Kapiti Coast District Council has scored a first in the country by ensuring that all new housing developments will have greywater recycling measures in place to mitigate the water use issues that have plagued the district.
The fast-growing district has been hamstrung by water shortages because of an over-reliance on in-river supply, but Plan Change 75 will ensure that demand issues from new development are alleviated by the addition of in-ground rainwater tanks and greywater recycling systems.
Mayor Jenny Rowan hailed this as a major step in the long term programme to manage water use and supply in the district and said it showed that the council was serious about conserving and managing the use of its potable treated water supplies.
“As much as 40 per cent of the water used during the summer months is for outdoor uses,” she said.
Plan Change 75 requires all new dwellings in the district to have either a 10,000 litre rain water storage tank or a combination of a smaller 4000 litre rainwater storage tank and a greywater irrigation system. There is also provision for consideration of other water solutions, which provide a non-potable water source for outdoor use.
The plan change builds on an existing policy in place since 2002 where water use in newly rezoned subdivisions has been controlled through a requirement for water saving devices and restricting the supply to 1000 litres per household per day.
“This is all part of our long term programme which recognises the need to reduce demand for water arising because of new development and to develop conservation packages,” Mayor Rowan said.
“Water quality and supply is clearly the number one concern in our District.
“We’ve set aside money in our long term plan for improving supply/storage capacity, and for a comprehensive conservation package, including public education and the investigation of a range of incentives for initiatives such as the installation of water conservation systems for consideration during next year’s Annual Plan process.”
“We know rainwater storage tanks reduce outdoor water use and, combined with greywater irrigation systems which apply waste water from washing machines and bathrooms through in-ground irrigation systems, there is the potential over time to reduce use of potable water for outdoor uses considerably, and extending the life of our supply systems,” she said.
The council’s water use co-ordinator Ben Thompson says the change came about as a result of a crippling drought back in 2002/03.
“Water is the main issue here and it is quite an emotional one,” he says.
The need for the Plan Change arose from the Water Matters Sustainable Water Use strategy adopted by the council in 2003. That set out the council’s vision for the management of the district’s water resource over the next 50 years, including the impacts of continued unmanaged water demand on natural systems. The strategy recognised that water was a finite resource and identified demand management as the key method for managing Kapiti’s water supply. It also emphasised decoupling use of potable water for essential water use from other water uses as a way of reducing environmental impacts as well as costs to the community.
The public potable water supply for the Kapiti Coast comes from three main catchments. All of these supplies have water take limits. The Waikanae catchment supplies the bulk of the District’s population. The council has experienced water shortages in the past due to a reliance on in-river supply. Council constructed a supplementary supply borefield in 2005 which provides water when the river flows drop. It provides greater certainty of supply for this area but the water take consent for the Waikanae catchment is limited to 23,000 cubic metres and in 2008 peak demand came close to this limit.
Greywater plan slashes water use
Former dairy engineer Steven Roberts knew that he had to do something when he saw his mother-in-law carting buckets of water from the bath out to the garden to water the plants.
It was in the big drought of 2002/03 and he had just moved to the Kapiti Coast with his wife.
“I had been working in engineering in the dairy sector and I thought I might be able to do something; it was a huge issue here. I did some research on how other parts of the world dealt with drought and I saw that a lot of people were using greywater recycling and that looked like it could work here for irrigation.”
He set to work and designed the Water Lily, an in-ground unit that collects water from sinks, baths and showers and pumps it onto gardens for irrigation. He is now managing director of Watersmart, an engineering company specialising in water conservation.
Roberts says the Kapiti Coast District Council’s Plan Change 75, which legislates for compulsory greywater recycling, should be applauded and that it will greatly benefit ratepayers.
He says Kapiti’s historical summer water shortages are caused by residents using up to 10
million litres of drinking quality water a day to water their gardens.
“This simply doesn’t make sense and is definitely not sustainable.
“As a result of the foresight shown by the council and this plan change, capital expenditure on increasing water capacity can be deferred and significant savings can also be made on stormwater and wastewater operating costs because there will be less volume needing treatment. At the moment 42 cents in every Kapiti ratepayer’s dollar is spent on water. This change will lessen the burden and help keep rate rises in check.”
KCDC water use co-ordinator Ben Thompson says the research the council did was compelling.
“We used the PURRS predictive modelling programme which allowed us to work out water use and we could predict demand for a good year and a dry year. We could also work out the effects of adding rainwater or greywater tanks. We found that adding greywater recycling into the mix gave much better savings than a rainwater system alone.”
The possible public health implications of using greywater for irrigation made them cautious about going down the greywater path, but the results were too compelling not to.
The council took a step-by-step approach to the issue, taking the community impetus to sort out the district’s water issues as a starting point. Then a strategy was formulated and modelling carried out to ensure it would work.
The next step was to incorporate it into the District Plan and ensure it dovetailed with the Building Act as well. Supporting information such as a code of practice and assessment tools were then developed and the last stage is ongoing support and development, involving working with stakeholders such as builders, developers, the regional council and public health.
One of the criticisms of the plan change has been that it could be seen to unfairly place restrictions on new dwellings while ignoring existing ones, but Thompson says that the council has plans to look at retrofitting greywater systems.
“There could also be scope to look at this in other areas, such as commercial/industrial developments and multi-occupancy dwellings.”
Overall, though, the plan change has been well received, even by developers and Mayor Jenny Rowan has a greywater system installed at her lifestyle block in the hills overlooking the coast, where greywater irrigates her thriving gardens.
Roberts is now encouraging other New Zealand authorities to follow Kapiti’s lead and use a common sense solution to tackle a common problem as well as calling on Central Government to back greywater irrigation.
“I’d love to see water efficiency given the same priority as energy efficiency which the
Government is tackling with their $300 million New Zealand Insulation Fund.
“A sprinkler uses 1000 litres of water an hour and over 1.4 million kiwis get out in the garden each year so it’s not hard to see the root cause of peak water use. There’s no reason changes to the Building Code, similar to those covering double-glazing and insulation standards, couldn’t be made.
“Making greywater irrigation compulsory in new homes and incentivising a retrofitting programme for existing homes is a much smarter way to manage our water and would stop local government spending more and more money on a resource which there is less and less of. Backing greywater irrigation guarantees a water supply for the garden and would keep New Zealand green for generations to come.”