What is Brackish Water?

In today’s article, we explain all things brackish water.

brackish estuary

If you’ve been conducting extensive research into different water conditions, because you’re a keen angler or have an interest in the environment and different changes occurring, you may have come across the term brackish water. If you’re not entirely sure what the name refers to, then you’ve come to the right place.

Whether you’re a fishing enthusiast or not, brackish water is a curious thing, that’s mostly naturally occurring, but often manmade and that’s when the problems start. So, what is it, what creates it and where is it generally found?

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So, What Exactly is Brackish Water?

Brackish water is, very simply, water with a salinity (that is, the salt levels present in a volume of the water) falls somewhere between that of sea or salt water and freshwater. If that sounds like a very vague and loose definition, that’s because it is. There isn’t a strictly defined salinity level that’s considered to be brackish. 

brackish water at river mouth

Experts agree that if water has anything from 0.5 to 20g of salt for every kg of water, it can correctly be identified as being brackish. A hydrometer is a device used to gather accurate measurements of the salinity. It does so by comparing the gravity, or denseness of water compared to freshwater.

Although this is the most accurate way to get a reading, the curious thing about brackish water and why it’s not easy to define is that salinity tests conducted in 

How does it Form and Where is Brackish Water Found?

Brackish water is naturally occurring, most of the time, and can be found in various places throughout the world. Different brackish water sources are also formed in different ways. Estuaries are by far, though, the most widely known and common brackish water sources in the world. The place where rivers meet with the sea.

Most well established and large enough rivers incorporate estuaries. However, the most famous of brackish water estuaries in the world are undoubtedly the River Thames in the UK, the Nile in Egypt and in the US, the East River, San Francisco Bay, and the Chesapeake Bay have estuaries. 

sea water estuary

Another type of body of water with brackish water is swamps. As those are characterized as having unique eco-systems and highly changeable levels of salt. Some lakes, seas and other complete water sources are categorized as brackish. Take the Caspian Sea for instance, which although it has that name is a lake and the Baltic Sea, which is the most famous of brackish water seas. 

It’s not just the naturally occurring bodies of brackish water we have nowadays. Over time, humans have contributed to creating some too. Manmade brackish water sources most commonly occur when we have established connections between the sea or ocean and marshlands and when we’ve built levees. 

There are also several fish farms that need brackish water as part of the food production process.

Don’t miss our awesome guide on fishing brackish waters more effectively!

brackish water

Environment for the Tough – Brackish Water Sources

Bodies of water with brackish water present dangerous and interesting challenges to plant and animal life. There are specific species of plants, for instance, that can thrive just a few meters from brackish water in the parts of rivers that are still notably fresh, that would possibly die or struggle to survive where salt levels are not as high as in the sea, but high enough to make it inhospitable. 

Curiously enough, though, there are animals and plants that not only can survive in the unique composition of brackish water but even hold their own successfully. In this regard, take the anubias as a prime example. Although this bright and lively green plant is mostly found in riverbeds and riverbanks, it can still handle brackish water.

The same goes for riverweed and fanwort. Riverweed are often used in brackish water aquariums and appreciated for their fast-growing and thick fronds.

estuary of river and sea

Fish have managed to adapt to brackish water bodies in an even bigger way. They can stay in brackish water while they grow old and get nice and plump and don’t have to worry about the fussier predators. Brackish water is also somewhere where you’ll find a healthy supply of both fresh and saltwater fish mixing. 

Striped bass and red drum fish are two fine saltwater fish examples who regularly swim into brackish environments. Along with scats, gars and arrowheads, who are more at home in freshwater conditions, but that take the chance and enjoy brackish conditions.

Recommended Reading: You can read about some of the most popular brackish water fish species in this guide.


The Effects of Brackish Water on the Environment

The increased occurrence and composition of brackish water has been impacted by the challenges we are facing with climate change and global warming. There is a direct correlation between the increase in salt levels throughout the world and the amount of brackish water there is, resulting in undesirable and unforeseen consequences to not just the surrounding areas, but the people there.

Perhaps the most damaging part of brackish water’s increase is how it decreases the biodiversity of areas it occurs. Although there are some species of flora and fauna that can survive in brackish water conditions, there are not quite as many as those that can survive in either salt or freshwater conditions. 

The real problem is as brackish water occurs in areas where it hasn’t in the past, it can cause numerous species to either migrate elsewhere or even just die.

It can also affect agricultural production too. It already has a similar salinity composition to a plant, which means osmosis doesn’t happen, meaning the plants in question just dry out and then die. As well as preventing harvests from happening or at the very least, reducing them, it also affects the soil and makes it arid. 

So, on one hand, brackish water makes for a great place to fish as you are better able to take on seawater and freshwater fish in the same location, while on the other hand, manmade sources of brackish water can cause far-reaching problems for animals, plants, and humans.

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