Getting to Grips with Water Salinity

What is salinity? Put simply, it refers to the ѳaltinessҠof a given body of water. It is the concentration of dissolved mineral salts therein נand is often measured either directly by its concentration or through electrical conductivity, which it affects.

But letҳ take a closer look at measuring water salinity and what it indicates.

How to measure water salinity

Water salinity is typically calculated by measuring theelectrical conductivity of water. Dissolved salts conduct electrical currents, so a higher conductivity measure indicates higher salinity.

Aquareadҳ salinity measurement, for example, is calculated using a mix of electrical conductivity, temperature, and other measurements in a constant equation. The output is shown in Practical Salinity Units (PSU), which can be translated into Parts per Thousand (PPT) if you prefer.

Whenmeasuring the salinity of water, our sensor can be used for both short and long-term recordings depending on your needs.

Typical water salinity ranges

In general, freshwater exhibits a salinity level of less than 0.5ppt and seawater usually sits around 35ppt. Of course, not all bodies of water are at either end of this spectrum, for example:

Brackish waters (Mesohaline) are usually between 5ppt and 18ppt
Salt marshes and swamps (Polyhaline) are usually between 18ppt and 30ppt.

Salinity slowly increases as you move away from freshwater sources andtowards the ocean.

What causes changes in salinity?

Fluctuations in salinity can be natural, including:

The weathering of rocks containing minerals, like salt, increases salinity
The input of rivers, rain, snow, and ice decrease the levels of salinity.

These twonatural processes tend to counterbalance each other when undisturbed.

But changes in the salinity of a body of water can be unnatural, too נthis is known as ѳecondary salinityҮ Agricultural and irrigation processes cause an increase in salinity because of the chemicals often used (such as chloride).

The over-irrigation of crops or inappropriate soil without drainage, for example, can cause salt to leak into groundwater. This, in turn, leads to irrigation salinity, whereby salts accumulate in soil and cause poor plant health.

The impacts of salinity on water quality

If a body of water exceeds its natural salinity levels because of pollution, the effects can be devastating.

The aquatic animals that live in freshwater like rivers and ponds are simply not able to tolerate a higher salinity level נand often die as a result. Scientists have also made some interesting correlations, like the fact that road salts have been associated with themasculinisation of frogs in North America, leading to an imbalance in the males to females ratio.

High-salinity water is heavier than low-salinity water, so when brine runs into surface waters it can sink to the bottom and form a barrier. This stops the natural exchange of nutrients and oxygen between the upper layers of the water column and the base. As a result, the environment can become low in oxygen, and become a deadzone where aquatic organisms canҴ survive.

Itҳ important to remember that seemingly small changes like these נones that affect, say, the fish population of a single pond נhave ripple effects beyond their initial impact. A single pond may feed many species of bird and mammal, which in turn feed larger animals, and so on.

Evidently, itҳ crucial to stay on top of salinity measurements! It can help determine the extent of the impact of effluent from industry, and is also a fundamental parameter for healthy fish farming. Discover ourwater quality monitoring equipment to get started.

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