Today we were joined by Cathy Driscoll from SCA to demonstrate the sampling and testing methodologies we’ll be using to keep track of water as it runs through our little part of the catchment in North Katoomba.

The first test is visual. With the aid of a glass tube with wavy lines at the bottom, we’ll be able to measure how clear the water is. Today’s sample runs very clear and so we give top marks for turbidity. Next comes ph, that’s how acid or alkaline the water is, and 5 groups all come in somewhere between 5 and 6 on the chart. It’s super easy to tell as there are four colours to match. As many gardeners will tell you, it’s not so much the ph reading itself that is important, but what it indicates about potential substances that might be easily available to the many lifeforms, from mocroscopic to crustaceans, fish, and turtles our waterways support. One thing we know has a big impact on the creatures that can live in water is the salinity level, that is how salty it is. There are a bunch of different salts that we might have present, and they all change the way electricity is conducted through water, the higher the conductivity, the more salt is present.

A probe is presented, we’ll use this to test for electrical conductivity. This reading is effected by the amount of dissolved salts, and so tells us the salinity level. Our reading today came out pretty good (not much salt)

For the next test we squeeze out precisely droppered amouts of reagents to our samples and insert the sample bottle into a colorimeter. Correctly done this can give us an tells us an accurate reading for oxygen and phosphates.

Now we’re all set, and we’ll continue to test the water on the last Friday of the month. If you’re interested to read about the chemistry, more details can all be found on the Sydney Catchment Authority’s website


2 thoughts on “Streamwatch

  1. Hi Kat, I am a year 10 student from St Columbas researching salinity.
    I came across your website and would like to ask you a couple of questions if I may.
    1. What Salinity results have you obtained, and where are you testing?
    2. What is affecting the salinity rate in the area you are testing?
    Thank you for your time.

    • We’ve not been testing very recently, so I can’t be too much help with current information. I think our testing generally showed low salinity levels I’d be happy to check our old results if that would help.

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