GPS stations are quietly rewriting what we know about drought and land movement.

Land rising in silence

Across South Africa, something unexpected is happening. The ground is slowly lifting—up to two millimeters per year in some areas. It’s not seismic or sudden, but a steady, quiet shift. For decades, scientists thought this uplift came from deep within the Earth—mantle plumes pushing the crust upward. But a recent study from the University of Bonn tells a different story.

Using advanced GPS networks and satellite data, researchers have found that South Africa’s land is rising because it’s drying out. As groundwater and surface moisture disappear during droughts, the Earth’s crust rebounds—just like a sponge when water is squeezed out.

Tracking drought from space—and from the ground

South Africa’s GNSS network, known as TrigNet, was never meant to track climate change. Originally built for land surveys, it has become a crucial tool in monitoring vertical land motion.

Between 2000 and 2021, data from 88 stations revealed a clear pattern: the land began rising around 2012, with a total average uplift of six millimeters by 2020. That timeline aligns with severe drought years. And it wasn’t just local weather—the team validated their findings with NASA’s GRACE satellites, which measure gravity shifts to detect water mass loss.

Hydrological models like GLDAS-Noah and GLWS confirmed the same trend. The ground rose most in provinces hardest hit by drought, such as Western Cape, Limpopo, and Gauteng.

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Cape Town’s “Day Zero” leaves a mark

During the infamous “Day Zero” drought from 2015 to 2017, the GNSS station near Cape Town recorded a marked uplift. Inland, depleted reservoirs near Pretoria and Johannesburg showed similar signals. These changes didn’t just match drought periods—they tracked them with surprising accuracy.

In fact, GNSS data correlated by up to 94% with hydrological model outputs, highlighting how land uplift can serve as an indirect yet powerful indicator of water loss.

Climate patterns add clarity

The El Niño–La Niña cycle helped explain the timing. Dry El Niño years—like 2002, 2015, and 2019—saw accelerated land rise. Wetter La Niña phases slowed or reversed the trend. These cycles underline a clear link between rainfall patterns, water mass loss, and vertical land motion.

From mantle myth to groundwater reality

Although deep mantle plumes like the Quathlamba hotspot still exist, their role in recent uplift appears limited. Tectonic activity is minimal, and earthquakes are rare in South Africa. The real driver today is hydrological: drought, drying soils, and groundwater extraction.

Dr. Makan Karegar and his team believe GPS tracking can revolutionize how we monitor water resources—especially the hidden ones underground.

A future shaped by precision monitoring

Compared to countries like the U.S., South Africa has fewer GNSS sites, limiting resolution. Yet even a sparse network has proven effective. As climate change intensifies water stress, expanding this infrastructure could offer low-cost, high-impact drought tracking.

Initiatives like the UN’s African Flood and Drought Monitor and ESA’s ANIN project are already working on better monitoring systems. But GNSS-based hydrogeodesy adds a crucial new layer: total water storage, including hard-to-reach groundwater.

“This effect can be used to record the extent of a drought more precisely than ever before—using a method that is comparatively inexpensive and requires less effort,” said researcher Christian Mielke.

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