The Regional Council on Wednesday deliberated on what to do about water consents in the Tukituki catchment.

The third model developed in this decade to understand water flows and the interplay between the Ruataniwha aquifer and the surface water running over it (in Central HB), recently completed by HBRC staff, confirms what the previous ones suggested … “abstract” too much water and you will deplete both the aquifer and the river flows.

Surprise, surprise!

So, what to do if landowners seek more water takes from the Ruataniwha basin?

The staff response is a great illustration of language crafting: “Applications for consent to abstract groundwater from the basin will generally be publicly notified, and the staff recommendation is likely to be to decline such applications.” Verbally, the staff insisted this posture did not amount to a “moratorium” on water takes in the basin, since they had no power to declare one. But as Darryl Lew, the Council’s “main man” on such matters noted (and I paraphrase): we’ve just spent nearly a year and about $100,000 to produce a model that tells us we shouldn’t allocate more water … to change our stance (and to win an appeal if we said NO), an applicant would need to make the same level of effort to produce a model of their own that indicated water was indeed available. And going to that trouble, their new model might simply confirm what ours already says.

Need he say more?! A rose is a rose is a rose.

Refreshingly, the main science presentation was given by a relative newcomer to the HBRC’s bureaucracy, Senior Groundwater Scientist Husam Baalousha, who produced the model. A very precise man, but not yet fully versed in tip-toeing through Councillors’ aspirations. He termed his presentation “not good news.” I can’t recall ever hearing any of our councils’ staffers utter such forbidden words!

So when Councillor Christine Scott, the Hearings Committee Chair, looked for possible ways to find more water to give away, he dashed her hopes. Having been told in the presentation that “younger” water replenished itself faster than “old” water (but that most of the water in the aquifer is very old … Baalousha said 100-200 years), Scott asked if the Council couldn’t simply allocate more of the “young” water. The scientist’s reply: “Well, it might be better to take younger water, but whether young or old, you can’t over-exploit it.”

Which, of course, is precisely what has been done.

Baalousha’s model indicates that groundwater abstraction has increased from 3 million cubic metres in 1990 to approximately 24 million cubic metres in 2009. The cumulative effect of current actual groundwater abstraction has resulted in a decline rate of 600 litres/second from surface waters in the basin area. Keep in mind that the current “minimum flow” for the Tukituki is 1900 l/s (“minimum flows” are set to ensure sufficient water is left in a river to maintain identified river values — cultural, ecological, economical, social — and might be raised by a pending new National Environmental Standard).

The staff report notes:

“Model results also showed that the actual groundwater abstraction across the basin over the last twenty years has caused a decline in aquifer storage of approximately 66 million cubic metres. This will result in a continued decline of aquifer water levels and more importantly stream and river flows within the basin until a new dynamic aquifer equilibrium is reached depending on the uptake and use of existing allocated volumes and any further allocation decisions. This will not only impact existing surface water consent holders, but also the ecological, cultural and other values associated with the rivers and streams in the basin and downstream beyond the basin.”

In over-allocated rivers, like the Tukituki, it is estimated that around 40% of water allocated is actually used. If all the water allocated was actually used, “all hell would break loose” as Councillor Tim Gilbertson once observed. Such far higher volume of actual water use in low flow periods would obviously trigger more bans on all abstraction.

Since existing groundwater consents alone authorise the irrigation of approximately 7,000 hectares, that would be a BIG problem!

Tom Belford

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2 Comments

  1. Hi Tom,Great stuff on the Tuki problems.Keep it up.

    How about some info on the degradation of the Mohaka from the intense farming on the Taharua ?river.

  2. Since when does one abstract water from an aquifer? Perhaps if we give consent to extract from the aquifer life may be a bit easier for the HBRC.

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