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Reducing demand and enhancing rainfed agriculture

As river basins adopt more water efficient irrigation, further gains will be limited and technological improvements may reach their capacity to deliver new value and reduce water use. Findings suggest that productivity gains may have reached a ceiling in some southern European river basins as various innovations, such as new crops, deficit irrigation, and water‐saving and conservation technologies, have reached their full capacity (Expósito and Berbel, 2017). Hence, other measures may be needed to match total water demand with water availability.

As river basin progress towards total resource limitations, the full impact of agriculture on the basins’ hydrology should be accounted for, including both its use of blue and green water. This would require managing water in rainfed and irrigated systems in an integrated way, looking at ways to maximize water savings by managing evapotranspiration and crop water demand, enhancing soil water retention capacity, and increasing the productivity of rainfed agriculture (Rockström et al., 2010; Molden et al., 2007b). This would also contribute to increase farms’ resilience to water scarcity and droughts.

Soil preservation and crop diversification practices promoted in conservation farming and agro-ecology contribute to these objectives, with evidence that farms practicing organic farming have shown greater resiliency to droughts by maintaining higher yields than non-organic farms (e.g. Milestad and Darnhofer, 2003; Altieri et al., 2015). Healthy, carbon-rich soils have higher water retention capacities (Adhikari and Hartemink, 2016). Various techniques can be used to increase the capacity to reduce crop water demand, including the use of modified crop calendars to benefit from higher rainfall and soil moisture content during wetter season, modified crop rotation and rotational fallowing, developing more water resistant varieties and adopting more water-stress resistant crops (Debaeke and Aboudrare, 2004; EIP-AGRI, 2016, 2020). Deficit irrigation has large potential in permanent cropping systems to optimize and reduce water use during drought conditions (Fereres and Soriano, 2006). Combining crops or pastures with trees in agroforestry systems can also buffer exposure to climate change extreme such as storm damage, heatwaves and droughts (OECD, 2014).

It is also important to acknowledge that a total switch to rainfed agriculture can reduce costs to farmers, but it also increases exposure to lower yields and crop failure during droughts. A coherent strategy on supplemental irrigation or adequate crop insurance for rainfed agriculture may be needed to mitigate risk.