Do most rivers flow south? Rivers are fascinating on so many levels, and one of those characteristics is their directional flow.
Rivers are capable of winding through various landscapes and traversing different longitudes and latitudes, but it is thought that most of them flow to the south.
It is a debated phenomenon, but you can find examples of so many rivers flowing south.
So, exactly why do rivers flow south?
Rivers often follow the path of least resistance, which is south, due to the combined effects of the Earth’s rotation and maybe the land’s topography.
Explanation of River Flow Patterns
Rivers are responsible for shaping much of Earth’s landscapes, forming river flow patterns that can be seen from above.
They resemble cracks in the planet that slice through continents as they make their way to the sea.
Like living organisms, rivers and their streams evolve over time but once established they persist for hundreds, if not thousands of years.
The only things likely to disturb the course of rivers are diversions caused by earthquakes, glaciation, volcanoes or human activity.
When we talk about rivers flowing downstream to meet the ocean, are most flowing north or south?
Examples of Rivers Flowing South
So, do most rivers flow north to south? Well, most of the planet’s rivers flow south, but that is not always true.
The longest river in the world, the Nile, runs north through Africa. Although the Nile is a famous example, there are many other north-flowing rivers in the world.
The US has 48, its famous example being the Snake Rivers in Idaho.
The Amazon is the widest river on Earth, it flows west to east through Guyana, Ecuador, Colombia, Venezuela, Bolivia and Peru.
The Ganges and the Yangtze run south to east. Europe’s second biggest river, the Danube flows east.
However, there are a lot more rivers that flow south including:
- The Mississippi, 2340 miles long flowing from Minnesota Lake Itasca discharging in the Gulf of Mexico.
- The Mekong, bordering Myanmar and China, rising in Yunnan running 2703 miles from the Tibetan plateau through China, Burma, Vietnam, Laos, Thailand and Cambodia to discharge in the South China Sea.
- The Volga, flowing 2.193 miles southeast through Russia into the Caspian Sea
Fact: With a length of 6,300 kilometers, the Yangtze River is the third-longest river in the world and the longest in China and Asia.
Why Do Most Rivers Flow South?
It is easy to imagine that the world’s major rivers flow downstream which is south in the Northern hemisphere.
Afterall, this is how water moves over more familiar roughly spherical surfaces, by flowing towards its equator like raindrops off a balloon or an umbrella.
Given the laws of nature and physics, all rivers would like to flow down toward the equator.
And they could if the surface of the earth was as smooth as a balloon or channeled like an umbrella.
Instead, the surface of the planet rises and falls with hollows, mountain ranges, plateaus and plains that influence the flow and direction of the rivers.
Let’s talk about factors causing rivers to flow south:
How the Slope of the Land Affects River Flow
Primarily, it is the slope of the land that determines the flow and the course of a river.
The steepness of the slope is referred to as the stream gradient. Even if forced to divert, a river will always take the easiest downhill route toward sea level.
The steeper the slope, the faster the river flows.
The flow rate increases as streams and rivers merge, pushed together by landscape features where the easiest routes down intersect.
Where the gradient is slow, the river’s flow rate decreases allowing it to deposit sediments picked up by erosion when rushing over the steeper gradient.
More on How Steeper Gradients Results in Faster Flow Downstream
Water is subject to gravity and its molecules are sticky.
Being a liquid, it has no internal structure and so will spread out flat if there is nothing to influence it.
It takes a force like gravity or the wind blowing on it to drive it, but the sticky H2O molecules linking together allow it to flow.
Gravity means water flowing downhill gathers potential energy but the amounts are unevenly distributed according to the gradient and the landscape of the riverbed.
Fact: Water flows in response to these potential energy differences, transferring its energy from areas of high potential to areas of low.
How Erosion and Deposition Processes Shape River Channels
Rivers are constantly reshaping their landscapes using erosion and deposition.
In erosion, the force of the water wears away and breaks down the rocks and soils of the river channel.
During its upper course, the erosion also happens vertically creating waterfalls and steep-sided valleys.
The fast-moving waters have the power to hold onto these sediments.
It sometimes transports them many miles and drops out of suspension and deposits where the river slows, such as within a bend forming beaches.
As it enters its middle course on ground with a low stream gradient it slows and spreads in vast deltas.
Impact of Tectonic Activity and Geological Formations on River Courses
The location, size, shape, orientation and longevity of a big river are governed mainly by plate tectonics and the effects of continental lifting, which creates the slope downhill.
Rivers always react to changes in topography and tectonic activity has the largest impact causing the river’s profile to tilt.
It results in adjustments to the river flow pattern to compensate for the changes in the slope and geology it encounters on the way.
The river meanders dropping sediments to reshape the landmasses.
Fact: A tectonic event near mountains may see a buildup of sediments blocking the river’s path forcing it to change its direction.
Influence of Rainfall and Precipitation on River Flow
Rainfall has a significant influence on how fast rivers flow and erode their beds and banks, which have an impact on their course.
In areas of particularly high rainfall the bedrock can become unstable as it succumbs to the effects of chemical weathering as slightly acidic rainwater interacts with bedrock.
In cold temperatures, most of the erosion is due to freeze-thaw weathering.
Both affect the river’s landscape by triggering rockfalls and ground slumping and sliding resulting in material falling into the channel.
Fact: Storms bring dramatic changes in the depth and flow that break out of the meanders as ox-bow lakes and flooding.
Prevailing Weather Patterns and their Impact on River Flow
Too little rain has as much of an impact on a river and its flow as excess rainfall and precipitation.
The reduced volume of water has much less energy and this reduces the river’s rate of flow.
Erosion and deposition come to a halt and rockfalls and landslides become less likely.
That said, rivers are constantly adjusting to compensate for the prevailing weather patterns and changes in the composition and geology of the river channel.
In high wind areas, the river’s current is driven on by the wind and pushed up against the banks where wave action undercuts and erodes them.
How Melting Snow and Glaciers Contribute to River Flow
Glacier meltwater’s high and lows and its effects on a river’s flow were seasonally predictable, as was when a river would be high and fast flowing due to snow melt.
So much so that Nepal, a country with low rainfall, uses meltwater as a reliable source of water and utilizes its flow to generate energy.
Climate modeling suggests that with warming, the extra water will destabilize global weather sending the hydrologic cycle into overdrive.
Fact: With more intense precipitation, all rivers will flow faster only to stop because the snow and ice melted away, which has worrying implications for countries like Nepal.
Takeaway
Why do most rivers flow south? Various geological, geographical, and gravitational factors have a role to play in explaining why most rivers flow south.
The direction in which rivers flow often depends on the Earth’s rotation and the inclination of the ground.
Many rivers do indeed have a general southerly flow pattern, but there are always outliers and numerous factors at the regional level can affect a river’s path.
The dynamic nature of rivers and the varied ways they shape our globe can be better understood if the complex interplay between these forces is known.
