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Earth from Space: Circles in the desert

Written by  Friday, 18 July 2025 07:00
This image from Copernicus Sentinel-1 shows circular agricultural structures near Tabarjal, in the barren desert of northern Saudi Arabia. Image: This image from Copernicus Sentinel-1 shows circular agricultural structures near Tabarjal, in the barren desert of northern Saudi Arabia.

This image from Copernicus Sentinel-1 shows circular agricultural structures near Tabarjal, in the barren desert of northern Saudi Arabia.

Zoom in or click on the circles to explore this image at its full resolution.

Most of Saudi Arabia has a desert climate and experiences temperatures as high as 50°C in summer. While there are virtually no permanent rivers or lakes in the country, large valleys called wadis fill with water during times of heavy rain. Most settlements are located along these valleys.

The area pictured lies within the Wadi As Sirhan basin and shows how Saudi Arabia’s desert is used for agriculture. Despite the dry climate, many irrigated crops are grown in the area.

The circles, each approximately one kilometre wide, are formed by central-pivot irrigation systems. These consist of a well at the centre of each circle, which supplies water from underground aquifers to rotating sprinklers. This type of irrigation helps farmers manage water in a more sustainable way to conserve this precious resource, which is not being replenished.

This composite combines three Copernicus Sentinel-1 radar images, acquired over seven months. Each acquisition has been given a different colour – blue for October 2024, green for January 2025 and red for May 2025. The three images are then layered on top of each other to map differences in land cover, to understand how land is used and to track changes between acquisitions.

The resulting bright colours provide information on the different types of crop and their growth stage, and variations in irrigation. White, grey or black mean small or no changes over the acquisition period, indicating bare soil, fallow or non-vegetated fields when appearing within the circles, or desert sand, low hills, dry riverbeds and rocky terrain in the overall surrounding areas.

Settlements in the image show up as white, irregular areas amid the colourful circles, with the largest visible being Tabarjal (or Tubarjal), in the top right of the image. Thanks to its agricultural production and strategic location, Tabarjal is an important town in northern Saudi Arabia. It serves as a central hub for surrounding rural communities and plays a vital role in the food supply for the region.


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