On the slopes of the Sierra Nevada massif in southern Spain, a medieval irrigation system has been slowing down the flow of water for the past millennium. The historian and landscape archeologist José María Martín Civantos helps us understand the importance of acequias, an ancient hydraulic technique that still provides an example of harmony between human activity and the natural environment.

An acequia seen from above. The small metal openings located along the water channel allow the surrounding fields to be watered. According to Sierra Nevada’s traditional agriculture, in addition to irrigating crops, flooding the land in a controlled manner allows the water to penetrate the soil, move into aquifers, or the spaces between rocks, and then resurface downstream (MeMoLab).

In the arid region of Andalusia, the Sierra Nevada's snowfields serve as a precious water source. There lies the Iberian Peninsula's highest peak, Mulhacén, at 11,421 feet (3,472 meters). Each year, on average, the massif stores approximately 198 billion gallons (750 billion liters) of water, including snow and rain. With the unfolding climate crisis, this resource is becoming critical in Spain, where periods of extreme drought and disruptions in hydrological cycles are increasingly affecting rural areas. Here, acequias have the dual function of irrigating the Sierra Nevada's terraced slopes and channeling water into the arid mountain soil, with the aim of "recharging" streams and springs downstream.

Highlighted in blue are all the acequias in the Sierra Nevada area, whose snowfields are seen in white in the center. The urbanized area in white in the lower right is what is called the 'sea of plastic,' El Ejido, a concentration of greenhouses that runs along the coast of Almería where fruits and vegetables are intensively produced for consumption in Spain and to be exported throughout Europe (Source: regadiohistorico.es).

Today, there are over 342 miles (550 kilometers) of these channels in the mountains between the provinces of Granada and Almería. These systems are a key part of the Sierra Nevada's landscape, distributing melting water from the snowfields 6,560 feet (2,000 meters) above to the villages, crops, and natural wells. Preserving existing systems and reviving those in disuse could have a fundamental impact on the landscape and watercourses originating from the Sierra, as reported by various international media (The New York Times; Bbc). I have also been researching the Sierra Nevada’s traditional water management a lot lately, as it could come in handy for other mountain systems, like the Alps and the Pyrenees, because of the changing climate. This is how I met José María Civantos.

JOSÉ MARÍA MARTÍN CIVANTOS: As a professor in the Department of Medieval History and Historiographical Sciences and Techniques at the University of Granada, he leads MeMoLab, a biocultural archaeology laboratory that studies historical processes related to the use of natural resources and landscape transformation in Europe and the Mediterranean, with the aim of conserving and promoting rural areas.

Professor Civantos, what is an acequia and where does this name come from?
An acequia is a water channel dug into the ground. In most cases, they are made of soil; sometimes they are partially paved with stones or even mortar. Their most common use is to transport water to places where irrigation is needed. In specific cases, they are also used to recharge aquifers. In this case, they are called "acequia de careo."

The term acequia comes from "al-sāqiyah" and is an almost literal translation from Arabic to Spanish, meaning “water channel.” In the Iberian Peninsula, this system began to develop during the Islamic period of Al-Andalus, starting in the eighth century, when entire farming families arrived from the Arabian Peninsula, in modern-day Yemen, Syria and Egypt.

In the following centuries, during the Spanish colonization of the Americas, this term spread to some areas of Latin America, Baja California, Alta California and Arizona, which were all regions under Spanish rule. Here, during colonization, irrigation practices were introduced, often through religious missions, which played a significant role. It's important to note that these colonial irrigation systems were overlaid or integrated with the pre-existing irrigation systems in many of these areas, including Mexico, Peru and Ecuador.

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