Guyana’s Rivers Reveal Mining’s Impact in Striking Satellite Imagery

A recent satellite image captured by Landsat 8 showcases the dramatic confluence of three rivers in Guyana – the Cuyuni, Mazaruni, and Essequibo – revealing a striking “half-and-half” waterway and highlighting the growing impact of mining on the region’s unique hydrology.

A Trio of Rivers Converge

Located near Bartica, Guyana [6.4073096658, -58.62373473], the merging of these three rivers creates a visually arresting contrast in water color. The Cuyuni River exhibits a light brown hue, while the Mazaruni and Essequibo rivers appear darker. This phenomenon is due to differing levels of suspended sediment and tannins in the water.

The Science Behind the Colors

The darker color of the Mazaruni and Essequibo rivers is likely caused by tannins – chemicals released from decaying vegetation that stain the water, similar to the process of brewing tea. The Cuyuni River’s lighter brown color, however, is attributed to high concentrations of suspended sediment .

Density Differences Prevent Mixing

The distinct colors don’t immediately mix upon convergence given that of differences in density caused by the varying sediment levels. This creates the striking visual effect captured in the satellite imagery.

Mining’s Increasing Influence

While tannins are a natural occurrence, particularly during periods of flooding, the elevated sediment levels in the Cuyuni River are increasingly linked to mining activities. Hydrologist Evan Dethier of Colby College in Maine, notes that the Cuyuni is a clear outlier in sediment concentration, attributing this to the intensity of mining upstream .

Guyana: A Land Rich in Resources

Guyana, often called the “land of many waters” in the Indigenous Arawak language, boasts 10 major rivers and numerous smaller waterways within an area roughly the size of South Carolina. The country is rich in mineral deposits, including gold, diamonds, bauxite, lithium, copper, and nickel, all linked to the ancient Guiana Shield , .

A Growing Trend in Sediment Levels

Mining in Guyana has expanded significantly since the mid-2000s, and sediment concentrations in the Cuyuni River have likely increased tenfold since then. This trend aligns with a 2022 study led by Dethier, which revealed a 40% rise in sediment concentrations in rivers across the Southern Hemisphere, largely due to mining and deforestation .

Global Implications

Changes in global sediment flow may also impact marine environments, as sediment input into the world’s oceans has drastically changed. However, the long-term effects of these changes are still being studied.

Bartica: Gateway to the Interior

The town of Bartica, with a population of approximately 8,000 people as of 2012 , is situated at the confluence of the three rivers and serves as a crucial access point to Guyana’s interior .