New Zealand's recent heatwave is likely to repeat in future years as hot, dry summers become increasingly frequent – requiring New Zealand to urgently plan to improve water storage to cope with future demand, says IrrigationNZ.

“New Zealand is water-rich by world standards, but we often don’t have enough water at the time it is most needed unless we store more water,” says Nicky Hyslop, IrrigationNZ Chair.

New Zealand’s recent average annual rainfall is estimated at around 550km3 by NIWA, and 2% of this is abstracted for human use. Just 1km3 is enough water to fill 400,000 Olympic size swimming pools.

“We experienced a relatively wet spring in many areas but in January our landscape has dried out. Soil moisture levels are now significantly below average in most of the North Island, particularly the Upper North, over Canterbury, Otago, Marlborough and Nelson and this is increasing demand for water for both domestic and agricultural use,” says Mrs Hyslop.

The drier conditions are forecast by NIWA scientists to continue in future summers, according to a report on Climate Change impacts on agricultural water resources and flooding.

The report highlights that soil conditions are projected to become drier over much of the country, including Auckland, during spring and summer during this century. Average river flows are also expected to decrease in the east and north of the North Island.

“The changes will mean that we will need to re-think how we manage water in the future. Our population will continue to increase. This, along with drier soils and lower river flows in places like Northland and east coast of the North Island will mean that demand for water will increase in cities and in rural areas and we need to plan to respond to this,” says Mrs Hyslop.

“Water availability is a critical issue for New Zealand and we need to be planning at a national level for how we will meet this increasing demand for water. There may be opportunities to develop multi-purpose water infrastructure which serves communities and farmers and growers and also has environmental benefits.”

The Kerikeri Irrigation Scheme is an example of a water storage project which has delivered multiple benefits for a community including higher household incomes, more employment and environmental benefits.

In many countries worldwide, developing water storage is increasingly being seen as key priority for governments and is centrally funded.

Mrs Hyslop says that during dry conditions such as this, irrigation plays an important role in ensuring Kiwis can continue to have access to affordable local food, but irrigators will need to manage their water allocation carefully over this period.

“Irrigators have a limit on the amount of water they can use in their resource consent. A number of irrigators will already be operating under river restrictions, while others will need to be planning for the likelihood that water restrictions may be introduced soon.”

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