At a Glance
- A new study in Water Resources Research identifies nine unusual rivers and lakes in the Americas that break conventional hydrological patterns, including those with dynamic watersheds or multiple outlets.
- The Casiquiare River in South America connects the Orinoco and Amazon basins. Due to its slight slope, it flows in both directions, acting as a “wormhole” between two major river systems.
- The Wayambo River in Suriname has a two-way flow that can change depending on rainfall and human alterations, complicating predictions about pollutant spread near mining and oil production areas.
- The Echimamish River in Canada connects the Hayes and Nelson Rivers but has unpredictable flow patterns. Some reports suggest it flows in both directions due to flat terrain and beaver dams.
- The study of these strange waterways highlights the complexity of Earth’s river systems, revealing that much is still unknown about their behavior and underscoring the need for further hydrological research.
Rivers and lakes usually follow predictable patterns: they flow downhill, join other waterways, and eventually empty into the ocean or a terminal lake. However, some waterways do not follow these rules. A new study published in Water Resources Research highlights nine unusual rivers and lakes in North and South America that break hydrological expectations. These strange waterways include rivers that flow in two directions or have two outlets; some even have unclear or dynamic watershed boundaries.
One of the most fascinating examples is the Casiquiare River in South America. This river connects two of the continent’s largest watersheds, the Orinoco and the Amazon basins. The Casiquiare splits from the Orinoco River, travels through rainforests, and eventually merges with the Rio Negro, which leads to the Amazon River. The river’s slight slope—less than 0.009%—is enough to allow water to flow in both directions, making it a hydrological “wormhole” between two major river systems.
Another unusual waterway discussed in the study is the Wayambo River in Suriname. This river can flow either east or west, depending on rainfall and human changes to its course. Because of its two-way flow, predicting the spread of pollutants along the river is difficult, especially since it is close to mining and oil production areas. This feature makes the river’s behavior unpredictable and challenging to manage.
The Echimamish River in Canada is also noted for its baffling behavior. The river connects the Hayes and Nelson Rivers, but its flow is unpredictable. Some sources claim the river flows in both directions due to flat terrain and beaver dams. This uncertainty and other examples, like lakes with two outlets, show how much is still unknown about the complex systems that govern Earth’s waterways and highlight the need for further exploration in hydrology.
References
- Sowby, R. B., & Siegel, A. C. (2025). Unusual drainages of the americas. Water Resources Research, 61(2), e2024WR039824. https://doi.org/10.1029/2024WR039824
- Dzombak, R. & American Geophysical Union. (2025, April 1). The rivers that science says shouldn’t exist. Phys.Org; American Geophysical Union. https://phys.org/news/2025-04-rivers-science-shouldnt.html
