Study Reveals Why South Africa’s Land is Rising Amid Drought

A recent study indicates that land in South Africa has risen by an average of 6 millimeters from 2012 to 2020 due to drought and water loss. Researchers used GPS data to establish a new model linking land uplift to changes in water storage. The findings reveal broader impacts than initially thought and suggest potential future declines in uplift if significant rainfall returns.

Recent research has illuminated a significant phenomenon: the land in South Africa is rising—and we finally understand why. A comprehensive GPS-based study revealed that between 2012 and 2020, the region experienced an uplift averaging 6 millimeters (0.2 inches), primarily linked to drought and associated water loss. This finding sheds new light on the dynamics of South Africa’s landscape, particularly during dry seasons.

Scientists have turned to GPS technology in their investigation. They discovered that patterns of land uplift closely correlate with periods of drought, as well as seasonal transitions between wet and dry phases. The results might not only explain the land’s movement but also offer a way to predict future drought conditions, as suggested by the researchers involved in the study.

For over a decade, geologists have known about the rising land, initially attributing the uplift to a so-called mantle plume—an upwelling of hot rock below Earth’s crust that pushes the surface upward. However, Makan Karegar, a geodesist from the University of Bonn, observed a notable pattern: the uplift coincided with significant drought periods, especially during the intense “Day Zero” drought that threatened Cape Town’s municipal water supply between 2015 and 2018. “We started to think there should be a link between this pattern and water loss,” Karegar noted.

To dive deeper into this connection, the research team gathered GPS data from numerous permanent stations across South Africa, which allow for precise height measurements over time, sometimes measuring down to fractions of a millimeter annually. Their findings, published recently in the Journal of Geophysical Research: Solid Earth, connected the uplift directly to changes in water storage within the country. As reservoir, soil, and groundwater levels diminished, the land responded accordingly—rising similarly to how a memory foam mattress rebounds once pressure is lifted.

Curiously, the uplift was not just localized to areas close to water reservoirs, as originally presumed by coauthor of the study, Christian Mielke. “The biggest surprise for us was that we saw an uplift over most parts of South Africa,” he explained, indicating a broader impact than anticipated.

The study successfully validated its model by correlating the changes in land height with existing water storage models, revealing that the GPS measurements agreed well with satellite data and climate indicators demonstrating water loss. While the research does not dismiss the possible influence of the mantle plume, the strong links between uplift and water storage changes suggest that drought is likely the predominant factor driving this phenomenon.

However, this uplift may not be permanent. If sufficient rainfall returns, there is potential for the land to gradually sink back down, as Karegar indicated. The intricacies of this scenario warrant further study, according to Bill Hammond from the University of Nevada Reno, who commented on the challenges faced in determining the timeframe for land movements given the limited 30 years of available GPS data, much of which occurs during drought.

In the meantime, Karegar advocates for the use of GPS measurements as a key method for monitoring drought conditions. Despite the relatively sparse placement of South Africa’s GPS network, other regions worldwide have denser systems that could assist in effective water management strategies. This research paves the way for better understanding drought impacts through advanced monitoring technologies.

In summary, a new study highlights the uplift of South Africa’s land as a response to drought and water loss, revealing an average rise of 6 millimeters over an eight-year period. Utilizing GPS technology, researchers have established a model to link land movements to water storage changes, suggesting that while the uplift is significant, it may not last if Rain returns. The implications of this research showcase the growing importance of advanced monitoring techniques to address drought-related challenges.

Original Source: www.livescience.com