Water is such a precious resource, a vital element to life. The fact that we can take for granted the quality of the water that flows through our rivers and streams is down to laws such as the Water Pollution Act and regular monitoring by water pollution officer Danielle Coombes.

Danielle tests both river water and bathing water quality and is also responsible for issuing the licences required by law to discharge certain less desirable substances into our watercourses.

She says she had always wanted to be involved in working in water pollution: ’I studied environmental science at Plymouth University when I was younger then I did my dissertation with the fisheries division. It looked into the environmental factors, so I’d always had a keen interest in it.’

Standing on the bank of the River Neb, she explains the procedures for testing our rivers: ’Three times a year the department [DEFA] does routine monitoring across the island at 87 different sites.

’We use that data to do five-year averages and summaries and we produce a monitoring report which is on our website.

’So, on every site there is a chemical water sample, which is two one-litre bottles of water which we have collected, and that is analysed by the government analyst back in Douglas.’

This will show how much oxygen there is in the water along with the levels of nitrates, phosphates and ammonia.

The oxygen level is obviously important to support the fish and other species living in our rivers and it is influenced by the amount of oxygen also being consumed by microorganisms in decomposing organic matter - in scientific terms the biochemical oxygen demand.

This in turn is influenced by the amount of nitrates and phosphates entering the water and this is where farmers play their part in maintaining good water quality.

Nitrate is derived from, among other things, land run off containing artificial fertiliser and farm slurry spreading.

Slurries and manures are a valuable source of nutrients to promote plant growth and if used optimally, reduce the need for artificial fertilisers but they must not spread on the land in adverse conditions. These include the soil being waterlogged, if heavy rain is forecast within 48 hours, and where land is steeply sloping with a significant risk of water pollution occurring.

The efficient use of artificial fertilisers containing phosphates is another element in protecting water quality.

At 31 of the river sites Danielle monitors she also takes an invertebrate sample from the riverbed, which is why she is now wearing a very impressive set of waders and carrying a catch net.

She explains: ’I kick and disturb the gravel and catch in my net what is disturbed and that sample is preserved.

’Then I go back to the Slieau Whallian lab and I will sit there and I will pick through the invertebrates and I will identify them. From that information you can tell the health of the river.’

These tiny creatures, she says, are a better indicator of water quality than the chemical water sample,

’That sample is just the water quality at that moment of time, whereas the invertebrates better represent the health of the river because they are influenced by the water quality over a period of time,’ she said.

’So you’ll have certain invertebrates that will show the presence of good water quality and certain ones that will show poorer water quality.

’For example, worms. If you get loads of worms then it can’t be a very good water quality, whereas the varieties of mayflies, stoneflies and cadis, for example would be a good water quality which is why we’re at the River Neb.

’Although there’s metals, it’s adapted, and you do get a variety of species here which is good. I would expect to find some mayflies from different families in the mayflies group, stoneflies, some cadis, you could also get a couple of worms and you might get some crustaceans like freshwater shrimps in here.’

And that is exactly what we do find. As Danielle carefully empties her net into a bowl we look closer to see what is there and she starts to pick through what at first glimpse looks like tiny bits of foliage.

But then you see a wriggle here and a dart through the water there.

She puts a finger in and there is a tiny but clearly distinguishable little creature on the end of it.

’This is the larvae stage of these flies and it’s what is food for the juvenile fish. The juveniles will grow up in the rivers and this is what they eat, so that’s why you need a variety of species for them to be able to grow.’

The River Neb has a large population of salmon and trout. Just in this small stretch where we are standing Danielle reckons there will be several hundred.

And she adds that, when it comes to water quality, we can all play our part: ’We like people to report to us and let us know if there is anything they are concerned about. We do try get to them and take a look as soon as possible.’