Researchers at the European Space Agency (ESA) have photographed a gigantic red trace in the desert of southern Morocco, using a European satellite.
In January 2026, the Sentinel-2 satellite, part of the ESA’s Copernicus mission, flew over the Ouarzazate region and captured a rather unsettling picture. A scarlet scar stretched across several dozen kilometers, winding between the foothills of the Anti-Atlas mountains like blood vessels running over ocher sand, or a lava flow.
The nearest volcano is only found some 2,000 km from the area, so the streak had a completely different origin. Understanding it, as it turns out, could greatly help scientists in monitoring a vital resource, one that is becoming harder and harder to come by in this part of the country.
Why The Red Isn’t Really Red?
The vivid red visible in the image doesn’t exist, at least not to the naked eye. As explained by ESA, it is a false-color image, built by assigning to red the data Sentinel-2 picks up in the near infrared, a portion of the electromagnetic spectrum to which human eyes are completely blind but which the satellite’s optical instruments detect perfectly well.
The color comes down to vegetation. Plants absorb red light from the visible spectrum to produce their energy and strongly reflect near infrared, which is what the satellite records. In a region receiving barely more than 100 mm of rain a year, knowing where vegetation concentrates means knowing where the water is, which is why the photo works so well as an environmental monitoring tool.
Close-up of the eastern section of the Sentinel-2 image captured in January 2026. Credit: ESA
What the Picture Actually Shows
Because it was taken in January, at the peak of the wet season, the image shows seasonal wadis (oueds) at their most active. They are lined with riparian vegetation, meaning plants growing along watercourses, dense enough to saturate the infrared sensor.
These intermittent rivers come down from the Anti-Atlas and flow only during the winter and spring months. On the image they draw a vast hydrographic network that would be impossible to map from the ground with such precision.
By comparing pictures from one Sentinel-2 pass to the next, researchers will be able to follow changes in the water resources of an entire area without setting foot on the ground. If the red patch shrinks somewhere between two flyovers, a wadi is drying up or a water table is receding.
If the patch grows, either the rains were more abundant or a new irrigation channel has been opened. With a pass every five days, scientists can routinely assess the area’s water balance instead of spending weeks collecting data on the ground.
A Country Short on Water
Such a tool is becoming a necessity. According to the article, this part of Morocco faces ever-increasing water stress year after year because of global warming and the overexploitation of groundwater for agriculture. The country as a whole has just emerged from a harsh drought that lasted seven long years.
Rainfall rose sharply in January 2026, but the respite was short-lived. The El Mansour Eddahbi dam, clearly visible on the right of the image, was only 35% full in January and 47% in October. That is a slight improvement, certainly, but Moroccans have never lacked renewable water so badly: availability has fallen to 620 m³ per person per year, four times less than in 1960. The province of Ouarzazate has even had to suspend drilling permits to slow the depletion of its groundwater.
