Water quality still mixed bag

The latest water quality information on Southland’s rivers, lakes and groundwater was presented to councillors at the Strategy and Policy Committee meeting yesterday. This latest analysis continues to show that Southland’s water quality is a mixed bag.

Some areas of the region have good water quality but improvements need to be made in other areas. There is an early indication that water quality deterioration may be slowing with more recent trend analyses showing some areas of improvement.

Environment Southland’s director of science and information Graham Sevicke-Jones said the analysis showed our rivers, streams and lakes are generally suitable for wading, fishing and boating but six out of the 55 river monitoring sites did not meet the national e.coli. “Our lakes are mostly suitable for swimming, with the exception of Waituna Lagoon. Our river swimming sites, with the exception of the Mararoa River, do not meet these standards the majority of the time,” he said.

All monitoring sites have nitrogen levels that meet national bottom lines for fish toxicity. However the majority of these sites have nitrogen levels above the more conservative national guideline for ecosystem health.

“Over the last 17 years, nitrogen levels have increased at nearly half (43%) of monitoring sites with only two sites showing an improving trend. However, there are signs of a change in direction, with 18% of sites showing decreasing nitrogen levels over the last 5 years and only two sites show increasing nitrogen levels.”

Phosphorus is also showing some signs of improvement. It is a concern in our rivers as excessive amounts can lead to increased algae and plant growth.

Since 2000, nine of our monitoring sites are showing improvement, while the other 12 sites aren’t showing any trend. This isn’t reflected in the shorter term analysis. Five-year phosphorus results are largely indeterminate of any trend, however one site is still showing an increase in phosphorus levels.

The analysis, available on Environment Southland’s website in a technical report, uses information collected by the council, the National Institute of Water and Atmospheric Research (NIWA) and GNS Science. It provides an assessment of the state and trends of water quality in Southland rivers, streams, lakes and groundwater against compulsory national standards where these are available.

Page reviewed: 04 May 2016 11:53am