Planning for the Future

When designing our biggest assets and planning for the future, Port Macquarie-Hastings Council's water supply team must take into consideration the impacts of drawing water on the Hastings River and natural environment. This is called the 'secure yield'.

The secure yield is the long-term annual water demand that can be safely supplied to consumers. It takes into consideration the capacity of the river, the capacity of transfer pipelines and storages to safely meet water demands without adversely impacting on the environment.

For example - the Hastings in 2008 had a total water consumption of approximately 5447 megalitres a year. As long as our system has a yield above that figure, we can continue to supply water according to the current demand, throughout the good years and bad years.

Council follows the NSW State Government guidelines known as the '5-10-20 rule' for this type of water supply planning and design:

1. Water Restrictions are not applied more than 5% of the time (Council continues to apply ongoing Mandatory Water Conservation Measures in a bid to avoid imposing restrictions).
2. Water Restrictions are not imposed more often than once every 10 years on average.
3. Water Restrictions aim for no more than a 20% reduction in water demands.

Underlying the above is the environment's capacity to supply.  Council commissioned several environmental impact studies resulting in the development of 'minimum environmental flow conditions'. 

Council ceases pumping water from the river when the river flows fall below the relevant minimum environmental flow.  

Minimum environmental flows vary from month to month depending on the different breeding seasons of key aquatic inhabitants. 

These levels minimum environmental river flow levels are required to protect the river's ecosystem, including fish, platypuses and aquatic plants.

After heavy rain or a flood event, pumping cannot occur because the water is too turbid (dirty and high in nutrients) to use.

When no pumping is enforced, consumers are then supplied from either the Port Macquarie or Cowarra storage dams.

Planning for an uncertain future

As the population increases, we must also increase the secure yield of the water supply system which can include increasing the size and number our assets, increasing the rate of pumping from the river and/or find new water sources such as reclaimed water or desalination.

Now more than ever, the potential impacts of climate change on our local environment also have to be factored into future planning.

The four areas of primary focus in future water supply planning include:

• Estimating population growth
• Predicting per capita water demand
• Potential climate change impacts
• Water system planning options

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Hastings Water Supply Map (for a larger version, click on thumbnail)

Population

By 2036, the Hastings population is predicted to top just over 113,000 (current average annual growth 1.46%).

Water Demand

In 2006/07, the average annual residential consumption was 184kl per person. This is a 20% decrease from 2001 figures (232kl/annum).

Further changes that continue to reduce the Hastings' annual water consumption include increased awareness of water conservation, retrofitting existing houses with water efficient washing machines, showers and toilets, new BASIX houses and dual reticulation to Thrumster and Ngamba.

However, studies indicate that water consumption during a drought is approximately 11% higher than average year demands.

Climate Change

Predicting the impacts of climate change is not an exact science. Council will prepare for the uncertainty by using the following key assumptions for their long term water supply planning and look at various different options or scenarios. 

By 2050:

• Temperatures are expected to rise by 1.5 degrees
• Rainfall is expected to reduce by 3.5%pa with significant seasonal changes
• Evaporation is expected to increase by 6%pa
• Annual streamflows are expected to reduce by 10.8%pa but will be affected by seasonal differences
• Annual water demands are expected to increase by 4.3%pa (mostly in the Spring).

Changes in river flows - residential water demands are expected to increase by 4.3%pa while streamflows are predicted to drop by more than 10%pa. In a drought event both predicted changes are likely to coincide making the impacts on water supply and the environment potentially a lot worse.

Water system planning so far

The Port Macquarie-Hastings region is in the fortunate position to have two water storage dams.

• Port Macquarie Off-Creek Storage Dam (our working dam) has a current capacity of 2500 megalitres.
• Cowarra Off-Creek Storage Dam (a 'back-up' storage facility) has a capacity of 10,000 megalitres.

The Hastings population has a current annual water consumption of 5 447 megalitres per annum.

Future asset planning includes:

• Constructing the 13 km 900/750mm diameter southern arm trunk main to increase transfer capacity between the two dams and improve supply to the Camden Haven area. The main will go from Cowarra Dam to Bonny Hills.
• Increasing treatment at Wauchope Water Treatment Plant to enable pumping from the river when the water is dirty. This will increase the number of days water can be pumped from the river thus increasing the total annual quantity of water available for consumption without increasing the daily quantity of water taken from the river. 
• Construct a large 900mm diameter trunk main from Koree Island direct to Cowarra Dam. Water will be abstracted from the Hastings River, stored in Rosewood Rd Reservoir and transferred to Cowarra Dam.
• Redevelop Hansons Quarry adjacent to the Wauchope Water Treatment Plant in Rosewood Road. The quarry will become an additional storage dam with a capacity to store 2000 megalitres of water. Water that currently cannot be captured during flood events because of its turbidity (poor quality) will be transferred to the quarry for temporary storage and settling before being run through the Wauchope Water Treatment Plant and then stored at Port Macquarie or Cowarra Dams for consumption.
• By 2034 the Hastings will require more storage. Port Macquarie Dam wall will be raised to increase storage capacity from 2500 megalitres to 4000 megalitres.

Further studies

• Sea level rise may affect the river's salinity at Koree Island during dry periods. Council has commissioned consultants to model the Hastings River to determine in a drought event, how far salinity will intrude up the river.