For New Zealand to transition towards land uses that have a greater economic value and smaller environmental footprint, as well as improved community resilience, we need to “act strategically – and to act now”.
That’s according to Water Security and Availability in Aotearoa New Zealand, a report released by the Ministry for Primary Industries last month.
The report says that while New Zealand is traditionally viewed as a green and water rich country, climate change trends show a country getting warmer and drier (with some regional variations), and more prone to climate extremes (floods and droughts).
“The frequency of these events is increasing rapidly. The declining natural availability of water, combined with the need to halt further degradation of our natural waterbodies and operate within environmental limits, pose significant challenges for the availability and security of water for the food and fibre sector and rural communities.”
As part of both demand and supply management there needs to be a better integration of practices and technologies to monitor, measure, and manage water to improve efficiency and climate proof water availability and security.
“Where demand responses are not sufficient to ensure water security there is a need to consider the role of supply solutions such as investment in water storage, ground water recharge and water distribution to supplement natural sources of freshwater.”
A key recommendation is that MPI establishes a Water Availability and Security Partnership comprising central and local government, iwi/Māori, food and fibre sector organisations, science providers, and community interest groups. Te Mana o te Wai should be the “guiding framework”. (TMoTW calls for management of freshwater, that ensures the health and well-being of the water is protected and human health needs are provided for before enabling other uses of water.)
Researchers for the report worked with an external Water Availability and Security Advisory Group, whose nine members include Canterbury-based Federated Farmers Senior Policy Advisor, Dr Lionel Hume.
He agrees that a strategy, better co-ordination and preparation of an action plan for what steps we take next on improving water storage are overdue.
“If we’re serious about building resilience to the impacts of climate change those are the sorts of discussions we need to have.
“We’ve got plenty of water and we’re still going to get plenty of water. We just need to fund some better infrastructure so we can store it and use it,” Dr Hume said.
Thinking about his home province of Canterbury, Dr Hume said climate change scenarios suggest we’re going to get less snow falling in the Southern Alps, less rainfall on the east coast but even greater rainfall on the west coast and Southern Alps.
“There could be more water in the alpine rivers but if more water is the main divide is falling as rain rather than snow, it’s not necessarily going to turn up on the east coast at the time it’s most needed.
“Historically, snow melt happens late spring early summer, exactly when water is needed for irrigation to drive food production. It’s probably not going to be that neat and tidy in the future.”
Better storage future-proofs our options, Dr Hume said.
“And this is not just about agriculture. We need water security for towns and cities too. The development of water infrastructure these days tends to be multi-purpose. I think that’s going to be increasingly the case.
“Planning – and funding – needs to be at community scale.
The MPI report said based on a national scale assessment, Canterbury, Hawke’s Bay, Tasman and southern Manawatu were identified as regions that would need medium to large storage infrastructure to enable a water security of 95% or greater.
While previous government and private sector investment models achieved the water infrastructure New Zealand currently relies on, future models are going to need to be more innovative to achieve multiple purposes and benefits.
“Security of a return on investment and unlocking the potential uptake across the system are key enablers that will drive new funding models. Financing and procurement of such models will bring in different types of partners and stakeholders for investment at different phases of the scheme,” the report said.
“Interventions such as a government underwrites, or guarantees are still very relevant tools that will be needed at certain stages to incentivise uptake. There remains a clear role for central and local government to co-invest where there is both public and private benefits from new infrastructure and regulatory and climate change uncertainty impacting the willingness for the private sector to invest.”
Frequency, intensity of droughts predicted to rise
New Zealand is getting drier on average, despite considerable year to year and region to region variability.
Average annual rainfall (including sleet and snow) across New Zealand for the five years to 2020 was 3.1% below the previous five-year average and 10.7% below the five-year average starting in 1996. The decrease in average rainfall was most apparent in the North Island.
In the Northland region, the drying trend is particularly severe. Northland’s average rainfall for the five years 2016 to 2020 was down 17.5% when compared with 1996-2000. For a single year in 2019, rainfall in Northland was 41% lower that the five-year average for 1996-2000.
MPI’s water security report said in 2019, seven out of the nine North Island regions experienced drought-like conditions, with their lowest rainfall over the last quarter century.
With warmer, drier conditions the soil moisture deficit associated with drought conditions (measured as potential evapotranspiration deficit – PED) increases. Relative PED estimates provide a robust measure of drought intensity and duration.
The frequency and intensity of droughts is also projected to increase, particularly in the north and the east of both main islands. Increases of PED by 2040 of an additional 50-100mm are projected for most of the country based on a middle-to-low greenhouse gas concentration pathway.
When it does rain there is likely to be a higher frequency of extreme rainfall events (potentially causing floods) for most of the country, and a reduction in moderate intensity rainfall events necessary to recharge ground water and replenish soil moisture.
To give an indication of the likely costs of the effects of increasing frequency of droughts a report by Butcher Partners Ltd in 2009 for the then Ministry of Agriculture estimated the regional and national impacts of the 2007-2009 drought at a loss of $2.8 billion over two years, of which $1.9 billion was on-farm loss and $900 million was off-farm loss. A report for the Reserve Bank on the 2013 drought affecting much of the North Island and parts of the South Island estimated the costs of that drought at around 0.6% of GDP ($1.3 billion).