity, we simulate scenarios with increased treated water potential as an additional water supply at NUTS 2 level.

Results provide insights into how climate change impacts agricultural production, food prices and international trade. For example, irrigation water availability limitations with a reduction in crop yields in some heavily irrigated Southern regions could necessitate reversion of cropland from irrigated to rainfed management. However, climate change could lead to increased irrigated cropland in some less water stressed regions. The reuse of reclaimed water is an opportunity to favour the management and efficient use of water resources and can be a solution to water deficit problems. Model results reveal the potential of treated water as an alternative supply source to address water stress and promote sustainable water management under climate change in the EU provided that some conditions are met. It is necessary to invest in the construction of purification infrastructures in areas where there is no control of discharges, as well as in infrastructures that bring this water closer to the consumers. A price competitive with traditional water sources must be achieved in order for its use to become widespread. It is essential to achieve consumer acceptance of the product obtained through the use of reclaimed water, influencing farmers’ decision-making.

Acknowledgements:  This research has received funding from the European Union’s Horizon 2020 research and innovation programme under the GoNEXUS project (grant agreement No 101003722).