Our water: 5 takeaways from today’s report

The first detailed report on New Zealand’s fresh water is out from the Ministry for the Environment and Statistics NZ. It’s the second big report to be issued under the Environmental Reporting Act 2015, which requires the ministries to report on the state of, and pressures on, our environment (the first was on the marine environment). The full series will be bundled together for a combined environmental assessment in 2019. Eloise Gibson picks the top five takeaways from today's water assessment.

1. There’s a shocking amount we don’t know about our water.

Considering the furious debate about water, there is a huge amount missing from the long-term data. The report lists in detail all the things we really should know, but don’t: how many rivers have problems with algal blooms, the state of health of our remaining wetlands, how much sediment is being deposited in our water bodies, and how many are left of some of our threatened native freshwater species (and where they live). Even some indicators we think we are tracking remain surprisingly blurry – like how much E.coli is in many lakes and waterways, whether that E.coli is going up or down, and how much water farmers are using for irrigation. While it seems logical to link dairy intensification with increased nitrogen pollution (which was worsening at 55 percent of monitored river sites) the report is shy of saying what kind of farms are increasing the run-off to water. Exactly what is coming from crops, sheep, beef or dairy is listed among the many unknowns. As the ministries’ technical experts pointed out in a media conference this morning, collecting the missing data will cost buckets of money. They called for a public conversation about what the top priorities should be. 

Some of the technical advisers who helped prepare the report pointed out that some of the knowledge gaps may be readily fixable. One of the big missing links was the lack of detail about what farming practices were causing what effects on nitrogen and phosphorus levels – but the chief scientist of the Our Land and Water National Science Challenge, Richard McDowell, said the ministries might be able to get more detailed information about land use if they simply anonymised the data. “The data is there, but privacy concerns rightly prevent it being used,” he told the Science Media Centre.

2. Government swim-ability estimates are different from officials’ estimates and nobody yet has a good handle on how to measure it.

There is already enormous confusion about what swimmable means when it comes to rivers and lakes, how many of our swimming spots are clean enough to splash around in, and whether the Government’s proposed standards will better or worsen matters. This report does little to clear that up, because the Ministry for the Environment is still gathering data and working out the best way to measure swim-ability. The Ministry says it is still evolving a good indicator of swim-ability, including deciding whether modelling E.coli levels is a reliable way to track the risk of getting sick from swimming.

The report adopts the grading system from the Government’s proposed Clean Water Package, but comes up with a different result. For a river to be swimmable under the new guidelines, the risk of getting sick from infection averaged across time is between 1 and 3.5 percent, it says. The report estimates 65–70 percent of river segments fall under the ‘swimmable’ category — different from the 72 percent figure stated in the Clean Water Package. The ministries put this gap down to the Government using different parameters, for example, making adjustments to reflect knowledge from regional councils and other sources. Clear as mud, then.

Again, the report highlights some glaring knowledge gaps: for example, the ministries had no E.coli data for lakes to work with. In fact, only 5 per cent of decent-sized lakes were monitored in any consistent way. In cities, they had so few monitored sites in urban areas that they couldn’t draw any conclusions about E.coli trends. And, of the 268 river sites they monitored in rural areas, they didn’t have enough data to declare a trend in 65 percent of them. This would seem to make it difficult to know if swim-ability is improving.

The report notes councils often monitor low-lying sites where they suspect there is a pollution problem, and ignore mountainous areas that are most likely clean, which can skew the data to make pollution look worse. They overcame this by modelling water quality data to estimate areas where no data was collected, but of course these were just estimates.

3. Canterbury farms account for about a quarter of New Zealand’s freshwater consumption … we think.

Irrigation is the largest consumer of water in New Zealand (accounting for just over half of consumption permits, with households next on 14 percent) and most of the water for irrigation is being taken in Canterbury. At last check, Canterbury accounted for nearly 65 percent of the total consented volume of water nationally, in other words, more than a quarter of the fresh water being used was being taken by Canterbury farms. But this may overstate things, because councils have no idea how much of the maximum amount allowed by people’s permits was actually being used. Data from the Canterbury region suggests some farmers consistently took much less than the amount they were allowed to under their water consents, even during times of water restrictions, while others were consistently over-reaching their permits (suggesting the council may have some enforcement to do). Otago was listed as taking 7 percent of irrigation water, but since half of its consents had no maximum volumes listed the real proportion may be much higher.

A new national regime requiring farmers to install water meters, which was in place from November last year, will fill this information gap. But the reports notes we still have little information about how our post-irrigation freshwater levels compare with “natural” flows, or the impact this has on fish and other native species.

4. City water is facing a multi-billion dollar stormwater problem, and animal urine is an amazingly potent rural polluter.

The report confirms a string of previous assessments showing city waterways are the most polluted in the country, but the trends are worse in rural areas. No surprises in the rural trends either: in pastoral areas, nitrogen pollution is getting worse, and phosphorous pollution is getting better (likely because of farming and urban improvements, though the report says no one knows this for sure). 

In monitored rivers, nitrogen levels were worsening (55 percent) at many more sites than were improving (28 percent), and phosphorus was improving (42 percent) at more sites than were worsening (25 percent) between 1994 and 2013. However, that trend was flipped in some places. In 2012, an estimated 137 million kilograms of nitrogen leached from agricultural soils, an increase of 29 percent since 1990. Computer modelling of farms suggests the main source of the nitrogen from farming is animal urine, which the report estimate accounted for more than three quarters of nitrogen leached in 2012 (most of the rest was from fertiliser). Waikato and Taranaki farms had the highest nitrogen leaching per hectare. 

The good news was that most, in fact almost all, rivers did not have high enough nutrient levels to be toxic to native fish, although information on what effects rising pollution was having was – you guessed it – lacking. But about 17 percent of the total length of big rivers was considered polluted enough to have regular or extended algal blooms. 

In cities, where large concreted areas cause heavy metals and other pollutants to sluice into the waterways through the stormwater system, the report highlighted our ageing and costly-to-fix infrastructure. The report cites Department of Internal Affairs sums saying the replacement value of the entire national infrastructure network for wastewater and stormwater is $36.7 billion, and one-quarter of the wastewater assets are more than 50 years old. Local Government NZ estimates between 10 and 20 percent of the network needs significant renewal or replacement.

5. Whitebait is in dire straits, and there’s a real prospect we will lose some of our other native fresh water species, too.

Of the native species that were well-monitored enough to report on, around three-quarters of fish, one-third of invertebrates, and one-third of plants were threatened with, or at risk of, extinction. Pests and changes to the natural flow of waterways were big pressures, though again the exact extent of the problem wasn’t clear. Of the 39 native freshwater fish species the report tracked, only eight were well-understood enough to declare a trend: four of these were sliding down the ranks of conservation status, and only two were getting less-threatened. Some species of whitebait were at risk of being lost forever, along with longfin eel and kanakana (lamprey). Physical changes to rivers from weirs, culverts, dams, planting willows on stream banks and other things were affecting native species but there wasn’t good information on the sum total of the effects. Another area for investigation, says the report …. when someone allocates the money.

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