No matter how large or small a body of water is, a stream is responsible for carrying water to everything in nature that needs it.
Plants, animals, and the population require enough water to share, so the world can never have too many streams popping up and helping towards the common cause.
Some streams, such as the ephemeral stream that is the main focus of our article, are only temporary and carry water for only a short period of time.
However, this doesn’t mean that an ephemeral stream is any less important to nature than a permanent body of water - sometimes it actually makes the temporary stream more valuable.
Below we’ll be taking a look into what an ephemeral stream is and how they occur in nature.
These streams are not the same as intermittent streams because the latter occurs seasonally. Now that we’ve piqued your interest, let’s get right into the definition of an ephemeral stream!
What is an ephemeral stream?
An ephemeral stream is a body of water that flows for only a short period of time before drying up and forgetting its past life of ever being a stream.
The main distinction between a perennial and an ephemeral stream is that the former is a permanent fixture in the earth’s make-up, and the latter only serves its purpose for a short period of time.
Ephemeral streams are made from precipitation and don’t receive any water from any sources such as melted snow or larger bodies of water. Instead, they take moisture from precipitation and pool it all in one place to create a stream.
These kinds of streams are most commonly found in either arid or semi-arid areas of the world where the most precipitation occurs. It will also rain infrequently in these places, but this is not where the stream gets the bulk of its water.
The water table distinction
Sometimes it can be difficult to distinguish between a perennial stream and an ephemeral stream. For example, if you’re not studying a stream for a prolonged period of time you might not know whether it’s permanent or temporary.
Luckily for stream enthusiasts out there, there is an easy method of distinguishing between the two - as long as you know what the water table is.
If you’re not aware of this term, we’ll quickly go through it now. In short, the water table is the line between the saturated and unsaturated zones underground. If there are any empty spaces below the water table, they will quickly be filled with water to create lakes, ponds, and rivers.
So, how does this relate to ephemeral water? Well, if the body of water is below the water table it will be a permanent stream because the groundwater will always keep it topped up.
However, ephemeral streams don’t find themselves below the water table and therefore they don’t get any groundwater to keep the streams around.
If you can find out whether the stream is above or below the water table, you’ll be able to determine whether it’s a perennial or ephemeral stream.
How are ephemeral streams formed?
I think that everyone can guess how a permanent stream is formed on earth, but how do ephemeral streams come about? If there is no source of water coming from underground, they must be getting the water supply from above ground, right?
This is correct, as when too much rain falls with not enough places for it to pool, a temporary stream must be made to carry the water away from where it is raining. This can be very helpful for some areas of land as the ephemeral streams can prevent the water from ruining the ground.
Depending on how much rainwater falls at once, it is possible for more than one ephemeral stream to be formed and meet with each other further away from where they were formed. The more rain that falls, the longer the streams will be as there is more water to be carried away.
Large quantities of water will be more likely to allow the ephemeral stream to join with a perennial stream. Here the rainwater will be carried all the way into the permanent body of water. The ephemeral stream will continue to lead the rain into the perennial river until there is no more water to offer.
On the other hand, if there is only a little amount of rainwater to carry away, the ephemeral stream might take the water a short distance before drying up and being forgotten forever. As ephemeral streams are only small bodies of water, they’re often evaporated or absorbed quickly.
What are arroyos?
Arroyos are channels in the earth that are created by larger and more substantial ephemeral streams.
The larger the ephemeral stream, the more it will cut into the earth on its path to wherever its destination might end up being. Once the ephemeral stream is dried up and forgotten, all that is left is an arroyo where the water once had been.
These remain in the earth as dried pathways and can be used multiple more times for new ephemeral streams every time that they’re created from precipitation. If an ephemeral stream uses a pre-existing arroyo, it will continue to eat away at the earth and therefore make the arroyo bigger.
The more ephemeral streams that are created, the more impressive these pathways become. In some arid and semi-arid areas, there are large networks of arroyos just waiting to carry more ephemeral streams around. These are very impressive naturally created sights to be seen!
‘Ephemeral’ comes from the Greek word ‘ephēmeros’, which translates to ‘lasting for a very short time’. Such a word could not be truer for an ephemeral stream, as they only grace the earth for a very short and sweet period of time.
Ephemeral streams have one purpose and ensure that it’s completed before they’re absorbed or evaporated. We hope that you’ve found some valuable insight into what ephemeral streams are and how they are formed.