Talking on Water 3: What the river-dwellers reveal

The ecological health of waterways is assessed using an internationally recognised index based on the tiny animals (macroinvertebrates) living in a river – including insects, crustaceans, molluscs, worms and leeches. Different species tolerate different levels of water quality and habitat, so the make-up of the macroinvertebrate population tells us a lot about the overall health of the waterway. It’s a more reliable guide to stream health than intermittent water sampling.

Across Taranaki , ecological health of waterways is improving at a majority of sites, and not showing any significant change elsewhere, apart from one site. In more and more rivers, ecological health is the best ever recorded since monitoring began in 1995.

Tiny bugs bring bright news

Taranaki Regional Council scientists assess the health of waterways using an ecological index (the MCI index) based on the macroinvertebrate communities (tiny animals including insects, crustaceans, molluscs, worms and leeches) found in rivers and streams.

Different species tolerate different levels of water quality, so the make-up of the macroinvertebrate population gives a good indication of the waterway’s overall health. It’s a more meaningful and reliable guide than intermittent water sampling of chemical and physical measures.

• Since 1995, the Council has analysed thousands of samples from 57 key sites on 25 rivers and streams across the region. Latest findings (up to and including 2015-2016):
• Ecological health is improving at 46 of the 53 sites at which changes can be determined – that’s 87%.
• Sites showing improvements currently outnumber those showing declines by 6.6 to one, an increase from 5.5 to one in the previous three years and 2.9 to one in 2008.
• ‘Statistically significant’ improvements are now evident at 30 sites, the highest ever recorded and double the number eight years ago.
• Most of the improvements are being recorded in middle to lower catchments of the Taranaki ring plain, in the same areas where intensive farming occurs.

Across the region, ecological health of waterways is improving. In more and more rivers, it is the best ever recorded since monitoring began. All our monitoring sites apart from one are showing improvement or no significant change. The one site showing significant deterioration is affected by natural erosion from the mountain.