IrrigationNZ says a recent expert discussion document on drought and climate change highlights that future national planning to improve water storage and look at a range of options to mitigate the effects of the more severe droughts forecast is urgently needed.
“More frequent droughts and more variable rainfall will affect both urban and rural communities and will mean that we will need to rethink how we manage water in the future.
For example with less rainfall forecast over summer in western areas of New Zealand, there will be more demand for water storage from both councils and farmers to provide a reliable water supply,” says IrrigationNZ Chief Executive Andrew Curtis.
“To adequately prepare for the future New Zealand needs to capture more of its plentiful water from rain and ice melt. Hopefully the issues highlighted in this document will lead to action to avoid our regions being crippled from future droughts,” Mr Curtis adds.
The document highlights that having been historically ‘water-rich’, New Zealand is not well-prepared to cope with a future that will involve more droughts in many areas. The report points out that: “much of our irrigation in drier areas is on a run-of-river basis, a model extremely vulnerable to drought given environmental obligations. New Zealand’s dependence on agricultural exports and urban reservoirs may yet be a recipe for drought vulnerability. Changing drought risk will have an impact on our society in many ways including on water supply, wastewater, stormwater and primary production among others.”
“It’s positive that the government is looking at how water services will be delivered in the future,” says Mr Curtis. “The next step is to develop a national approach to plan for improved water storage for both urban and rural communities.”
“Local and regional water storage infrastructure can be expensive to design and construct but the need for this investment will become more critical in the future. We will also need new infrastructure in regions where this hasn’t previously been required as rainfall and river flows change.”
Mr Curtis says that the recent decision by Tasman District Council to proceed with constructing a new dam to supply residents, businesses and growers with water, is the kind of investment that will increasingly be needed in the future.
“The project is critical to avoid severe water restrictions for urban and rural water users, and also provide for environmental river flows” he adds.
The recently completed Central Plains Water scheme is another example of a project which is designed to help mitigate the impacts of future droughts.
Mr Curtis says that improving water use efficiency will also continue to be a priority.
“Farmers are already investing in more efficient irrigation systems and New Zealand has very efficient systems operating by world standards. Regional councils are continuing to require that farmers adopt more efficient irrigation systems and irrigation schemes are also modernising their networks to install piped systems which reduce water loss. Urban areas are also looking at programmes to improve and encourage water use efficiency.”
NIWA projections included in the discussion document indicate that droughts are expected to become more severe in most areas and more frequent and severe in already drought prone regions. Seasonal rainfall patterns will also change according to the Ministry for the Environment – for example in spring there may be less rainfall in eastern and northern regions and more rainfall in the summer in eastern areas while western areas will experience drier summers.
The economic impacts of droughts in New Zealand were estimated at $720 million from 2007 to 2017 in a 2018 report for Treasury – with estimated costs significantly higher for drought than for flood related insurance claims over the same period.
New Zealand’s recent average annual rainfall is estimated at around 550km 3 by NIWA. Just 1km 3 is enough water to fill 400,000 Olympic size swimming pools.