18 January 2022

Should New Zealand be more proactive in collecting rainwater?

As the annual rainfall in New Zealand becomes more and more erratic, is there more we should be doing to collect our rainwater and put it to good use for homes and businesses?

Back in August 2020, Stuff ran a piece asking whether the tide is turning on the use of rainwater tanks in New Zealand. The answer, at the time, was not really.

In their research, Stuff asked 66 of the nation’s 67 territorial authorities (excluding the Chatham Islands) about their policies on the collection of rainwater. They found that, at least for urban households, 40 councils were neutral when it came to encouraging the use of rainwater, 21 could be classed as supportive, and only a few – including Masterton and Carterton – offered assistance such as discounts on tanks.

There were some outliers. Kapiti and Gore are both leading the way when it comes to encouraging residents to capture rainwater for use around the home. Since as far back as 2009, Kapiti has required residents to capture rainwater for flushing the toilet and for use outside and offers homeowners a discount if they hit certain targeted rates.

In Gore, all new residential buildings are required to install a rainwater tank with a minimum capacity of 3,000 litres.

These are shining examples of the work we could be doing to not only capture more of our rainwater but put this natural resource to good use.

Aucklanders feeling the heat

Since the early part of 2020, water restrictions have been in place for Auckland to varying degrees and this has put a real strain on the water supply to New Zealand’s largest city.

Severe drought conditions in the summer of 2019-20 – a record dry spell – took the region’s dam levels to a quarter-century low of just 42 per cent. This led to some of the harshest restrictions being placed on Aucklanders, with gardens drying up and plants withering across the region.

Thanks to the good work of Aucklanders who cut water consumption significantly, a boost of 104 million litres a day from other sources and some heavy spring rains, water levels across the dams in Auckland are currently sitting at around 93 per cent – slightly higher than the average at this time of year.

That means it is likely that Auckland will head into this summer and autumn without the strict restrictions that have been in place for the past 17 months.

Whilst this is a positive for the summer of 2021-22, who is to say what’s around the corner and with long term predictions of hotter, drier summers and less rainfall, is it time to put measures in place to collect more of our rainwater, not only in Auckland but across New Zealand?

Feeling the cost of the drought

Whilst Aucklanders may celebrate being able to water their gardens, wash their cars and hose down their boats with no restrictions this summer, it is likely they will be feeling the cost of this drought for some time to come.

The cost of boosting the dam levels with supplies from the Waikato River will be felt by Aucklanders in their water bills for a decade to come.

And who knows when another summer drought like the one in 2019-20 will strike again. This could continue to push up water bills across the region for the foreseeable future so is it time to do something about the likely issues now rather than waiting for another drought to strike?

Is it worth getting a water tank?

We recently published an article asking whether it was worth getting a water tank, and for many of us, the simple answer is yes, especially if we want to keep doing the things we love outdoors and enjoying a beautiful garden.

Water tanks are becoming more accessible, both thanks to some updates to policy but also thanks to some clever designs.

When we think about water tanks, a lot of us think about large bulky tanks we often see on the outside of houses that take up a lot of real estate. Whilst these are still popular, underground tanks are becoming more common and are installed as part of new build projects, helping to improve the overall aesthetics of a property whilst maximizing water collection.

There is also a much wider variety of tanks sizes and designs available, many of which offer a slimline design that fits to the style and shape of your property. People are even installing this slimline water tanks up against a fence where they can provide a softer aesthetic whilst capturing valuable rainwater.

Auckland Council is one of those councils trying to make rainwater collection more affordable and more attractive to residents although they still have some way to go.

In 2020, they pushed through one policy change and one further change is currently under review:

1.       Auckland Council has removed resource consent fees for the installation of rainwater tanks at residential properties - APPROVED

2.       Through a change to the Auckland Unitary Plan, water tanks are now a requirement for new residential property developments – UNDER REVIEW

The introduction of more water tanks, especially those in any new development in Auckland, could help to reduce the reliance on central water supplies and reduce the strain on Auckland dams.

How much water can you catch and store?

There are several different calculations that people use to work out how much water can be captured and stored but we like this model:

1.       Estimate the size of your roof by calculating the length x width of your property. You can also visit websites like homes.co.nz where you can find out the overall size of your property and use this as a guide i.e., 170m²

2.       Look up the annual rainfall for your area. Head over to the NIWA website where you will find that information.

Once you know these two bits of information, then it’s a simple equation to calculate your harvestable water potential:

Litres per square metre of catchment x catchment area (roof area) = litres of harvestable water

You can calculate the litres per square metre of catchment based on the annual rainfall for your area. The annual rainfall for your area in mm is equal to the litres per square metre of catchment.

Example:

The average rainfall in Auckland is 1,114mm per year. My property is 172m².

1,114 litres x 172m² = 191,608 of harvestable water per year

You can read more about rain collection and the size of water tank you might need in our recent post, What size water tank do I need?

Round-Up

We asked a question at the start of this post about whether New Zealand should be doing more to collect rainwater and the simple answer is yes. Stuff’s Forever Project is a great way to find out more about the changes we can make to positively impact climate change and collecting rainwater is one of the things we could all look to do to help reduce our reliance of the mains water supply and harvest one of our natural resources.

If you already have a tank installed or once you decide to take the plunge and install one at your property, make sure you keep on top of your water usage as well as accurately measure the amount of water in your tank with a Smart Water sensor.

Our award-winning products provide state-of-the-art monitoring systems that not only provide you with an accurate reading of the water level in your tank but also work intuitively for the everyday user, providing you with all the information you need about your water consumption on an easy-to-read display or through our app. Read more about measuring the water level in your tank in our recent post.