Proposed national bottom lines for water quality

By Waiology 08/11/2013 10


By Daniel Collins

Un-muddying the Waters : Waiology : Oct-Dec 2013The Government recently released a new round of freshwater reform proposals. A significant part of them included additions to the National Policy Statement for Freshwater Management with regards to water quality.

The NPSFM currently directs Councils to undergo a process of setting limits for water quality degradation, but neither the process nor consistent numerical targets had been outlined. Until now.

FWManagementCycleTargets that have now been proposed within the National Objectives Framework (NOF) include “national bottom lines” – thresholds of water quality attributes that good management should prevent our waterways from crossing. For Version 1 of the NOF, the proposed attributes, their limits, and implications are summarised in the table below.

It is important to understand, though, that Councils are obliged to maintain or improve water quality within their regions. They cannot simply let conditions degrade down to the bottom line. And so the NOF also includes other water quality bands, much like a report card, where the bottom lines separate a C grade from a failing D.

Attribute Water body Bottom line Description
Chlorophyll a Lakes 12 mg/m3 (ann. median), 60 mg/m3 (ann. max.) Lake ecological communities are moderately impacted by additional algal and plant growth arising from nutrients levels that are elevated well above natural reference conditions.
Total Nitrogen Lakes 750 mg/m3 (ann. median, seasonally stratified/brackish*), 800 mg/m3 (ann. median, polymictic) (same as above)
Total Phosphorus Lakes 50 mg/m3 (ann. median) (same as above)
Nitrate toxicity Lakes and Rivers 6.9 mg NO3-N/L (ann. median), 9.8 (ann. max.) 80% species protection level: Starts impacting regularly on the 20% most sensitive species (12% reduction in growth)
Ammonia Toxicity** Lakes and Rivers 1.3 mg NH4-N/L (ann. median), 2.2 (ann. 95%ile) 80% species protection level: Starts impacting regularly on the 20% most sensitive species (reduced survival of most sensitive species)
Dissolved Oxygen Rivers (below point sources) 5 mg/L (7-day mean minimum), 4 (1-day minimum) Moderate stress on a number of aquatic organisms caused by dissolved oxygen levels exceeding preference levels for periods of several hours each day. Risk of sensitive fish and macroinvertebrate species being lost.
Periphyton*** Rivers 200 mg chl-a/m2 Periodic short-duration nuisance blooms reflecting moderate nutrient enrichment and/or alteration of the natural flow regime or habitat.
E. coli (Escherichia coli) Lakes and Rivers 1000 E. coli/100 mL People are exposed to a moderate risk of infection (between 1 and 5% risk) from exposure to water used for wading or boating (except boating where there is high likelihood of immersion).
Cyanobacteria – Planktonic Lakes and Rivers Biovolume equivalent of < 1.8 mm3/L of potentially toxic cyanobacteria OR < 10 mm3/L total biovolume of all cyanobacteria Low risk of health effects from exposure to cyanobacteria
Suitability for Recreation Grade (SFRG) Lakes and Rivers Fair Water-quality tests and assessment of potential contamination sources indicate recreational beaches within this category have a moderate risk of infection. The beach is generally satisfactory for contact recreation, though there are potential contamination sources. Caution should be taken during periods of high rainfall, and contact recreation avoided if water is discoloured.

* Intermittently closing and opening lagoons (ICOLs) are not included in brackish lakes.
** Based on pH 8 and temperature of 20⁰C.
*** Exceeded on no more than 2 occasions, with no exceedances in successive months (based on a monthly monitoring regime).

This covers many of the water quality attributes already discussed in the current Waiology series, or will be discussed in future articles, but what’s missing?

The Government’s proposal also lists attributes that will come under consideration during 2016-2019. These cover wetlands, groundwater, mahinga kai, and further attributes for rivers and lakes. Massey University’s Russell Death argues that there should have been no need to delay inclusion of some of these limits.

No limits have been proposed for estuaries, as of yet, but there is progress in that direction.

No limits have been proposed with regards to invertebrates as bioindicators, which Massey University’s Mike Joy points out should be included, however the bioindicators periphyton, chlorophyll-a, and cyanobacteria are there.

And there is some debate about the utility of the SFRG, and of lumping all sources of E. coli together (see pending Waiology article).

We can now expect continued progress on community-based limit-setting as well as expansion of the list of attributes within the national bottom lines. This is a very significant opportunity for prioritising science directions: How do we fill the gaps in the water quality limits?


Dr Daniel Collins is a hydrologist and water resources scientist at NIWA.


10 Responses to “Proposed national bottom lines for water quality”

  • Jenny Webster-Brown, Canterbury/Lincoln Universities, also notes the absence of limits regarding heavy metals, arsenic and organic compounds. And in some weeks time we’ll hear about novel contaminants. [Daniel]

  • While the bioindicators of chlorophyll A, periphyton and E. coli are very useful, these organisms have a fast generation rate, thus they give a short-term picture. Macroinvertebrates and fishes are much longer lived, which can give an idea of habitat suitability and changes over a much longer period. The presence or absence of sensitive, migratory or longer-lived species tells us so much more about the health of the waterbody over time. Unevenness in the size class structure or ages of these organisms in a single, thorough sampling session at a single site can indicate improvements or declines in the local habitat, water quality both above and below the site sampled and barriers to inland migration below the site. In comparison, the microorganisms give a snap-shot of recent conditions and require long-term repeated monitoring to show trends.
    Short-term bioindicators are very useful but the health of a river over the long term and broader scale show a far more detailed picture.

  • Indeed, instantaneous measurements of quickly varying physio-chemical is one thing, but biological attributes are another – the longer-lived and higher in the food chain the more they integrate conditions over time and fill in our observational gaps. I have invited an article on this, so hopefully it can be added to the series. [Daniel]

  • Doesn’t this measure seem very untrusting of councils and communities in the collaborative process. Is that a good way to start collaboration? Without trust?

  • Setting a “bottom line”. Why? Why not trust councils and communities to do a good job of setting limits?

    Setting “bottom lines” seems untrusting to me.

  • I see. This gets into governance and values issues which are a little more peripheral for me, but I gather that Councils were actually calling for national, consistent guidelines. It saves them reinventing some of the science wheels, and gives them more time for the deliberative community processes. But there’s more to the proposals than bottom lines (Councils are obliged to maintain or improve conditions), and more to limit-setting than science. I hope this provides at least some of an answer, though MfE would be better placed to answer. I am expecting an MfE article on the NOF, so I’ll see if it can cover off your question. [Daniel]

  • I realise that I am on a science blog making emotional statements but I think it is important. Collaboration requires managing people and their emotions. The first step of collaboration is one of mistrust. It hacks me off and I am not the only one.
    I’d suggest those defining collaboration employ some social science people. Either that or stare at themselves in the mirror for some time.

  • I agree. This is why I expanded Waiology’s scope from just science (and originally just hydrology) to all freshwater issues. The science is advanced and understood better with appreciation of the societal drivers. Chris Abruckle’s article, from the water governance series, gets very close to this point. And Landcare Research are progressing with the social science and freshwater front (we’ll hear from them later), among others, though I believe NZ is lagging behind N.America on this one – too few social scientists who focus on and understand water, and too few freshwater scientists willing/able to collaborate with soc.sci. As the water quality series progresses, we will see a shift from numerical values to societal ones. [Daniel]

  • Please may I request a copy of the diagram – managing fresh water in NZ – friom above – emailed to me – as it is not clear on this website page, and I have saved a copy and still not clear.

    Thanks
    Warren