For centuries, the canals of Sierra Nevada in southern Spain have been much more than simple irrigation ditches. These structures, whose origin dates back to the Roman Empire and which reached their peak during the Andalusian period, make up a sophisticated water management system that distributes water and infiltrates it into highland areas so that it resurfaces later at lower elevations.
Now, a team of researchers from the University of Córdoba (UCO) has managed to quantify, using satellite images taken over 26 years, the extent to which these canals influence soil water content and the vigor of surrounding vegetation.
The study was conducted by researchers Javier Aparicio, Rafael Pimentel, and María José Polo, from the Fluvial Dynamics and Hydrology group, together with Francisco Bonet, from Terrestrial Ecology. It focused on analyzing the impact of these infrastructures within a radius of more than 200 meters around the canals.
To do this, they used the Normalized Difference Vegetation Index (NDVI), a tool that allows the evaluation of vegetation health and density using satellite images taken between 1984 and 2020, some of which were processed as part of the ECOPOTENTIAL project.
The Natural Park of Sierra Nevada is home to more than 700 kilometers of these canals, many of which are still in operation. Their function is not limited to transporting water for irrigation—they play a fundamental role in aquifer recharge, infiltrating meltwater in high-altitude zones so that, months later, it emerges in springs and natural fountains in the lower-lying villages. But what the UCO team has discovered goes even further: the hydrological effect of these canals extends far beyond their immediate surroundings.
The results were revealing: although, as expected, NDVI values—and therefore vegetation vigor—were higher in areas closest to the canals, significantly elevated levels were also recorded in more distant areas, indicating that the moistening effect of these channels reaches much farther than previously thought.
What’s surprising is that even in the zone from 50 to 200 meters, NDVI values remained high, suggesting that the influence of the canals goes beyond the first 50 meters, explains Javier Aparicio. Furthermore, the study detected a seasonal pattern in the data, with a clear correlation between the basin’s hydrological dynamics and vegetation behavior—a link that is especially strong in areas closest to the canals.
In addition to the general analysis, which included 45 of the longest canals in Sierra Nevada, the team focused part of their work on a specific case: the Barjas canal, restored in 2014 by the MEMOLA project from the University of Granada. The results left no room for doubt—after the intervention, NDVI values increased by 19%, with a particularly notable rise in the lower part of the canal, where water had not reached properly before the restoration.
This finding demonstrates the effectiveness of these structures in a context where technological water management in remote areas proves extremely complex. These traditional systems continue to provide invaluable benefits both for local populations and for the environment, Aparicio emphasizes.
One of the challenges the researchers faced was the lack of previous studies on such specific hydraulic infrastructures, which forced them to adapt methodologies usually used for rivers or larger-scale systems. However, the success of this approach opens the door to its application in other environments with similar systems, such as those found in the Moroccan Atlas.
SOURCES
Javier Aparicio-Ibáñez, Rafael Pimentel, et al., Using NDVI-derived vegetation vigour as a proxy for soil water content in Mediterranean-mountain traditional water management systems: Seasonal variability and restoration impacts. Ecological Indicators, Volume 174, May 2025, 113468. doi.org/10.1016/j.ecolind.2025.113468
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