Why are rivers important?

From the creek whispering through a forest, to the confusion of huge currents twisting against each other in the channel. Rivers take on many forms. They are the direct connection between us and the Ocean but why are rivers important?  

Read about the wider water cycle and how rivers fit into it here. 

Why are rivers amazing? What is an estuary? And what are the threats to these wet wonders? 

What are rivers?  

Let’s start with a quick definition. Rivers are large, natural flowing streams of water. They have banks on either side, they have a source and a mouth. They meander through every continent, from a few kilometres to thousands long.  

Which is the biggest river?  

What does ‘biggest’ mean? Let us start with length, and to answer that, let us start with another question: where do rivers start? Finding where a river begins is notoriously difficult.  

It’s tricky to work out where that first drop comes from. Some rivers begin from a lake or a melting glacier. Others, like the Danube in Europe, start from a spring (water bubbling out of the ground). 

River origin leads to debates over which the longest river is – the Nile or the Amazon.  

The Guinness Book of World Records gives the award to the Nile but does concede “which is longer is more a matter of definition than simple measurement”.  

The Nile, in Africa, has been estimated as great as 7,088 km (4,404 miles) in length, and the same paper puts the Amazon, in South America, at 6,575km (4,085 miles). 

However, a quick search will reveal some debate. 6,650 km (4,132 miles) is more commonly quoted for the Nile, and 6,400 km (3,976 miles) for the Amazon. 

Explorers are always trying to prove otherwise, measuring in a different way, from a different point, to a different point. 
We are #TeamNile.

Next, there is the deepest river in the world: the river Congo.  

It reaches depths of 220m. That is about as deep as the world record for SCUBA diving. By that depth there is little light, and the pressure from the water above is equivalent to having three adult orcas lying on top of you.  

The Amazon stands alone in the amount of water it gathers.  

Once rivers start their journey, they gather in momentum on their mission back to the Ocean. More precipitation and groundwater help fuel their flow, and other streams, known as tributaries, join it along the way.   

Approximately 209,000m^3/s of water enters the Atlantic from the Amazon. This is equivalent to almost 20% of the total global river discharge, the total volume of water rivers release into the Ocean.  

The Amazon is more than the Nile, the Mississippi, in the USA, and the Chang Jiang (Yangtze), in Asia, combined. The brown waters can be seen as far as 100km (62 miles) out to sea, which provided an important navigation tool for sailors hundreds of years ago.  

Where are estuaries? 

Where the river reaches the Ocean, the interface is an estuary. They usually have a mix of fresh and salty water, known as brackish (there are some examples of freshwater estuaries in the Great Lakes of North America). 

Estuaries are highly productive, unique ecosystems. For many different animals they provide food, places to breed, nursery grounds and hosting migratory species.  

But why do rivers matter? 

Rivers are important, as fresh water is key to all life. Rivers have influenced our world historically, geologically and culturally. They support life where it would otherwise be unviable, on land and in the Ocean. They are the ultimate connector. 

Approximately 40 trillion cubic metres of water enters the Ocean from rivers every year. But it doesn’t come alone.  

As water moves over the land, it picks up hitchhikers (such as ions, making the sea salty – see more here). Material dissolves into the river, or the water pulls it along. These can lend colour to the river waters (and often their names). 

There is the Rio Negro in Brazil, named due to the humic acid from decomposing vegetation colouring the water black. The Red Rivers in Peru and North America, from the small pieces of rock containing iron oxides. The Drina in central Europe is green due to the limestone it flows over and the Hwang Ho (Yellow River) in China is named so because of the loess (a type of soil or sediment) it carries. 

They do more than just look good; these multicoloured masses are changing the world. 

How do rivers change the world? 

Flowing over rocks, mud and sand, each particle that the waters pick up change the course of the river and the shape of the land. Look around where you live, you can usually find the fingerprints of water at work.  

Rivers can cut away land and form new land, depositing the sediment it has picked up on the bank or in deltas where they meet the Ocean.  

The Colorado River, in North America, has produced the most remarkable example, carving away the landscape to produce the Grand Canyon, while the Nile Delta shows us how rivers build land too.  

The waters are full of nutrients, iron, nitrates and other essential building blocks for life. When these enter the Ocean, life flourishes.  

How are rivers and estuaries important for us? 

Rivers are incredibly important for one species in particular: us.  

The first great civilisations all rose up on rivers. The Nile, the Indus, the Tigris and Euphrates and the Huang all supported some of the earliest great cities in human history. Think of a big city – if it isn’t on the coast, we bet it is on a river. 

Rivers provide food: the last two very long uninterrupted rivers in Southeast Asia, the Irrawaddy and Salween, provide 1.2 million tonnes of catch annually and support agriculture of over 30 million people. In the US, approximately 68% of the commercial fish caught were caught in estuaries. 

The water rivers carry is crucial for drinking, domestic use and agriculture. More recently, we use it for power and industry, and transport.  

Rivers have held a central place in culture as well, connecting us and our world metaphysically.  

The Whanganui river in New Zealand has been regarded as an ancestor by the Māori people for centuries, and the Ganges is upheld as a place of healing and purity, personified by the goddess Ganga. In Japan, Shinto beliefs hold that each river has its own divine guardian, the Kawa-no-Kami.  

Across many different cultures, rivers have been celebrated and protected.  

What are the threats to the rivers? 

As much as rivers have impacted human civilisation, we have had our impact on them.  

Changes to our water cycle due to climate change have reduced the resilience of our rivers as they experience larger variations in flow. Add that to pollution, developing on their banks, extracting their flora and fauna and even stopping their flow – rivers have had it tough. 

In order to harness the power of our rivers, we have been interrupting their flow. Just 23% of rivers over 1000km long flow uninterrupted into the Ocean, broken up by an estimated 2.8 million dams. 

How does pollution affect rivers? 

It is important to realise there are lots of different types of pollution. The first and most obvious is big pollution – plastic, waste, shopping trolleys – that kind of thing. This rubbish can damage the life in the river itself, spoil the water for use and clog and disrupt the water flow.

The other kind of pollution is the small stuff – chemicals, microplastics and pharmaceuticals. These can disrupt aquatic wildlife, make the water unsafe to drink and accumulate through the food chain.  

The Ganges, in India, is now a stark example of river pollution. In Hinduism, the river is personified as the goddess Ganga, the goddess of purity.   

Just 37% of sewage is treated before entering the river. The banks are lined with tanneries, slaughterhouses, textile mills, chemical plants and hospitals. The waste that fills the river has an estimated 66% occurrence of waterborne disease and contains super-bacteria resistant to antibiotics.  

How are estuaries under threat? 

Estuaries face many of the same threats as rivers. An estimated 55% of global wetland areas has been lost since 1900, due to developing coastal areas. These wetlands provide unique habitats for their inhabitants, who often are not suited to either the freshwater or marine environments.  

We also benefit from the carbon dioxide absorption, offsetting our emissions, and the reduction in the risks of flooding and coastal erosion. 

But we are poisoning them too. Chemicals – pesticides and fertilisers – used in agriculture, are washed into rivers and accumulate in estuaries. This leads to nutrient overloading, or eutrophication, with harmful algal blooms appearing. When these die, the decomposition uses up the oxygen in the water – impacting the animals living there.

How can we look after our rivers? 

Everything is connected, which means you can make a difference from anywhere. Simply being aware of the connection you have with the Ocean is an important step. You can look after it, wherever you are.

Rivers connect us directly to the Ocean. A hot take? All life is essentially marine – everything is connected to and dependent on the Ocean. 

Along with estuaries, they provide important habitats, give us the water we need to survive and bring us closer together through transport and culture. But they are threatened in our new world. As ever, being aware is such a crucial first step to solving any issue.  

Educate others:  

• Share information about river conservation and encourage others to take action. 
• Engage in local initiatives that promote sustainable water management practices. 

Join community and advocacy events:

• Participate in local river clean-up events to help maintain waterways and raise awareness 

Advocate for sustainable practices:

• Support policies that protect rivers from pollution and over-abstraction 
• Promote low-impact renewable energy to preserve free-flowing rivers 
• Be aware of what you use. Harsh chemicals for cleaning and gardening will eventually enter our Ocean. Check your shampoo for harmful chemicals and microplastics. 

Next time you are by a river, take a moment. That is a direct line to the Ocean. See if you can understand the connection humans have felt with rivers throughout our history. Wonder at the power and beauty. Appreciate the importance of our rivers.