Why we might give a dam

April 3, 2010
Could there really be a way to bring badly needed irrigation water to the Waimea Plains and keep everybody else happy in the process? Geoff Collett looks at the ambitious plan to dam a river to save a river.
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Start talking about irrigation and tapping wild rivers for their lifeblood and it seems everybody has some kind of startling, remarkable or sobering fact or anecdote to throw at you.
Take Murray King, the Appleby dairy farmer who is leading the most ambitious irrigation and river management plan seen in this region.
"It was really brought home to me back in 2003, " he says. He was on a scholarship-funded trip to study irrigation issues in the United States. "I remember driving through Idaho, through what they call the high desert, and there's nothing - and all of a sudden, I came across this field growing probably 1000 acres of potatoes. You just think, 'Man - that is the power of water'."
Or Joseph Thomas, the Tasman District Council hydrology expert who is also central to the same plans for building a dam high in the hills behind Brightwater to bring water security to the Waimea Plains for the first time in decades.
"I'll show you some statistics that will shock you, " he says, brandishing an A4 piece of paper with a chart on it. Actually, the numbers, setting out flow rates on the Waimea River system, are more bamboozling than frightening to the layman, but their basic message is clear: the present use of the Waimea and its underground aquifers to fuel the district's productive heartland is hopelessly over-subscribed.
Depending on how you cut the numbers, to keep the river flowing at an acceptable rate through a dry summer could require taking away 70 per cent of the amount allocated for irrigating the plains' orchards, glasshouses, farms, market gardens, process growers and what-have-you. If it ever came to that, Mr Thomas says, "basically, people may as well shut shop and walk away".
Nelson MP and Environment Minister Nick Smith can chip in a couple of mind-focusing factoids too, about the wider debate over irrigation and water use that is building momentum around New Zealand.
They include his discovery that "the expansion of irrigation in New Zealand during the past couple of decades has been huge in international terms. Thirty-five per cent of new irrigated land in OECD countries during the past two decades has been in New Zealand - and New Zealand makes up 1 per cent of the population of the OECD."
One of Dr Smith's favourite lines, reflecting the Government's enthusiasm for irrigation as a driver of economic growth, is that "fresh water is to New Zealand what oil is to Saudi Arabia".
And now, it looks like Tasman's turn to tap the wellhead has arrived.
Most Nelsonians will know the Lee Valley, but only a little bit - probably its first few kilometres as it twists its way up the steep, forest-covered hill country behind Brightwater. Thousands head up there each summer to cool off in the scattering of swimming holes in the Lee River as it winds from high in those hills down to the flats, joining with the Wairoa River and then the Waimea.
But keep going a long way up, past where the the road turns to shingle, the picnic areas run out and the houses stop.
It's tough country, the edge of Mt Richmond Forest Park but rarely visited; as Department of Conservation Nelson Marlborough technical services manager Martin Heine recalls, the last person who tried coming down that way from Mt Rintoul took searchers four or five days to find.
It's way up there that the search for a way to let Tasman join the growing stampede to harness fresh water has led.
It is an ingenious idea: build a dam across the river, big enough to flood 65ha of the hinterland and create a freshwater lake; fill it with the heavy winter rainfalls common in these hills; then use the lake to control flows in the river system all the way down to the sea at Appleby.
The experts reckon this scheme would mean the Waimea River would always have a good, steady flow - enough to keep the swimming holes filled, to keep the fish and their angling enemies happy, to flush out the weed and nurture the ecosystems, to sustain what Maori talk of as its mauri, its life force.
But more than all that, there would be enough water to keep recharging the network of underground reservoirs beneath the Waimea Plains, to the extent that almost 6000ha of land could eventually be watered, large parts of it now without any irrigation source.
Depending on how you look at the world, that's where the real gold - or oil - lies.
Those aquifers are already the plains' main water source, tapped by numerous farmers' bores and wells, as well as Richmond's and Brightwater's town supplies.
The beauty of being able to draw water straight from the aquifer, at least for those with land on top of it, is that it does away with the need for expensive pipes or canals to deliver the water to the crops.
The catch is that flows through the Waimea aquifer are, as Mr Thomas explains, closely and quickly influenced by the state of the river. If the river dries up, the aquifers soon follow.
The closest things got to this kind of disaster was in 2001, after a months-long drought saw the river stop flowing for three weeks. Saltwater started coming up the river from the sea and threatened to make its way into the aquifers.
The Tasman District Council was considering building a barrier to keep the sea out; swingeing restrictions on water use were put in place.
It was April before the rain arrived and saved the day.
That was the worst experience to date but in most years since, some kind of restrictions on water use have been imposed as the rain has stopped and irrigation has sucked up the groundwater.
Among the lessons rammed home in 2001 was that the Tasman council, and before it, the Nelson Catchment Board, had badly miscalculated the demands they could put on the river.
As Mr Thomas explains, the council's modelling of how the river worked was pioneering but flawed. It let the river run down to a trickle during summer (a minimum flow rate of 250 litres per second near the Appleby Bridge), but also allowed irrigators to then draw down more than the river could bear even at such a derisory flow - 22 per cent more, it turned out.
In fact, the river's ideal minimum flow was eventually determined to be around five times as much, and under that sort of requirement, the over-allocation of irrigation water during droughts could be up to 70 per cent.
There are various ways of sorting out a crisis of that magnitude, Mr Thomas says. One would be to impose cuts when drought strikes and risk ruining more than a few growers and driving productive business off the plains. One is to call in the lawyers and get the courts to decree how the water should be allocated - a guaranteed "lose-lose", as Fish and Game Nelson-Marlborough manager Neil Deans puts it, under which no-one would get what they wanted.
A more hopeful scenario suggested itself: a group of irrigators and the Tasman District Council were driving through plans for a small dam to feed the Wai-iti River and their efforts were generally judged a success. Their experience suggested that some form of water "harvesting" and storage could be achieved without resorting to crippling disputes with opponents. The Wai-iti group offered those looking for solutions on the Waimea a simple but crucial lesson, as Murray King recalls: engage as many stakeholders as possible at an early stage.
If it sounds banal, think again. The traditional model for water-use debates around the country has been the adversarial one. For the likes of iwi interests in particular, and Fish & Game and the Department of Conservation to a lesser extent, it was a novel experience to be asked by irrigation interests to sit down and figure out the best way to manage a river so everybody might get their share.
This inclusive and consensus approach has been the most telling aspect of the group so formed in 2003, the Waimea Water Augmentation Committee, a coalition of farmers, growers, local government, conservationists, tangata whenua and anglers who agreed to try to hammer out a lasting, long-term plan for the Waimea.
They have tried, too, to be as open as possible; having just spent many tens of thousands of dollars on feasibility plans, which will form the basis of an eventual resource consent application, they have made all the plans freely available. Their meeting minutes have been widely circulated. They have talked wherever they have found interest and approached groups who are not part of the committee to seek out obstacles in advance. "The last thing we want is something coming out of the woodwork that we hadn't thought about, " Mr King says.
Neil Deans - who has long and occasionally unpleasant experience in dealing with water allocation debates far and wide - says that while it has not all been sweetness and light and some concerns linger, "I'm conscious that this model we've got with the Waimea is being looked at very carefully by other parts of the country . . . It has got a long way . . . and other parties have been saying, 'How have they been able to do that?' "
That it has taken seven years so far just to get a detailed plan to test whether it will work for the wider community reflects, Mr King says, the grinding wheels of the system, but also the long-term horizon they've set - 100 years out - and the scale of their vision.
The group has explored numerous possibilities and settled on a handful of variations for a Lee dam; their favoured one is the biggest and most expensive, with a cost in the rough order of $40 million. Of the many big calls that are going to be needed if the dam finally happens, the bill is obviously the biggest. (See separate story.)
But presuming for the moment it can negotiate both the mountainous financial hurdle and then the years of politics and process that still lie ahead, the even bigger question would be, what if it does happen? Might it change the character of the Waimea Plains in some profound manner?
Murray King is cautious about reading the future. But he knows that what could be seen as a big advantage for the project is that the plains are not, and are never likely to be, a big dairy area, so should be spared the heated arguments over the environmental effects of dairying that mark so many irrigation debates elsewhere.
Mr King knows those arguments as well as anyone. With extensive business interests in the industry, including in Canterbury, he can talk all day about the enormous issues, political, commercial, technical and much else, that dairy farmers are increasingly ensnared in.
But up here, it's of largely academic interest; his small Appleby farm is one of only three or four left on the plains, where the land is too valuable to run cows. Put water on it to add to the abundant sunshine, and its capacity to produce intensively grown crops is vast. Glasshouses are a more likely symbol of the future there than rotary milking sheds, he suggests.
But there is much water to flow under the Appleby bridge before the current impasse facing the Waimea River can be broken. While at one level, Mr King could moan about how long it has taken to guide the project this far - seven years is an eternity in many private businesses - he knows that if they do it properly first time, they are far more likely to have the community applauding when the ribbon is finally cut on a Lee Valley dam, maybe in four years' time.
So - how confident is he? Supremely? "Highly confident, " he decides. "We can't afford not to do anything. That's probably the more important thing."
Or, as Neil Deans puts it: "The alternative isn't very nice, frankly, to think about."
Or Joseph Thomas: "To me, the question of whether we need the water or not is a no-brainer . . . I know it's a challenge. But it's a challenge the community as a whole needs to rise up to."