Background
The Akaroa Harbour basin has water shortages in some of its settlements during summer and some settlements discharge their treated wastewater into the sensitive and enclosed harbour waters.
The Council and the community have an opportunity now to consider all the water issues around Akaroa in a coordinated manner. To achieve this, the Council is developing a water strategy focusing on Akaroa and the Takamatua area.
With the exception of Wainui, all the harbour settlements’ water supplies are taken from streams that flow into the harbour. These water supplies are all treated. Low flows in these streams in summer mean that, in Akaroa township for example, water restrictions have to be imposed. While Akaroa also has a very small well supply, most of its water comes from the three streams that flow through the township and into the harbour.
The treated wastewater from Akaroa, Duvauchelle and Wainui is discharged into the harbour through outfall pipes in accordance with the respective resource consents. The treated wastewater from Tikao Bay is irrigated onto a small forest block, by a land irrigation system. A new treatment plant and land irrigation system is also planned for Wainui, to be completed by 2014. Other harbour basin settlements and houses have individual septic tanks on each property.
Water supply management
As indicated above, water restrictions are often required in Akaroa during parts of the summer months due to a shortage of supply. The Council is therefore committed to explore longer term water demand options, and to this end will be working with a community working party which was convened to assist with wastewater planning options.
Development of such a strategy will address issues and provide information on and options for the following areas:
- Water resources availability
- Water demands
- Water efficiency measures
- Water supply and treatment options
- Reticulation options (including a system model)
- Wastewater treatment and disposal options
While further work is required in each of these areas, some information has already been gathered and will be further developed with the community working party.
A brief summary of these topics follows:
Water resources availability
Identifies the range of existing and potential water sources in Akaroa, Takamatua and further afield, that could contribute toward an integrated water management strategy. The sources identified are additional surface water, storage options, desalination, and wastewater reclamation and reuse.
Water demands
Establishes a baseline for the present and future requirements of the Akaroa and Takamatua water supply by identifying existing demands, and population growth demands.
Water efficiency measures
Identifies a range of existing and potential ways to reduce water demand that could become part of the integrated water management strategy. Reducing demand enhances reliability of the existing water supply. It could also mean a reduction in the amount of money that may need to be spent in future on increasing capacity of the water supply. Therefore, management of demands is closely linked to future water supply requirements.
Water supply and treatment options
Considers various options for securing enough water to meet the long-term demands of Akaroa, makes recommendations and also suggests short and medium term measures to help achieve the long term strategy.
The existing treatment plant is old and in need of a significant upgrade to ensure water reliably meets the New Zealand Drinking Water Standards. Planning for future water supply management include protecting the existing river stream sources; investigate the potential for new sources i.e. the Takamatua north stream, and the potential that on-site rainwater tanks and flow restrictors may have for reducing demand from domestic properties.
Reticulation options
A model of the existing reticulation system has been completed that will be used to identify the most cost effective way of improving pressure and flow in areas that have a reduced level of service.
Wastewater management options
Future demand for wastewater treatment and options for the reuse of treated wastewater, along with the treatment plant upgrades required for those routes, are under consideration. Two primary options have been identified:
Treating wastewater to a substantially higher standard and continuing to discharge it to the harbour,
Treating wastewater to a higher standard and applying treated wastewater onto land.
Combining these options is also possible in which, for example, treated flows could be applied to land during dry weather, and treated flows only discharged to the harbour during wet weather.
The possibility of discharging treated wastewater out to sea via a long ocean outfall to a point outside the harbour heads has been found to be unaffordable.
The current short-term discharge consent permits the continued discharge of treated wastewater from Akaroa township into the harbour. A condition of the current consent stipulates that the Council meets a series of milestones or target dates to ensure clear progress is being made toward a long term solution for the improved management of wastewater. The consent required that a community working party be established to provide community perspectives to help guide development of long term options for improved wastewater management.
By December 2011 a preferred option for long term wastewater management is likely to have been selected by the Council taking account of recommendations made by the working party.
Frequently asked questions
What is wastewater?
Wastewater (sewage) is all the water that goes down the drains, toilets, sinks, plugholes, showers and baths inside your house and into the sewerage system. Pipes and pumps take this wastewater to a treatment plant.
What is potable water?
Potable water (drinking water) is all the treated water supplied to each tap on your property.
What is stormwater?
Stormwater is all the rainwater that falls on your property and onto your roof. This stormwater can soak into the ground, flow over the ground, or flow into pipes that take it to streams or into the harbour.
