What's in our waterways?
Understanding what's in our waterways, the contaminants and where they come from is an important part of taking action to stop them impacting on our environment.
The health of Southland’s freshwater and estuaries has declined due to excess nutrients, pathogens, sediment and other contaminants.
- Up to 35% of groundwater monitoring sites across Murihiku Southland do not meet drinking water standards in relation to nitrogen and/or microbial contamination.
- E. coli at monitored sites (not bathing sites) show a clear pattern of higher concentrations with no lowland river sites meeting the National Bottom Line.
- 44% of SOE macroinvertebrate monitoring sites in the Southland region show declining MCI trends for the last 10 years while 14% show improvements.
- For ammonia and nitrate toxicity three and nine sites respectively are below the national bottom line for toxicity. While this suggests that toxicity may not be causing the compromised ecological condition we’re finding, both ammonia and nitrate contribute to instream plant and algal growth.
- This means that sites assessed as A and B bands (very good and good) for in-stream toxicity effects can still have nitrate levels that increase the risk of excessive algal growth, because this occurs at much lower concentrations than toxicity.
- For dissolved reactive phosphorus, 12 sites are in the D band (poor). Three of the seven monitored estuaries are experiencing nuisance macroalgal blooms and fine sediment problems which has resulted in sea grass loss.
To understand the scale of change required to meet Murihiku Southland draft freshwater objectives, Environment Southland has undertaken modelling of the contaminants nitrogen, phosphorus, E. coli and sediment.
Modelling to date has tested eight of the objectives relating to eutrophication in rivers, lakes and estuaries (for nutrients), visual clarity in rivers (for sediment) and E. coli in rivers.
Find out more about each of the key contaminants we monitor, and some of the scientific modelling we've done to understand how much reduction is required to achieve our goals.
We have estimated the load reductions required to achieve the minimum state required to reach hauora and meet our draft freshwater objectives. Alternative outcomes are also modelled to provide context on risk. The table shows load reductions required to achieve water quality standards in the proposed Southland Water and Land Plan or to maintain current state. It also shows load reductions to achieve the National Bottom Lines for national compulsory attributes and the minimum acceptable state for Southland waterbodies (shown as ‘Bottom Lines’).
Regional reductions needed to meet targets
E. coli in rivers
River suspended sediment
River visual clarity
National bottom lines
47% (33 – 61)
21% (13 – 33)
Proposed Southland Water and Land Plan standards
66% (58 – 74)
69% (59 – 77)
82% (72 – 94)
Hauora - Draft freshwater objectives
70% (61 – 78)
70% (62 – 77)
90% (80 – 96)
Note: the numbers in brackets provide the top and bottom of the 90% confidence interval. The figures use a 20% exceedance criteria.