List of 7 Rivers That Flow Backward in the World ~ PARN HARIT

When we think of rivers, we think of water generally flowing, in a linear fashion, from high ground to the sea. Did you know there are some rivers on Earth that actually flow in reverse from their source to the sea? Rivers that defy the normal flow of water can do so because of a geological shift, tidal forces, earthquakes, or changes in sea levels.

Although it seems hard to believe, these rivers have baffled the scientific community and explorers for hundreds of years. From the Amazon River to the odd Chicago River, they each have a unique story regarding their reversal. Let's dive into the seven fascinating rivers that go against nature and flow upriver in a unique way, it is very interesting that the rivers themselves do not follow the rules of geography. This list has been curated based on data by Mekong River Commission.

7 Rivers That Flow Backward in the World

Here are the top 7 rivers that flow backwards along with their location and the reason for their backward flow:

Rank	River Name	Location	Reason for Backward Flow
1	Amazon River	South America	Caused by ancient tectonic shifts in the Andes Mountains
2	Chicago River	United States	Reversed artificially through engineering to protect Lake Michigan
3	Mississippi River	United States	Reversed temporarily during hurricanes and earthquakes
4	Fraser River	Canada	Tidal forces near its mouth can cause reverse flow
5	Tonle Sap River	Cambodia	Reverses seasonally due to Mekong River floodwaters
6	Humber River	England	Tidal surges from the North Sea cause occasional reversal
7	Orinoco River	Venezuela	Seasonal rains and tidal influences cause backward currents

1. Amazon River (South America)

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The Amazon River at one time flowed westward, but the uplift of the Andes Mountains about 10 million years ago reversed the river's direction toward the Atlantic Ocean.

This tectonic and geological activity created the largest river basin in the world. The Amazon River carries more water than any river has ever carried, and it is proof of the power of Earth's natural forces to even make rivers flow backward.

2. Chicago River (United States)

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As a man-made river, the Chicago River flows backward by design. In 1900, engineers reversed the flow of the river to prevent sewage from being dumped into Lake Michigan, which provided drinking water to the city.

By building canals and locks, the engineers successfully redirected the river toward the Mississippi basin. It was a monumental historic solution to an environmental problem as well as one of the greatest engineering feats in American history.

3. Mississippi River (United States)

Mississippi River

The Mississippi River has flowed backward on multiple occasions, such as in the 1812 New Madrid Earthquake and Hurricane Katrina. Because of violent seismic activity and storms, the river, for short periods of time, reversed during the shaking and stranding the river's waves upstream.

These moments, though brief, were a powerful lesson about nature and even one of the world's strongest rivers being detoured from its original course.

4. Fraser River (Canada)

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The Fraser River runs through British Columbia and experiences occasional backward flow, influenced by significant ocean tides from the Pacific. In certain conditions, usually involving exceptionally high tides, seawater progresses against the river’s flow, causing some short-term backward flow energy near the mouth of the river.

This fascinating natural occurrence captures the attention of scientists and travelers, and it demonstrates the ways that tidal actions can influence the behavior of even the largest rivers in unexpected ways.

5. Tonle Sap River (Cambodia)

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The Tonle Sap River in Cambodia reverses flow direction in a unique way each year. During the monsoon season rain, floodwaters from the Mekong River push the river backward, greatly increasing the size of the Tonle Sap Lake.

However, when the dry season returns and water levels drop, the Tonle Sap River returns to normal forward flow. This predictable, yet extraordinary, natural cycle feeds millions of people by replenishing fish stocks and nourishing Cambodia's rich agricultural ecosystem.

6. Humber River (Canada)

The Humber River in Canada is sometimes talked about because it will sometime flow backwards in some spots during major storms and winds.

Winds can be so intense that, rather than the river flowing downstream out to Lake Ontario, the water is pushed upstream into the river lake out and reversed its flow.

It runs through Toronto and is an important part of local ecology and history; a natural heritage river and example of the power of nature at work.

7. Orinoco River (South America)

The Orinoco River is among the longest rivers in South America and runs through the countries of Venezuela and Colombia. Interestingly, you will see parts of the river flowing “backwards” during times of rain because of all the water from its tributaries and from the Amazon River through the Casiquiare Canal.

This natural occurrence creates currents that flow temporally in reverse order. The river system is an example of the dynamic power in nature and complex hydrology associated with a river system such as the Amazon and Orinoco rivers.

Conclusion

Rivers that flow in reverse teach us how dynamic and unpredictable the Earth is. Whether caused by the moon, tectonic shifts, or engineering decisions, rivers flowing backward are the epitome of change and dynamism in nature. Whether the Amazon River or the Tonle Sap, these remarkable rivers represent an incredible story of nature's dynamism and unpredictable reality.

While most rivers follow the pull of gravity toward the sea, a few rare exceptions "defy" this rule due to geological shifts, human engineering, or extreme weather.

Here are 7 rivers known for flowing backward:

1. Tonlé Sap River (Cambodia)

This is the most famous example of a seasonal reversal. During the dry season, the river flows southeast into the Mekong River. However, during the monsoon season (June to October), the Mekong swells so much that its waters push back into the Tonlé Sap, reversing its flow and expanding the Tonlé Sap Lake to five times its normal size.

2. Chicago River (USA)

Unlike natural reversals, this was a massive engineering feat. In 1900, engineers used a system of locks and canals to permanently reverse the river's flow. Originally, it emptied into Lake Michigan, but it was redirected toward the Mississippi River basin to move sewage away from the city's drinking water supply.

3. The Amazon River (South America)

Millions of years ago, the Amazon actually flowed westward into the Pacific Ocean. The uplift of the Andes Mountains caused by tectonic activity eventually blocked this path, creating a massive inland sea that eventually broke through to the east, reversing the river's entire course toward the Atlantic.

4. Mississippi River (USA)

The Mississippi typically flows south, but it has been forced backward temporarily by natural disasters. Powerful storm surges from Hurricane Katrina (2005) and Hurricane Isaac (2012) forced the river to flow north for several hours. In 1812, a series of massive earthquakes in New Madrid also reportedly caused sections of the river to run backward.

5. Hudson River (USA)

The Hudson is technically a tidal estuary. Twice a day, the tide from the Atlantic Ocean is strong enough to push the river's current northward (upstream). This phenomenon is so regular that the Native American name for the river, Muhheakantuck, means "the river that flows both ways."

6. Saint John River (Canada/USA)

Located near the Bay of Fundy (which has the highest tides in the world), this river experiences "Reversing Falls." When the tide comes in, the force of the ocean water is higher than the river, pushing the water back upstream over a series of underwater ridges and creating the appearance of backward-flowing rapids.

7. River Thames (UK)

Similar to the Hudson, the Thames is a tidal river. The North Sea tides push water upstream as far as Teddington Lock in London. Before the construction of modern flood defenses like the Thames Barrier, these tidal surges were strong enough to cause significant upstream flooding.

River	Primary Cause of Reversal	Duration
Tonlé Sap	Monsoon Flooding	Seasonal (Months)
Chicago	Human Engineering	Permanent
Amazon	Tectonic/Geological Shift	Permanent (Ancient)
Mississippi	Hurricanes/Earthquakes	Temporary (Hours)
Hudson	Ocean Tides	Daily

How the Tonle Sap River Reverses

This video provides a visual explanation of how the Mekong River's water pressure forces the Tonlé Sap to change direction every year.

PARN HARIT