Maybe. Maybe not.

The Board of Inquiry (BOI), in its final decision, appears to think it has rescued the Tukituki.

It has required Farm Environmental Management Plans (FEMPs) in which farmers must commit to how they will meet specified nutrient (nitrogen) leaching limits deemed acceptable for their soil conditions (as indicated by the so-called LUC system). Farmers will need to use farming practices that best enable them to meet the limits.

In turn, the cumulative nutrient load in the river (measured most critically in terms of dissolved inorganic nitrogen, DIN) associated with all farming cannot exceed 0.8  mg/L. This compares to DIN limits of 0.44 mg/L set for the Manawatu-Wanganui and Otago regions. So it’s a good limit, not the best.

This limit – opposed by HBRC – was accepted by the BOI on the basis of evidence from environmentalists, who argued that the overall biological health of the river ecosystem was already harmfully affected by current nutrient run-off in the river. HBRC had argued for significantly higher nitrogen limits based on a more narrow measure – fish toxicity. The higher HBRC limit was seen as an enabler of farming intensification in the catchment (i.e., an enabler of the dam).

That the BOI accepted the case for a DIN limit is a victory for the health of the Tukituki.

Some measuring points in the Tukituki catchment presently exceed the 0.8 DIN limit; some do not. In its own calculations, the BOI considered that a small amount of ‘headroom’ for more nitrogen in the river presently existed and therefore the DIN limit was not unduly harsh.

The individual on-farm leaching limits and the overall catchment DIN limit are intended to work together. As the BOI sees it:

“Effective nitrogen management requires a two-pronged approach. The first component involves the setting of on-land root zone leaching limits which will serve as an important control at the source of the leaching process (the fence at the top of the cliff). The other component involves the setting of in-stream nitrate-nitrogen and DIN limits which will serve as a check as to the effectiveness of the LUC leaching rate control.”

Will this approach improve water quality in the Tukituki?

Environmental advocates believe the on-farm leaching limits will ultimately need to be ratcheted lower and embedded in consents in order to meet the DIN limit … and that the DIN limit itself might need to be lowered.

In its final decision, the BOI seemed to anticipate that outcome, saying:

“It is the responsibility of HBRC to avoid the exceedence of DIN limits in the receiving water by regulating the level of nitrogen discharged at the root zone by the farmer and monitoring subsequent DIN concentration in the receiving water. If observed DIN levels are too high then future adjustment by HBRC of the LUC root zone leaching rates may be required.”

And further, in its reasoning for not now setting a lower/tougher DIN limit, the BOI says:

“As water quality science advances a different DIN limit may emerge as a more appropriate level. In the meantime the Board sees the DIN limit of 0.8 mg/L as a pragmatic level that appropriately protects ecological health while enabling more intensive land use.”

But can we, as the “pragmatic” BOI hopes, both have our cake and eat it too? Or has the BOI simply pushed back the day of reckoning when we finally actually decide whether, as Councillor Rex Graham says, “It’s time for farmers to adapt to the river instead of the river adapting to the farmers”?

In all likelihood, if the BOI-ordered regime stands (at this writing, the involved parties have 10 more working days to file legal appeals), sooner or later the Regional Council will have the same political hot potato back on its hands.

If the DIN limit is exceeded a few years down the road, environmentalists will argue for ratcheting down the on-farm leaching rates, as the BOI foresees. But the HBRC, if it maintains its historic and current mindset, can be expected to say: NO, we can’t do that … we’ve already built a dam and farmers have borrowed millions to irrigate and intensify. We must raise the DIN limit instead … or better still, toss that approach entirely, and switch to more accommodating fish toxicity limits.

Surely, you say, that’s not a possibility. Hasn’t the BOI, having studied the matter for over a year, definitively ordered a regime based on DIN limits?

Yes, they did. But, for all practical purposes, the BOI is already history. The political wheel is already turning.

Today, the Government announced its new National Policy Statement for Freshwater Management (download here). It’s a wimpy disappointment, as expected. And what measure does this NPS adopt for assessing and protecting water quality – fish toxicity! Exactly what the BOI rejected.

So stay tuned folks, the Tukituki ain’t getting better yet. And that’s without the farming intensification a potential dam will encourage.

The BOI might well turn out to be a minor bump in the road — mere road kill — for the dam juggernaut.

Tom Belford

Join the Conversation

3 Comments

  1. Seems to be a foregone conclusion that the BOI was going to become roadkill if it kicked up dust. There is a far bigger agenda coming from the government to soften ALL environmental protection in beautiful Aotearoa. The Tukituki is probably just peanuts compared to our pristine Fiordland parks and Maui dolphin reserves!

  2. Tom, very selective interpretation of BOI’s findings on your part. A balanced view, I think not, but s’pose anybody is entitled to blog an opinion even if it misrepresents published decisions! The BOI didn’t exactly “reject” fish toxicity. It is still there as well as the new 0.8DIN figure. Two different limits, two different purposes, yet both complimentary to a healthy and sustainable Tuki.
    As for Government’s “wimpy” disappointing announcement, can ya really blame them for not setting a bottom line on DIN or other similar attribute? If the best 70+ freshwater scientific minds in country can’t yet agree on a national limit, who can?! Some agreements were reached and MfE should be commended for that first-step initiative; to be followed by further scientific debate and analysis of what limits can work as a nationalised limit. Those discussions won’t be easy because of the many exceptions and local conditions of our rivers and lakes, plus perhaps some professional and academic egos thrown in for good measure. Seems many want their cake and eat it too in wanting tougher nationalised limits while also having local communities deciding what they want their own waterways look like.

  3. Placing meaningful limits on nitrogen levels in water bodies is a serious problem!

    Having spent some years myself carrying out water analysis for all manner of substances including ammonium nitrogen, nitrate nitrogen and nitrite nitrogen all of which can be in a state of equilibrium; has so much variability.

    When we talk about a metre length we know precisely what that is!

    However these species may be in constant variability depending upon the time of day or night, the seasonal situation and precipitation(rainfall) and many other environmental factors.

    The pH of the water varies through-out the day and night largely from the change in carbon dioxide in the air and thus water according to Henry’s Law! as a result of plant respiration
    …….plants producing carbon dioxide at night make the water more acidic (lower pH at night) this follows a wave similar to that of a sine wave diurnally!

    All chemical species in atmospherically exposed water bodies are affected from this!

    The time of sampling for a given nitrogen species may have a significant variability as a result this, not to mention discharges from point sources such as the Waipukurau and Waipawa sewage disposal points which themselves will be highly variable both in volume and concentration of various chemical species.

    1/ Often it is not possible to get a reliable consistent sample.

    2/ Sample methodology can yield highly variable results.

    3/ Highly turbid water can cause adherence of these and other chemical species to particulate ( suspended solids) surfaces, producing meaningless results!

    What we are then comparing in these results, is more a relative value of nitrogen rather than an absolute value since the real value cannot be determined accurately !

    The trouble with the DIN is that it is an idealized measure and in practice can be quite meaningless; other factors like BOD and COD and dissolved oxygen all are inter-active; so in many ways we have a bit of a pea soup situation; where for legal reasons there must be a measure even if that measure sometimes will tell us little about the real DIN and in my professional opinion has little validity.

Leave a comment

Your email address will not be published. Required fields are marked *