By Amelia Nurse
What do whitebait need in a stream? How can you tell if a stream is healthy or not? Just some of the questions that school students across the country are being encouraged to ask when they’re taken out to visit local waterways, and encouraged to get their hands and feet wet in a practical session of water testing.
This week we join students from the Koraunui School in Stokes Valley as they discover what the meaning of a healthy waterway is. Two groups are on a fieldtrip led by Zoe Studd, a coordinator from Whitebait Connection and the Island Bay Marine Education Centre, to the Catchpool Valley Stream in the Rimutaka Forest Park, south of the Hutt Valley.
Whitebait Connection is an experiential education programme which operates throughout New Zealand to educate school children about how to evaluate the health of waterways, how upstream and land-based activities can harm waterways and what they can do to take action in their local environment.
As the students measure a series of physical qualities, including water clarity, flow, temperature, pH and conductivity, they learn how all these contribute to the health of a stream.
Conductivity is a measurement of nutrients in a stream, says Zoe Studd.
'If we were in a place where there are a lot of cows, or farm land, or fertiliser or sewage going in, we’d expect a really high number, which means there’s a lot of nutrients in the water. Some nutrients is important but too much and we get lots of algal growth … choking up the waterways.' _Zoe Studd
Next, the students collect invertebrates such as mayflies and caddisflies. Each of these macro invertebrates has a different level of tolerance to pollution and is a good indicator of stream health. Each has a sensitivity score, which “tells us how well it can adapt to poorer water quality or if a habitat has been degraded quite severely.”
After their visit to the Catchpool Valley Stream, the students continued on to the mouth of the Wainuiomata River at Baring Head. The stream is a tributary to this river and the students conducted the same series of tests to see what effects unfenced agricultural land and urban development has on the water and the life it supports.
Here’s the outcome of the students’ big day in the water.
Catchpool Valley Stream
Water Clarity: Average 99cm
Rating: Excellent (enough nutrients to help plants and animals grow)
10 caddisflies, 13 stoneflies, 34 mayflies, 14 Dobsonflies, 7 water boatmen, 9 damselflies.
Overall, the students found that the water quality at Catchpool was excellent.
Wainuiomata River/ Baring Head
Water Clarity: Average 73cm
Rating: quite a lot of nutrients in the water
53 freshwater snails, 2 flatworms, 3 mayflies, 1 stonefly, lots of midges and a few mosquito larvae.