How do rivers form? Where they Start and End

There are over 400,000 rivers worldwide and they vary in size. They range from the mighty Amazon, with an estimated 2,500 miles of river, to the short and meandering streams found in a desert. 

Rivers can be defined as a natural stream of water that flows downslope towards an ocean or other large body of water (like a lake or sea). Let’s take a look at how rivers are formed.


How rivers are formed or start

Rivers often start out small but get bigger as they get more water in them. They are generally formed in 3 ways: snow that melts, rivers that split, or from a water source under the ground. 

Rivers can be formed (or start) when two different land surfaces meet. This can release water from the earth. This is often called a spring.  When water flows over these low points it creates an erosion channel or valley that becomes longer and deeper as it moves downstream. The water piles up and starts to flow away.

This water can be very clean as it has to travel through multiple layers of rock for several decades. Two-thirds of the earth exist out of water. A lot of it exists under layers of ground. This can come up when there is a hole in the rocks that contain water. If there is a lot of water there, it can form a river.

Another way in which rivers can be formed is by melting snow. Mountains often contain a lot of snow. This is formed by evaporating water from oceans and rivers. When it falls down, it can stay there for a long period of time as the top of the mountains can be quite cold. This can melt when the sun heats it up and this can create a river.

This water is often very clean and usable. It can be colder though. These rivers can dry up when there is no snow melting anymore. For this reason, some of these rivers only exist during the summer. Rivers often have multiple sources and snow from the mountain might be only one. This can explain why rivers can be a lot wider during certain periods of the year than others. A lot of time is being spent to make sure that rivers don’t overflow or don’t dry up. This is done by using water locks and (artificial) lakes. 

Water is also often cleaned before it gets in the river. This ensures us that we have clean and healthy rivers. This ranges from getting plastic out of the water to cleaning wastewater. In the past few decades a lot of time has been spent on cleaning rivers and making sure that they don’t contain pollutants. 

A final way in which rivers are created is by subdividing an exciting river. The river gets split and this can create a new river. This can happen naturally or this can be done by humans. Water is essential for cities as they make it easier to transport wastewater and get fresh water. This is why humans often spend a lot of time channeling water and rivers. Rivers are dynamic and floods can easily occur if the water is not managed.

What makes a river?

A river is a natural stream of water that flows downslope towards an ocean or other large body of water (like a lake or sea). 

From the erosion channel, silt and sand particles are deposited by the moving current to form what we call alluvial fans. Alluvial fans are deposits of sediment that create branching channels that lead to deeper valleys and eventually makeup hillsides. Rivers have carved deep valleys into the bedrock which are called canyons.

Canyons are formed in areas with a porous rock known as karst topography while mountains with more resistant rock called granitic topography do not experience much erosion from flowing streams so they remain relatively flat-topped hillsides known as tablelands or mesas.

How do rivers flow and where do they end?

Rivers flow in a certain direction. This flow is created by the force of gravity. Water is therefore pushed to lower areas. Some rivers flow in only one direction like the Mississippi River. Other rivers flow in both directions like the Colorado River.  This can make it harder to manage them. 

Rivers flow downhill, but when it rains or snow melts, the water in a river can also flow uphill. When that happens, the river will create an erosion channel called a “jerkwater” which is usually very narrow and shallow.

Rivers that flow into oceans and lakes are called estuaries. Once the water flows in seas, oceans or lakes, it stops being a river and become part of a bigger water body.

 Rivers don’t flow straight and often twist and turn as they move forward. This can make their path rather unpredictable. It can also change over time as water can break down rocks and soil. Water banks are often reinforced to make sure that they don’t break away over time. Water has a lot of power and can affect the landscape over time. 


Rivers are formed in three main ways: either as a tributary of another river, snow melts, or when water comes from the ground. Often multiple sources are combined to create rivers. Geographic elements allow the water to flow and create rivers. There are many different factors that determine where a river flows, including the shape of the land, the slope of the land, the amount of rainfall, and temperature.

Rivers and oceans are essential for cities. We use their water to shower and go to the toilet. Rivers are also used to transport our (cleaned) wastewater. This is why a lot of cities are formed around waterways. They make it easier to install plumbing as we don’t have to transport water over a long distance. This also explains why we have to take care of our rivers and oceans as we need them to sustain our current lifestyle.