New Zealand’s water in context

Gareth MorganEnvironment

We have lots of water relative to our population but has that made us blasé about how we manage our water resources? Do we squander it in terms of how much we use, how we use it and abuse it?

The OECD has compiled a number of interesting statistics comparing countries’ water resources, use and quality. The data is a little dated but shows that we are amongst the highest consumers of water per capita, but because we have such a lot of it we consume just a small proportion of our total water resource, and our water is still relatively pristine.

It’s clear from the data that high latitude countries with small populations relative to their physical size tend to have a similar water resource/management profile.

Water consumption

We consume 950m3/capita a year and that puts us second only to the US as the most profligate consumers of water per person in the developed world. In contrast UK water consumption per person is 240m3 a year and in Denmark (where agricultural production is a significant part of the economy) just 130m3 per person per year.

However, when put in the context of total water resources we consume just 1.2% of our total renewable water resources each year, whereas Denmark consumes 4.2% of its total available resources and the UK 18.1%. Americans are the real guzzlers, consuming a whopping 1690m3/capita and 19.2% of their total renewable resources.

Our use of water is skewed toward agriculture (irrigation), which accounts for over half (51.5%) of all water consumption and around a quarter for public, or household consumption. Manufacturing accounts for the balance. There are a number of countries in the OECD with a much higher proportion of their total consumption allocated to agriculture: Mexico and Turkey both allocate around three quarters of total consumption to irrigation, and irrigation accounts for two thirds of total water consumption in both Japan and Australia. So while we appear to have markedly increased the amount of water we pour onto our pastures and crops we look relatively restrained especially given how important agriculture is to our economy.

Waste water treatment

Around 80% New Zealanders are connected to public sewerage systems. That’s not bad for such a sparsely populated country and compares favourably with countries like Canada (72%), Italy (69%), Japan (70%), Ireland (70%), Belgium (55%), and it’s about the same as France and Finland.

But how well treated is the sewerage? We know that many small towns in New Zealand have been pretty basic sewerage treatment facilities. The OECD data is patchy when it comes to the proportion of the population connected to primary, secondary or tertiary sewerage treatment facilities. New Zealand has reported figures for 2000 showing that of the 80% of the population connected to public sewerage facilities 14% are primary treatment facilities (basic), 26% secondary and 40% are tertiary treatment plants. Since 2000 many of the smaller and some of the bigger facilities will have been upgraded improving all the above percentages for New Zealand, and no doubt the same is true for other countries.

Quality of our water

The rapid growth in dairying in New Zealand is making many people nervous about the impact on water quality. Dairying, or course, is not the only source of contaminants – urban waste water, other forms of agriculture and introduced plant and animal pests have all been factors degrading the water quality in our waterways. But intensive dairying is the most obvious and potentially potent source of nitrates as well as adding to phosphate and e coli loads.

The OECD data is interesting in that it shows the three New Zealand rivers covered (Waikato, Waitaki and Clutha) have very low levels of nitrates and relatively low levels of total phosphorous compared to major rivers in other developed countries.

Indeed the Waitaki and Clutha rivers have the lowest and second lowest nitrate levels of any of the 98 rivers reported on. The Waikato has the fourth lowest level of nitrates. Furthermore the differences between our rivers with levels of around 0.02mgN/litre and those with some of the highest nitrate levels, such as France’s Seine at 5.6, and England’s Thames at 6.6mgN/litre, is enormous.

The Government’s Freshwater Policy Statement has set the national bottom line for nitrate concentrations for our lakes and rivers at around 6.9mgN/litre – about the level of the Thames, the worst of the 98 rivers covered by the OECD data for nitrate levels.

The news isn’t quite so good for total phosphates where the Clutha comes in at 8th lowest, Waitaki 12th and the Waikato 22nd out of the 98 rivers for which the OECD reported data.

These comparisons are based on averages of the data from 1990 to the latest reported year – generally 2004. That raises an important point. The latest data is now ten years old. In New Zealand we have added a lot of dairy cows to the Waitaki and Clutha catchments in that time so nitrates levels will be rising in those rivers. But it’s hard to know by how much. Despite having some quite long term data for many of the rivers few exhibit clear long term trends in nitrates or total phosphorous levels.

The fact is nitrogen can take a long time (20-40 years) to leach into waterways and so what we see in the water now is by no means an accurate gauge of the impact that current land use and farming practices will have on water quality over the next few decades.

We really can’t afford to keep making the mistake of going for quick fixes (stouts to kill rabbits), or short-term satisfaction (profits on the back of pollution). The multi million dollar cost of mitigating nitrogen pollution in the Taupo basin is a compelling example of why reducing excessive nitrogen loadings now makes sense. The cost needed to keep nitrate concentrations in our water amongst the lowest in the world will only get higher if we don’t act now.


New Zealand is a lucky country when it comes to water – we have a lot of it and not many people to consume it or bugger it up. However we’re pouring a lot more of it onto parched land to create lush pastures and there’s growng evidence we’re degrading what’s left.

On most measures of water quality New Zealand’s rivers (three of them) rate well in comparison to 98 major rivers in OECD countries. The challenge is to at least maintain but ideally improve water quality.

The National Objectives Framework (NOF) for setting water quality objectives in each region of New Zealand promises to meet that challenge. The jury is out though on whether it will be enough. Does the NOF offer too much wriggle room? Can the government and especially regional councils be confident that the objective of maintaining or improving water quality will be achieved in practice? Time will tell.

New Zealand’s water in context was last modified: December 15th, 2015 by Gareth Morgan
About the Author

Gareth Morgan

Facebook Twitter

Gareth Morgan is a New Zealand economist and commentator on public policy who in previous lives has been in business as an economic consultant, funds manager, and professional company director. He is also a motorcycle adventurer and philanthropist. Gareth and his wife Joanne have a charitable foundation, the Morgan Foundation, which has three main stands of philanthropic endeavour – public interest research, conservation and social investment.