Data reveals the impact of land cover on river water quality

Today, the team at Land, Air, Water Aotearoa (LAWA) released the annual update of New Zealand’s river water quality monitoring data. Data analysis by Cawthron Institute has revealed water quality is poorest in New Zealand’s urban waterways and a large percentage of rivers in catchments dominated by pasture are under pressure. Unsurprisingly, the best water quality is found at sites surrounded by native bush.

Cawthron Freshwater Ecologist Dr Roger Young led the analysis for the LAWA River Water Quality National Picture Summary (2010 – 2019) and said, “Looking across four key indicators of water quality, it’s clear that land cover, and by implication land use, has a strong effect on the health of our waterways.

“For the national level analysis, we focused on the state of our rivers and streams and looked at how this compares for different land cover types, and how it has changed over time. We found water quality was best in our native vegetation streams and worst in our urban waterways.

“Unfortunately, we found the overall state of E. coli, MCI (macroinvertebrate community index), ammonia toxicity, and DRP (dissolved reactive phosphorus) has not improved over the past 10 years and that more work and time is needed for the benefits of restoration efforts to become apparent,” said Dr Young.

Environment Canterbury Chief Scientist and LAWA River Water Quality Lead Dr Tim Davie said through improved regional council monitoring networks and science programmes, the sector is learning more about where the pressures are.

“Since 2015, the number of river and stream sites regularly monitored by the regional sector and reported on the LAWA website has increased by more than a third. This represents significant investment and a commitment to better understanding our freshwater quality and the interventions that can help.

“Interventions to improve river health include preventing sediment and nutrients entering waterways, upgrading infrastructure, using water sensitive urban design, restoring stream habitats, and ensuring appropriate flows.

“Regional sector science will continue to help inform freshwater management and restoration through regular monitoring, researching, and reporting. There’s a lot of work ahead to give effect to Te Mana o te Wai; the concept that the health of our waterways is paramount,” said Dr Davie.

The LAWA project website shows the most up-to-date water quality data for rivers and streams monitored by regional and unitary councils, and National Institute of Water and Atmospheric Research (NIWA). Here New Zealanders wanting to learn about local river water quality can explore the state and trends of monitored waterways in their catchment: www.lawa.org.nz/explore-data/river-quality.

"Hawke’s Bay Regional Council Chief Executive and Ministry for the Environment Freshwater Implementation Group member James Palmer said the updated data released today adds weight to need for greater action on the ground to improve water quality.

The LAWA River Water Quality National Picture Summary indicates that an acceleration of efforts is required to move the needle on freshwater improvements, and it provides further information on where the most degradation has occurred.

“The challenges at our urban, pastoral, and non-native forest monitoring sites shows the stress rivers are under following more than 150 years of population growth and changes to land use.

“While the Government’s Essential Freshwater package moves us in the right direction, to see meaningful progress in water quality is going to take time and will require a joined-up response from communities, industry, iwi, councils, and central government,” said Mr Palmer.

LAWA is a collaboration between New Zealand’s 16 regional and unitary councils, Cawthron Institute, and Ministry for the Environment, with support from Department of Conservation and Statistics New Zealand.

 LAWA presents river water quality data for waterways in all 16 regions in New Zealand.