Archive 2013

Happy holidays from Waiology! Waiology Dec 23

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By Daniel Collins

After the recent water quality series, Waiology will be taking a break over the holidays, springing back to action mid-January.

Over the course of the year, Waiology published 67 articles and hosted four series – on wetlands, water governance, water quality, and native freshwater fauna. See the archives for the complete list. Based on visits to specific articles, the most popular one this year was Bob Wilcock’s on dicyandiamide (DCD), at 4500 pageviews. The second most popular, at 2500 pageviews, was my article from last year on the water footprint of milk. A few other highlights from this year were:

Thanks to all the contributors and all the visitors for making Waiology the constructive and informative forum it is. I hope you got a lot out of it.

Have a very Merry Christmas, Happy New Year, and a great time for whatever you get up to. And remember, if you spend time in or beside any water – liquid or frozen – stay safe. Here’s a light-hearted public service announcement from 1951 about water safety…

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

Un-muddying the waters: Series conclusion Waiology Dec 20


By Daniel Collins

Un-muddying the Waters : Waiology : Oct-Dec 2013After 10 weeks and 26 articles, Waiology’s series on water quality draws to a close. We have heard from 26 different contributors from 10 different organisations. Articles spanned topics from states and trends in observational data to diverse management solutions. There were some glaring omissions, for which I apologise, but not all requests translated into articles for one reason or another.

It is hard to provide a summary of the series, and no such summary could canvas the entirety of the science and management or water quality in New Zealand, but I shall offer you some of the more pertinent points.

  • Water quality is generally declining due to land use intensification, and without significant action from a range of sectors it is likely to degrade further. Climate change could add to the problem.
  • Agriculture is the primary culprit for the decline, and dairying in particular, but let’s not forget urban pollution and emerging contaminants, and nor should we tar an entire industry for the activities of a fraction.
  • Also, don’t forget estuaries – they’re on the receiving end of catchment contaminant runoff.
  • Consequences of poor water quality include elevated health risk, shifts or declines in freshwater biodiversity, and diminished recreational opportunities.
  • Recreational water quality guidelines for swimming suitability don’t satisfactorily reflect the science.
  • Water quality limits are being set at the national and local levels, incorporating science, economics, and the myriad of values held dear by community members. But to be effective the limits need to be as precise as the desired outcomes.
  • Many management solutions are being implemented to maintain or improve water quality, from the stream and farm to the catchment and country, informed in part by scientific and economic modelling, but these efforts will take time to pay off.

While the series was running, it was also interesting to see that the news cycle was punctuated by water quality events of its own. The hearings for the Ruataniwha Plains water storage proposal began. The Government’s second round of freshwater reforms were announced, along with an initial suite of water quality limits with the National Objectives Framework. The Parliamentary Commissioner for the Environment released another report on water quality. And a report from Lincoln University identified water as New Zealander’s environmental issue of greatest concern (PDF).

Of ten aspects of our environment, rivers and lakes were ranked the worst condition in the Lincoln report, though they were not necessarily bad. In terms of management, people were also most negative about river and lakes combined, followed by groundwater. The main threats for freshwaters were thought to come from farming, followed by sewage and stormwater, and then industrial activities. And over the 13 years of these Lincoln reports, more and more people blame farming for freshwater degradation.

But why do people believe what they believe? How do these beliefs diverge from reality (if they do)? And how do they affect directions in the science and management? These are three Science, Technology and Society questions that I would dearly love answered.

So turning back to the series, what did you learn? Are the waters less muddied for you now, so to speak? If you would, please fill out the feedback form for the series, it would be most helpful. I would also be some reward for the time I put into the series after hours.

Waiology will of course continue next year with more than just water quality on the agenda. Your requests would help guide article selection.

And finally, in the interests of providing an accessible resource for future readers, here is the final list of articles.

  1. Un-muddying the Waters: Series on NZ water quality. Daniel Collins, NIWA.
  2. A primer on water quality. Clive Howard-Williams, NIWA.
  3. An overview of the water quality in New Zealand rivers. Rob Davies-Colley, NIWA.
  4. Pipes, ponds and beyond: Measuring and managing urban stormwater quality. Jonathan Moores and Jenni Gadd, NIWA.
  5. Bugs in the system: How do we make sense of recreational water quality? Gary Bedford, Taranaki Regional Council.
  6. Effects of water quality on freshwater fish. David Rowe, NIWA.
  7. Water quality – What about the fish and the anglers? Neil Deans, Fish and Game NZ.
  8. Estuaries on the receiving end of catchment runoff. Judi Hewitt, NIWA.
  9. Proposed national bottom lines for water quality. Daniel Collins, NIWA.
  10. Why freshwater management needs to include estuaries? Malcolm Green, NIWA.
  11. Managing nitrogen in the Lake Taupo catchment. Bill Vant and Jon Palmer, Waikato Regional Council.
  12. Monitoring the diversity of NZ groundwater quality. Magali Moreau, Chris Daughney and Zara Rawlinson, GNS Science.
  13. Science and policy merge in water plan. Paul Reynolds, Ministry for the Environment.
  14. Overcoming obstacles to setting water quality limits. Ned Norton, NIWA/Environment Canterbury, and Helen Rouse, NIWA.
  15. Nuisance periphyton – too much of a good thing. John Quinn, NIWA.
  16. Nitrate in Canterbury groundwater. Carl Hanson, Environment Canterbury.
  17. Emerging organic contaminants: A threat to New Zealand freshwaters? Sally Gaw, University of Canterbury.
  18. Water quality models – are they good enough for management? Sandy Elliott, NIWA.
  19. Estuary water quality for ecosystem health and recreation, Christchurch. Lesley Bolton-Ritchie, Canterbury Regional Council.
  20. How does agriculture affect New Zealand’s water quality? Bob Wilcock, NIWA.
  21. Vague expectations get vague results: Freshwaters need targets. Mike Scarsbrook, DairyNZ.
  22. Understanding groundwater quality – why it’s not easy. Chris Daughney and Magali Moreau, GNS Science.
  23. Impacts of climate change on water quality. Daniel Collins, NIWA.
  24. How much dairying is too much in terms of water quality? Daniel Collins, NIWA.
  25. Better water quality won’t happen overnight … but it must happen. Jenny Webster-Brown, Canterbury and Lincoln Universities.
  26. Water quality series: What do you think? Daniel Collins, NIWA.

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

Water quality series: What do you think? Waiology Dec 19

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By Daniel Collins

Un-muddying the Waters : Waiology : Oct-Dec 2013We have almost finished Waiology’s series on water quality, with 25 articles running from the science to solutions. I would now like to take the time to ask what you think about the series and Waiology in general.

Please take a few moments to answer the following survey. All 12 questions are optional. It would be of considerable help in shaping how Waiology serves you in the future. Individual feedback will be kept anonymous and pooled results will be shared on Waiology depending on sample size. And you can always contact me directly. Thanks!

1. What did you like most about the water quality series?

2. Which was your favourite article? (Select from the list below)

3. What did you like least about the water quality series?

4. What topics would you like covered in the future?

5. What about freshwater is most important to you? (preferably up to three) (use the ctrl key to select multiple options)

6. Who do or would you like to receive freshwater science information from? (use the ctrl key to select multiple options)

7. How do you like to learn about freshwater science? (use the ctrl key to select multiple options)

8. Why do you follow Waiology?

9. How do you follow Waiology? (use the ctrl key to select multiple options)

10. Is water related to what you do for a living?

11. If yes, where do you work primarily?

12. Where do you live?

Are you a human? Please enter the following text.

Better water quality won’t happen overnight … but it must happen Waiology Dec 18


By Jenny Webster-Brown

Un-muddying the Waters : Waiology : Oct-Dec 2013If we cannot stop ongoing water quality degradation, and effectively restore degraded water environments, we stand to lose much that we value about New Zealand and our way of life. We will lose recreational opportunities, fisheries and our reputation for primary produce from a “clean” environment. We will lose functioning ecosystems, the ecosystem services they provide and the beauty of our iconic water features. We will have to pay for increasingly higher technology to treat drinking, stock and even irrigation water … like so many drier, more populous or older nations, who have long since lost their natural water amenities. This is not what we have known, or what we wish for our children, or their children. To improve water quality, we need only three things: the will, the means and the time.

This is the final invited article in this Waiology series on aspects of water quality. On the basis of the preceding articles, augmented by my own experience as a water quality scientist, I would like to reflect on where we currently stand with respect to these three requirements. A ‘will’ to improve water quality is clearly evident. Over the last 5 years we have seen an unprecedented level of activity from national government seeking to change NZ’s freshwater management policy, via various primary industry initiatives, the broad, consensus-based Land and Water Forum and the ‘Fresh Start for Freshwater’ programme. A greater role for community decision-making in setting water quality targets for local catchments is a key component of the Freshwater Reforms.

A Lincoln University research student measuring changes in water quality parameters over a 24 hr period in Lake Ellesmere/Te Waihora,  to understand how this large shallow lake responds to catchment land use.  (Photo: J. Webster-Brown)

A Lincoln University research student measuring changes in water quality parameters over a 24 hr period in Lake Ellesmere/Te Waihora, to understand how this large shallow lake responds to catchment land use. (Photo: J. Webster-Brown)

The ‘means’ include the new National Policy Statement for Freshwater Management, highlighted in two of the Waiology articles (1, 2), and its recent amendment to include a more prescriptive National Objectives Framework (NOF). However, the devil is, as always, in the detail. The devil, in this case, is in the science information that underpins this new policy. Water quality degradation is a classic “wicked problem”, with multiple contributing factors, unexpected interactions and often inexplicable environmental responses. The Waiology blog has included articles by some of NZ’s top freshwater scientists, conveying their understanding of the cause and effects of the ongoing water quality decline; causes such as urban stormwater drainage and agricultural activities, and effects as manifested in surface freshwaters, ground waters and estuaries. The authors have also often noted the limits of their current understanding, the difficulties imposed by insufficient data, and how this creates uncertainty in predicted outcomes. This same uncertainty can lead to disagreement amongst scientists asked for comment or advice, as it has with the setting of numerical ‘attribute states’ in the NOF, for example.

To quote author Sheldon Kopp … ‘All important decisions must be made on the basis of insufficient data’. Although robust scientific debate is considered a healthy way to get at the truth in the world of science, it is not particularly helpful to policy makers or to the communities tasked with making decisions about the value of a water body. So how can scientists best support the immediate needs of this brave new world of freshwater management? While acknowledging the need for better data and information about water environments, we can try to communicate the concepts and facts that we do have confidence in, as simply as possible and without contradiction. We can help the policy-writers formulate straightforward, practical policies. Recent freshwater management policy introduces increasingly unfamiliar terminology and complex application principles. In the field of water quality science, there are many examples of simpler guidelines and standards taking precedence over more rigorous, but difficult to use, alternatives.

Scientists can help to manage expectations, by providing guidance on realistic targets for water quality and being honest about likely timescales for change. Which brings us to ‘time’. Even if every positive action taken has the anticipated positive effect, improvements in water quality will not be immediate or perhaps, in some cases, even detectable within our lifetimes. This is just the beginning of a critical time for NZ water quality and good things, in the words of Mainland Cheese, do take time. More reliable predictions of future conditions will be critical during this period to reassure those who grow impatient, that change won’t happen overnight … but it will happen.

Professor Jenny Webster-Brown is a water quality chemist, and the Director of the Waterways Centre for Freshwater Management at the universities of Canterbury and Lincoln.

How much dairying is too much in terms of water quality? Waiology Dec 17


By Daniel Collins

Un-muddying the Waters : Waiology : Oct-Dec 2013On 21 November the Parliamentary Commissioner for the Environment, Jan Wright, released her second report on water quality. It warned that business-as-usual dairy expansion by 2020 would leave our lakes and rivers more degraded than they are now, even with improved mitigation. I’d now like to re-cap what the report concluded, how it got there, and how it was received.

The report

The purpose of the report was to illustrate how land use change could affect future nutrient runoff – nitrogen and phosphorus – based on a simple, business-as-usual scenario for 2020.

Motu used a combined economics-land use model called LURNZ to project what land use changes are likely by 2020, driven by commodity process and knowledge of land use practices and landscape characteristics. Sheep and beef farming were expected to give way to dairying, forestry, and even reversion to shrubland.

A team from AgResearch, Motu and Horizons Regional Council then assessed what mitigation measures would likely be adopted by 2020, such as wintering barns or artificial wetlands. In the end, they assumed that nutrient losses for a given area would remain about the same even as productivity increased – more intense production for the same environmental cost, what DairyNZ promotes as ‘holding the line’.

Large-scale land use change to dairy farming leads to an increase in the amount of nitrogen that gets into freshwater. (From the PCE report)

Large-scale land use change to dairy farming leads to an increase in the amount of nitrogen that gets into freshwater. (From the PCE report)

The land use changes and increased agricultural efficiencies then fed into NIWA’s water quality model, CLUES. This produced projections of nitrogen and phosphorus yields based on land use and landscape characteristics.

In general, based on the single scenario considered, phosphorus loads were expected to change little while nitrogen loads were expected to climb. There was a roughly linear relationship between change in dairying area and change in annual nitrogen load. The report’s conclusion was simple: Anticipated expansion of dairying area would lead to increased nitrogen levels in our rivers and lakes, even with anticipated improved management.

Mixed reactions

News of the report understandably precipitated a range of responses from the agricultural and freshwater communities.

Fish and Game NZ’s CE Bryce Johnson welcomed the report, saying

“…it serves as a stark warning that the nation is at a crossroads: we can either continue with the Government’s and primary production sector’s agenda of doubling agricultural output by 2025 – completely wrecking the environment, our waterways, our estuaries and beaches, our tourism sector, our international brand, and the kiwi way of life in the process – or we can look at smarter ways to grow the economy.”

IrrigationNZ’s CEO Andrew Curtis dismissed the report as an unfair representation of recent land use management innovations.

“IrrigationNZ believes win-wins are possible for agriculture and the environment… . It’s disappointing the report disagrees with this. However that’s what happens when you get carried away with gross assumptions that are then modelled.”

Canterbury and Lincoln University’s Professor Jenny Webster-Brown called the report a wake-up call, based on valid modelling and defensible assumptions.

“However, it would be wrong to treat this outcome as inevitable. … We can use this combined land use-nutrient leaching model to see how the outcome changes for alternative economic and land use scenarios. Identifying alternative agricultural and horticultural uses for our land, ones that can provide a similar economic benefit but have significantly less impact on water quality, would surely be a major step forward in future proofing NZ’s water quality.”

AgResearch’s Rich McDowell, on the other hand, calls the assumptions about mitigation simplistic, going on to say:

“…the PCE report does not give due consideration to current policy (which tend to focus on obvious bad practice) and the recently announced freshwater reforms which could require a step change in N and P management on-farm.”

And these are but a fraction of the responses to the report, public and private.

So what now?

The report is a reminder that unless we significantly improve nutrient management in relation to dairy farming, and/or put limits to the extent of dairy farming, then water quality will degrade across New Zealand. The report was not a simulation of what will come to pass, but one of many possible scenarios. Management is of course improving (e.g., Horizon’s One Plan, Environment Canterbury’s proposed Land and Water Regional Plan, National Objectives Framework), and in time we’ll see their effects. But we cannot be sure how far technical and policy innovations will take us until it happens.

Scenario-based modelling studies, like the PCE’s, are an insightful way of presenting alternative visions for New Zealand’s future, adding to the national conversation of where we wish to be heading. Another part of that conversation was put forward by Shaun Hendy and Paul Callaghan in their recent book, ‘Get Off the Grass’. Nations never get rich through agriculture, they say, so we should diversify our portfolio of economic earners. And setting water quality limits at the national and local scale is yet another part of the conversation being held to answer how much dairying, and intensive land use in general, is too much.

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

Impacts of climate change on water quality Waiology Dec 16


By Daniel Collins

Un-muddying the Waters : Waiology : Oct-Dec 2013Climate change goes beyond warmer weather and more extreme floods and droughts. Effects are expected to include changes to the water quality of our rivers and lakes as well. This has implications for the vulnerability and sensitivity of freshwater ecosystems, as well as water quality limit-setting and catchment nutrient management. These issues, and more, were discussed at a Department of Conservation workshop held last week on the implications of climate change for freshwater conservation.

Middle-of-the-road projections of climate change indicate about a rise of about 2 degC in average temperatures across New Zealand by 2080-2099 compared with 1980-1999.

Middle-of-the-road projections of climate change indicate a rise of about 2°C in average temperatures across New Zealand by 2080-2099 compared with 1980-1999.

One of the most important aspects of water quality is temperature, and as the air warms so too will the water. New Zealand has already seen an increase in air temperature of about 1°C over the last century; over the next century, projected changes are closer to 2°C, depending on how global greenhouse gas emissions develop. Warmer waters would shift the range of freshwater fish south and higher in elevation, depending on the species. The ranges of some species may increase, while others may decline. For natives, this would be influenced further by shifts in the ranges of predator species such as trout. Warmer waters also make algal blooms more common.

Water temperature is also susceptible to changes in the flow regimes of rivers and streams. With more frequent or longer droughts over much of the country, particularly the east, we can expect more pronounced periods of low flow, at least the smaller catchments. These lower flows would mean that water temperatures climb even higher.

At the other extreme, the more intense rainfalls would lead to more intense erosion, delivering sediment to waterbodies – another important aspect of water quality. But we must be careful about extrapolating here. While the most intense storms are likely to become more intense, the less intense storms may not and there may be fewer of them. Studies of long-term erosion under climate change have thus been equivocal.

For nutrient such as nitrate (N) and phosphorus (P), there is little we can say at present, as a lot will depend on land use change. One study out of the University of Waikato warns that by the end of the century the warming of lakes could have a similar effect on trophic status as a 25-50% increase in catchment nutrient loads.

With rising sea levels of about 50-100 cm by 2100, lakes, rivers, wetlands and aquifers along the coast would experience an increase in salinity. Intermittently closed and open lakes would be open to the sea more often, and salt wedges and tidal influence in streams would reach further inland, both influencing aquatic habitat and biodiversity.

Waterborne diseases are also on researchers’ radars with an interactive map of projected impacts recently released by ESR in collaboration with other organisations. Changes in temperature and precipitation, floods and droughts, can influence the potential to contract these diseases for better or for worse.

But on top of climate change we also have land use change, and the two will act in concert. Some land use changes are themselves liable to result from climate change, whether for the purposes of mitigation (e.g., carbon-farming forests or smaller herds of methane-emitting ruminants) or adaptation (e.g., shifts in crop choice and management in response to water resource stress).

So what can we do about all of this? In some respects water quality is almost bound to change (temperature, salinity near the coast), in others it’s unclear (sediment). The first suite of options to consider, then, would be those with no regrets: riparian planting along streams, erosion control, no more than optimal fertiliser use, and so on. These are actions with benefits no matter how the climate changes. Another matter to consider, at some point in the future, is the setting of water quality and catchment load limits that account for the “likely effects of climate change”, as recommended by the Land and Water Forum‘s third report. And of particular relevance to DoC would be the development of conservation strategies that account for the biodiversity threats posed by degrading or shifting water quality in a warming world.

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

Understanding groundwater quality – why it’s not easy Waiology Dec 11

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By Chris Daughney and Magali Moreau

Un-muddying the Waters : Waiology : Oct-Dec 2013Groundwater resources are very important for New Zealand. Groundwater supplies about a third of our abstractive water needs and an even greater proportion of the water required by the agricultural sector.

There is understandably much concern about groundwater quality, particularly in terms of nitrate. High concentrations of nitrate in groundwater that is used for drinking can impair oxygen transport through the bloodstream, particularly in infants. High concentrations can also pose risks to aquatic ecosystems where nitrate-rich groundwater discharges to rivers, lakes and estuaries.

So what is the state of health of New Zealand’s aquifers, as far as nitrate goes? There are a couple of reasons why this question is not easy to answer.

The first challenge is to determine the concentration of nitrate that we should expect in the absence of human influence. It is hard to define this “baseline” because many of our aquifers are already impacted to some degree by human influence, meaning that nitrate concentrations are not representative of natural conditions. One elegant way to estimate the baseline condition is to compare the age of groundwater to the concentration of nitrate that it contains. Application of this technique shows that nitrate concentrations in New Zealand’s groundwater were typically below 1 mg/L (as NO3-N) before the export meat industry started. A similar conclusion was reached in a separate study that used a statistical technique (without water dating) to show that nitrate concentrations above 1.6 mg/l are probably indicative of human influence, whereas nitrate concentrations above 3.5 mg/L are almost certainly caused by human activity.

Idealised shape of the capture zone for a well in a homogeneous isotropic unconfined aquifer. The regional groundwater flow direction is from right to left (modified from Ministry of the Environment, British Columbia 2004).

Idealised shape of the capture zone for a well in a homogeneous isotropic unconfined aquifer. The regional groundwater flow direction is from right to left (modified from Ministry of the Environment, British Columbia 2004).

The second difficulty is that capture zones have been mapped for very few wells in New Zealand. A capture zone is the area of land through which rain or river water enters the aquifer and is ultimately extracted from the well of interest. The land use activities within the well’s capture zone can alter the groundwater quality. So if the capture zone has not been mapped, if we find nitrate concentrations above the baseline, the source of the nitrate may not be identifiable. This leaves us asking “where did this nitrate come from?”

A third difficulty is that groundwater flow is relatively slow. This results in a time lag between nitrate infiltration into the aquifer in a well’s capture zone and detection of that nitrate at the well some distance away. The groundwater dating techniques mentioned above can assist us to understand these time lags, but there are still many locations around New Zealand at which groundwater ages remain unknown. This leaves us with the question “when did this nitrate enter the aquifer?”

Returning to the question posed above, what is the state of health of New Zealand’s aquifers, as far as nitrate goes?

A recent survey evaluated the concentrations of nitrate in groundwater from over 900 wells across the country, using measurements made between 1995 and 2008. Roughly 1/3 of the tested wells had median nitrate concentrations above 3.5 mg/L, which as mentioned above is the upper threshold for natural conditions. The wells with above-baseline nitrate concentrations were found across the country, indicating pervasive degradation of groundwater quality. At roughly 5% of the wells tested, the nitrate concentration was in excess of the drinking water standard that is set for protection of human health.

Although relationships between groundwater nitrate concentrations and well depth were observed, no relationships to land use or land cover around the wells were detected. This lack of relationship between groundwater quality and land use around the wells is in fact a common result that has been observed in several studies in New Zealand and overseas. It can be explained by the factors presented above: it is hard to understand relationships between groundwater quality and land use unless the age and source (capture zone) of the groundwater are known.

Given the importance of groundwater to this country, and given the evidence that groundwater quality is pervasively degraded relative to natural conditions, there is urgency for better understanding of our aquifers. Determining groundwater age and mapping capture zones must become priority activities. Without the ability to unequivocally relate cause (land use) to effect (increasing nitrate concentrations), we will keep telling each other “it wasn’t me!”

Dr. Chris Daughney is the Director of the National Isotope Centre, and Magali Moreau is a groundwater geochemist, both GNS Science.

Ministry of Environment (British Columbia). (2004) Well Protection Toolkit Step 2 (electronic resource). 24 p.; last accessed 30/01/2013.
Morgenstern, U.: Daughney, C.J. 2012. Groundwater age for identification of baseline groundwater quality and impacts of landuse intensification – The National Groundwater Monitoring Programme of New Zealand. J. Hydrol., Vol. 456–457: 79–93.
Daughney, C.J.; Raiber, M.; Moreau-Fournier, M.; Morgenstern, U.; van der Raaij, R.W. 2012. Use of hierarchical cluster analysis to assess the representativeness of a baseline groundwater quality monitoring network : comparison of New Zealand’s national and regional groundwater monitoring programs. Hydrogeology journal, 20(1): 185-200
Daughney, C.; Randall, M. 2009. National Groundwater Quality Indicators Update: State and Trends 1995-2008, GNS Science Consultancy Report 2009/145. 60p. Prepared for Ministry for the Environment, Wellington, New Zealand.

Vague expectations get vague results: Freshwaters need targets Waiology Dec 09


By Mike Scarsbrook

Un-muddying the Waters : Waiology : Oct-Dec 2013You’ll have heard this saying before. You may have even used it as an excuse when talking to your boss at the end of the year. It is equally valid in managing our water resources. If we cannot provide clarity on what we are trying to achieve, how can we expect anyone to make effective decisions and change behaviours?

What should a waterbody draining a highly modified catchment look like? Should it be physically, chemically and biologically indistinguishable from a paired waterbody in an unmodified catchment? Should it be swimmable and fishable? Should it achieve environmental bottom lines, but no more? Should it remain in its current state, or move to an agreed, alternate state? Over what timeframes should change occur?

These are not questions for scientists, regional council staff, or economists to answer. They need to be answered through the frameworks provided in law and under the guidance of instruments such as the National Policy Statement for Freshwater Management (2011).

Communities have been given a more clearly-defined role in water resource management under the NPS for Freshwater Management. Reforms of the RMA, currently under consideration by our government, may even enshrine collaborative processes for community engagement in our legislation. However, the challenge for communities under a collaborative model is no less fraught than the existing Schedule 1 process in the RMA. Drawing the line between what is acceptable, or unacceptable in terms of water quality across a range of values, many of which are conflicting, or even mutually exclusive, is a massive challenge for New Zealand.

From a dairy industry perspective we support the limit setting process set out in the NPS for Freshwater Management and we broadly support the National Objectives Framework that guides the setting of clear freshwater objectives. Having communities more robustly define the water quality outcomes they want is a healthy and desirable attribute of a mature society. Farmers, as part of the community want clear direction on what is acceptable and not acceptable. Furthermore, the dairy industry is fully committed to supporting farmers to meet the limits or constraints a fully-informed community deems appropriate. We are investing heavily in research, development and extension to prepare landowners for farming within limits. There will inevitably be disagreements on the details of methods and pace of change, but the drive to engage all sectors of the community in decision-making is encouraging.

Communities recognise different suites of values in highly-modified catchments versus unmodified catchments. Contaminant concentrations, driven by catchment modification, do underpin the expression of values (e.g. levels of faecal indicator bacteria indicate suitability for recreation), but changes in contaminant levels may or may not change the state of any particular value. To interpret increasing contaminant concentrations as decreasing water quality is unhelpful, particularly in the context of science’s role in informing communities and decision-makers, and especially when the water quality outcomes have not even been clearly defined.

The recent PCE report on land use intensity would have come as no surprise to anyone involved in water quality debates. The report highlighted the relationship between land use intensity and levels of nutrients in rivers. The final figure in that report showed a future prediction of increasing land used for dairy farming and associated increases in nitrate concentrations. The PCE’s analysis provides a very accessible summary of the issues around land use and contaminant loads, but contributes little to the more important debate about what is acceptable or unacceptable in terms of water quality outcomes for catchments where land use is intensifying. Is a 20, 30 or even 50% increase in nitrate loads over the next 10 years acceptable to the community? Science (and economics, matuaranga maori, plus other disciplines) can help inform the community on what are the likely effects of those nutrient increases on the water quality outcomes the community, but the ultimate decision on acceptability rests with communities through the legislated frameworks provided to them.

Let’s not give anyone the excuse of not having clear expectations of what we are asking them to achieve. And let’s not set anyone up to fail in setting unrealistic or unachievable expectations.

Dr Mike Scarsbrook is Environment Policy Manager at DairyNZ.

How does agriculture affect New Zealand’s water quality? Waiology Dec 05


By Bob Wilcock

Un-muddying the Waters : Waiology : Oct-Dec 2013About 40% of the land area of New Zealand is in some form of agriculture. Sheep and beef farming are the most extensive (33%) followed by dairy farming at 6%, and the remainder being horticulture and cropping. Based on a large number of comparative land use studies we have a good understanding of how agriculture affects water quality and know that about 97% of the nutrient loads entering our freshwaters are from diffuse sources, in contrast with point-sources such as pipes and wastewater discharges.

Effluent from a cowshed over 1 km away. (J. Horrox)

Effluent from a cowshed over 1 km away. (J. Horrox)

Pastoral land use contributes three principal pollutant types: the nutrients nitrogen (N) and phosphorus (P), sediment, and faecal microbes. Nutrient enrichment of waterways can lead to unwanted growth of plants (waterweeds and algae). Excess sediment may cause siltation, impair oxygen transfer processes and degrading water clarity. Faecal matter and its associated pathogens presents a risk to human and animal health through waterborne infectious diseases. The extent of this risk is assessed by measuring water concentrations of the benign indicator organism, Escherichia coli (E. coli).

The cumulative effects of more than one of these contaminant may be greater than the sum of their individual parts. For example, elevated levels of N and P may stimulate vigorous plant growth that results in high pH levels during late afternoon and thereby exacerbate the toxicity of ammonia to fish and aquatic insects.

Cattle crossing in Southland. (A. Wright-Stow)

Cattle crossing in Southland. (A. Wright-Stow)

Inputs from specific land uses to waterways are characterised by their ‘yields’, which are the loads of pollutant per unit area per year. Significant differences occur in the amounts of contaminant delivered to surface waters, according to slope and elevation of land. Nitrogen enters surface waters via leaching to groundwater, whereas sediment, faecal matter and P enter streams mostly in surface runoff. Hill-country farms have lower stocking rates than flatland farms, but greater runoff potential because of the steeper landforms. This affects sediment, P and faecal microbes in particular. In contrast, N losses are highest on flatter lands, where the highest stocking rates are.

In general, the order for yields from greatest to least, is as follows:
N: flat > rolling ~ easy ~ steep land
P: steep > easy ~ rolling > flat land
Sediment: steep > easy > rolling ~ flat land

The major source of E. coli in most farming systems is via overland flow from ruminant faeces and this is likely to be greatest on steeper land, although this is not the case where large herds of cattle are allowed direct access to waterways.

Box plots showing the median concentration, bounded by the 25th and 75th percentiles, the 10th and 90th percentiles as whiskers, and outliers as dots, for N, P and sediment annual loads for each stock class of land use.   ‘None’ refers to non-agricultural rural land uses, such as exotic plantation and native forest, while ‘mixed’ refers to a catchment with more than one stock land use class (McDowell & Wilcock 2008).

Box plots showing the median concentration, bounded by the 25th and 75th percentiles, the 10th and 90th percentiles as whiskers, and outliers as dots, for N, P and sediment annual loads for each stock class of land use. ‘None’ refers to non-agricultural rural land uses, such as exotic plantation and native forest, while ‘mixed’ refers to a catchment with more than one stock land use class (McDowell & Wilcock 2008).

A comparative study of different sorts of pastoral farming found that dairy farms on flat land at low elevations lost the most N, but very little sediment, although it was not statistically different from forest, sheep and mixed land uses. Deer farming tends to be on rolling land at a significantly greater elevation than dairy, but not other land uses. Deer farms lost significantly more sediment than any other farming type but had similar losses of N, except for dairy farming. The remaining land uses (sheep and mixed), were in lands with similar slope, elevation, and sediment and N loss. However, it should be noted that loads reported from non-agricultural land uses demonstrated the least loss of N, P, sediment or E. coli.

Estimates have been made using the SPARROW (SPAtially Referenced Regressions On Watershed attributes) model to estimate their relative contributions of nitrogen (N) and phosphorus (P) to freshwaters and to the coasts of New Zealand. Dairying and sheep+beef farming each contribute 30-40% of N entering freshwaters and the coast, with forests contributing most of the remainder. About 50% of P entering freshwaters and the coast is in sediment, about 20% from sheep+beef farming and 10% from dairying.

A broad suite of mitigation measures is available to farmers and offers some hope that increased production need not be accompanied by water quality degradation, so long as they are widely adopted (PDF; Waikato Regional Council’s ‘menus of practices’).

Dr Bob Wilcock is a NIWA Principal Scientist and Programme Leader – Causes and Effects of Water Quality Degradation

Elliott, A.H.; Alexander, R.B.; Schwarz, G.E.; Shankar, U.; Sukias, J.P.S.; McBride, G.B. (2005). Estimation of nutrient sources and transport for New Zealand using the hybrid mechanistic-statistical model SPARROW. Journal of Hydrology (NZ) 44: 1–27. (Abstract and PDF)
McDowell, R.W.; Wilcock, R.J. (2008). Water quality and the effects of different pastoral animals. New Zealand Veterinary Journal 56(6): 289-296. (Abstract)

Estuary water quality for ecosystem health and recreation, Christchurch Waiology Dec 04


By Lesley Bolton-Ritchie

Un-muddying the Waters : Waiology : Oct-Dec 2013The quality of the water in an estuary influences the health, abundance and survival of the plants and animals that live in or pass through it and the suitability of estuary water for contact recreation. For the plants and animals it is the concentration of toxicants and oxygen in the water that can affect the survival of species and excessive nutrient concentrations can affect the growth of nuisance macroalgae, phytoplankton and microphytobenthos. For contact recreation it is the concentration of faecal indicator bacteria and hence the likely presence of pathogens that can affect human health.

Aerial view of the Estuary of the Heathcote and Avon Rivers/Ihutai. Red areas – Coastal AE water, the remainder of the estuary is classified Coastal CR water.

Aerial view of the Estuary of the Heathcote and Avon Rivers/Ihutai
Red areas – Coastal AE water, the remainder of the estuary is classified Coastal CR water.

The following is a case study on water quality in the Estuary of the Heathcote and Avon Rivers/Ihutai in the south-east of Christchurch. The Canterbury Regional Coastal Environment Plan has assigned two water quality classes to this estuary. The red shaded areas in the map are designated as Coastal AE water, i.e. for the maintenance of aquatic ecosystems. The remainder of the estuary is designated as coastal CR water, i.e. for contact recreation and the maintenance of aquatic ecosystems.

For many years Christchurch tertiary treated wastewater was discharged into this estuary. This wastewater was a source of ammonia nitrogen, phosphorus, faecal indicator bacteria and pathogens to estuary water. Ammonia nitrogen often occurred at potentially toxic (to marine life) concentrations at sites in the vicinity of the wastewater discharge point. When the Christchurch City Council applied to Canterbury Regional Council to renew its’ resource consent to discharge this wastewater into the estuary, it was declined. On 4 March 2010 the wastewater discharge was diverted away from the estuary; the wastewater is now discharged into Pegasus Bay some 3 km from shore.

Ammonia nitrogen concentrations around the time of high tide at Penguin Street, South Shore, January 2007 – December 2012.

Ammonia nitrogen concentrations around the time of high tide at Penguin Street, South Shore, January 2007 – December 2012.

Within months of the diversion of the wastewater there was up to a 90% decrease in ammonia nitrogen and phosphorus concentrations in estuary water. This decrease was interrupted by the 2010-2011 earthquake sequence when raw sewage was discharged to the rivers and directly into the estuary because of broken infrastructure (raw sewage was discharged directly into the estuary in the Penguin Street area).

The dissolved inorganic nutrients in the wastewater also meant more than enough nutrients in estuary water to allow for the prolific growth of the nuisance algae sea lettuce and the red algae Gracilaria chilensis.

Sea lettuce (green) and Gracilaria chilensis (red) on the mudflats.

Sea lettuce (green) and Gracilaria chilensis (red) on the mudflats.

While there are still post-earthquake issues with infrastructure, in the main the quality of the river water flowing into the estuary now has the largest influence on nutrient concentrations in estuary water. Both rivers arise from springs that are fed from groundwater in the shallow aquifers. Notable concentrations of nitrate occur in the spring water (PDF). It is the nitrates in the spring water that now have the greatest influence on dissolved inorganic nitrogen concentrations in estuary water. However, there are other nutrients sources to the river and directly into the estuary including stormwater (at least 67 outlets into the estuary), point source discharges from industrial sites, infrequent sewage overflows, catchment geology and the presence of large numbers of waterfowl (PDF).

When wastewater was discharged into the estuary the suitability for recreation grade at all estuary sites was Poor or Very Poor. With the removal of the wastewater sites now have either a Poor or Good grade The three sites that still have a Poor grade are within the area classified as coastal AE water. The concentration of faecal indicator bacteria at these sites is primarily influenced by faecal indicator bacteria loads in river water (from waterfowl and dogs; PDF) and one area supports an abundance of waterfowl.

Future improvements in nutrient and faecal indicator bacteria concentrations in estuary water can be achieved by improved stormwater quality and reducing the number of industrial point source discharges. It is unlikely that waterfowl or dog numbers will decrease. As this is an urban estuary there will always be human influences on water quality. However, the aim is to minimise the impact on aquatic ecosystems and to allow people to be able to use the estuary for contact recreation without having their health compromised.

Lesley Bolton-Ritchie is a coastal water quality and ecology scientist at the Canterbury Regional Council.

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