Talking Point: Too much, then too little - Hawke’s Bay’s water seesaw is why we need dams

Hawke's Bay's rivers would be topped up in dry seasons using the water in storage. Photo / Warren Buckland

OPINION

We have already had way too much water this year and if you’re a betting man you would say the next environmental and economic challenge is a drought.

The El Nino weather pattern is on its way and that means a dry east coast. It could be the driest we have ever had because everything points to weather extremes becoming, well, more extreme.

The regional council recognised this some time ago and commissioned Tom Skerman and others to undertake a Regional Water Assessment (RWA).

The RWA is an excellent piece of work that tells us how much water we have, both above ground (rivers, lakes and streams) and below ground (aquifers).

It also tells us how much we use. The RWA used 2019/20, which was a dry year, as a base and in that year we used 138 million cubic metres.

The RWA makes predictions on our future requirements and it’s not pretty. Here’s a scenario. Let’s say we all reduce our consumption of water by 20 per cent between now and 2040.

You might think that’s a lot, but even if we do that, we are still likely to have a water shortfall of 25 million cubic metres at that time.

The reason is climate change.

Jock Mackintosh.

Increasingly we will have too much water when we don’t need it and not enough when we do.

This looming water deficit matters on many levels. If river flows get too low, for too long, the damaging effect on the rivers and the plant and marine life they support, is massive. As a community this is unacceptable, but it is exactly what we will get if we don’t become better managers of water.

Water shortages have a similarly damaging effect on our economy, in particular the horticultural and agricultural sector which is reliant on water for irrigation.

These are major contributors to our community. They are our biggest employers, they feed us, generate $2 billion in exports and help us pay for many of the things we take for granted.

But the good news is there are solutions, and they are staring us in the face.

Actually, we have plenty of water, we just don’t have enough when we need it – in summer.

There are several “levers” available to us. One is to save water – to be more efficient in the way we use it. In fact, this is not so much a lever as a requirement. Technology is helping here, especially with irrigation. There is also promising work being undertaken to recharge our underground water levels, especially in Central Hawke’s Bay and potentially in the Heretaunga plains.

Arguably, the most significant lever we have is water storage. It’s an emotive subject in Hawke’s Bay, but it shouldn’t be. Storage is a commonly used option in other parts of New Zealand and the rest of the world.

The main difference between potential Hawke’s Bay storage schemes and others in New Zealand, is that the environment is likely to be the main beneficiary.

Te Mana o Te Wai (the mana of water) is a key principle of our fresh-water management regulations. It addresses potential inequities in the allocation of water. In particular, it means our first priority must be to ensure the life-supporting capacity of freshwater, especially its quality and quantity.

Remember the earlier comment about river flows getting too low in summer. The primary aim of any community scale storage is likely to focus on topping up low river flows during summer.

Other users, including irrigators, will come after that. They still benefit though because topping-up river flow from stored water “underwrites” the water that irrigators are already using.

So we can think of storage as being “insurance” with our rivers being the first to be paid out in a drought.

This is a win for our environment and our economy. Both of these things matter and they do not have to be mutually exclusive. We all know that we have to be better environmental managers, but we don’t all know that our economy (GDP) ranks 11th out of 15 regions in New Zealand. In other words, we are below average. Storage aids our environmental and economic aspirations.

Storage just makes sense. We know that droughts (like floods) are going to be more severe and more frequent. We can choose to reduce the effects of droughts, or not and it will depend on two main things – our ability to fund a community-based scheme and public support.

Jock Mackintosh is a Hawke’s Bay Regional Councillor. The opinions expressed are his own and not necessarily those of the Council