Why is the Colorado River brown? Once called the Grand River before its official name change in 1921, The Colorado River has a fascinating history.
The river’s name, “Colorado,” was first recorded by the Spaniards, and it means “colored” or “ruddy,” which perfectly describes the remarkable hue it possesses.
However, many people wonder, “Why is the Colorado River grayish brown?” Is it really dirt or something else? Let’s find out now!
The Colorado River is brown – or red – mainly because it has dirt, mud, sedimentation, and silt, which is why parts of the river are rather clear.
A Brief History of the Colorado River
Frequently referred to as the “river of justice,” the Colorado River has been a focal point for many legal conflicts.
The Colorado River, a crucial resource for the American Southwest, is famous for its breathtaking scenery.
It also helps support:
- Ecosystems
- Communities
- Industries
It has an impact on seven U.S. states and two Mexican states.
An Important Consideration
In a crucial moment in 1948, a groundbreaking agreement was made, dividing the river’s valuable waters among the states it passes through.
In this agreement, Colorado receives the majority share of 51.75% of the water, while Utah, Wyoming, and New Mexico receive 23%, 14%, and 11.25%, respectively.
Why Is the Colorado River Brown?
It is easy to observe that presently, the Colorado River has transformed from a deep navy-blue hue to a rich chocolate-milk brown shade.
But why is the Colorado River so brown? This occurrence is commonly triggered by a surge of sediment moving upstream.
The Ever-Changing Turbidity Levels
Turbidity levels of the Colorado River have changed considerably over the years.
A significant change was noticed following the Grizzly Creek wildfire, which burned over 32,631 acres in Glenwood Canyon in 2020.
Additionally, a unique rain event in the summer of 2021 resulted in significant debris flow in the same region.
According to data, the Colorado River typically experiences 200 NTUs or lower turbidity levels.
During July 20-22, the readings experienced a significant surge, surpassing 600 NTUs. And that truly contributes to its changing color.
Is All of the Colorado River Brown?
Not really! Only some sections of the Colorado River have a brown color.
Just like most rivers, the color of the water is determined by the color and amount of dirt and silt floating in it. If there is not much dirt, the water looks clear.
But the water will look darker if the dirt and silt are dark and black. Interestingly, the part of the Colorado River above Rifle, CO, is pretty clean.
Also, you will notice that the water from the Glen Canyon Dam to Marble Canyon, just above the Grand Canyon, is also clear.
Possible Explanations to Why the Colorado River is Brown
The Colorado River has a unique grayish-brown color, which is truly eye-catching, captivating both visitors and researchers.
However, there are different factors contributing to this specific color.
For instance:
Rock Formations and Sedimentary Influence
The unique grayish-brown hue of the Colorado River is closely tied to the geological makeup of its basin.
It actually meanders through a wide range of rock formations, such as:
- Sedimentary
- Igneous
- Metamorphic rocks
The river’s color is greatly influenced by sedimentary rocks, which comprise a substantial part of the basin’s composition.
Fact: Roughly 75% of the Earth's surface is composed of sedimentary rocks, playing a crucial role in the sedimentary processes within river systems.
Sedimentation Dynamics
The Colorado River’s unique hue is due to complex sedimentation dynamics.
The river’s currents are always carrying sediment, which includes particles like sand, silt, and clay.
The sediment comes from different sources, such as:
- Tributaries upstream
- Erosion of riverbanks
- Human activities like construction and agriculture
The suspended sediment particles in the water column engage with light, causing the scattering and absorption of various wavelengths.
This interaction can potentially make the water look cloudy, which can add to its grayish-brown hue.
An Important Consideration
When the river experiences intense flow, like during the melting of spring snow or heavy rain, its speed rises, resulting in increased sediment movement.
The river’s grayish-brown color can become more intense due to an increase in sediment load as larger amounts of suspended particles are transported downstream.
The Impact of Erosion
Sedimentary rocks, being what they are, consist of minerals and materials that are extremely prone to erosion and transportation by water.
As the Colorado River winds its way along its path, it comes across these rocks that have been transformed and sculpted by countless years of natural forces.
The mighty currents of the river serve as catalysts for transformation, slowly wearing away the rocks and dislodging delicate particles and minerals.
Fact: Over countless millennia, the awe-inspiring Grand Canyon has been sculpted by the mighty Colorado River.
Red Sandstone and Iron Rich Minerals
One fascinating geological aspect that catches attention is the abundance of red sandstone and shale formations throughout the Colorado River basin.
This is quite noticeable in renowned locations such as the Grand Canyon.
The abundance of iron-rich minerals in these formations enhances the river’s vibrant hues.
When water comes into contact with these minerals, it can color the river reddish-brown.
An Important Consideration
The Supai Group, a series of sedimentary rock layers in the Grand Canyon, showcases iron minerals that lend the rocks their distinctive reddish hue.
As time passes, the erosion of these formations causes the release of iron particles into the river, which impacts its color.
The Power of Human Impact
The river’s grayish-brown color has been intensified by agricultural activities in the area, such as irrigation and plowing.
These activities disrupt the integrity of the soil, making it susceptible to erosion caused by wind and water.
The river’s composition and turbidity have changed as sediments containing agricultural chemicals and nutrients are carried into it.
Fact: Around 80% of water usage in the Colorado River basin is attributed to agriculture, resulting in significant soil disruption.
Dams and Flow Regime Alterations
Building dams and water diversion projects along the Colorado River has brought about a fresh era of human influence.
These structures have a significant impact on altering the river’s natural flow regime and patterns of sediment transport.
Dams hinder the natural flow of sediment downstream, resulting in its buildup in reservoirs.
As a consequence of sediment entrapment, there is a decrease in the amount of sediment that reaches downstream areas. This leads to an increase in the presence of finer particles.
Because these finer sediments can be easily stirred up in the water, they add to the grayish-brown hue.
An Important Consideration
The Glen Canyon Dam, responsible for creating Lake Powell, has captured significant amounts of sediment.
This results in a noticeable change in sediment levels downstream, ultimately impacting the river’s appearance.
Fact: More than 15 significant dams have been built in the Colorado River basin, causing changes in the way water flows and sediment is carried.
Climate Change and Future Outlook
Just like the rest of the world, the Colorado River and the area around it are also under serious threat from climate change.
The unique grayish-brown hue of the Colorado River faces a significant threat from climate change.
Here is a bit about that impact:
| Aspect | Impact |
| Changing rainfall patterns | Changes in precipitation can interrupt river flow, impacting sediment movement and water quality. |
| Increasing temperatures | A 1.5°F (0.8°C) temperature rise in a century changes snow melting timing and water networks, affecting sediment migration. |
| Decreased snowpack with accelerated snowmelt | Reduced snowpack and quick snowmelt disrupt sediment flow, lowering silt downstream. |
| Wildfires and vegetation issues | Increased wildfire frequency harms vegetation and erodes soil, and then rainfall brings sediment to the river. |
Climate change that keeps happening could make the problems worse. It can mess up how the river looks, the plants and animals that live there, and how clean the water is.
Takeaway
Why is the Colorado River brown? The Colorado River’s unique hue, a blend of gray and brown, is a result of a fascinating mix of geological elements, sedimentation patterns, and human influences.
The river’s grayish-brown color has been intensified by human activities such as land use changes and the construction of dams.
What affects the color of a river is important to understand to manage its resources and safeguard its ecological and cultural importance.
